Articoli di riviste: "Patella Physiology"

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Stanescu, A., Anh-Vu Ngo, Marguerite Parisi, Ramesh Iyer e Ezekiel Maloney. "The Pediatric Patella: Normal Development, Anatomical Variants and Malformations, Stability, Imaging, and Injury Patterns". Seminars in Musculoskeletal Radiology 22, n. 01 (febbraio 2018): 081–94. http://dx.doi.org/10.1055/s-0037-1608004.

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AbstractWe discuss the pediatric patella, with an emphasis on diagnostic imaging. Topics include normal patellar development, anatomical variants and their physiologic significance, genetic syndromes that alter the appearance of the patella, physiology of patellar tracking and stability, patellofemoral instability, and injury patterns and classification. Recognition of appropriate development on imaging prevents diagnostic error and unnecessary evaluation. Knowledge of the pertinent features of syndromes associated with morphological patellar abnormalities can aid in generating a succinct and relevant differential diagnosis. In patellofemoral instability, the patient's baseline anatomy, factors that predispose to instability, and the specific injuries that occur as a result are critical considerations for determining the course of treatment. Patellar sleeve fractures are unique to pediatric patients, and timely identification is critical to achieving an optimal treatment outcome.

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Li, Guoan, Ramprasad Papannagari, Kyung Wook Nha, Louis E. DeFrate, Thomas J. Gill e Harry E. Rubash. "The Coupled Motion of the Femur and Patella During In Vivo Weightbearing Knee Flexion". Journal of Biomechanical Engineering 129, n. 6 (19 aprile 2007): 937–43. http://dx.doi.org/10.1115/1.2803267.

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The movement of the knee joint consists of a coupled motion between the tibiofemoral and patellofemoral articulations. This study measured the six degrees-of-freedom kinematics of the tibia, femur, and patella using dual-orthogonal fluoroscopy and magnetic resonance imaging. Ten normal knees from ten living subjects were investigated during weightbearing flexion from full extension to maximum flexion. The femoral and the patellar motions were measured relative to the tibia. The femur externally rotated by 12.9deg and the patella tilted laterally by 16.3deg during the full range of knee flexion. Knee flexion was strongly correlated with patellar flexion (R2=0.91), posterior femoral translation was strongly correlated to the posterior patellar translation (R2=0.87), and internal-external rotation of the femur was correlated to patellar tilt (R2=0.73) and medial-lateral patellar translation (R2=0.63). These data quantitatively indicate a kinematic coupling between the tibia, femur, and patella, and provide base line information on normal knee joint kinematics throughout the full range of weightbearing flexion. The data also suggest that the kinematic coupling of tibia, femur, and patella should be considered when investigating patellar pathologies and when developing surgical techniques to treat knee joint diseases.

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Sheehan, F. T., F. E. Zajac e J. E. Drace. "In Vivo Tracking of the Human Patella Using Cine Phase Contrast Magnetic Resonance Imaging". Journal of Biomechanical Engineering 121, n. 6 (1 dicembre 1999): 650–56. http://dx.doi.org/10.1115/1.2800868.

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Improper patellar tracking is often considered to be the cause of patellar-femoral pain. Unfortunately, our knowledge of patellar-femoral-tibial (knee) joint kinematics is severely limited due to a lack of three-dimensional, noninvasive, in vivo measurement techniques. This study presents the first large-scale, dynamic, three-dimensional, noninvasive, in vivo study of nonimpaired knee joint kinematics during volitional leg extensions. Cine-phase contrast magnetic resonance imaging was used to measure the velocity profiles of the patella, femur, and tibia in 18 unimpaired knees during leg extensions, resisted by a 34 N weight. Bone displacements were calculated through integration and then converted into three-dimensional orientation angles. We found that the patella displaced laterally, superiorly, and anteriorly as the knee extended. Further, patellar flexion lagged knee flexion, patellar tilt was variable, and patellar rotation was fairly constant throughout extension.

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Steen, H., K. F. Tseng, S. A. Goldstein e J. E. Carpenter. "Harvest of Patellar Tendon (Bone–Tendon–Bone) Autograft for ACL Reconstruction Significantly Alters Surface Strain in the Human Patella". Journal of Biomechanical Engineering 121, n. 2 (1 aprile 1999): 229–33. http://dx.doi.org/10.1115/1.2835108.

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The purpose of this study was to measure the effect of bone–patellar tendon–bone autograft harvest for anterior cruciate ligament (ACL) reconstruction on the surface strain of the human patella. Through progressive removal of bone from the patella, three different defect shapes as well as the intact patella were tested in each of seven knees. Maximum principal strain and corresponding principal direction were determined from each of three gages around the defect for the four conditions (intact plus three defect shapes). There were no statistically significant differences in overall average surface strain between any of the defect shapes. Following graft harvest, overall average strain (all three defects combined) increased in the patella both medial (15 percent increase) and lateral (34 percent increase) to the defect, while decreasing in the region directly proximal (22 percent increase) to the harvest site compared to the intact patella. A statistically significant 7.5 deg shift of principal direction from longitudinal toward a more transverse (lateral-superior to medial-inferior) direction was observed in the medial region when a shallow-dome defect was made. We conclude that removal of a bone block from the anterior, inferior part of the patella induces a significant redistribution of the surface strain. This results in greater local strain adjacent to the upper border of the bone block, increasing the risk for patella fracture. This effect may be of importance in various complications known to occur after ACL reconstruction.

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Tu¨mer, Sami Turgut, e Ali Erkan Engin. "Three-Body Segment Dynamic Model of the Human Knee". Journal of Biomechanical Engineering 115, n. 4A (1 novembre 1993): 350–56. http://dx.doi.org/10.1115/1.2895497.

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In this paper, a two-dimensional, three-body segment dynamic model of the human knee is introduced. The model includes tibio-femoral and patello-femoral articulations, and anterior cruciate, posterior cruciate, medial collateral, lateral collateral, and patellar ligaments. It enables one to obtain dynamic response of the knee joint to any one or combination of quadriceps femoris, hamstrings, and gastrocnemius muscle actions, as well as any externally applied forces on the lower leg. A specially developed human knee animation program is utilized in order to fine tune some model parameters. Numerical results are presented for knee extension under the impulsive action of the quadriceps femoris muscle group to simulate a vigorous lower limb activity such as kicking. The model shows that the patella can be subjected to very large transient patello-femoral contact force during a strenuous lower limb activity even under conditions of small knee-flexion angles. The results are discussed and compared with limited data reported in the literature.

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Witzgall, Ralph. "Nail-patella syndrome". Pflügers Archiv - European Journal of Physiology 469, n. 7-8 (5 luglio 2017): 927–36. http://dx.doi.org/10.1007/s00424-017-2013-z.

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Kubo, Keitaro, Toshihiro Ikebukuro, Katsutoshi Yaeshima, Hideaki Yata, Naoya Tsunoda e Hiroaki Kanehisa. "Effects of static and dynamic training on the stiffness and blood volume of tendon in vivo". Journal of Applied Physiology 106, n. 2 (febbraio 2009): 412–17. http://dx.doi.org/10.1152/japplphysiol.91381.2008.

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The purpose of this study was to investigate the effects of static and dynamic training on the stiffness and blood volume of the human tendon in vivo. Ten subjects completed 12 wk (4 days/wk) of a unilateral training program for knee extensors. They performed static training on one side [ST; 70% of maximum voluntary contraction (MVC)] and dynamic training on the other side (DT; 80% of one repetition maximum). Before and after training, MVC, neural activation level (by interpolated twitch), muscle volume (by magnetic resonance imaging), stiffness of tendon-aponeurosis complex and patella tendon (by ultrasonography), and blood volume of patella tendon (by red laser lights) were measured. Both protocols significantly increased MVC (49% for ST, 32% for DT; both P < 0.001), neural activation level (9.5% for ST, 7.6% for DT; both P < 0.01), and muscle volume (4.5% for ST, 5.6% for DT; both P < 0.01). The stiffness of tendon-aponeurosis complex increased significantly after ST (55%; P = 0.003) and DT (30%; P = 0.033), while the stiffness of patella tendon increased significantly after ST (83%; P < 0.001), but not for DT ( P = 0.110). The blood volume of patella tendon increased significantly after DT (47%; P = 0.016), but not for ST ( P = 0.205). These results implied that the changes in the blood volume of tendon would be related to differences in the effects of resistance training on the tendon properties.

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Ahmed, A. M., N. A. Duncan e M. Tanzer. "In Vitro Measurement of the Tracking Pattern of the Human Patella". Journal of Biomechanical Engineering 121, n. 2 (1 aprile 1999): 222–28. http://dx.doi.org/10.1115/1.2835107.

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This study sought to determine whether a general pattern describing the three-dimensional tracking characteristics of the human patella could be established, and if not, then to determine the extent and nature of interspecimen variations in the characteristics in a normal population. Using 32 fresh-frozen knees subjected to extensor moment magnitudes similar to those in “static-lifting” and “leg-raising against resistance” maneuvers, patellar displacements were measured in the knee extension range 120 to 0 deg. For static-lifting, a constant foot-floor reaction of 334 N was applied. For leg-raising, a constant net quadriceps tension of 668 N was used throughout the extension range. Measurements were taken with a calibrated six-degree-of-freedom electromechanical goniometer and a displacement coordinate system referenced to the geometry of individual specinens. The three patellar displacements in the plane of knee extension/flexion (extension rotation, and anterior and proximal translations) consistently demonstrated the same pattern in the entire knee extension range with an average coefficient of variation of 13 percent. For knee angles greater than 45 deg, the three other displacements (medial lateral translation, and rotations about the anterior–posterior and proximal–distal axes) followed a general pattern. However, for knee angles less than 45 deg, these displacements differed considerably between specimens for each loading condition, both in terms of magnitude (average coefficient of variation: 70 percent), and direction.

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Carroll, C. C., J. M. Dickinson, J. M. Haus, G. A. Lee, C. J. Hollon, P. Aagaard, S. P. Magnusson e T. A. Trappe. "Influence of aging on the in vivo properties of human patellar tendon". Journal of Applied Physiology 105, n. 6 (dicembre 2008): 1907–15. http://dx.doi.org/10.1152/japplphysiol.00059.2008.

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Tendons are important for optimal muscle force transfer to bone and play a key role in functional ability. Changes in tendon properties with aging could contribute to declines in physical function commonly associated with aging. We investigated the in vivo mechanical properties of the patellar tendon in 37 men and women [11 young (27 ± 1 yr) and 26 old (65 ± 1 yr)] using ultrasonography and magnetic resonance imaging (MRI). Patella displacement relative to the tibia was monitored with ultrasonography during ramped isometric contractions of the knee extensors, and MRI was used to determine tendon cross-sectional area (CSA) and signal intensity. At peak force, patellar tendon deformation, stress, and strain were 13 ( P = 0.05), 19, and 12% less in old compared with young ( P < 0.05). Additionally, deformation, stiffness, stress, CSA, and length were 18, 35, 41, 28, and 11% greater ( P < 0.05), respectively, in men compared with women. After normalization of mechanical properties to a common force, no age differences were apparent; however, stress and strain were 26 and 22% higher, respectively, in women compared with men ( P < 0.05). CSA and signal intensity decreased 12 and 24%, respectively, with aging ( P < 0.05) in the midregion of the tendon. These data suggest that differences in patellar tendon in vivo mechanical properties with aging are more related to force output rather than an age effect. In contrast, the decrease in signal intensity indirectly suggests that the internal milieu of the tendon is altered with aging; however, the physiological and functional consequence of this finding requires further study.

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Clark, D. A., D. L. Simpson, J. D. Eldridge, V. Pai e G. R. Colborne. "Functional assessment of outcome of surgery to correct patellofemoral instability in human patients". Comparative Exercise Physiology 16, n. 3 (23 marzo 2020): 161–67. http://dx.doi.org/10.3920/cep190045.

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A case-control study with 6 months of patient follow up. This study sought to determine if surgery followed by rehabilitation for patellar instability could restore normal gait function. A previous study has established abnormalities in gait pattern and joint congruence in patients with a history of patellar instability. We hypothesised that surgery for patellofemoral instability would improve knee function. Eight human patients (mean age 29, range 17-42) who were awaiting patella stabilisation surgery (5 tibial tuberosity osteotomy, 2 medial patellofemoral ligament reconstruction, 1 trochleoplasty) were compared against eight normal Controls (mean age 28, range 19-31). Patients were assessed pre-operatively and six months after surgery by biomechanical gait analysis. Gait trials involved simultaneous collection of kinematic and force data. Patients were grouped into two subgroups pre-operatively based on knee joint net moment during stance, and their joint moments during stance pre- and post-operatively were compared against the Control subjects. In pre-operative gait analysis, four patients (P1) produced some extensor moment in early stance and four (P2) demonstrated a severe gait deficiency with failure to generate a knee extensor moment during stance. Normalisation in gait pattern was observed in all patients post-operatively. Those who had the most severe gait abnormality (P2) demonstrated the most improvement in their knee joint moments. Improvements were observed in the milder (P1) cases, but these were less dramatic. Patella stabilisation by surgery can restore normal gait function. Normalising the anatomy of the knee extensor mechanism is the objective of surgery. Normal anatomy facilitates the rehabilitation objectives of optimising extensor function during the weight-bearing phase of gait.

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Clifford, Amanda M., e Elaine Harrington. "The Effect of Patellar Taping on Squat Depth and the Perception of Pain in People with Anterior Knee Pain". Journal of Human Kinetics 37, n. 1 (1 giugno 2013): 109–17. http://dx.doi.org/10.2478/hukin-2013-0031.

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Patellar taping is a treatment adjunct commonly used in the management of anterior knee pain. The aim of this cross sectional study was to investigate the effects of medial glide patellar taping on sagittal plane lower-limb joint kinematics and knee pain during a unilateral squat in a symptomatic population complaining of anterior knee pain. Ten participants with a history of unilateral or bilateral anterior knee pain were included in the study. Subjects were required to squat on the symptomatic leg under three conditions: placebo tape, patellar tape and no tape. Kinematic data was recorded using the CODA mpx64 motion analysis system and subjects’ pain was assessed using the Numerical Rating Scale. Patellar taping resulted in a significantly greater single-legged squat depth compared to placebo tape (p=0.008) and no tape (p=0.001) and a statistically significant reduction in pain during a squat compared to placebo tape (p=0.001) or no tape (p=0.001). Significant differences were not identified for maximum knee flexion in the patella taping compared to the no tape condition. This study may have significant clinical implications as participants reported less pain and alterations in sagittal plane movement following the application of patellar tape.

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Haraldsson, B. T., P. Aagaard, M. Krogsgaard, T. Alkjaer, M. Kjaer e S. P. Magnusson. "Region-specific mechanical properties of the human patella tendon". Journal of Applied Physiology 98, n. 3 (marzo 2005): 1006–12. http://dx.doi.org/10.1152/japplphysiol.00482.2004.

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The present study investigated the mechanical properties of tendon fascicles from the anterior and posterior human patellar tendon. Collagen fascicles from the anterior and posterior human patellar tendon in healthy young men (mean ± SD, 29.0 ± 4.6 yr, n = 6) were tested in a mechanical rig. A stereoscopic microscope equipped with a digital camera recorded elongation. The fascicles were preconditioned five cycles before the failure test based on pilot data on rat tendon fascicle. Human fascicle length increased with repeated cycles ( P < 0.05); cycle 5 differed from cycle 1 ( P < 0.05), but not cycles 2–4. Peak stress and yield stress were greater for anterior (76.0 ± 9.5 and 56.6 ± 10.4 MPa, respectively) than posterior fascicles (38.5 ± 3.9 and 31.6 ± 2.9 MPa, respectively), P < 0.05, while yield strain was similar (anterior 6.8 ± 1.0%, posterior 8.7 ± 1.4%). Tangent modulus was greater for the anterior (1,231 ± 188 MPa) than the posterior (583 ± 122 MPa) fascicles, P < 0.05. In conclusion, tendon fascicles from the anterior portion of the human patellar tendon in young men displayed considerably greater peak and yield stress and tangent modulus compared with the posterior portion of the tendon, indicating region-specific material properties.

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Amr, R., e Q. Choudry. "Monostotic Paget's disease of the patella". Bone 39, n. 6 (dicembre 2006): 1382–84. http://dx.doi.org/10.1016/j.bone.2006.06.020.

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Caruntu, Dumitru I., e Mohamed Samir Hefzy. "3-D Anatomically Based Dynamic Modeling of the Human Knee to Include Tibio-Femoral and Patello-Femoral Joints". Journal of Biomechanical Engineering 126, n. 1 (1 febbraio 2004): 44–53. http://dx.doi.org/10.1115/1.1644565.

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An anatomical dynamic model consisting of three body segments, femur, tibia and patella, has been developed in order to determine the three-dimensional dynamic response of the human knee. Deformable contact was allowed at all articular surfaces, which were mathematically represented using Coons’ bicubic surface patches. Nonlinear elastic springs were used to model all ligamentous structures. Two joint coordinate systems were employed to describe the six-degrees-of-freedom tibio-femoral (TF) and patello-femoral (PF) joint motions using twelve kinematic parameters. Two versions of the model were developed to account for wrapping and nonwrapping of the quadriceps tendon around the femur. Model equations consist of twelve nonlinear second-order ordinary differential equations coupled with nonlinear algebraic constraint equations resulting in a Differential-Algebraic Equations (DAE) system that was solved using the D_ifferential/A_lgebraic S_ystem S_ol_ver (DASSL) developed at Lawrence Livermore National Laboratory. Model calculations were performed to simulate the knee extension exercise by applying non-linear forcing functions to the quadriceps tendon. Under the conditions tested, both “screw home mechanism” and patellar flexion lagging were predicted. Throughout the entire range of motion, the medial component of the TF contact force was found to be larger than the lateral one while the lateral component of the PF contact force was found to be larger than the medial one. The anterior and posterior fibers of both anterior and posterior cruciate ligaments, ACL and PCL, respectively, had opposite force patterns: the posterior fibers were most taut at full extension while the anterior fibers were most taut near 90° of flexion. The ACL was found to carry a larger total force than the PCL at full extension, while the PCL carried a larger total force than the ACL in the range of 75° to 90° of flexion.

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Maden-Wilkinson, Thomas M., Thomas G. Balshaw, Garry J. Massey e Jonathan P. Folland. "What makes long-term resistance-trained individuals so strong? A comparison of skeletal muscle morphology, architecture, and joint mechanics". Journal of Applied Physiology 128, n. 4 (1 aprile 2020): 1000–1011. http://dx.doi.org/10.1152/japplphysiol.00224.2019.

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Here we demonstrate that the larger muscle strength (+60%) of a long-term (4+ yr) resistance-trained group compared with untrained controls was due to their similarly larger muscle volume (+56%), primarily due to a larger physiological cross-sectional area and modest differences in fascicle length, as well as modest differences in maximum voluntary specific tension and patella tendon moment arm. In addition, the present study refutes the possibility of regional hypertrophy, despite large differences in muscle volume.

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Tsakoniti, Aikaterini E., Christoforos A. Stoupis e Spyros I. Athanasopoulos. "Quadriceps cross-sectional area changes in young healthy men with different magnitude of Q angle". Journal of Applied Physiology 105, n. 3 (settembre 2008): 800–804. http://dx.doi.org/10.1152/japplphysiol.00961.2007.

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Knee pain and dysfunction have been often associated with an ineffective pull of the patella by the vastus medialis (VM) relative to the vastus lateralis (VL), particularly in individuals with knee joint malalignment. Such changes in muscular behavior may be attributed to muscle inhibition and/or atrophy that precedes the onset of symptoms. The aim of this study was to investigate possible effects of knee joint malalignment, indicated by a high quadriceps (Q) angle (HQ angle >15°), on the anatomic cross-sectional area (aCSA) of the entire quadriceps and its individual parts, in a group of 17 young asymptomatic men compared with a group of 19 asymptomatic individuals with low Q angle (LQ angle <15°). The aCSA of the entire quadriceps (TQ), VM, VL, vastus intermedius (VI), rectus femoris (RF), and patellar tendon (PT) were measured during static and dynamic magnetic resonance imaging (MRI) with the quadriceps relaxed and under contraction, respectively. A statistically significant lower aCSA was obtained in the HQ angle group, compared with the LQ angle group, for the TQ, VL, and VI in both static (TQ = 9.9%, VL = 12.9%, and VI = 9.1%; P < 0.05) and dynamic imaging (TQ = 10.7%, P < 0.001; VL = 13.4%, P < 0.01; and VI = 9.8%, P < 0.05) and the aCSA of the VM in dynamic MRI (11.9%; P < 0.01). The muscle atrophy obtained in the HQ angle group may be the result of a protective mechanism that inhibits and progressively adapts muscle behavior to reduce abnormal loading and wear of joint structures.

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Li, Xiaowei, Roger C. Haut e Nicholas J. Altiero. "An Analytical Model to Study Blunt Impact Response of the Rabbit P-F Joint". Journal of Biomechanical Engineering 117, n. 4 (1 novembre 1995): 485–91. http://dx.doi.org/10.1115/1.2794212.

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While mechanisms of post-traumatic osteoarthrosis are largely unknown, excessive stresses and strains generated in articular cartilage and the underlying bone may play a role. In this manuscript a technique is described for studying the impact response of a diarthrodial joint. A mathematical model of the rabbit PF joint indicated that contact pressures predicted by a quasi-static plane strain linear elastic model compared well with experimental data when Poisson’s ratio and Young’s modulus of the cartilage were 0.49 and 2 MPa, respectively. This value for the elastic modulus compared well with that obtained from elastic analysis of short-time indentation experiments on cartilage from a previous study. The model analysis also suggested that surface fissuring of patellar cartilage occurs near areas where shear stresses and tensile strains are high. Impact location on the patella significantly influenced the distributions of shear stress along the bone-cartilage interface and tensile strains in the cartilage. These results may help explain some of the mechanisms of initial tissue damage reported elsewhere. Limited experimental data are presented here but the value of such mathematical models for estimation of material properties and for analysis of damage creation is clearly demonstrated.

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SHULTZ, JEFFREY W. "Muscle Firing Patterns in two Arachnids using different methods of Propulsive Leg Extension". Journal of Experimental Biology 162, n. 1 (1 gennaio 1992): 313–29. http://dx.doi.org/10.1242/jeb.162.1.313.

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Activity patterns of six morphologically similar, homologous muscles were recorded from the fourth leg pair in two species of arachnids that use different mechanisms to extend the femur-patella (knee) joint during locomotion. The giant whipscorpion Mastigoproctus giganteus (Uropygi) lacks femur-patella extensor muscles but extends this joint with hydraulic pressure, a mechanism that appears to be phylogenetically primitive in arachnids. The black emperor scorpion Pandinus imperator (Scorpiones) has an unusual muscle that promotes simultaneous extension at the femur-patella joint and distally adjacent patella-tibia joint. Comparison of electromyograms from freely walking animals revealed similarities in muscle firing patterns of the two species, including asymmetrical alternation of trochanter-femur levator and depressor muscles, transfemoral muscle activation during protraction and abrupt termination just prior to levator activation, and persistence of flexor activity during retraction (extension). These results indicate that the apparent evolutionary transition from hydraulic to muscular extension occurred without substantial alteration of several components of the primitive motor programme. It is suggested that the patterns of extension force generated by hydraulic pressure and by bifunctional extensors are similar and that this similarity is associated with conservation of the motorprogramme.

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Luo, Zong-Ping, Horng-Chaung Hsu, James A. Rand e Kai-Nan An. "Importance of Soft Tissue Integrity on Biomechanical Studies of the Patella After TKA". Journal of Biomechanical Engineering 118, n. 1 (1 febbraio 1996): 130–32. http://dx.doi.org/10.1115/1.2795938.

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This study evaluated the effects of soft tissue integrity on patellar tracking and patellofemoral joint force after total knee arthroplasty. The results indicate that partial dissection of the soft tissue integrity in the in vitro biomechanical studies of the patellofemoral joint can alter patellar tracking and joint force significantly, leading to improper conclusions.

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Miller, Benjamin F., Jens L. Olesen, Mette Hansen, Simon Døssing, Regina M. Crameri, Rasmus J. Welling, Henning Langberg et al. "Coordinated collagen and muscle protein synthesis in human patella tendon and quadriceps muscle after exercise". Journal of Physiology 567, n. 3 (settembre 2005): 1021–33. http://dx.doi.org/10.1113/jphysiol.2005.093690.

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Singerman, R., J. Berilla, M. Archdeacon e A. Peyser. "In Vitro Forces in the Normal and Cruciate-Deficient Knee During Simulated Squatting Motion". Journal of Biomechanical Engineering 121, n. 2 (1 aprile 1999): 234–42. http://dx.doi.org/10.1115/1.2835109.

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Three orthogonal components of the tibiofemoral and patellofemoral forces were measured simultaneously for knees with intact cruciate ligaments (nine knees), following anterior cruciate ligament resection (six knees), and subsequent posterior cruciate ligament resection (six knees). The knees were loaded using an experimental protocol that modeled static double-leg squat. The mean compressive tibial force increased with flexion angle. The mean anteroposterior tibial shear force acted posteriorly on the tibia below 50 deg flexion and anteriorly above 55 deg. Mediolateral shear forces were low compared to the other force components and tended to be directed medially on both the patella and tibia. The mean value of the ratio of the resultant tibial force divided by the quadriceps force decreased with increasing flexion angle and was between 0.6 and 0.7 above 70 deg flexion. The mean value of the ratio of the resultant tibiofemoral contact force divided by the resultant patellofemoral contact force decreased with increasing flexion and was between 0.8 and 1.0 above 55 deg flexion. Cruciate ligament resection resulted in no significant changes in the patellar contact forces. Following resection of the anterior cruciate ligament, the tibial anteroposterior shear force was directed anteriorly over all flexion angles tested. Subsequent resection of the posterior cruciate ligament resulted in an approximately 10 percent increase in the quadriceps tendon and tibial compressive force.

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Farzam, Parisa, Peyman Zirak, Tiziano Binzoni e Turgut Durduran. "Pulsatile and steady-state hemodynamics of the human patella bone by diffuse optical spectroscopy". Physiological Measurement 34, n. 8 (17 luglio 2013): 839–57. http://dx.doi.org/10.1088/0967-3334/34/8/839.

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Gawda, Piotr, Michał Ginszt, Magdalena Zawadka, Maria Skublewska-Paszkowska, Jakub Smołka, Edyta Łukasik e Piotr Majcher. "Bioelectrical Activity of Vastus Medialis and Rectus Femoris Muscles in Recreational Runners with Anterior Knee Pain". Journal of Human Kinetics 66, n. 1 (27 marzo 2019): 81–88. http://dx.doi.org/10.2478/hukin-2018-0065.

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Abstract Patellofemoral pain syndrome (PFPS), the most common source of knee pain among physically active individuals, is defined as anterior knee pain involving the patella and retinaculum that excludes other intraarticular and peri-patellar pathology. Differences in the activation and endurance of the quadriceps components, causing an imbalance in the forces controlling patellar tracking during flexion and extension in the knee joint, appear to be the most commonly reported risk factors for PFPS. The aim of this study was to determine the differences in bioelectric activity of vastus medialis and rectus femoris muscles during half knee bend position in runners with PFPS. The sample comprised 20 recreational runners (15 males, 5 females; aged 27 ± 5 years) reporting knee pain and diagnosed with PFPS. The age- and sex-matched control group consisted of recreational runners who did not report knee pain. The myon electromyographic system was used to determine the changes in the electromyographic median frequency during a half squat position. The decrease in the median frequency of vastus medialis and rectus femoris muscles was significantly greater in runners with PFPS in comparison to the control group (p < 0.01 for right and left vastus medialis and right rectus femoris; p < 0.05 for left rectus femoris). There is a relationship between knee pain related to PFPS and the imbalance of bioelectric activity of vastus medialis and rectus femoris muscles. Achieving the muscular balance within the thigh muscles can be an important factor in the rehabilitation process of PFPS.

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Hicks, K. M., G. Onambélé-Pearson, K. Winwood e C. I. Morse. "Oral contraceptive pill use and the susceptibility to markers of exercise-induced muscle damage". European Journal of Applied Physiology 117, n. 7 (11 maggio 2017): 1393–402. http://dx.doi.org/10.1007/s00421-017-3629-6.

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Abstract Purpose Firstly, to establish whether oral contraceptive pill (OCP) users are more susceptible to muscle damage compared to non-users, and secondly, to establish whether differences can be attributed to differences in patella tendon properties. Methods Nine female OCP users and 9 female non-users participated in the investigation. Combining dynamometry, electromyography and ultrasonography, patella tendon properties and vastus lateralis architectural properties were measured pre and during the first of 6 sets of 12 maximal voluntary eccentric knee extensions. Serum oestrogen levels were measured on the 7th day of the pill cycle and the 14th day of menstrual cycle in OCP users and non-users, respectively. Maximal voluntary isometric knee extension torque loss, creatine kinase and muscle soreness were measured 48 h pre-damage, post-damage, and 48, 96 and 168 h post-damage. Results Oestrogen levels were significantly lower in OCP users compared to non-users (209 ± 115 and 433 ± 147 pg/ml, respectively, p = 0.004). Proposed determinants of muscle damage, patella tendon stiffness and maximal eccentric torque did not differ between OCP users and non-users. The change in creatine kinase from pre to peak was significantly higher in OCP users compared to non-users (962 ± 968 and 386 ± 474 Ul, respectively, p = 0.016). There were no other differences in markers of muscle damage. Conclusion Although our findings suggest that, when compared to non-users, the OCP may augment the creatine kinase response following eccentric exercise, it does not increase the susceptibility to any other markers of muscle damage.

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Spang, Robert, Jonathan Egan, Philip Hanna, Aron Lechtig, Daniel Haber, Joseph P. DeAngelis, Ara Nazarian e Arun J. Ramappa. "Comparison of Patellofemoral Kinematics and Stability After Medial Patellofemoral Ligament and Medial Quadriceps Tendon–Femoral Ligament Reconstruction". American Journal of Sports Medicine 48, n. 9 (18 giugno 2020): 2252–59. http://dx.doi.org/10.1177/0363546520930703.

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Background: There is a lack of evidence regarding the optimum extensor-sided fixation method for medial patellofemoral ligament (MPFL) reconstruction. There is increased interest in avoiding patellar drilling via soft tissue–only fixation to the distal quadriceps, thus reconstructing the medial quadriceps tendon–femoral ligament (MQTFL). The biomechanical implications of differing extensor-sided fixation constructs remain unknown. Hypothesis: The null hypothesis was there would be no differences between traditional MPFL reconstruction and MQTFL reconstruction with respect to resistance to lateral translation, patellar position, or patellofemoral contact pressures. Study Design: Controlled laboratory study. Methods: Nine adult knee specimens were mounted on a jig that applied static, physiologic loads to the quadriceps tendons. Patellar position and orientation, knee flexion angle, and patellofemoral pressure were recorded at 8 different flexion angles between 0° and 110°. Additionally, a lateral patellar excursion test was conducted wherein a load was applied directly to the patella in the lateral direction with the knee at 30° of flexion and subjected to 2-N quadriceps loads. Testing was conducted under 4 conditions: intact, transected MPFL, MQTFL reconstruction, and MPFL reconstruction. For MQTFL reconstruction, the surgical technique established by Fulkerson was employed. For MPFL reconstruction, a traditional technique was utilized. Results: The patellar excursion test showed no significant difference between the MQTFL and intact states with respect to lateral translation. MPFL reconstruction led to significantly less lateral translation ( P < .05) than all other states. There were no significant differences between MPFL and MQTFL reconstructions with respect to peak patellofemoral contact pressure. MPFL and MQTFL reconstructions both resulted in increased internal rotation of the patella with the knee in full extension. Conclusion: Soft tissue-only extensor-sided fixation to the distal quadriceps (MQTFL) during patella stabilization appears to re-create native stability in this time 0 cadaver model. Fixation to the patella (MPFL) was associated with increased resistance to lateral translation. Clinical Relevance: Evolving anatomic knowledge and concern for patellar fracture has led to increased interest in MQTFL reconstruction. Both MQTFL and MPFL reconstructions restored patellofemoral stability to lateral translation without increasing contact pressures under appropriate graft tensioning, with MQTFL more closely restoring native resistance to lateral translation at the time of surgery.

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26

Lin, Ying, Juan Zhao, Shipei Chen, Xuebin Zeng, Qiong Du, Yang Yang, Fang Lu, Yonghong Pu e Zhenglin Yang. "A novel mutation in LMX1B gene causes nail-patella syndrome in a large Chinese family". Bone 43, n. 3 (settembre 2008): 591–95. http://dx.doi.org/10.1016/j.bone.2008.04.025.

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27

Michaelidis, B., A. Lazou e I. Beis. "Purification, catalytic and regulatory properties of pyruvate kinase from the foot of Patella caerulea (L.)". Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 82, n. 2 (gennaio 1985): 405–12. http://dx.doi.org/10.1016/0305-0491(85)90260-3.

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28

Lazou, A., C. Gaitanaki, B. Michaelidis, A. Papadopoulos e Is Beis. "Purification, catalytic and regulatory properties of malate dehydrogenase from the foot of Patella caerulea (L.)". Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 88, n. 4 (gennaio 1987): 1033–40. http://dx.doi.org/10.1016/0305-0491(87)90002-2.

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29

Newberry, W. N., J. J. Garcia, C. D. Mackenzie, C. E. Decamp e R. C. Haut. "Analysis of Acute Mechanical Insult in an Animal Model of Post-traumatic Osteoarthrosis". Journal of Biomechanical Engineering 120, n. 6 (1 dicembre 1998): 704–9. http://dx.doi.org/10.1115/1.2834882.

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Chronic degeneration of articular cartilage and bone in a rabbit model of post-traumatic osteoarthrosis has been hypothesized to occur due to acute stresses that exceed a threshold for injury. In this study, we impacted the rabbit patellofemoral joint at low and high intensities. High-intensity impacts produced degenerative changes in the joint, such as softening of retropatellar cartilage, as measured by indentation, an increase in histopathology of the cartilage, and an increase in thickness of sub-chondral bone underlying the cartilage. Low-intensity impacts did not cause these progressive changes. These data suggest that low-intensity impacts produced acute tissue stresses below the injury threshold, while high-intensity impacts produced stresses that exceeded the threshold for disease pathogenesis. This study begins to identify “safe” and “unsafe” ranges of acute tissue stress, using the rabbit patella, which may have future utility in the design of injury prevention devices for the human.

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30

Brazão, Sónia, Sofia Morais, Diana Boaventura, Pedro Ré, Luı́s Narciso e Stephen J. Hawkins. "Spatial and temporal variation of the fatty acid composition of Patella spp. (Gastropoda: Prosobranchia) soft bodies and gonads". Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 136, n. 3 (novembre 2003): 425–41. http://dx.doi.org/10.1016/s1096-4959(03)00243-4.

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31

Michaelidis, Basile, e Isidoros Beis. "Studies on the anaerobic energy metabolism in the foot muscle of marine gastropod Patella caerulea (L.)". Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 95, n. 3 (gennaio 1990): 493–500. http://dx.doi.org/10.1016/0305-0491(90)90009-i.

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32

Rådegran, G., E. Blomstrand e B. Saltin. "Peak muscle perfusion and oxygen uptake in humans: importance of precise estimates of muscle mass". Journal of Applied Physiology 87, n. 6 (1 dicembre 1999): 2375–80. http://dx.doi.org/10.1152/jappl.1999.87.6.2375.

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The knee extensor exercise model was specifically developed to enable in vivo estimates of peak muscle blood flow and O2 uptake in humans. The original finding, using thermodilution measurements to measure blood flow in relation to muscle mass [P. Andersen and B. Saltin. J. Physiol. (Lond.) 366: 233–249, 1985], was questioned, however, as the measurements were two- to threefold higher than those previously obtained with the133Xe clearance and the plethysmography technique. As thermodilution measurements have now been confirmed by other methods and independent research groups, we aimed to address the impact of muscle mass estimates on the peak values of muscle perfusion and O2 uptake. In the present study, knee extensor volume was determined from multiple measurements with computer tomography along the full length of the muscle. In nine healthy humans, quadriceps muscle volume was 2.36 ± 0.17 (range 1.31–3.27) liters, corresponding to 2.48 ± 0.18 (range 1.37–3.43) kg. Anthropometry overestimated the muscle volume by ∼21–46%, depending on whether quadriceps muscle length was estimated from the patella to either the pubic bone, inguinal ligament, or spina iliaca anterior superior. One-legged, dynamic knee extensor exercise up to peak effort of 67 ± 7 (range 55–100) W rendered peak values for leg blood flow (thermodilution) of 5.99 ± 0.66 (range 4.15–9.52) l/min and leg O2 uptake of 856 ± 109 (range 590–1,521) ml/min. Muscle perfusion and O2 uptake reached peak values of 246 ± 24 (range 149–373) and 35.2 ± 3.7 (range 22.6–59.6) ml ⋅ min−1 ⋅ 100 g muscle−1, respectively. These peak values are ∼19–33% larger than those attained by applying anthropometric muscle mass estimates. In conclusion, the present findings emphasize that peak perfusion and O2 uptake in human skeletal muscle may be up to ∼30% higher than previous anthropometric-based estimates that use equivalent techniques for blood flow measurements.

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33

Michaelidis, B., A. Lazou e Is Beis. "The possible role of glycolytic enzyme binding in the control of glycolysis in Patella caerulea foot muscle during stimulation". Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 93, n. 2 (gennaio 1989): 247–50. http://dx.doi.org/10.1016/0305-0491(89)90076-x.

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34

Seyfarth, E. A., e A. S. French. "Intracellular characterization of identified sensory cells in a new spider mechanoreceptor preparation". Journal of Neurophysiology 71, n. 4 (1 aprile 1994): 1422–27. http://dx.doi.org/10.1152/jn.1994.71.4.1422.

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1. We have developed an isolated mechanoreceptor-organ preparation in which the intact sensory structures are available for mechanical stimulation and electrical recording. The anterior lyriform slit sense organ on the patella of the spider, Cupiennius salei Keys., consists of seven or eight cuticular slits, each innervated by a pair of large bipolar sensory neurons. The neurons are fusiform, and the largest somata are < or = 120 microns long. The innervation of the organ was characterized by light microscopy of neurons backfilled with neuronal tracers. Intracellular recording was used to measure the passive and active electrical properties of the neurons, in several cases followed by identification with Lucifer yellow injection. Both neurons of each pair from one slit responded with action potentials to depolarization by a step current injection. Approximately half of the sensory neurons adapted very rapidly and generated only one or two action potentials in response to a sustained depolarizing step, while a second group produced a burst of action potentials that adapted to silence in approximately 1 s or less. Recordings from identified neuron pairs indicated that each pair consists of one rapidly adapting and one bursting neuron. Measurements of cell membrane impedances and time constants produced estimates of neuronal size that agreed with the morphological measurements. This new preparation offers the possibility of characterizing the mechanisms underlying transduction and adaptation in primary mechanosensory neurons.

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35

Li, Guoan, Louis DeFrate, Jeremy Suggs e Thomas Gill. "Determination of Optimal Graft Lengths for Posterior Cruciate Ligament Reconstruction—A Theoretical Analysis". Journal of Biomechanical Engineering 125, n. 2 (1 aprile 2003): 295–99. http://dx.doi.org/10.1115/1.1554409.

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Various graft materials have been used in posterior cruciate ligament (PCL) reconstruction. However, it is unclear if these grafts can reproduce the structural behavior of the PCL. This paper analyzed the effect of graft length on the structural behavior of the graft using a minimal deformation energy method. An analytical solution was obtained to determine the optimal effective graft length that can best reproduce the structural behavior of the PCL. This optimal graft length was determined as a function of the axial rigidity of the graft. Two typical grafts, bone-patella tendon-bone (BPTB) and Achilles tendon, were analyzed. The data demonstrated that in order to reproduce the PCL behavior, the effective length of a BPTB graft (10 mm width) should be 34 mm, while the Achilles tendon graft (with a cross sectional area of 55 mm2) needs to be 48 mm in length. Longer grafts result in less resistance and shorter graft increased the graft resistance. An initial graft tension cannot help recreate the overall structural behavior of the PCL. These results suggest that graft length is an important surgical variable in PCL reconstruction. An optimal reconstruction of the PCL should reproduce the structural properties of the PCL by using a graft with an optimal length.

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36

Höger, Ulli, Päivi H. Torkkeli, Ernst-August Seyfarth e Andrew S. French. "Ionic Selectivity of Mechanically Activated Channels in Spider Mechanoreceptor Neurons". Journal of Neurophysiology 78, n. 4 (1 ottobre 1997): 2079–85. http://dx.doi.org/10.1152/jn.1997.78.4.2079.

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Abstract (sommario):

Höger, Ulli, Päivi H. Torkkeli, Ernst-August Seyfarth, and Andrew S. French. Ionic selectivity of mechanically activated channels in spider mechanoreceptor neurons. J. Neurophysiol. 78: 2079–2085, 1997. The lyriform slit-sense organ on the patella of the spider, Cupiennius salei, consists of seven or eight slits, with each slit innervated by a pair of mechanically sensitive neurons. Mechanotransduction is believed to occur at the tips of the dendrites, which are surrounded by a Na+-rich receptor lymph. We studied the ionic basis of sensory transduction in these neurons by voltage-clamp measurement of the receptor current, replacement of extracellular cations, and application of specific blocking agents. The relationship between mechanically activated current and membrane potential could be approximated by the Goldman-Hodgkin-Katz current equation, with an asymptotic inward conductance of ∼4.6 nS, indicating that 50–230 channels of 20–80 pS each would suffice to produce the receptor current. Amiloride and gadolinium, which are known to block mechanically activated ion channels, also blocked the receptor current. Ionic replacement showed that the channels are not permeable to choline or Rb+, but are partly permeable to Li+. The receptor current was inward at all membrane potentials (−200 to +200 mV) and never reversed, indicating high selectivity for Na+ over K+. This situation contrasts strongly with insect mechanoreceptors, vertebrate hair cells, and mechanically activated ion channels in nonsensory cells, most of which are either unselective for monovalent cations or selective for K+.

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37

Boyd, S. K., J. L. Ronsky, D. D. Lichti, D. Sˇalkauskas e M. A. Chapman. "Joint Surface Modeling With Thin-Plate Splines". Journal of Biomechanical Engineering 121, n. 5 (1 ottobre 1999): 525–32. http://dx.doi.org/10.1115/1.2835083.

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Mathematical joint surface models based on experimentally determined data points can be used to investigate joint characteristics such as curvature, congruency, cartilage thickness, joint contact areas, as well as to provide geometric information well suited for finite element analysis. Commonly, surface modeling methods are based on B-splines, which involve tensor products. These methods have had success; however, they are limited due to the complex organizational aspect of working with surface patches, and modeling unordered, scattered experimental data points. An alternative method for mathematical joint surface modeling is presented based on the thin-plate spline (TPS). It has the advantage that it does not involve surface patches, and can model scattered data points without experimental data preparation. An analytical surface was developed and modeled with the TPS to quantify its interpolating and smoothing characteristics. Some limitations of the TPS include discontinuity of curvature at exactly the experimental surface data points, and numerical problems dealing with data sets in excess of 2000 points. However, suggestions for overcoming these limitations are presented. Testing the TPS with real experimental data, the patellofemoral joint of a cat was measured with multistation digital photogrammetry and modeled using the TPS to determine cartilage thicknesses and surface curvature. The cartilage thickness distribution ranged between 100 to 550 μm on the patella, and 100 to 300 μm on the femur. It was found that the TPS was an effective tool for modeling joint surfaces because no preparation of the experimental data points was necessary, and the resulting unique function representing the entire surface does not involve surface patches. A detailed algorithm is presented for implementation of the TPS.

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38

Gouze-Decaris, Elvire, Lionel Philippe, Alain Minn, Philippe Haouzi, Pierre Gillet, Patrick Netter e Bernard Terlain. "Neurophysiological basis for neurogenic-mediated articular cartilage anabolism alteration". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 280, n. 1 (1 gennaio 2001): R115—R122. http://dx.doi.org/10.1152/ajpregu.2001.280.1.r115.

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This study was designed to investigate the pathways involved in neurogenic-mediated articular cartilage damage triggered by a nonsystemic distant subcutaneous or intra-articular inflammation. The cartilage damage was assessed 24 h after subcutaneous or intra-articular complete Freund's adjuvant (CFA) injection measuring patellar proteoglycan (PG) synthesis (ex vivo [Na2 35SO4] incorporation) in 96 Wistar rats. Unilateral subcutaneous or intra-articular injection of CFA induced significant decrease (25–29%) in PG synthesis in both patellae. Chronic administration of capsaicin (50 mg · kg−1 · day−1 during 4 days), which blunted the normal response of C fiber stimulation, prevented the bilateral significant decrease in cartilage synthesis. Similarly, intrathecal injection of MK-801 (10 nmol/day during 5 days), which blocked the glutamatergic synaptic transmission at the dorsal horn of signal originating in primary afferent C fibers, eliminated the CFA-induced PG synthesis decrease in both patellae. Chemical sympathectomy, induced by guanethidine (12.5 mg · kg−1 · day−1 during 6 wk), also prevented PG synthesis alteration. Finally, compression of the spinal cord at the T3-T5 level had a similar protective effect on the reduction of [Na2 35SO4] incorporation. It is concluded that the signal that triggers articular cartilage synthesis damage induced by a distant local inflammation 1) is transmitted through the afferent C fibers, 2) makes glutamatergic synaptic connections with the preganglionic neurons of the sympathetic system, and 3) involves spinal and supraspinal pathways.

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Haut, R. C., T. M. Ide e C. E. De Camp. "Mechanical Responses of the Rabbit Patello-Femoral Joint to Blunt Impact". Journal of Biomechanical Engineering 117, n. 4 (1 novembre 1995): 402–8. http://dx.doi.org/10.1115/1.2794199.

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Abstract (sommario):

Various studies suggest impact trauma may initially soften cartilage, damage subchondral bone, or a combination thereof. The initial damages are commonly thought due to excessive contact pressures generated on cartilage and the underlying bone. The objective of this research was to develop a small animal model for studying post-traumatic OA and to correlate contact pressures with tissue damage. Blunt insult was graded by dropping a rigid mass onto the hyperflexed hind limb of rabbits. Contact pressure in the patello-femoral joint was measured with pressure sensitive film. One, 3, 6, and 14 days later the animals were euthanized. Damage to cartilage and the underlying bone was assessed visually and in microscopic sections. Indentation experiments were performed on the patellar cartilage with a rigid, flat probe. Contact pressures were nonuniform over the articular surfaces and a high frequency of surface fissures were generated on the lateral facet in severe insults. The appearance of surface fissures correlated better with the magnitude of contact pressure gradients in the damage zone than the magnitude of contact pressures on the facet, per se. Blunt trauma causing surface fissures resulted in a measurable degree of softening in the patellar cartilage, especially close to the defects. Surgical intervention of the joint to insert pressure sensitive film, however, also resulted in significant softening of the cartilage.

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40

Kenny, Glen P., Frank D. Reardon, Michel B. Ducharme, Mark L. Reardon e Wytek Zaleski. "Tissue Temperature Transients in Resting Contra-Lateral Leg Muscle Tissue During Isolated Knee Extension". Canadian Journal of Applied Physiology 27, n. 6 (1 dicembre 2002): 535–50. http://dx.doi.org/10.1139/h02-030.

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Abstract (sommario):

This study was designed to evaluate the role of non-active tissue in the retention and dissipation of heat during and following intense isolated muscle activity. Six subjects performed an incremental isotonic test (constant angular velocity, increases in force output) on a KIN-COM' isokinetic apparatus to determine their maximal oxygen consumption during single knee extensions [Formula: see text] In a subsequent session, a thin wire multi-sensor temperature probe was inserted into the left vastus medialis under ultrasound guidance at a specific internal marker. The deepest temperature sensor (tip, Tmu10) was located ∼10 mm from the femur and deep femoral artery with 2 additional sensors located at 15 (Tmu25) and 30 (Tmu40) mm from the tip. Implant site was midway between and medial to a line joining the anterior superior iliac spine and base of patella. Esophageal temperature (Tes) temperature was measured as an index of core temperature. Subjects rested in a supine position for 60 min followed by 30 min of seated rest in an ambient condition of 22 °C. Subjects then performed 15 min of isolated single right knee extensions against a dynamic resistance on a KIN COM corresponding to 60% of [Formula: see text] at 60° • sec−1. Exercise was followed by 60 min of seated rest. Resting Tes was 37 °C while Tmu10, Tmu25, and Tmu40 were 36.58, 36.55 and 36.45 °C, respectively. Exercise resulted in a Tes increase of 0.31 °C above pre-exercise resting. Tmu of the non-exercising leg increased 0.23, 0.19 and 0.09 °C for Tmu10, Tmu25, and Tmu40, respectively. While Tes decreased to baseline values within ∼15 min of end-exercise, Tmu10 reached resting values following ∼40 min of recovery. These results suggest that during isolated muscle activity, convective heat transfer by the blood to non-active muscle tissue may have a significant role in maintaining resting core temperature. Key words: heat load, thermoregulation, hyperthermia

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41

Garcia, J. J., N. J. Altiero e R. C. Haut. "An Approach for the Stress Analysis of Transversely Isotropic Biphasic Cartilage Under Impact Load". Journal of Biomechanical Engineering 120, n. 5 (1 ottobre 1998): 608–13. http://dx.doi.org/10.1115/1.2834751.

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Abstract (sommario):

Stress analysis of contact models for isotropic articular cartilage under impacting loads shows high shear stresses at the interface with the subchondral bone and normal compressive stresses near the surface of the cartilage. These stress distributions are not consistent, with lesions observed on the cartilage surface of rabbit patellae from blunt impact, for example, to the patello-femoral joint. The purpose of the present study was to analyze, using the elastic capabilities of a finite element code, the stress distribution in more morphologically realistic transversely isotropic biphasic contact models of cartilage. The elastic properties of an incompressible material, equivalent to those of the transversely isotropic biphasic material at time zero, were derived algebraically using stress-strain relations. Results of the stress analysis showed the highest shear stresses on the surface of the solid skeleton of the cartilage and tensile stresses in the zone of contact. These results can help explain the mechanisms responsible for surface injuries observed during blunt insult experiments.

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42

Hagan, Kenton L., Todd Hullfish, Ellen Casey e Josh R. Baxter. "Tendon structure quantified using ultrasound imaging differs based on location and training type". Journal of Applied Physiology 125, n. 6 (1 dicembre 2018): 1743–48. http://dx.doi.org/10.1152/japplphysiol.00723.2018.

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Abstract (sommario):

Achilles tendinopathy is 10 times more common among running athletes compared with age-matched peers. Load-induced tendon remodeling and its progression in an at-risk population of developing symptomatic tendinopathy are not well understood. The purpose of this study was to prospectively characterize Achilles and patellar tendon structure in competitive collegiate distance runners over different competitive seasons using quantitative ultrasound imaging. Twenty-two collegiate cross-country runners and eleven controls were examined for this study. Ultrasound images of bilateral Achilles and patellar tendons were obtained near the start and end of the collegiate cross-country season and the conclusion outdoor track season. Collagen organization, mean echogenicity, tendon thickness, and neovascularity were determined using well-established image processing techniques. Achilles tendon collagen was less aligned in runners compared with controls (28% greater) but improved slightly (7% decrease) after the completion of the track season. Conversely, patellar tendons in runners were similar to control tendons throughout the cross-country season but underwent collagen alignment (17% decrease) and tendon hypertrophy (21% increase). Our findings indicate that Achilles tendon structure in trained runners differs structurally from control tendons but is stable throughout training while patellar tendon structure changes in response to the transition in training volume between cross-country and track seasons. These findings expand upon prior reports that some degree of tendon remodeling may act as a protective adaptation for sport specific loading. NEW & NOTEWORTHY In this study we prospectively examined the Achilles and patellar tendon structure of distance runners to determine if continued training through multiple seasons elicits tendon remodeling or pathology. We found that Achilles and patellar tendons respond uniquely to the changing loads required during each season. Achilles tendon collagen alignment is mostly stable throughout the competitive cycle, but the patellar tendon structurally remodels following the transition from cross-country to track season.

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43

Hsieh, Yeou-Fang, Louis F. Draganich, Sherwin H. Ho e Bruce Reider. "The Effects of Removal and Reconstruction of the Anterior Cruciate Ligament on Patellofemoral Kinematics". American Journal of Sports Medicine 26, n. 2 (marzo 1998): 201–9. http://dx.doi.org/10.1177/03635465980260020901.

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Abstract (sommario):

Patellofemoral pain may be associated with anterior cruciate ligament deficiency or may occur after anterior cruciate ligament reconstruction. We investigated the effects of the removal and reconstruction of the anterior cruciate ligament on the kinematics of the tibiofemoral and patellofemoral joints during physiologic levels of quadriceps muscle loads in seven cadaveric knees. A bone-patellar tendon-bone graft was used for intraarticular reconstruction of the anterior cruciate ligament. The spatial positions of the tibiofemoral and patellofemoral joints were measured between 0° and 90° of knee flexion in 15° increments with a six degree-of-freedom digitizing system. Excision of the anterior cruciate ligament resulted in statistically significant increases in anterior tibial translation between 0° and 90° and valgus tibial rotation between 30° and 90°; intraarticular reconstruction returned these to levels not significantly different from those of the intact knee. Excision of the anterior cruciate ligament resulted in significant increases in lateral patellar tilt, ranging from 6.3° to 9.0° between full extension and 90° of knee flexion, and in lateral patellar shift, ranging from 2.9 mm at 15° of knee flexion to 5.9 mm at 90°; intraarticular reconstruction returned these to levels not significantly different from those of the intact knee. Neither removal nor reconstruction of the anterior cruciate ligament significantly affected tibial internal-external rotation, patellar flexion, patellar mediolateral rotation, patellar anteroposterior translation, or patellar proximodistal translation.

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44

Safronov, V. A. "Patellar reflex: II. Associated activation". Human Physiology 32, n. 4 (luglio 2006): 445–49. http://dx.doi.org/10.1134/s0362119706040104.

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45

Kalliokoski, Kari K., Henning Langberg, Ann Kathrine Ryberg, Celena Scheede-Bergdahl, Simon Doessing, Andreas Kjaer, Robert Boushel e Michael Kjaer. "The effect of dynamic knee-extension exercise on patellar tendon and quadriceps femoris muscle glucose uptake in humans studied by positron emission tomography". Journal of Applied Physiology 99, n. 3 (settembre 2005): 1189–92. http://dx.doi.org/10.1152/japplphysiol.00283.2005.

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Abstract (sommario):

Both tendon and peritendinous tissue show evidence of metabolic activity, but the effect of acute exercise on substrate turnover is unknown. We therefore examined the influence of acute exercise on glucose uptake in the patellar and quadriceps tendons during dynamic exercise in humans. Glucose uptake was measured in five healthy men in the patellar and quadriceps tendons and the quadriceps femoris muscle at rest and during dynamic knee-extension exercise (25 W) using positron emission tomography and [18F]-2-fluoro-2-deoxy-d-glucose ([18F]FDG). Glucose uptake index was calculated by dividing the tissue activity with blood activity of [18F]FDG. Exercise increased glucose uptake index by 77% in the patellar tendon (from 0.30 ± 0.09 to 0.51 ± 0.16, P = 0.03), by 106% in the quadriceps tendon (from 0.37 ± 0.15 to 0.75 ± 0.36, P = 0.02), and by 15-fold in the quadriceps femoris muscle (from 0.31 ± 0.11 to 4.5 ± 1.7, P = 0.005). The exercise-induced increase in the glucose uptake in neither tendon correlated with the increase in glucose uptake in the quadriceps muscle ( r = −0.10, P = 0.87 for the patellar tendon and r = −0.30, P = 0.62 for the quadriceps tendon). These results show that tendon glucose uptake is increased during exercise. However, the increase in tendon glucose uptake is less pronounced than in muscle and the increases are uncorrelated. Thus tendon glucose uptake is likely to be regulated by mechanisms independently of those regulating skeletal muscle glucose uptake.

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46

Carroll, C. C., J. M. Dickinson, J. K. LeMoine, J. M. Haus, E. M. Weinheimer, C. J. Hollon, P. Aagaard, S. P. Magnusson e T. A. Trappe. "Influence of acetaminophen and ibuprofen on in vivo patellar tendon adaptations to knee extensor resistance exercise in older adults". Journal of Applied Physiology 111, n. 2 (agosto 2011): 508–15. http://dx.doi.org/10.1152/japplphysiol.01348.2010.

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Millions of older individuals consume acetaminophen or ibuprofen daily and these same individuals are encouraged to participate in resistance training. Several in vitro studies suggest that cyclooxygenase-inhibiting drugs can alter tendon metabolism and may influence adaptations to resistance training. Thirty-six individuals were randomly assigned to a placebo (67 ± 2 yr old), acetaminophen (64 ± 1 yr old; 4,000 mg/day), or ibuprofen (64 ± 1 yr old; 1,200 mg/day) group in a double-blind manner and completed 12 wk of knee extensor resistance training. Before and after training in vivo patellar tendon properties were assessed with MRI [cross-sectional area (CSA) and signal intensity] and ultrasonography of patellar tendon deformation coupled with force measurements to obtain stiffness, modulus, stress, and strain. Mean patellar tendon CSA was unchanged ( P > 0.05) with training in the placebo group, and this response was not influenced with ibuprofen consumption. Mean tendon CSA increased with training in the acetaminophen group (3%, P < 0.05), primarily due to increases in the mid (7%, P < 0.05) and distal (8%, P < 0.05) tendon regions. Correspondingly, tendon signal intensity increased with training in the acetaminophen group at the mid (13%, P < 0.05) and distal (15%, P = 0.07) regions. When normalized to pretraining force levels, patellar tendon deformation and strain decreased 11% ( P < 0.05) and stiffness, modulus, and stress were unchanged ( P > 0.05) with training in the placebo group. These responses were generally uninfluenced by ibuprofen consumption. In the acetaminophen group, tendon deformation and strain increased 20% ( P < 0.05) and stiffness (−17%, P < 0.05) and modulus (−20%, P < 0.05) decreased with training. These data suggest that 3 mo of knee extensor resistance training in older adults induces modest changes in the mechanical properties of the patellar tendon. Over-the-counter doses of acetaminophen, but not ibuprofen, have a strong influence on tendon mechanical and material property adaptations to resistance training. These findings add to a growing body of evidence that acetaminophen has profound effects on peripheral tissues in humans.

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47

Vailas, A. C., D. M. Deluna, L. L. Lewis, S. L. Curwin, R. R. Roy e E. K. Alford. "Adaptation of bone and tendon to prolonged hindlimb suspension in rats". Journal of Applied Physiology 65, n. 1 (1 luglio 1988): 373–76. http://dx.doi.org/10.1152/jappl.1988.65.1.373.

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The rat hindlimb suspension model was used to ascertain the importance of ground reaction forces in maintaining bone and tendon homeostasis. Young female Sprague-Dawley rats were randomly assigned to either a suspended or a nonsuspended group. After 28 days, femur bones and patellar tendons were obtained for morphological and biochemical analyses. Prolonged suspension induced a significant change in the geometric configuration of the femur middiaphysis by increasing the minimum diameter (12%) without any significant alterations in cortical area, density, mineral, and collagen concentrations. Femur wet weight, length, DNA, and uronic acid concentrations of suspended animals were not significantly different from bones of nonsuspended rats. However, the collagen and proteoglycan concentrations in patellar tendons of suspended rats were 28% lower than the concentrations of matrix proteins in tissues obtained from nonsuspended animals. These data suggest that elimination of ground reaction forces induces alterations in tendon composition and femur diaphyseal shape by changing regional rates in bone remodeling and localized tendon strain. Therefore it appears that ground reaction forces are an important factor in the maintenance of cortical bone and patellar tendon homeostasis during weight-bearing conditions.

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48

Adams, D. J., K. M. Brosche e J. L. Lewis. "Effect of Specimen Thickness on Fracture Toughness of Bovine Patellar Cartilage". Journal of Biomechanical Engineering 125, n. 6 (1 dicembre 2003): 927–29. http://dx.doi.org/10.1115/1.1635405.

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Fracture toughness and crack tip opening angle were measured for bovine patellar cartilage using modified single-edged notch specimens of two thicknesses. There was no difference in fracture toughness between thin (0.7 mm) versus relatively thick (2.7 mm) specimens, but the crack tip opening angle at initiation of crack propagation was larger for the thin specimens (106 deg) than for the thick specimens (70 deg). Fracture toughness of the bovine patellar cartilage 1.03kJ/m2 was not statistically different than that reported previously for canine patellar cartilage 1.07kJ/m2 employing the same methods. Large variation in measurements for both bovine and canine cartilage are in part attributable to variation between individual animals, and are consistent with variation in other mechanical property measurements for articular cartilage. The observed reduction in crack tip opening angle with increased specimen thickness is consistent with behavior of some engineering materials, and demonstrates that specimen thickness influences fracture behavior for bovine patellar cartilage.

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49

Wilson, Nicole A., Joel M. Press e Li-Qun Zhang. "In vivo strain of the medial vs. lateral quadriceps tendon in patellofemoral pain syndrome". Journal of Applied Physiology 107, n. 2 (agosto 2009): 422–28. http://dx.doi.org/10.1152/japplphysiol.00024.2009.

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Patellofemoral pain (PFP) is thought to be related to patellar maltracking due to imbalances in the knee extensor. However, no study has evaluated the in vivo biomechanical properties of the quadriceps tendon in PFP syndrome. Our purpose was to compare the biomechanical properties of the quadriceps tendons in vivo and noninvasively in patients with PFP syndrome to those of control subjects. The null hypothesis was that the quadriceps tendons of PFP subjects would have significantly decreased strain compared with control subjects. Fourteen subjects (7 control, 7 PFP) performed voluntary ramp isometric contractions to a range of torque levels, while quadriceps tendon elongation was measured using ultrasonography. Tendon strain was calculated for the vastus medialis obliquus (VMO) and vastus lateralis (VL) portion of the quadriceps tendon and compared between subjects (control vs. PFP) and within subjects (VMO vs. VL). PFP subjects showed significantly less VMO tendon strain than control subjects ( P < 0.001), but there was no difference in VL tendon strain between PFP and control subjects ( P = 0.100). Relative weakness of the VMO is the most likely cause of the decreased tendon strain seen in subjects with PFP. VMO weakness not only explains the decreased medial tendon strain but also explains the presence of increased lateral patellar translation and lateral patellar spin (distal pole rotates laterally) reported in the literature in this population. This technique can potentially be used in a clinical setting to evaluate quadriceps tendon properties and infer the presence of muscle weakness in PFP.

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50

Safronov, V. A. "Patellar reflex: I. Studies in healthy subjects". Human Physiology 32, n. 2 (marzo 2006): 157–60. http://dx.doi.org/10.1134/s036211970602006x.

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