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1
Got, C., B. G. Vopat, P. K. Mansuripur, P. M. Kane, A. P. C. Weiss, and J. J. Crisco. "The effects of partial carpal fusions on wrist range of motion." Journal of Hand Surgery (European Volume) 41, no. 5 (October 9, 2015): 479–83. http://dx.doi.org/10.1177/1753193415607827.
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The objective of this investigation was to evaluate the effects of different partial wrist fusions on wrist motion. A total of 20 cadaveric wrists were tested in the intact state and after undergoing either a four-corner fusion or 2- and 3-bone fusion. The moment-rotation behaviour was measured in 24 directions of wrist motion about the forearm axis. The 2- and 3-bone fusion groups demonstrated increased radial deviation and pure flexion. Pure flexion was decreased in the four-corner fusion group. Radial extension and pure extension were decreased in all treatments compared with normal range of motion. Increasing the number of carpal bones within the fusion construct did not alter the functional axis of the wrist. Essentially equivalent motion is possible with 2-bone, 3-bone and four-corner fusions, with the exceptions of pure flexion and radial deviation. This data may influence surgeons when choosing between treatment methods. Level of evidence: N/A
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Qiu, Tian-Xia, Ee-Chon Teo, and Qing-Hang Zhang. "VALIDATION OF FINITE ELEMENT MODELS OF THORACOLUMBAR T11-T12 AND T12-L1 AND COMPARISON OF THEIR BIOMECHANICAL RESPONSES." Journal of Musculoskeletal Research 09, no. 03 (September 2005): 133–43. http://dx.doi.org/10.1142/s0218957705001576.
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The objective of this study was to build and validate the FE models of thoracolumbar junctional T11-T12 and T12-L1 functional spinal units (FSUs) and compare the biomechanical responses of the two FSUs under physiological loading modes: flexion, extension, lateral bending and axial rotation. Anatomically accurate FE models of thoracolumbar T11-T12 and T12-L1 FSUs were developed and validated against published experimental results in terms of load displacement responses and range of motion (ROM) under flexion and extension pure moments of 7.5 Nm, left and right lateral bending pure moments of 7.5 Nm and left and right axial torque of 7.5 Nm. The overall responses predicted by the T11-T12 and T12-L1 FE models showed differences in stiffness under different load configurations. Amongst all loading configurations, the motions at T11-T12 and T12-L1 were the stiffest under axial torque. The lateral bending motions of T11-T12 and T12-L1 were relatively flexible. Under sagittal moments, the motion in extension was greater than in flexion at level T11-T12, while the rotation in flexion was greater than in extension at level T12-L1.
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Frediani, Gabriele, Federica Vannetti, Leonardo Bocchi, Giovanni Zonfrillo, and Federico Carpi. "Monitoring Flexions and Torsions of the Trunk via Gyroscope-Calibrated Capacitive Elastomeric Wearable Sensors." Sensors 21, no. 20 (October 9, 2021): 6706. http://dx.doi.org/10.3390/s21206706.
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Reliable, easy-to-use, and cost-effective wearable sensors are desirable for continuous measurements of flexions and torsions of the trunk, in order to assess risks and prevent injuries related to body movements in various contexts. Piezo-capacitive stretch sensors, made of dielectric elastomer membranes coated with compliant electrodes, have recently been described as a wearable, lightweight and low-cost technology to monitor body kinematics. An increase of their capacitance upon stretching can be used to sense angular movements. Here, we report on a wearable wireless system that, using two sensing stripes arranged on shoulder straps, can detect flexions and torsions of the trunk, following a simple and fast calibration with a conventional tri-axial gyroscope on board. The piezo-capacitive sensors avoid the errors that would be introduced by continuous sensing with a gyroscope, due to its typical drift. Relative to stereophotogrammetry (non-wearable standard system for motion capture), pure flexions and pure torsions could be detected by the piezo-capacitive sensors with a root mean square error of ~8° and ~12°, respectively, whilst for flexion and torsion components in compound movements, the error was ~13° and ~15°, respectively.
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Gál, J. M. "Mammalian spinal biomechanics. I. Static and dynamic mechanical properties of intact intervertebral joints." Journal of Experimental Biology 174, no. 1 (January 1, 1993): 247–80. http://dx.doi.org/10.1242/jeb.174.1.247.
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Four-point bending was used to apply pure extension and flexion moments to the ligamentous lumbosacral spine and pelvic girdle of monkey (Macaca fascicularis), rabbit (domestic and wild, Oryctolagus cuniculus), badger (Meles meles), wallaby (Wallabia rufogrisea frutica), sheep (Ovis aries), seal (Phoca vitulina) and tiger (Panthera tigris). The absolute ranges of angular change in lumbar-lumbar joints (from X-radiographs) were considerable and similar in monkey and wallaby (greater in flexion) and in rabbit and badger (symmetrical in extension and flexion). Mass-specific bending comparisons showed that monkey and seal joints were the most and least resistant, respectively, to these moments. The patterns of mobility showed no clear scaling effects. Subsequently, additional ligamentous joint complexes (three vertebrae and two intervertebral discs) of monkey, wallaby, tiger, jaguar (Panthera onca) and seal (Halichoerus grypus) were subjected to cyclic extension and flexion moments. Changes in intervertebral angle (y, from X-radiographs) were modelled as functions of applied specific bending moments (x):y=A(1-e-Bx). A and B values represented bending capacities and joint compliances respectively. Homologous monkey and wallaby joints had considerable flexion capacities, with low compliances. Homologous jaguar and tiger joints had limited flexion capacities, but greater compliances. The data suggest that flexion resistance may be controlled by different mechanisms in different species.
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Malavolta, Michele, Andrea Cochetti, Silvio Mezzari, Alberto Residori, and Gianpietro Lista. "Evaluation of Femoral–Tibial Flexion Gap in Total Knee Arthroplasty with Everted or Lateralized Patella." Journal of Knee Surgery 32, no. 10 (November 9, 2018): 1028–32. http://dx.doi.org/10.1055/s-0038-1675422.
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AbstractIntraoperative patellar position (eversion, lateralization, or in situ) influences the ligamentous balancing in knee flexion and thereby the correct positioning of the femoral component during total knee arthroplasty. The correct ligament balancing is crucial when, as in our experience, prostheses with medial pivot design are used. It was shown that the flexion gap in the normal knee is not rectangular and that the lateral compartment is significantly slacker than the medial. Therefore, to obtain a correct kinematics of a medial pivot anatomical prosthesis, it is essential to recreate an anatomical flexion gap slacker in the lateral compartment. We conducted a prospective study on a consecutive series of 87 total knee prostheses. The objective of this study is to evaluate the femoral external rotation angle in each patient with everted patella as well as with pure subluxated patella. The purpose of this study is to offer guidance about the optimal femoral rotation angle to achieve best outcomes of a knee replacement. The evaluation was done using an instrument developed by Medacta International (Switzerland) with our direct collaboration (Tensor, Medacta, Switzerland) and standardizing the basic conditions of each patient (knee 90 degrees flexed, medial transquadricipital surgical access, lateral displacement of the patella, tourniquet inflated at 250 mm Hg, spinal anesthesia). Each group was subdivided into subgroups according to gender, preoperative varus or valgus deformity, and patellar height. Our study advises against evaluating the flexion gap with everted patella due to high risk of underestimation of the lateral compartment laxity (differences up to + 3 degrees with pure subluxated patella compared with everted patella).
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Teo, Ee-Chon, Tian-Xia Qiu, Kai Yang, Hong-Wan Ng, and Kim-Kheng Lee. "BIOMECHANICAL EFFECT OF THORACIC POSTERIOR VERTEBRAL ELEMENTS ON PATTERNS OF THE LOCI OF INSTANTANEOUS AXES OF ROTATION IN SAGITTAL PLANE." Journal of Musculoskeletal Research 07, no. 03n04 (September 2003): 191–200. http://dx.doi.org/10.1142/s0218957703001095.
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The objective of this study was to investigate the effect of the thoracic posterior vertebral elements on the kinematics of T10–T11 motion segment in sagittal plane by assessing the locations and loci of the instantaneous axes of rotation (IARs) under flexion and extension pure moments using finite element (FE) method. The IAR has proven to be a useful parameter of vertebral motion and it is an indicator of spinal instability. An anatomically accurate FE model of thoracic T10–T11 functional spinal unit (FSU) was used to characterize the loci of centers of rotation for the intact T10–T11 FSU and disc body unit (without posterior vertebral elements) under flexion and extension pure moments. The centers of rotation predicted by the intact model and disc body unit of thoracic T10–T11 for both flexion and extension were directly below the geometrical center of the moving vertebra. However, the loci of the IARs were significantly affected by the posterior vertebral elements. The loci of instantaneous axes of rotation for the intact model were tracked superoanteriorly and inferoposteriorly for flexion and extension with rotation, respectively. While, for the disc body unit, the loci were detected to diverge lateroinferiorly from the mid-height of the intervertebral disc, they converge medio-inferiorly toward the superior endplate of the inferior vertebra T11 with increased moment. These findings may offer an insight to better understanding the kinematics of the human thoracic spine and provide clinically relevant information for the evaluation of spinal stability and implant devices functionality.
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Dumas, G. A., D. A. Bednar, and J. P. Dickey. "Comparison of porcine and human lumbar spine flexion mechanics*." Veterinary and Comparative Orthopaedics and Traumatology 16, no. 01 (2003): 44–49. http://dx.doi.org/10.1055/s-0038-1632753.
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SummaryAnimal models have been proposed as an alternative to human spinal specimens for in vitro mechanical testing due to the limited availability, poor reproducibility, high cost, and potential health risk associated with human specimens. The purpose of this study was to directly compare the flexion biomechanics of porcine and human lumbar spines. We determined the range of motion, laxity zone and the stiffness under pure-moment flexion loading. The porcine and human specimens showed qualitative similarities in mechanical behaviour. However the porcine specimens demonstrated a number of quantitative differences including a less-stiff, more extensive, low-stiffness region around the neutral position and a larger flexion range of motion. The results suggest that the porcine lumbar spine may be a potential model for the human lumbar spine for certain in vitro mechanical tests including comparisons between spinal fixation constructs.
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Davis, Kermit G., Riley E. Splittstoesser, and William S. Marras. "Kinematic contribution and synchronization of the trunk, hip, and knee during free-dynamic lifting." Occupational Ergonomics 3, no. 2 (July 24, 2003): 99–108. http://dx.doi.org/10.3233/oer-2003-3202.
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Although there have been numerous studies evaluating the difference between stooped and squat lifting styles, there remains a lack of understanding of whole body kinematics during unrestricted lifting. The current study evaluated nine males and nine females while lifting two box weights (9.1 kg, 18.2 kg) from five origins below the waist (0, 19, 38, 57, and 76 cm above the floor) and from three task asymmetries (sagittally symmetric, 45° clockwise, 45° counter-clockwise). While the lifting style was significantly influenced by the height of lift origin and to a lesser extent gender, box weight, and task asymmetry, none of the conditions resulted in pure squat or stoop lifting style. However, for lifts above knee height, the lifting style resembled more of a stoop lift while lifts originating below knee height were more of a squat lift. As the origin moved closer to the floor, participants relied more on their hips to accomplish the sagittal flexion but overall adopted a more coordinated whole-body lifting style. All together, as more sagittal flexion is required, more joints are relied upon in a more coordinated effort. The current study indicates that caution needs to be exercised when applying results of pure squat or pure stoop lifting studies to free-style (realistic) lifting.
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WILLIAMS, N. W., J. M. T. PENROSE, and D. R. HOSE. "Computer Model Analysis of the Swanson and Sutter Metacarpophalangeal Joint Implants." Journal of Hand Surgery 25, no. 2 (April 2000): 212–20. http://dx.doi.org/10.1054/jhsb.1999.0352.
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A representative model which mimics the behaviour of Silastic® finger metacarpophalangeal joint implants was constructed using a finite element software package. The modelled implants were moved through a range of flexion, lateral deviation and a combination of both. Pistoning of both implants stems occurred within the modelled medullary cavities. For equivalent flexion angles, the Sutter implant produced a higher stress field than the Swanson implant, and the field was positioned at the central hinge mechanism. In both implants, lateral deviation increased the internal stress concentrations more than when pure flexion was applied. Overall the Swanson style of implant had lower stress magnitudes than the Sutter implant, and it is predicted that the Sutter implant will be more likely to fail than the Swanson. The failure mode for the Sutter implant would be at the central hinge region. The Swanson implant is likely to fail at the central hinge-stem interface regions.
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Karam, Bashaer Hameed, Hussain S. Hasan, and Hassan Thabit Saeed. "A study on the association of cervical spondylosis severity, as indicated by cervical motions, with hearing impairment." Biomedical Human Kinetics 13, no. 1 (January 1, 2021): 43–48. http://dx.doi.org/10.2478/bhk-2021-0006.
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Abstract Study aim: The present study investigates the possible relation between the limitation of cervical motion in a patient with cervical spondylosis and hearing impairment. Material and methods: Cross-sectional research was performed based on 60 participants suffering from cervical spondylosis (CS) selected from an orthopaedic and physiotherapy department. The data collection techniques included questionnaire, electronic tools, measurements with a mechanical device including measuring the cervical range of motion (ROM) by goniometer, and physical examination including pure tone audiometry (PTA) and tympanogram. Results: Right rotation was the most common limitation, which affected 43 patients, followed by left rotation limitation, which was recorded in 40 patients. The extension, left lateral flexion, flexion, and right lateral flexion limitation showed less effect. Conclusions: Left rotation limitation was found to be an independent predictor of hearing impairment especially in men. Age was also a risk factor for sensory neural hearing loss (SNHL). These findings are important in the facilitation of investigating SNHL in cervical spondylosis patients.
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Moon, Myung-Sang, Young-Wan Moon, Jeong-Lim Moon, Sung-Sim Kim, and Yong-Shik Shim. "TREATMENT OF FLEXION INSTABILITY OF LUMBAR SPINE WITH GRAF BAND." Journal of Musculoskeletal Research 03, no. 01 (March 1999): 49–63. http://dx.doi.org/10.1142/s0218957799000075.
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This study focused mainly on the long-lasting effectiveness of Graf band stabilization system on the stabilized lumbar motion segment together with the band fate and the final outcome. Graf soft stabilization operation was carried out to suppress the forward flexion and rotatory instability. Fifty-one patients were subjected to this study. Forty-five had pure forward flexion instability preoperatively. Among the 51 patients, 20 were irreducible mild spondylolisthesis and 8 reducible mild spondylolisthesis; 17 excessive flexion angular motion; one disc disease with mild stenotic symptoms; and 5 post-laminectomy instability. In this series, good or excellent results were obtained in 40 cases (78.7%); fair in 4; no improvement in 4; and poor in 3. JOA lumbar score increased from 16 at preoperative exam to 26.5 on average at the final examination. In 3 cases screws were malpositioned. In 2 cases, mild transient drop foot developed, and spontaneous fusion occurred in one disc surgery patient. There was no implant loosening or breakage, and no overstretch and tear of bands or disengagement. There was no recurrence of segmental instability at the immobilized segment. Also, there were no adjacent joint problems. In summary, the Graf procedure appears to be a good alternative to spinal fusion for the stabilization of the unstable segment with forward flexion instability.
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Lang, Catherine E., and Marc H. Schieber. "Reduced Muscle Selectivity During Individuated Finger Movements in Humans After Damage to the Motor Cortex or Corticospinal Tract." Journal of Neurophysiology 91, no. 4 (April 2004): 1722–33. http://dx.doi.org/10.1152/jn.00805.2003.
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We investigated how damage to the motor cortex or corticospinal tract affects the selective activation of finger muscles in humans. We hypothesized that damage relatively restricted to the motor cortex or corticospinal tract would result in unselective muscle activations during an individuated finger movement task. People with pure motor hemiparesis attributed to ischemic cerebrovascular accident were tested. Pure motor hemiparetic and control subjects were studied making flexion/extension and then abduction/adduction finger movements. During the abduction/adduction movements, we recorded muscle activity from 3 intrinsic finger muscles: the abductor pollicis brevis, the first dorsal interosseus, and the abductor digit quinti. Each of these muscles acts as an agonist for only one of the abduction/adduction movements and might therefore be expected to be active in a highly selective manner. Motor cortex or corticospinal tract damage in people with pure motor hemiparesis reduced the selectivity of finger muscle activation during individuated abduction/adduction finger movements, resulting in reduced independence of these movements. Abduction/adduction movements showed a nonsignificant trend toward being less independent than flexion/extension movements in the affected hands of hemiparetic subjects. These changes in the selectivity of muscle activation and the consequent decrease in individuation of movement were correlated with decreased hand function. Our findings imply that, in humans, spared cerebral motor areas and descending pathways that remain might activate finger muscles, but cannot fully compensate for the highly selective control provided by the primary motor cortex and the crossed corticospinal system.
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Kumaresan, Srirangam, Narayan Yoganandan, Frank A. Pintar, Dennis J. Maiman, and Shashi Kuppa. "Biomechanical Study of Pediatric Human Cervical Spine: A Finite Element Approach." Journal of Biomechanical Engineering 122, no. 1 (August 22, 1999): 60–71. http://dx.doi.org/10.1115/1.429628.
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Although considerable effort has been made to understand the biomechanical behavior of the adult cervical spine, relatively little information is available on the response of the pediatric cervical spine to external forces. Since significant anatomical differences exist between the adult and pediatric cervical spines, distinct biomechanical responses are expected. The present study quantified the biomechanical responses of human pediatric spines by incorporating their unique developmental anatomical features. One-, three-, and six-year-old cervical spines were simulated using the finite element modeling technique, and their responses computed and compared with the adult spine response. The effects of pure overall structural scaling of the adult spine, local component developmental anatomy variations that occur to the actual pediatric spines, and structural scaling combined with local component anatomy variations on the responses of the pediatric spines were studied. Age- and component-related developmental anatomical features included variations in the ossification centers, cartilages, growth plates, vertebral centrum, facet joints, and annular fibers and nucleus pulposus of the intervertebral discs. The flexibility responses of the models were determined under pure compression, pure flexion, pure extension, and varying degrees of combined compression–flexion and compression–extension. The pediatric spine responses obtained with the pure overall (only geometric) scaling of the adult spine indicated that the flexibilities consistently increase in a uniform manner from six- to one-year-old spines under all loading cases. In contrast, incorporation of local anatomic changes specific to the pediatric spines of the three age groups (maintaining the same adult size) not only resulted in considerable increases in flexibilities, but the responses also varied as a function of the age of the pediatric spine and type of external loading. When the geometric scaling effects were added to these spines, the increases in flexibilities were slightly higher; however, the pattern of the responses remained the same as found in the previous approach. These results indicate that inclusion of developmental anatomical changes characteristic of the pediatric spines has more of a predominant effect on biomechanical responses than extrapolating responses of the adult spine based on pure overall geometric scaling. [S0148-0731(00)00501-X]
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Wang, Wei, Chao Kong, Fumin Pan, Wei Wang, Xueqing Wu, Baoqing Pei, and Shibao Lu. "Influence of Sagittal Lumbopelvic Morphotypes on the Range of Motion of Human Lumbar Spine: An In Vitro Cadaveric Study." Bioengineering 9, no. 5 (May 20, 2022): 224. http://dx.doi.org/10.3390/bioengineering9050224.
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Background: Although spinopelvic radiographs analysis is the standard for a pathological diagnosis, it cannot explain the activities of the spine in daily life. This study investigates the correlation between sagittal parameters and spinal range of motion (ROM) to find morphological parameters with kinetic implications. Methods: Six L1–S1 human lumbar specimens were tested with a robotic testing device. Eight sagittal parameters were measured in the three-dimensional model. Pure moments were applied to simulate the physiological activities in daily life. Results: The correlation between sagittal parameters and the ROM was moderate in flexion and extension, but weak in lateral bending and rotation. In flexion–extension, the ROM was moderately correlated with SS and LL. SS was the only parameter correlated with the ROM under all loading conditions. The intervertebral rotation distribution showed that the maximal ROM frequently occurred at the L5–S1 segment. The minimal ROM often appeared near the apex point of the lumbar. Conclusion: Sagittal alignment mainly affected the ROM of the lumbar in flexion and extension. SS and apex may have had kinetic significance. Our findings suggest that the effect of sagittal parameters on lumbar ROM is important information for assessing spinal activity.
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Lloyd, D. G., and T. S. Buchanan. "A Model of Load Sharing Between Muscles and Soft Tissues at the Human Knee During Static Tasks." Journal of Biomechanical Engineering 118, no. 3 (August 1, 1996): 367–76. http://dx.doi.org/10.1115/1.2796019.
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In this study, we had subjects voluntarily generate various forces in a transverse plane just above their ankles. The contributions of their muscles and soft tissues to the support of the total external knee joint moment were determined by analyzing the experimental data using a biomechanical model of the knee. In this model, muscle forces were estimated using the recorded EMGs. To account for subject variability, various muscle parameters were adjusted using a nonlinear least-squares fit of the model’s estimated flexion and extension joint moments to those recorded externally. Using the estimated muscle forces, the contributions from the muscles and other soft tissues to the total joint moment were obtained. The results showed that muscles were primarily used to support flexion and extension loads at the knee, but in so doing, were able to support some part of the varus or valgus loads. However, soft tissue loading was still required. Soft tissues supported up to an average maximum of 83 percent of the external load in pure varus and valgus. Soft tissue loading in pure varus and valgus was less than 100 percent of the external load as the muscles, on average, were able to support 17 percent of the external load. This muscle support was by virtue of muscle cocontraction and/or specific muscle activation.
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Formica, Domenico, Steven K. Charles, Loredana Zollo, Eugenio Guglielmelli, Neville Hogan, and Hermano I. Krebs. "The passive stiffness of the wrist and forearm." Journal of Neurophysiology 108, no. 4 (August 15, 2012): 1158–66. http://dx.doi.org/10.1152/jn.01014.2011.
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Because wrist rotation dynamics are dominated by stiffness (Charles SK, Hogan N. J Biomech 44: 614–621, 2011), understanding how humans plan and execute coordinated wrist rotations requires knowledge of the stiffness characteristics of the wrist joint. In the past, the passive stiffness of the wrist joint has been measured in 1 degree of freedom (DOF). Although these 1-DOF measurements inform us of the dynamics the neuromuscular system must overcome to rotate the wrist in pure flexion-extension (FE) or pure radial-ulnar deviation (RUD), the wrist rarely rotates in pure FE or RUD. Instead, understanding natural wrist rotations requires knowledge of wrist stiffness in combinations of FE and RUD. The purpose of this report is to present measurements of passive wrist stiffness throughout the space spanned by FE and RUD. Using a rehabilitation robot designed for the wrist and forearm, we measured the passive stiffness of the wrist joint in 10 subjects in FE, RUD, and combinations. For comparison, we measured the passive stiffness of the forearm (in pronation-supination), as well. Our measurements in pure FE and RUD agreed well with previous 1-DOF measurements. We have linearized the 2-DOF stiffness measurements and present them in the form of stiffness ellipses and as stiffness matrices useful for modeling wrist rotation dynamics. We found that passive wrist stiffness was anisotropic, with greater stiffness in RUD than in FE. We also found that passive wrist stiffness did not align with the anatomical axes of the wrist; the major and minor axes of the stiffness ellipse were rotated with respect to the FE and RUD axes by ∼20°. The direction of least stiffness was between ulnar flexion and radial extension, a direction used in many natural movements (known as the “dart-thrower's motion”), suggesting that the nervous system may take advantage of the direction of least stiffness for common wrist rotations.
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Grunert, Peter, Phillip M. Reyes, Anna G. U. S. Newcomb, Sara B. Towne, Brian P. Kelly, Nicholas Theodore, and Roger Härtl. "Biomechanical Evaluation of Lumbar Decompression Adjacent to Instrumented Segments." Neurosurgery 79, no. 6 (August 30, 2016): 895–904. http://dx.doi.org/10.1227/neu.0000000000001419.
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Abstract BACKGROUND: Multilevel lumbar stenosis, in which 1 level requires stabilization due to spondylolisthesis, is routinely treated with multilevel open laminectomy and fusion. We hypothesized that a minimally invasive (MI) decompression is biomechanically superior to open laminectomy and may allow decompression of the level adjacent the spondylolisthesis without additional fusion. OBJECTIVE: To study the mechanical effect of various decompression procedures adjacent to instrumented segments in cadaver lumbar spines. METHODS: Conditions tested were (1) L4-L5 instrumentation, (2) L3-L4 MI decompression, (3) addition of partial facetectomy at L3-L4, and (4) addition of laminectomy at L3-L4. Flexibility tests were performed for range of motion (ROM) analysis by applying nonconstraining, pure moment loading during flexion-extension, lateral bending, and axial rotation. Compression flexion tests were performed for motion distribution analysis. RESULTS: After instrumentation, MI decompression increased flexion-extension ROM at L3-L4 by 13% (P = .03) and axial rotation by 23% (P = .003). Partial facetectomy further increased axial rotation by 15% (P = .03). After laminectomy, flexion-extension ROM further increased by 12% (P = .05), a 38% increase from baseline, and axial rotation by 17% (P = .02), a 58% increase from baseline. MI decompression yielded no significant increase in segmental contribution of motion at L3-L4, in contrast to partial facetectomy and laminectomy (<.05). CONCLUSION: MI tubular decompression is biomechanically superior to open laminectomy adjacent to instrumented segments. These results lend support to the concept that in patients in whom a multilevel MI decompression is performed, the fusion might be limited to the segments with actual instability.
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Bishop, Frank S., Mical M. Samuelson, Michael A. Finn, Kent N. Bachus, Darrel S. Brodke, and Meic H. Schmidt. "The biomechanical contribution of varying posterior constructs following anterior thoracolumbar corpectomy and reconstruction." Journal of Neurosurgery: Spine 13, no. 2 (August 2010): 234–39. http://dx.doi.org/10.3171/2010.3.spine09267.
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Object Thoracolumbar corpectomy is a procedure commonly required for the treatment of various pathologies involving the vertebral body. Although the biomechanical stability of anterior reconstruction with plating has been studied, the biomechanical contribution of posterior instrumentation to anterior constructs remains unknown. The purpose of this study was to evaluate biomechanical stability after anterior thoracolumbar corpectomy and reconstruction with varying posterior constructs by measuring bending stiffness for the axes of flexion/extension, lateral bending, and axial rotation. Methods Seven fresh human cadaveric thoracolumbar spine specimens were tested intact and after L-1 corpectomy and strut grafting with 4 different fixation techniques: anterior plating with bilateral, ipsilateral, contralateral, or no posterior pedicle screw fixation. Bending stiffness was measured under pure moments of ± 5 Nm in flexion/extension, lateral bending, and axial rotation, while maintaining an axial preload of 100 N with a follower load. Results for each configuration were normalized to the intact condition and were compared using ANOVA. Results Spinal constructs with anterior-posterior spinal reconstruction and bilateral posterior pedicle screws were significantly stiffer in flexion/extension than intact spines or spines with anterior plating alone. Anterior plating without pedicle screw fixation was no different from the intact spine in flexion/extension and lateral bending. All constructs had reduced stiffness in axial rotation compared with intact spines. Conclusions The addition of bilateral posterior instrumentation provided significantly greater stability at the thoracolumbar junction after total corpectomy than anterior plating and should be considered in cases in which anterior column reconstruction alone may be insufficient. In cases precluding bilateral posterior fixation, unilateral posterior instrumentation may provide some additional stability.
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Lapsiwala, Samir B., Paul A. Anderson, Ashish Oza, and Daniel K. Resnick. "Biomechanical Comparison of Four C1 to C2 Rigid Fixative Techniques: Anterior Transarticular, Posterior Transarticular, C1 to C2 Pedicle, and C1 to C2 Intralaminar Screws." Neurosurgery 58, no. 3 (March 1, 2006): 516–21. http://dx.doi.org/10.1227/01.neu.0000197222.05299.31.
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Abstract OBJECTIVE: We performed a biomechanical comparison of several C1 to C2 fixation techniques including crossed laminar (intralaminar) screw fixation, anterior C1 to C2 transarticular screw fixation, C1 to 2 pedicle screw fixation, and posterior C1 to C2 transarticular screw fixation. METHODS: Eight cadaveric cervical spines were tested intact and after dens fracture. Four different C1 to C2 screw fixation techniques were tested. Posterior transarticular and pedicle screw constructs were tested twice, once with supplemental sublaminar cables and once without cables. The specimens were tested in three modes of loading: flexion-extension, lateral bending, and axial rotation. All tests were performed in load and torque control. Pure bending moments of 2 nm were applied in flexion-extension and lateral bending, whereas a 1 nm moment was applied in axial rotation. Linear displacements were recorded from extensometers rigidly affixed to the C1 and C2 vertebrae. Linear displacements were reduced to angular displacements using trigonometry. RESULTS: Adding cable fixation results in a stiffer construct for posterior transarticular screws. The addition of cables did not affect the stiffness of C1 to C2 pedicle screw constructs. There were no significant differences in stiffness between anterior and posterior transarticular screw techniques, unless cable fixation was added to the posterior construct. All three posterior screw constructs with supplemental cable fixation provide equal stiffness with regard to flexion-extension and axial rotation. C1 lateral mass-C2 intralaminar screw fixation restored resistance to lateral bending but not to the same degree as the other screw fixation techniques. CONCLUSION: All four screw fixation techniques limit motion at the C1 to 2 articulation. The addition of cable fixation improves resistance to flexion and extension for posterior transarticular screw fixation.
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Karahalios, Dean G., Taro Kaibara, Randall W. Porter, Udaya K. Kakarla, Phillip M. Reyes, Ali A. Baaj, Ali S. Yaqoobi, and Neil R. Crawford. "Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion." Journal of Neurosurgery: Spine 12, no. 4 (April 2010): 372–80. http://dx.doi.org/10.3171/2009.10.spine09305.
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Object An interspinous anchor (ISA) provides fixation to the lumbar spine to facilitate fusion. The biomechanical stability provided by the Aspen ISA was studied in applications utilizing an anterior lumbar interbody fusion (ALIF) construct. Methods Seven human cadaveric L3–S1 specimens were tested in the following states: 1) intact; 2) after placing an ISA at L4–5; 3) after ALIF with an ISA; 4) after ALIF with an ISA and anterior screw/plate fixation system; 5) after removing the ISA (ALIF with plate only); 6) after removing the plate (ALIF only); and 7) after applying bilateral pedicle screws and rods. Pure moments (7.5 Nm maximum) were applied in flexion and extension, lateral bending, and axial rotation while recording angular motion optoelectronically. Changes in angulation as well as foraminal height were also measured. Results All instrumentation variances except ALIF alone reduced angular range of motion (ROM) significantly from normal in all directions of loading. The ISA was most effective in limiting flexion and extension (25% of normal) and less effective in reducing lateral bending (71% of normal) and axial rotation (71% of normal). Overall, ALIF with an ISA provided stability that was statistically equivalent to ALIF with bilateral pedicle screws and rods. An ISA-augmented ALIF allowed less ROM than plate-augmented ALIF during flexion, extension, and lateral bending. Use of the ISA resulted in flexion at the index level, with a resultant increase in foraminal height. Compensatory extension at the adjacent levels prevented any significant change in overall sagittal balance. Conclusions When used with ALIF at L4–5, the ISA provides immediate rigid immobilization of the lumbar spine, allowing equivalent ROM to that of a pedicle screw/rod system, and smaller ROM than an anterior plate. When used with ALIF, the ISA may offer an alternative to anterior plate fixation or bilateral pedicle screw/rod constructs.
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Lee, Wen-Tzong, Kevin Russell, and Raj S. Sodhi. "On Transfemoral Prosthetic Knee Design for Natural Human Knee Motion." Recent Patents on Mechanical Engineering 13, no. 1 (February 12, 2020): 49–59. http://dx.doi.org/10.2174/2212797613666191219154947.
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Background: A transfemoral prosthetic knee is an artificial knee used by above-the-knee amputees. There are two major categories of transfemoral prosthetic knee designs: pin joint-based and polycentric designs. While pin joint-based knee designs only allow pure rotation of the knee, polycentric knee designs allow a combination of rotational and translational knee motion which is exhibited in natural knee motion. Objective: This work presents both the recently-patented design process and the resulting design of a polycentric transfemoral prosthetic knee that approximates natural spatial human knee motion during flexion and extension. Methods: The design process includes tibial motion acquisition, Revolute-Revolute-Spherical-Spherical linkage (or RRSS) motion generation, RRSS linkage axode generation and circle fitting. The polycentric transfemoral prosthetic knee design produced from this process includes a gear joint with a specific spatial orientation to approximate natural spatial human knee motion. Results: Using the design process, a polycentric transfemoral prosthetic knee was designed to replicate a group of five tibial positions over 37.5° of knee flexion (the amount of knee flexion in a standard human gait cycle) with a minimal structural error. Conclusion: The circular gear-based knee design accurately replicated natural spatial knee motion over the tibial position data given for a standard human gait cycle. The knee design method must be implemented over a broader sampling of tibial position data to determine if a circular gear-based knee design is consistently accurate.
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Cook, Daniel J., Matthew S. Yeager, Michael Y. Oh, and Boyle C. Cheng. "Lumbar Intrafacet Bone Dowel Fixation." Neurosurgery 76, no. 4 (January 23, 2015): 470–78. http://dx.doi.org/10.1227/neu.0000000000000652.
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Abstract BACKGROUND: The efficacy of intrafacet bone dowels in promoting lumbar fusion has not been established. A recently published study indicates a low fusion rate, along with device migration. OBJECTIVE: To evaluate the mechanical stability of 2 lumbar facet fixation technologies before and after repeated cyclic loading. METHODS: Six human lumbar specimens were implanted with both types of allograft, one at L2-3 and the other at L4-5, on a randomized basis. All specimens were subjected to pure-moment flexibility testing before and after implantation and after 2500 and 5000 cycles of flexion-extension bending. Each specimen was scanned with computed tomography before and after cyclic loading to measure device migration. RESULTS: Only dowel 1 resulted in a statistically significant reduction in flexion-extension range of motion at the treatment level. This reduction was significant at baseline testing (P = .03) and after 2500 cycles of flexion-extension loading (P = .048) but was not significant after 5000 cycles of loading. One of the bone dowels extruded posteriorly out of the joint space during baseline axial torsion flexibility testing, which was before any cyclic loading. CONCLUSION: The data obtained in this study do not indicate efficacy of fixation for cylindrical bone dowels in the lumbar facet joint. Significant fixation was detected only for one of the devices and was no longer present after a relatively short duration of repeated loading. Furthermore, considerable magnitudes of device migration were detected.
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Niemeyer, Thomas K., Marco Koriller, Lutz Claes, Annette Kettler, Kathrin Werner, and Hans J. Wilke. "IN VITRO STUDY OF BIOMECHANICAL BEHAVIOROF ANTERIORAND TRANSFORAMINAL LUMBARINTERBODY INSTRUMENTATION TECHNIQUES." Neurosurgery 59, no. 6 (December 1, 2006): 1271–77. http://dx.doi.org/10.1227/01.neu.0000245609.01732.e4.
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Abstract OBJECTIVE To study the biomechanical behavior of lumbar interbody instrumentation techniques using titanium cages as either transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion (ALIF), with and without posterior pedicle fixation. METHODS Six fresh-frozen lumbar spines (L1–L5) were loaded with pure moments of ±7.5 Nm in unconstrained flexion-extension, lateral bending, and axial rotation. Specimen were tested intact, after implantation of an ALIF or TLIF cage “stand-alone” in L2–L3 or L3–L4, and after additional posterior pedicle screw fixation. RESULTS In all loading directions, the range of motion (ROM) of the segments instrumented with cage and pedicle screw fixation was below the ROM of the intact lumbar specimen for both instrumentation techniques. A significant difference was found between the TLIF cage and the ALIF cage with posterior pedicle screw fixation for the ROM in flexion-extension and axial rotation (P< 0.05). Without pedicle screw fixation, the TLIF cage showed a significantly increased ROM and neutral zone compared with an ALIF cage “stand-alone” in two of the three loading directions (P< 0.05). CONCLUSION With pedicle screw fixation, the ALIF cage provides a higher segmental stability than the TLIF cage in flexion-extension and axial rotation, but the absolute biomechanical differences are minor. The different cage design and approach show only minor differences of segmental stability when combined with posterior pedicle screw fixation.
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Lazaro, Bruno C. R., Leonardo B. C. Brasiliense, Anna G. U. Sawa, Phillip M. Reyes, Nicholas Theodore, Volker K. H. Sonntag, and Neil R. Crawford. "Biomechanics of a Novel Minimally Invasive Lumbar Interspinous Spacer: Effects on Kinematics, Facet Loads, and Foramen Height." Operative Neurosurgery 66, suppl_1 (March 1, 2010): ons—126—ons—133. http://dx.doi.org/10.1227/01.neu.0000348561.59062.a2.
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Abstract Objective: To study the alteration to normal biomechanics after insertion of a lumbar interspinous spacer (ISS) in vitro by nondestructive cadaveric flexibility testing. Methods: Seven human cadaveric specimens were studied before and after ISS placement at L1–L2. Angular range of motion, lax zone, stiff zone, sagittal instantaneous axis of rotation (IAR), foraminal height, and facet loads were compared between conditions. Flexion, extension, lateral bending, and axial rotation were induced using pure moments (7.5 Nm maximum) while recording motion optoelectronically. The IAR was measured during loading with a 400 N compressive follower. Foraminal height changes were calculated using rigid body methods. Facet loads were assessed from surface strain and neural network analysis. Results: After ISS insertion, range of motion and stiff zone during extension were significantly reduced (P < .01). Foraminal height was significantly reduced from flexion to extension in both normal and ISS-implanted conditions; there was significantly less reduction in foraminal height during extension with the ISS in place. The ISS reduced the mean facet load by 30% during flexion (P < .02) and 69% during extension (P < .015). The IAR after ISS implantation was less than 1 mm from the normal position (P > .18). Conclusion: The primary biomechanical effect of the ISS was reduced extension with associated reduced facet loads and smaller decrease in foraminal height. The ISS had little effect on sagittal IAR or on motion or facet loads in other directions.
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Zahari, Siti Nurfaezah, Mohd Juzaila Abd Latif, Nor Raihanah Abdull Rahim, Mohammed Rafiq Abdul Kadir, and Tunku Kamarul. "The Effects of Physiological Biomechanical Loading on Intradiscal Pressure and Annulus Stress in Lumbar Spine: A Finite Element Analysis." Journal of Healthcare Engineering 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/9618940.
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The present study was conducted to examine the effects of body weight on intradiscal pressure (IDP) and annulus stress of intervertebral discs at lumbar spine. Three-dimensional finite element model of osseoligamentous lumbar spine was developed subjected to follower load of 500 N, 800 N, and 1200 N which represent the loads for individuals who are normal and overweight with the pure moments at 7.5 Nm in flexion and extension motions. It was observed that the maximum IDP was 1.26 MPa at L1-L2 vertebral segment. However, the highest increment of IDP was found at L4-L5 segment where the IDP was increased to 30% in flexion and it was more severe at extension motion reaching to 80%. Furthermore, the maximum annulus stress also occurred at the L1-L2 segment with 3.9 MPa in extension motion. However, the highest increment was also found at L4-L5 where the annulus stress increased to 17% in extension motion. Based on these results, the increase of physiological loading could be an important factor to the increment of intradiscal pressure and annulus fibrosis stress at all intervertebral discs at the lumbar spine which may lead to early intervertebral disc damage.
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Hott, Jonathan S., James J. Lynch, Robert H. Chamberlain, Volker K. H. Sonntag, and Neil R. Crawford. "Biomechanical comparison of C1–2 posterior fixation techniques." Journal of Neurosurgery: Spine 2, no. 2 (February 2005): 175–81. http://dx.doi.org/10.3171/spi.2005.2.2.0175.
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Object. In a nondestructive, repeated-measures in vitro flexibility experiment, the authors compared the acute stability of C1–2 after placement of C-1 lateral mass and C-2 pars interarticularis (LC1—PC2) instrumentation with that of C1–2 transarticular screw fixation. Methods. The effect of C-1 laminectomy and C1–2 interspinous cable/graft fixation on LC1—PC2 stability was studied. Screw pullout strengths were also compared. Seven human cadaveric occiput—C3 specimens were loaded nondestructively with pure moments while measuring nonconstrained atlantoaxial motion. Specimens were tested with graft alone, LC1—PC2 alone, LC1—PC2 combined with C-1 laminectomy, and graft-augmented LC1—PC2. Interspinous cable/graft fixation significantly enhanced LC1—PC2 stability during extension. After C-1 laminectomy, the LC1—PC2 construct allowed increased motion during flexion and extension. There was no significant difference in lax zone or range of motion between LC1—PC2 fixation and transarticular screw fixation, but graft-assisted transarticular screws yielded a significantly smaller stiff zone during extension. The difference in pullout resistance between C-1 lateral mass screws and C-2 pars interarticularis screws was insignificant. The LC1—PC2 region restricted motion to within the normal range during all loading modes. Atlantal laminectomy reduced LC1—PC2 stability during flexion and extension. Conclusions. The instrumentation-augmented LC1—PC2 construct performed biomechanically similarly to the C1–2 transarticular screw fixation. The LC1—PC2 construct resisted flexion, lateral bending, and axial rotation well. The weakness of the LC1—PC2 fixation in resisting extension can be overcome by adding an interspinous graft to the construct.
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Viljoen, Stephanus V., Nicole A. DeVries Watson, Nicole M. Grosland, James Torner, Brian Dalm, and Patrick W. Hitchon. "Biomechanical analysis of anterior versus posterior instrumentation following a thoracolumbar corpectomy." Journal of Neurosurgery: Spine 21, no. 4 (October 2014): 577–81. http://dx.doi.org/10.3171/2014.6.spine13751.
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Object The objective of this study was to evaluate the biomechanical properties of lateral instrumentation compared with short- and long-segment pedicle screw constructs following an L-1 corpectomy and reconstruction with an expandable cage. Methods Eight human cadaveric T10–L4 spines underwent an L-1 corpectomy followed by placement of an expandable cage. The spines then underwent placement of lateral instrumentation consisting of 4 monoaxial screws and 2 rods with 2 cross-connectors, short-segment pedicle screw fixation involving 1 level above and below the corpectomy, and long-segment pedicle screw fixation (2 levels above and below). The order of instrumentation was randomized in the 8 specimens. Testing was conducted for each fixation technique. The spines were tested with a pure moment of 6 Nm in all 6 degrees of freedom (flexion, extension, right and left lateral bending, and right and left axial rotation). Results In flexion, extension, and left/right lateral bending, posterior long-segment instrumentation had significantly less motion compared with the intact state. Additionally, posterior long-segment instrumentation was significantly more rigid than short-segment and lateral instrumentation in flexion, extension, and left/right lateral bending. In axial rotation, the posterior long-segment construct as well as lateral instrumentation were not significantly more rigid than the intact state. The posterior long-segment construct was the most rigid in all 6 degrees of freedom. Conclusions In the setting of highly unstable fractures requiring anterior reconstruction, and involving all 3 columns, long-segment posterior pedicle screw constructs are the most rigid.
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Liu, Fubing, Zhenzhou Feng, Tianze Liu, Qinming Fei, Chun Jiang, Yuanchao Li, Xiaoxing Jiang, and Jian Dong. "A biomechanical comparison of 3 different posterior fixation techniques for 2-level lumbar spinal disorders." Journal of Neurosurgery: Spine 24, no. 3 (March 2016): 375–80. http://dx.doi.org/10.3171/2015.7.spine1534.
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OBJECT This study sought to make a biomechanical comparison of 3 different posterior fixation techniques for 2-level lumbar spinal disorders. METHODS Eight fresh-frozen human cadaver lumbar spines (4 from L-1 to L-5, 4 from L-1 to S-1) were tested by applying pure moments of ± 8 Nm. Each specimen was first tested intact, and then the left facetectomies of L3–4 and L4–5 were performed to establish an unstable condition without removal of discs. Three instrumentation systems were then tested randomly: unilateral pedicle screw (UPS), UPS with contralateral translaminar facet screw (UPSFS), and bilateral pedicle screw (BPS). The range of motion (ROM) and the neutral zone (NZ) of L3–5 were measured. RESULTS All fixation types could reduce the ROM of L3–5 significantly in flexion, extension, and lateral bending, compared with the intact state. In axial torsion, only BPS reduced the ROM significantly, compared with the intact state. The UPSFS technique provided intermediate stability, which was superior to the UPS in flexion-extension and lateral bending, and inferior to the BPS in lateral bending. Compared with the intact state, the NZs decreased significantly for UPS, UPSFS, and BPS in flexion-extension, while not significantly in lateral bending and axial torsion. CONCLUSIONS In this study, among the 3 fixation techniques, BPS offered the highest stability, UPSFS provided intermediate stability, and UPS was the least stable for 2-level lumbar spinal disorders. UPSFS appeared to be able to offer a less invasive choice than BPS in well-selected patients with 2-level lumbar spinal disorders.
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Trofimova, Svetlana Ivanovna, and Olga Evgenievna Agranovich. "Restoration of active forearm flexion in children with arthrogryposis:results of transfer of long head of triceps." Pediatric Traumatology, Orthopaedics and Reconstructive Surgery 3, no. 1 (March 15, 2015): 15–21. http://dx.doi.org/10.17816/ptors3115-21.
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The purpose of this study was to analyze resultsof the long head of triceps transfer for active elbowflexion restoration in children with arthrogryposis. Materials and Methods. 29 patients with lack of active elbow flexion aged from 10 months to 15 years were examined and treated in Turner Scientific and Research Institute for Children’s Orthopedics from2008 to 2014. The relation between potential donormuscle condition and the level of segmental spinalcord lesions was determined on the basis of clinical,neurological, physiological and ultrasound examina-tions. 35 transpositions of long head of the triceps in29 children were performed (17 - with mobilizationand 18 - without mobilization of the elbow). Results and Conclusion. Analysis of long-termresults of long head of triceps transposition as a ped-icle flap in patients with arthrogryposis has shown theeffectiveness of restoration of active forearm flexion.Good results were noted in 35 %, satisfactory in 35 %and pure in 30 % of cases in the series.
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Bozkuş, Hakan, Mehmet Şenoğlu, Seungwon Baek, Anna G. U. Sawa, Ali Fahir Özer, Volker K. H. Sonntag, and Neil R. Crawford. "Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization." Journal of Neurosurgery: Spine 12, no. 2 (February 2010): 183–89. http://dx.doi.org/10.3171/2009.9.spine0951.
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Object It is unclear how the biomechanics of dynamic posterior lumbar stabilization systems and traditional rigid pedicle screw-rod systems differ. This study examined the biomechanical response of a hinged-dynamic pedicle screw compared with a standard rigid screw used in a 1-level pedicle screw-rod construct. Methods Unembalmed human cadaveric L3–S1 segments were tested intact, after L4–5 discectomy, after rigid pedicle screw-rod fixation, and after dynamic pedicle screw-rod fixation. Specimens were loaded using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording motion optoelectronically. Specimens were then loaded in physiological flexion-extension while applying 400 N of compression. Moment and force across instrumentation were recorded from pairs of strain gauges mounted on the interconnecting rods. Results The hinged-dynamic screws allowed an average of 160% greater range of motion during flexion, extension, lateral bending, and axial rotation than standard rigid screws (p < 0.03) but 30% less motion than normal. When using standard screws, bending moments and axial loads on the rods were greater than the bending moments and axial loads on the rods when using dynamic screws during most loading modes (p < 0.05). The axis of rotation shifted significantly posteriorly more than 10 mm from its normal position with both devices. Conclusions In a 1-level pedicle screw-rod construct, hinged-dynamic screws allowed a quantity of motion that was substantially closer to normal motion than that allowed by rigid pedicle screws. Both systems altered kinematics similarly. Less load was borne by the hinged screw construct, indicating that the hinged-dynamic screws allow less stress shielding than standard rigid screws.
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Lazaro, Bruno C. R., Phillip M. Reyes, Anna G. U. S. Newcomb, Ali S. Yaqoobi, Leonardo B. C. Brasiliense, Volker K. H. Sonntag, and Neil R. Crawford. "Biomechanics of Dynamic Rod Segments for Achieving Transitional Stiffness With Lumbosacral Fusion." Neurosurgery 73, no. 3 (June 14, 2013): 517–27. http://dx.doi.org/10.1227/neu.0000000000000009.
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Abstract BACKGROUND: Transitioning from rigid to flexible hardware at the distal rostral or caudal lumbar or lumbosacral level hypothetically maintains motion at the transition level and protects the transition level and intact adjacent levels from stresses caused by fusion. OBJECTIVE: To biomechanically compare transitional and rigid constructs with uninstrumented specimens in vitro. METHODS: Human cadaveric L2-S1 segments were tested (1) intact, (2) after L5-S1 rigid pedicle screw-rod fixation, (3) after L4-S1 rigid pedicle screw-rod fixation, and (4) after hybrid fixation rigidly spanning L5-S1 and dynamically spanning L4-L5. Pure moments (maximum 7.5 Nm) induced flexion, extension, lateral bending, and axial rotation while motion was recorded optoelectronically. Additionally, specimens were studied in flexion/extension with a 400-N compressive follower load. Strain gauges on laminae were used to extract facet loads. RESULTS: The range of motion at the transition segment (L4-L5) for the hybrid construct was significantly less than for the intact condition and significantly greater than for the rigid 2-level construct during lateral bending and axial rotation but not during flexion or extension. Sagittal axis of rotation at L4-L5 shifted significantly after rigid 2-level or hybrid fixation (P < .003) but shifted significantly farther posterior and rostral with rigid fixation (P < .02). Instrumentation altered L4-L5 facet load at more than the L3-L4 facet load. CONCLUSION: The effect of the dynamic rod segment on the kinematics of the transition level was less pronounced than that of a fully rigid construct in vitro with this particular rod system. This experimental model detected no biomechanical alterations at adjacent intact levels with hybrid or rigid systems.
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Buchanan, T. S., G. P. Rovai, and W. Z. Rymer. "Strategies for muscle activation during isometric torque generation at the human elbow." Journal of Neurophysiology 62, no. 6 (December 1, 1989): 1201–12. http://dx.doi.org/10.1152/jn.1989.62.6.1201.
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1. We studied the patterns of electromyographic (EMG) activity in elbow muscles of 14 normal human subjects. The activity of five muscles that act in flexion-extension and forearm supination-pronation was simultaneously recorded during isometric voluntary torque generation, in which torques generated in a plane orthogonal to the long axis of the forearm were voluntarily coupled with torques generated about the long axis of the forearm (i.e., supination-pronation). 2. When forearm supination torques were superimposed on a background of elbow flexion torque, biceps brachii activity increased substantially, as expected; however, brachioradialis and brachialis EMG levels decreased modestly, a less predictable outcome. The pronator teres was also active during pure flexion and flexion coupled with mild supination (even though no pronation torque was required). This was presumably to offset inappropriate torque contributions of other muscles, such as the biceps brachii. 3. When forearm supination torque was superimposed on elbow extension torque, again the biceps brachii was strongly active. The pronator teres also became mildly active during extension with added pronation torque. These changes occurred despite the fact that both the pronator and biceps muscles induce elbow flexion. 4. In these same elbow extension tasks, triceps brachii activity was also modulated with both pronation or supination loads. It was most active during either supination or pronation loads, again despite the fact that it has no mechanical role in producing forearm supination-pronation torque. 5. Recordings of EMG activity during changes in forearm supination-pronation angle demonstrated that activation of the biceps brachii followed classic length-tension predictions, in that less EMG activity was required to achieve a given supination torque when the forearm was pronated (where biceps brachii is relatively longer). On the other hand, EMG activity of the pronator teres did not decrease when the pronator was lengthened. Triceps EMG was also more active when the forearm was supinated, despite its having no direct functional role in this movement. 6. Plots relating EMG activity in biceps brachii, brachialis, and brachioradialis at three different forearm positions revealed that there was a consistent positive near-linear relationship between brachialis and brachioradialis and that biceps brachii is often most active when brachioradialis and brachialis are least active. 7. We argue that, for the human elbow joint at least, fixed muscle synergies are rather uncommon and that relationships between muscle activities are situation dependent.(ABSTRACT TRUNCATED AT 400 WORDS)
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CAILLERIE, D., and E. SANCHEZ-PALENCIA. "ELASTIC THIN SHELLS: ASYMPTOTIC THEORY IN THE ANISOTROPIC AND HETEROGENEOUS CASES." Mathematical Models and Methods in Applied Sciences 05, no. 04 (June 1995): 473–96. http://dx.doi.org/10.1142/s0218202595000280.
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Asymptotic (two-scale) methods are used to derive thin shell theory from three-dimensional elasticity. The asymptotic process is done directly for the variational formulations, and existence and uniqueness theorems are given for the shell problem. The asymptotic behavior is the same as that recently derived by the authors using classical hypotheses of shell theory. The role of the subspace G of pure bendings (inextensional motions) appears in a natural way. The asymptotic is basically described by a leading order term contained in G and a lower order term contained in the orthogonal to G. As in anisotropic heterogeneous plates, which exhibit a coupling between flexion and traction, in heterogeneous shells there is coupling between the terms in G and in its orthogonal.
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Martínez-Estrada, Marc, Ignacio Gil, and Raúl Fernández-García. "An Alternative Method to Develop Embroidery Textile Strain Sensors." Textiles 1, no. 3 (November 13, 2021): 504–12. http://dx.doi.org/10.3390/textiles1030026.
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In this paper, a method to develop embroidered textile strain resistive sensors is presented. The method is based on two overlapped zigzag conductive yarn patterns embroidered in an elastic textile. To demonstrate the functionality of the proposed configuration, a textile sensor embroidered with a conductor yarn composed of 99% pure silver-plated nylon yarn 140/17 dtex has been experimentally characterised for an elongation range from 0% to 65%. In order to show the sensor applicability, a second test with the sensor embroidered in a knee-pad has been done to evaluate the flexion knee angle from 180° to 300°. The experimental results show the usefulness of the proposed method to develop fabric strain sensors that can help to manufacture commercial applications on the healthcare sector.
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Brasiliense, Leonardo B. C., Bruno C. R. Lazaro, Phillip M. Reyes, Douglas Fox, Volker K. H. Sonntag, and Neil R. Crawford. "Stabilization of the Atlantoaxial Joint With C1-C3 Lateral Mass Screw Constructs: Biomechanical Comparison With Standard Technique." Operative Neurosurgery 67, suppl_2 (December 1, 2010): ons422—ons428. http://dx.doi.org/10.1227/neu.0b013e3181fb414c.
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ABSTRACT BACKGROUND: Anatomically and biomechanically, the atlantoaxial joint is unique compared with the remainder of the cervical spine. OBJECTIVE: To assess the in vitro stability provided by 2 C2 screw sparing techniques in a destabilized model of the atlantoaxial joint and compare with the gold standard system. METHODS: The 3-dimensional intervertebral motion of 7 human cadaveric cervical spine specimens was recorded stereophotogrammetrically while applying nonconstraining, nondestructive pure moments during flexion-extension, left and right axial rotation, and left and right lateral bending. Each specimen was tested in the intact state, followed by destabilization (odontoidectomy) and fixation as follows: (1) C1 and C3 lateral mass screws rods with sublaminar wiring of C2 (LC1-C3 + SW), (2) C1 and C3 lateral mass screws rods with a cross-link in the C1-2 interlaminar space (LC1-C3 + CL), (3) C1 and C3 lateral mass screw rods alone (negative control), and (4) C1 lateral mass and C2 pedicle screws rods augmented with C1-2 interspinous wire and graft (LC1-PC2, control group). RESULTS: Compared with the intact spine, each instrumented state significantly stabilized range of motion and lax zone at C1-2 (P < .001, 1-way repeated-measures analysis of variance). LC1-C3 + SW was equivalent to LC1-PC2 during flexion and lateral bending and superior to LC1-C3 + CL during lateral bending, while LC1-C3 + CL was equivalent to LC1-PC2 only during flexion. In all other comparisons, LC1-PC2 was superior to both techniques. CONCLUSION: From a biomechanical perspective, both C2 screw sparing techniques provided sufficient stability to be regarded as an alternative for C1-2 fixation. However, because normal motion across C2-3 is sacrificed, these constructs should be used in patients with unfavorable anatomy for standard fixations.
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Spicher, Anna, Werner Schmoelz, Rene Schmid, Hannes Stofferin, and Niall J. A. Craig. "Functional and radiographic evaluation of an interspinous device as an adjunct for lumbar interbody fusion procedures." Biomedical Engineering / Biomedizinische Technik 65, no. 2 (April 28, 2020): 183–89. http://dx.doi.org/10.1515/bmt-2018-0086.
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AbstractIn the last decades, several interspinous process devices were designed as a minimally invasive treatment option for spinal stenosis. In order to minimise surgical trauma, interspinous process devices were recently discussed as an alternative posterior fixation in vertebral interbody fusions. Therefore, the purpose of this study was to evaluate the effect of a newly designed interspinous device with polyester bands (PBs) on range of motion (RoM) and centre of rotation (CoR) of a treated motion segment in comparison with an established interspinous device with spikes (SC) as well as with pedicle screw instrumentation in lumbar fusion procedures. Flexibility tests with an applied pure moment load of 7.5 Nm were performed in six monosegmental thoracolumbar functional spinal units (FSUs) in the following states: (a) native, (b) native with PB device, (c) intervertebral cage with PB device, (d) cage with SC and (e) cage with internal fixator. The resulting RoM was normalised to the native RoM. The CoR was determined of X-ray images taken in maximal flexion and extension during testing. In flexion and extension, the PB device without and with the cage reduced the RoM of the native state to 58% [standard deviation (SD) 17.8] and 53% (SD 15.7), respectively. The SC device further reduced the RoM to 27% (SD 16.8), while the pedicle screw instrumentation had the most reducing effect to 17% (SD 17.2) (p < 0.01). In lateral bending and axial rotation, the interspinous devices had the least effect on the RoM. Compared to the native state, for all instrumentations the CoR showed a small shift towards cranial. In the anterior-posterior direction, the SC device and the pedicle screw instrumentation shifted the CoR towards the posterior wall. The interspinous devices significantly reduced the RoM in flexion/extension, while in axial rotation and lateral bending only the internal fixator had a significant effect on the RoM.
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TANG, QIAOHONG, LIZHEN WANG, ZHONGJUN MO, QI LI, JIE YAO, CHENGFEI DU, and YUBO FAN. "BIOMECHANICAL ANALYSIS OF DIFFERENT PRODISC-C ARTHROPLASTY DESIGNS AFTER IMPLANTATION: A NUMERICAL SENSITIVITY STUDY." Journal of Mechanics in Medicine and Biology 15, no. 01 (February 2015): 1550007. http://dx.doi.org/10.1142/s0219519415500074.
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Ball-and-socket disc prostheses are the leading type of artificial disc replacement (ADR) and are typically used to treat degenerative cervical spine instability. Previous publications focused on the influence of different ProDisc-C design parameters in view of biomechanics. However, more beneficial data could be gathered if the implant was implanted prior to testing. Therefore, this study aimed to estimate the effect of different ProDisc-C arthroplasty designs and alignments when implanted at the C5-6 segment. This research can provide advice on the design of artificial discs as well as optimal placement. The geometry of the vertebrae was developed based on computed tomography (CT) images of a 32-year-old healthy male (170 cm height and 68 kg weight) with a slice thickness of 0.625 mm. A finite element (FE) model of intact C5–C6 segments including vertebrae and disc was developed and validated. A ball-and-socket artificial disc prosthesis model (ProDisc-C, Synthes) was implanted into the validated FE model. The curvature of the ProDisc-C prosthesis as well as the implanted position was varied. All models were loaded with a 74 N compressive force and pure moments of 1.8 Nm in flexion-extension, bilateral bending and axial torsion. The radius of the artificial disc influenced the ROM, facet joint force and capsule ligament tension only in flexion, while the position influenced these aspects in all loading conditions. The disc with a 6 mm radius had a greater ROM in flexion, and lower stress on the polyethylene (PE) insert without apparent stress concentrations, but it had a greater facet joint force and ligament tension compared to other radii. For all the designs, the implant position in the anterior–posterior direction had a significant influence on the disc biomechanics. Disc design and surgical procedure, such as implantation position, are important factors in postoperative rehabilitation, especially regarding the ROM in flexion/extension and implant stress. Thus, a suitable disc design should consider preserving an adequate range of motion (ROM) as well as a moderate facet joint force or stress, and proper implant positioning along the anterior–posterior direction should be monitored.
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Rodríguez-Merchán, E. Carlos. "Total knee arthroplasty using hinge joints: Indications and results." EFORT Open Reviews 4, no. 4 (April 2019): 121–32. http://dx.doi.org/10.1302/2058-5241.4.180056.
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Possible indications for a rotating hinge or pure hinge implant in primary total knee arthroplasty (TKA) include collateral ligament insufficiency, severe varus or valgus deformity (> 20°) with relevant soft-tissue release, relevant bone loss, including insertions of collateral ligaments, gross flexion-extension gap imbalance, ankylosis and hyperlaxity. The use of hinged implants in primary TKA should be limited to the aforementioned selected indications, especially for elderly patients. Potential indications for a rotating hinge or pure hinge implant in revision TKA include infection, aseptic loosening, instability and bone loss. Rotating hinge knee implants have a 10-year survivorship in the range of 51% to 92.5%. Complication rates of rotating hinge knee implants are in the range of 9.2% to 63%, with infection and aseptic loosening as the most common complications. Although the results reported in the literature are inconsistent, clinical results generally depend on the implant design, appropriate technical use and adequate indications. Considering that the revision of implants with long cemented stems can be challenging, in the future it would be better to use shorter stems in modular versions of hinged knee implants.Cite this article: EFORT Open Rev 2019;4:121-132. DOI: 10.1302/2058-5241.4.180056
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Healy, Andrew T., Swetha J. Sundar, Raul J. Cardenas, Prasath Mageswaran, Edward C. Benzel, Thomas E. Mroz, and Todd B. Francis. "Zero-profile hybrid fusion construct versus 2-level plate fixation to treat adjacent-level disease in the cervical spine." Journal of Neurosurgery: Spine 21, no. 5 (November 2014): 753–60. http://dx.doi.org/10.3171/2014.7.spine131059.
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Object Single-level anterior cervical discectomy and fusion (ACDF) is an established surgical treatment for cervical myelopathy. Within 10 years of undergoing ACDF, 19.2% of patients develop symptomatic adjacent-level degeneration. Performing ACDF adjacent to prior fusion requires exposure and removal of previously placed hardware, which may increase the risk of adverse outcomes. Zero-profile cervical implants combine an interbody spacer with an anterior plate into a single device that does not extend beyond the intervertebral disc space, potentially obviating the need to remove prior hardware. This study compared the biomechanical stability and adjacent-level range of motion (ROM) following placement of a zero-profile device (ZPD) adjacent to a single-level ACDF against a standard 2-level ACDF. Methods In this in vitro biomechanical cadaveric study, multidirectional flexibility testing was performed by a robotic spine system that simulates flexion-extension, lateral bending, and axial rotation by applying a continuous pure moment load. Testing conditions were as follows: 1) intact, 2) C5–6 ACDF, 3) C4–5 ZPD supraadjacent to simulated fusion at C5–6, and 4) 2-level ACDF (C4–6). The sequence of the latter 2 test conditions was randomized. An unconstrained pure moment of 1.5 Nm with a 40-N simulated head weight load was applied to the intact condition first in all 3 planes of motion and then using the hybrid test protocol, overall intact kinematics were replicated subsequently for each surgical test condition. Intersegmental rotations were measured optoelectronically. Mean segmental ROM for operated levels and adjacent levels was recorded and normalized to the intact condition and expressed as a percent change from intact. A repeated-measures ANOVA was used to analyze the ROM between test conditions with a 95% level of significance. Results No statistically significant differences in immediate construct stability were found between construct Patterns 3 and 4, in all planes of motion (p > 0.05). At the operated level, C4–5, the zero-profile construct showed greater decreases in axial rotation (–45% vs –36%) and lateral bending (–55% vs –38%), whereas the 2-level ACDF showed greater decreases in flexion-extension (–40% vs –34%). These differences were marginal and not statistically significant. Adjacent-level motion was nearly equivalent, with minor differences in flexion-extension. Conclusions When treating degeneration adjacent to a single-level ACDF, a zero-profile implant showed stabilizing potential at the operated level statistically similar to that of the standard revision with a 2-level plate. Revision for adjacent-level disease is common, and using a ZPD in this setting should be investigated clinically because it may be a faster, safer alternative.
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Mewes, K., and P. D. Cheney. "Primate rubromotoneuronal cells: parametric relations and contribution to wrist movement." Journal of Neurophysiology 72, no. 1 (July 1, 1994): 14–30. http://dx.doi.org/10.1152/jn.1994.72.1.14.
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1. Fifty-nine rubromotoneuronal (RM) cells were identified in two rhesus monkeys on the basis of their postspike facilitation (PSpF) of rectified electromyographic (EMG) activity. These cells were studied in relation to a step tracking task requiring wrist movements between fixed target zones in flexion and extension. Movement away from a 0 position was opposed by spring-like loads (auxotonic). Additionally, nine cells were evaluated using an isometric task. Neuronal discharge could be divided into three basic components: background discharge in the absence of movement, phasic modulation during movement, and tonic modulation during sustained holding against external loads. 2. Four basic patterns of RM cell activity were observed in relation to ramp-and-hold wrist movements: phasic-tonic (44%), pure phasic (22%), pure tonic (2%), and unmodulated (24%). The discharge of unmodulated cells did not covary with movement parameters but, as with other RM cells, background discharge did increase in association with task performance. 3. The phasic discharge of RM cells led to the onset of target muscle EMG activity by an average of 89 +/- 82 ms (mean +/- SD, n = 104) in extensors and 88 +/- 74 ms (n = 30) in flexors. Target muscles are defined as ones showing PSpF of EMG activity. It was found that 94% of extensor and 87% of flexor RM cells discharged before or synchronous with the onset of target muscle EMG activity. 4. Thirty-one RM cells (53%) showed a tonic increase in cell activity during the static hold phase of the task. Twenty-three of these were tested for relations to static torque. Fifteen extension related cells and one flexion cell had significant, positive regression slopes for the relation between tonic discharge rate and static torque. The mean rate-torque slope for extension related cells was 160 Hz/Nm and 103 Hz/Nm for flexion related cells. These mean slopes are about one-third those of corticomotoneuronal (CM) cells. 5. Cell discharge rate was correlated with velocity and rate of change of torque (dT/dt) for 32 RM cells with a phasic component of discharge during movement. The peak increase in phasic discharge above tonic firing rate (PDI, peak dynamic index) was significantly correlated only with velocity in eight cells and only with dT/dt in five cells. The phasic discharge of four additional cells was correlated with both velocity and dT/dt, but for three of these cells, the correlation was stronger for velocity. The mean slope for the relation between velocity and PDI was 0.31 Hz.deg-1.s-1.(ABSTRACT TRUNCATED AT 400 WORDS)
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Pitzen, Tobias R., Dieter Matthis, Dragos D. Barbier, and Wolf-Ingo Steudel. "Initial stability of cervical spine fixation: predictive value of a finite element model." Journal of Neurosurgery: Spine 97, no. 1 (July 2002): 128–34. http://dx.doi.org/10.3171/spi.2002.97.1.0128.
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✓ The purpose of this study was to generate a validated finite element (FE) model of the human cervical spine to be used to analyze new implants. Digitized data obtained from computerized tomography scanning of a human cervical spine were used to generate a three-dimensional, anisotropic, linear C5–6 FE model by using a software package (ANSYS 5.4). Based on the intact model (FE/Intact), a second was generated by simulating an anterior cervical fusion and plate (ACFP) C5–6 model in which monocortical screws (FE/ACFP) were used. Loading of each FE model was simulated using pure moments of ± 2.5 Nm in flexion/extension, axial left/right rotation, and left/right lateral bending. For validation of the models, their predicted C5–6 range of motion (ROM) was compared with the results of an earlier, corresponding in vitro study of six human spines, which were tested in the intact state and surgically altered at C5–6 with the same implants. The validated model was used to analyze the stabilizing effect of a new disc spacer, Cenius (Aesculap AG, Tuttlingen, Germany), as a stand-alone implant (FE/Cenius) and in combination with an anterior plate (FE/Cenius+ACFP). In addition, compression loads at the upper surface of the spacer were investigated using both models. As calculated by FE/Intact and FE/ACFP models, the ROM was within 1 standard deviation of the mean value of the corresponding in vitro measurements for each loading case. The FE/Cenius model predicted C5–6 ROM values of 5.5° in flexion/extension, 3.1° in axial rotation (left and right), and 2.9° in lateral bending (left and right). Addition of an anterior plate resulted in a further decrease of ROM in each loading case. The FE/Cenius model predicted an increase of compression load in flexion and a decrease in extension, whereas in the FE/Cenius+ACFP model an increase of graft compression in extension and unloading of the graft in flexion were predicted. The current FE model predicted ROM values comparable with those obtained in vitro in the intact state as well as after simulation of an ACFP model. It predicted a stabilizing potential for a new cage, alone and in combination with an anterior plate system, and predicted the influence of both loading modality and additional instrumentation on the behavior of the interbody graft.
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Reis, Marco T., Phillip M. Reyes, and Neil R. Crawford. "Biomechanical Assessment of Anchored Cervical Interbody Cages: Comparison of 2-Screw and 4-Screw Designs." Operative Neurosurgery 10, no. 3 (September 1, 2014): 412–17. http://dx.doi.org/10.1227/neu.0000000000000351.
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Abstract BACKGROUND: A new anchored cervical interbody polyetheretherketone spacer was devised that uses only 2 integrated variable-angle screws diagonally into the adjacent vertebral bodies instead of the established device that uses 4 diagonal fixed-angle screws. OBJECTIVE: To compare in vitro the stability provided by the new 2-screw interbody spacer with that of the 4-screw spacer and a 4-screw anterior plate plus independent polyetheretherketone spacer. METHODS: Three groups of cadaveric specimens were tested with 2-screw anchored cage (n = 8), 4-screw anchored cage (n = 8), and standard plate/cage (n = 16). Pure moments (1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while measuring 3-D motion optoelectronically. RESULTS: In all 3 groups, the mean range of motion (ROM) and lax zone were significantly reduced relative to the intact spine after discectomy and fixation. The 2-screw anchored cage allowed significantly greater ROM (P < .05) than the standard plate during flexion, extension, and axial rotation and allowed significantly greater ROM than the 4-screw cage during extension and axial rotation. The 4-screw anchored cage did not allow significantly different ROM or lax zone than the standard plate during any loading mode. CONCLUSION: The 2-screw variable-angle anchored cage significantly reduces ROM relative to the intact spine. Greater stability can be achieved, especially during extension and axial rotation, by using the 4-screw cage or standard plate plus cage.
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Brinckmann, Paul, Burkhard Drerup, Thomas Kretschmer, Daniel Schulze-Frenking, Andre Wohlatz, and Hans Henning Wetz. "Locating the Axis of Rotation when Fitting an Elbow Orthosis: A Comparison of Measurement and Palpation." Prosthetics and Orthotics International 31, no. 1 (March 2007): 36–44. http://dx.doi.org/10.1080/03093640600982354.
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No other previously published studies consider the relative motion of orthotic components positioned on the upper arm and the forearm. This study therefore measured the location and direction of the axis of rotation of an orthotic component fixed to the forearm in relation to an orthotic component fixed to the upper arm, and compared the results with those obtained by palpation. A plane flexion or extension motion of the forearm component in relation to the component on the upper arm can be described as a pure rotation about a fixed centre. However, activation of the biceps or triceps shifts that centre by around 2 cm, due to a displacement of the humerus within the orthotic component on the upper arm. Within a range of approximately 1 cm, the location of the axis of rotation was similar to that obtained by palpation. Neither custom-made plastic/foam orthoses with their hinges aligned to the measured axis, nor orthoses with their hinges aligned to the palpated axis, exhibited any difference in the wearer's comfort. It is concluded that the best choice for the location of the axis of a hinge-type orthosis for the elbow constitutes a compromise between the axes for active flexion and active extension. In view of the large influence that muscle activation has on axis location, errors in the order of 1 cm seem to be negligible when adjusting the hinge of an orthosis in individual cases.
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Lederman, Richard J. "Anterior Interosseous Neuropathy in Instrumental Musicians." Medical Problems of Performing Artists 21, no. 3 (September 1, 2006): 137–41. http://dx.doi.org/10.21091/mppa.2006.3026.
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The anterior interosseous nerve is a pure motor branch of the median nerve supplying the flexor pollicis longus, flexor digitorum profundus of the index and middle fingers, and pronator quadratus. Anterior interosseous neuropathy is rare and typically causes weakness of flexion of the tips of the thumb and index finger. Four instrumentalists, 3 violinists and 1 pianist (3 males, 1 female), seen from 1986 to 2002 at our clinic, are the subjects of this report. Age at onset ranged from 16 to 76 yrs. A possible precipitating factor was identified in each. One violinist could not hold the bow; two others noted inability to stabilize the distal left first (index) finger. The pianist noted impaired dexterity of the right hand. Examination showed weakness of flexion of the distal phalanx of the index finger and thumb and variable weakness of forearm pronation. Electrodiagnostic testing confirmed the diagnosis in all four patients. All improved over time. One symphony violinist continued to play for over 15 yrs, despite some persisting difficulty with the left index finger. Another violinist recovered function almost completely but suffered a stroke affecting the opposite hand 2.5 years later. The third violinist retired from the symphony on disability because his recovery was delayed for >1 yr. The young pianist is playing 4 to 5 hrs/day. It is likely that at least three of the four had a localized form of neuralgic amyotrophy.
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Dumas, G. A., B. R. Hewlett, D. A. Bednar, and J. P. Dickey. "Quantitative morphology of the human and porcine mid-lumbar interspinous ligament." Veterinary and Comparative Orthopaedics and Traumatology 15, no. 03 (2002): 150–57. http://dx.doi.org/10.1055/s-0038-1632730.
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SummaryAnimal models are essential in spine research for evaluating implants and for studying spinal mechanics. Several studies have compared the geometrical characteristics of animal and human vertebrae, but few studies have compared the structure of the spinal ligaments. The purpose of this study was to systematically quantify the collagen fibre orientation of the porcine and human interspinous ligament and thereby allow clearer interpretation of function. Human and porcine lumbar spine segments were loaded with a 10 Nm pure-flexion moment and chemically fixed. The sagittal plane collagen fibre orientation in the mid-lumbar interspinous ligaments was quantified by examining histological sections using a plane-polarized light macroscope and custom analysis software. The specimens showed collagen fibres in a posterior-cranial orientation originating from the superior aspect of the spinous process of the inferior vertebra and merging into the supraspinous ligament. There were not any statistically significant differences in interspinous ligament collagen fibre orientation between the human and porcine specimens. The middle and ventral spaces between the spinous processes of the human specimens contained loose disorganized collagen, skeletal muscle, and voids. The main load-bearing component of porcine and human interspinous ligament at the midlumbar level appears to be the dorsal portion, which is oriented at approximately 77-79 degrees with respect to the mid-disc plane. This dorsal aspect has a long moment arm and therefore is well suited to prevent excessive flexion. The similarity of the interspinous ligament morphology suggests that the porcine lumbar spine is a good model of the human lumbar spine.
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Doğan, Şeref, Seungwon Baek, Volker K. H. Sonntag, and Neil R. Crawford. "Biomechanical Consequences of Cervical Spondylectomy Versus Corpectomy." Operative Neurosurgery 63, suppl_4 (October 1, 2008): ONS303—ONS308. http://dx.doi.org/10.1227/01.neu.0000327569.03654.96.
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Abstract Objective: To evaluate the differences in spinal stability and stabilizing potential of instrumentation after cervical corpectomy and spondylectomy. Methods: Seven human cadaveric specimens were tested: 1) intact; 2) after grafted C5 corpectomy and anterior C4–C6 plate; 3) after adding posterior C4–C6 screws/rods; 4) after extending posteriorly to C3–C7; 5) after grafted C5 spondylectomy, anterior C4–C6 plate, and posterior C4–C6 screws/rods; and 6) after extending posteriorly to C3–C7. Pure moments induced flexion, extension, lateral bending, and axial rotation; angular motion was recorded optically. Results: After corpectomy, anterior plating alone reduced the angular range of motion to a mean of 30% of normal, whereas added posterior short- or long-segment hardware reduced range of motion significantly more (P < 0.003), to less than 5% of normal. Constructs with posterior rods spanning C3–C7 were stiffer than constructs with posterior rods spanning C4–C6 during flexion, extension, and lateral bending (P < 0.05), but not during axial rotation (P > 0.07). Combined anterior and C4–C6 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during lateral bending (P = 0.019) and axial rotation (P = 0.001). Combined anterior and C3–C7 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during extension (P = 0.030) and axial rotation (P = 0.0001). Conclusion: Circumferential fixation provides more stability than anterior instrumentation alone after cervical corpectomy. After corpectomy or spondylectomy, long circumferential instrumentation provides better stability than short circumferential fixation except during axial rotation. Circumferential fixation more effectively prevents axial rotation after corpectomy than after spondylectomy.
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Kang, Inhan, Minwook Choi, Deukhee Lee, and Gunwoo Noh. "Effect of Passive Support of the Spinal Muscles on the Biomechanics of a Lumbar Finite Element Model." Applied Sciences 10, no. 18 (September 9, 2020): 6278. http://dx.doi.org/10.3390/app10186278.
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Finite element (FE) modeling of the passive ligamentous spine is widely used to assess various biomechanical behaviors. Currently, FE models that incorporate the vertebrae, ligaments, and the personalized geometry of the bony spine may be used in conjunction with external loads from the muscles. However, while the muscles place a load (moment) on the spine and support it simultaneously, the effect of the passive support from the adjacent spinal muscles has not been considered. This study thus aims to investigate the effect of passive support from the psoas major, quadratus lumborum, and erector muscles on the range of motion (RoM) and intradiscal pressure (IDP) of the lumbar spine. Various L2-sacrum spinal models that differed only in their muscle properties were constructed and loaded with a pure moment (2.5–15.0 Nm) alone or combined with a compressive (440 or 1000 N) follower load. The RoM and IDP of the model that excluded the effect of muscles closely matched previous FE results under the corresponding load conditions. When the muscles (40–160 kPa) were included in the FE model, the RoM at L2 was reduced by up to 6.57% under a pure moment (10 Nm). The IDP was reduced by up to 6.45% under flexion and 6.84% under extension. It was also found that the erector muscles had a greater effect than the psoas major and quadratus muscles.
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Lang, Catherine E., and Marc H. Schieber. "Differential Impairment of Individuated Finger Movements in Humans After Damage to the Motor Cortex or the Corticospinal Tract." Journal of Neurophysiology 90, no. 2 (August 2003): 1160–70. http://dx.doi.org/10.1152/jn.00130.2003.
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The purpose of this study was to quantify the long-term loss of independent finger movements in humans with lesions relatively restricted to motor cortex or corticospinal tract. We questioned whether damage to the motor cortex or corticospinal tract would permanently affect the ability to move each finger to the same degree or would affect some fingers more than others. People with pure motor hemiparesis due to ischemic cerebrovascular accident were used as our experimental sample. Pure motor hemiparetic and control subjects were tested for their ability to make cyclic flexion/extension movements of each finger independently. We recorded their finger joint motion using an instrumented glove. The fingers of control subjects and of the unaffected hands (ipsilateral to the lesion) of hemiparetic subjects moved relatively independently. The fingers of the affected hands (contralateral to the lesion) of hemiparetic subjects were differentially impaired in their ability to make independent finger movements. The independence of the thumb was normal; the independence of the index finger was slightly impaired, while the independence of the middle, ring, and little fingers was substantially impaired. The differential long-term effects of motor cortical or corticospinal damage on finger independence may result from rehabilitative training emphasizing tasks requiring independent thumb and index movements, and from a greater ability of the spared components of the neuromuscular system to control the thumb independently compared with the other four fingers.
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Nguyen, Jacqueline, Bryant Chu, Calvin C. Kuo, Jeremi M. Leasure, Christopher Ames, and Dimitriy Kondrashov. "Changes in foraminal area with anterior decompression versus keyhole foraminotomy in the cervical spine: a biomechanical investigation." Journal of Neurosurgery: Spine 27, no. 6 (December 2017): 620–26. http://dx.doi.org/10.3171/2017.2.spine141237.
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OBJECTIVEAnterior cervical discectomy and fusion (ACDF) with or without partial uncovertebral joint resection (UVR) and posterior keyhole foraminotomy are established operative procedures to treat cervical disc degeneration and radiculopathy. Studies have demonstrated reliable results with each procedure, but none have compared the change in neuroforaminal area between indirect and direct decompression techniques. The purpose of this study was to determine which cervical decompression method most consistently increases neuroforaminal area and how that area is affected by neck position.METHODSEight human cervical functional spinal units (4 each of C5–6 and C6–7) underwent sequential decompression. Each level received the following surgical treatment: bilateral foraminotomy, ACDF, ACDF + partial UVR, and foraminotomy + ACDF. Multidirectional pure moment flexibility testing combined with 3D C-arm imaging was performed after each procedure to measure the minimum cross-sectional area of each foramen in 3 different neck positions: neutral, flexion, and extension.RESULTSNeuroforaminal area increased significantly with foraminotomy versus intact in all positions. These area measurements did not change in the ACDF group through flexion-extension. A significant decrease in area was observed for ACDF in extension (40 mm2) versus neutral (55 mm2). Foraminotomy + ACDF did not significantly increase area compared with foraminotomy in any position. The UVR procedure did not produce any changes in area through flexion-extension.CONCLUSIONSAll procedures increased neuroforaminal area. Foraminotomy and foraminotomy + ACDF produced the greatest increase in area and also maintained the area in extension more than anterior-only procedures. The UVR procedure did not significantly alter the area compared with ACDF alone. With a stable cervical spine, foraminotomy may be preferable to directly decompress the neuroforamen; however, ACDF continues to play an important role for indirect decompression and decompression of more centrally located herniated discs. These findings pertain to bony stenosis of the neuroforamen and may not apply to soft disc herniation. The key points of this study are as follows. Both ACDF and foraminotomy increase the foraminal space. Foraminotomy was most successful in maintaining these increases during neck motion. Partial UVR was not a significant improvement over ACDF alone. Foraminotomy may be more efficient at decompressing the neuroforamen. Results should be taken into consideration only with stable spines.
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Schmieder, Kirsten, Annette Kettner, Christopher Brenke, Albrecht Harders, Ioannis Pechlivanis, and Hans-Joachim Wilke. "In vitro flexibility of the cervical spine after ventral uncoforaminotomy." Journal of Neurosurgery: Spine 7, no. 5 (November 2007): 537–41. http://dx.doi.org/10.3171/spi-07/11/537.
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Object Degenerative spine disorders are, in the majority of cases, treated with ventral discectomy followed by fusion (also known as anterior cervical discectomy and fusion). Currently, nonfusion strategies are gaining broader acceptance. The introduction of cervical disc prosthetic devices was a natural consequence of this development. Jho proposed anterior uncoforaminotomy as an alternative motion-preserving procedure at the cervical spine. The clinical results in the literature are controversial, with one focus of disagreement being the impact of the procedure on stability. The aim of this study was to address the changes in spinal stability after uncoforaminotomy. Methods Six spinal motion segments derived from three fresh-frozen human cervical spine specimens (C2–7) were tested. The donors were two men whose ages at death were 59 and 80 years and one woman whose age was 80 years. Bone mineral density in C-3 ranged from 155 to 175 mg/cm3. The lower part of the segment was rigidly fixed in the spine tester, whereas the upper part was fixed in gimbals with integrated stepper motors. Pure moment loads of ± 2.5 Nm were applied in flexion/extension, axial rotation, and lateral bending. For each specimen a load-deformation curve, the range of motion (ROM), and the neutral zone (NZ) for negative and positive directions of motion were calculated. Median, maximum, and minimum values were calculated for the six segments and normalized to the intact segment. Tests were done on the intact segment, after unilateral uncoforaminotomy, and after bilateral uncoforaminotomy. Results In lateral bending a strong increase in ROM and NZ was detectable after unilateral uncoforaminotomy on the right side. Overall, the ROM during flexion/extension was less influenced after uncoforaminotomy. The ROM and NZ during axial rotation to the left increased strongly after right unilateral uncoforaminotomy. Changes after bilateral uncoforaminotomy were marked during axial rotation to both sides. Conclusions Following unilateral uncoforaminotomy, a significant alteration in mobility of the segment is found, especially during lateral bending and axial rotation. The resulting increase in mobility is less pronounced during flexion and least evident on extension. Further investigations of the natural course of disc degeneration and the impact on mobility after uncoforaminotomy are needed.