Artículos de revistas: "Stabilità posteriore"

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RE, M., M. IACOANGELI, L. DI SOMMA, L. ALVARO, D. NASI, G. MAGLIULO, F. M. GIOACCHINI, D. FRADEANI y M. SCERRATI. "Approccio endoscopico endonasale alla giunzione craniocervicale: l’importanza di preservare o ricostruire l’arco anteriore dell’atlante". Acta Otorhinolaryngologica Italica 36, n.º 2 (abril de 2016): 107–18. http://dx.doi.org/10.14639/0392-100x-647.

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Riportiamo la nostra esperienza con l’approccio endoscopico endonasale (EEA) in una serie consecutiva di 10 pazienti affetti da lesioni anteriori della giunzione cranio-cervicale. L’obiettivo dello studio è analizzare l’outcome di questi pazienti focalizzando l’attenzione sulla possibilità di preservare o ricostruire l’arco anteriore di C1, quale importante elemento di stabilità della giunzione cranio-cervicale. Dal gennaio 2009 al dicembre 2013, 10 pazienti con patologia della giunzione craniocervicale sono stati operati mediante approccio endoscopico endonasale. Le lesioni trattate includevano 4 casi di non riducibile compressione bulbo-midollare extradurale anteriore della giunzione (secondarie ad artrite reumatoide o anomalie della giunzione), 4 casi di fratture inveterate di C1 o del dente dell’epistrofeo e 2 casi lesioni tumorali. La valutazione clinica pre- e postoperatoria è stata effettuata mediante la scala di Ranawat per i casi di artrite reumatoide e di Nurick per gli altri. Il follow-up radiologico comprendeva invece RM, TC e RX con prove morfo-dinamiche per eventuale preesistente severa instabilità. Dopo l’approccio EEA puro alla giunzione craniocervicale, nessun paziente ha presentato un peggioramento neurologico, né si sono verificate significative complicanze. Al follow-up medio di 31 mesi (range 14-73 mesi), un miglioramento di almeno un livello della classificazione Ranawat o Nurick si è osservato in 6 pazienti mentre gli altri 4 sono rimasti stabili. Il follow-up neuroradiologico ha documentato in tutti i casi un’adeguata decompressione bulbo-midollare, mentre nei casi di frattura di C1 o C2 una regolare fusione ossea delle rime di frattura. Nessun paziente ha presentato segni di instabilità e non è stata pertanto necessaria alcuna procedura di stabilizzazione e fusione posteriore. L’approccio endoscopico endonasale garantisce un’adeguata esposizione delle lesioni antero-mediali della giunzione craniocervicale. Nella nostra serie di pazienti tale procedura ha permesso di preservare o ricostruire l’arco anteriore di C1, evitando quindi una sintesi posteriore e la relativa perdita di movimento rotazionale C0-C2 e l’instabilità subassiale.

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Biroli, F., F. De Gonda, L. Torcello, D. Prosetti, O. Manara y V. Cassinari. "Fratture del dente dell'epistrofeo". Rivista di Neuroradiologia 2, n.º 3 (octubre de 1989): 273–78. http://dx.doi.org/10.1177/197140098900200309.

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Le fratture del dente dell'epistrofeo rappresentano circa il 15% delle fratture del rachide cervicale. Vengono esaminati venti casi consecutivi osservati presso la Divisione di Neurochirurgia di Bergamo nel triennio 1984–1987: undici casi erano del secondo tipo di Anderson-D'Alonzo, e nove casi del terzo tipo. In diciassette casi la diagnosi fu tempestiva, mentre in tre la frattura fu misconosciuta e trattata tardivamente. Nel primo gruppo, dopo aver costantemente ottenuto una buona riduzione della frattura, il trattamento iniziale è stato sempre l'applicazione di un presidio di Halo, sotto controllo scopico. II periodo medio di applicazione è stato di 115 giorni. L'unica complicazione osservata è stata il frequente allentamento delle viti del cerchio, talora con flogosi localizzate in relazione al prolungato mantenimento dell'anello. Nel secondo gruppo di pazienti, in cui è sempre stata constatata l'assenza di un callo riparativo, il nostro atteggiamento è stato interventistico, praticando un'artrodesi per via posteriore seguita da applicazione di Halo. Il protocollo di monitoraggio prevede l'esecuzione mensile di radiogrammi standard nelle due proiezioni associati ad uno studio tomografico al fine di valutare la formazione del callo osseo e l'allineamento tra i monconi di frattura. Solo dopo l'osservazione di una soddisfacente riparazione ossea si procede alla rimozione dell'Halo ed all'esecuzione di radiogrammi nelle prove funzionali di estensione e flessione per confermare la stabilità dei monconi. I risultati sono stati complessivamente buoni. Nel primo gruppo tutte le fratture di terzo tipo sono guarite con formazione di callo osseo. Una sola frattura del secondo tipo non ha mostrato alcun fenomeno riparativo a tre mesi, per cui è stata sottoposta ad intervento chirurgico come già indicato, con successiva guarigione. Nel secondo gruppo abbiamo avuto un solo parziale insuccesso dovuto ad un'infezione della ferita chirurgica, guarita comunque per seconda intenzione. In conclusione, le fratture non significativamente dislocate o angolate, siano di secondo o di terzo tipo, meritano a parer nostro un primo approccio conservativo, avendo un'alta probabilità di guarigione. Se dislocate od angolate significativamente, può essere corretto proporre elettivamente la stabilizzazione chirurgica, the rimane comunque la scelta obbligata nei casi di mancata saldatura, di pseudoartrosi o di fratture inveterate. Nel primo caso il trattamento più efficace appare quello con Halo. L'intervento chirurgico è preferibilmente eseguito, secondo varie tecniche fra cui quella da not descritta, per via posteriore.

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Manfrè, L., L. Tomarchio, D. Materazzo, M. Leonardo y C. Cristaudo. "La vertebroplastica nelle neoplasie del rachide". Rivista di Neuroradiologia 15, n.º 4 (agosto de 2002): 461–72. http://dx.doi.org/10.1177/197140090201500416.

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Nonostante il primo trattamento di vertebroplastica percutanea su uomo sia stato eseguito in un paziente affetto da angioma espansivo dell'odontoide, la letteratura scientifica ha focalizzato maggiormente l'attenzione sulle possibilità applicative dell'introduzione del cemento al polimetilmetacrilato nell'ambito di vertebre affette da crolli primitivi da patologia osteoporotica. Negli ultimi anni tuttavia la comunità scientifica ha tuttavia guardato con interesse crescente l'uso della vertebroplastica in corso di neoplasie benigne o maligne a localizzazione vertebrale. La riduzione del rischio di crollo vertebrale fa della vertebroplastica uno dei trattamenti principali nella patologia tumorale vertebrale. La metodica appare quindi sostitutiva, o comunque di sostegno, ai trattamenti radioterapici, non sempre in grado di ottenere un soddisfacente effetto antalgico, meno invasiva della vertebrectomia. In caso di angioma espansivo, infine, la vertebroplastica può precedere, ove necessario, un eventuale trattamento embolizzante con colle della lesione, riducendo il letto vascolare della stessa. Le patologie espansive delle vertebre ove è indicato il trattamento percutaneo di vertebroplastica sono rappresentate dagli angiomi espansivi, dalle localizzazioni intrasomatiche di malattia neoplastica (solitamente neoplasie della serie ematica come la Leucemia Mieloide Cronica o il Mieloma Multiplo) e dalle metastasi, purché sia risparmiato l'arco posteriore vertebrale: una sua eventuale compromissione infatti precluderebbe nella maggior parte dei casi una vera stabilità vertebrale, anche dopo il trattamento, e ridurrebbe comunque le potenzialità antalgiche dello stesso. La scomparsa del dolore dipendente dalla vertebroplastica avviene solitamente in un periodo oscillante tra le prime 24–48 h sino a 30 giorni, con una media di 7 giorni. Il principale rischio della vertebroplastica in corso di patologia tumorale consiste nella fuoriuscita del cemento in sede extravertebrale durante la sua introduzione. La vertebroplastica rappresenta oggi una nuova arma dell'arsenale a disposizione della Neuroradiologia Interventiva per il trattamento di lesioni singole o multiple di natura tumorale della colonna vertebrale.

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Hawthorne, Benjamin C., Michael R. Mancini, Ian J. Wellington, Michael B. DiCosmo, Matthew E. Shuman, Maxwell T. Trudeau, Caitlin G. Dorsey, Elifho Obopilwe, Mark P. Cote y Augustus D. Mazzocca. "Deltotrapezial Stabilization of Acromioclavicular Joint Rotational Stability: A Biomechanical Evaluation". Orthopaedic Journal of Sports Medicine 11, n.º 1 (1 de enero de 2023): 232596712211195. http://dx.doi.org/10.1177/23259671221119542.

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Background: Despite advances in surgical management of acromioclavicular (AC) joint reconstruction, many patients fail to maintain sustained anatomic reduction postoperatively. Purpose: To determine the biomechanical support of the deltoid and trapezius on AC joint stability, focusing on the rotational stability provided by the muscles to posterior and anterior clavicular rotation. A novel technique was attempted to repair the deltoid and trapezius anatomically. Study Design: Controlled laboratory study. Methods: Twelve human cadaveric shoulders (mean ± SD age, 60.25 ± 10.25 years) underwent servohydraulic testing. Shoulders were randomly assigned to undergo serial defects to either the deltoid or trapezius surrounding the AC joint capsule, followed by a combined deltotrapezial muscle defect. Deltotrapezial defects were repaired with an all-suture anchor using an anatomic technique. The torque (N·m) required to rotate the clavicle 20° anterior and 20° posterior was recorded for the following conditions: intact (native), deltoid defect, trapezius defect, combined deltotrapezial defect, and repair. Results: When compared with the native condition, the deltoid defect decreased the torque required to rotate the clavicle 20° posteriorly by 7.1% ( P = .206) and 20° anteriorly by 6.1% ( P = .002); the trapezial defect decreased the amount of rotational torque posteriorly by 5.3% ( P = .079) and anteriorly by 4.9% ( P = .032); and the combined deltotrapezial defect decreased the amount of rotational torque posteriorly by 9.9% ( P = .002) and anteriorly by 9.4% ( P < .001). Anatomic deltotrapezial repair increased posterior rotational torque by 5.3% posteriorly as compared with the combined deltotrapezial defect ( P = .001) but failed to increase anterior rotational torque ( P > .999). The rotational torque of the repair was significantly lower than the native joint in the posterior ( P = .017) and anterior ( P < .001) directions. Conclusion: This study demonstrated that the deltoid and trapezius play a role in clavicular rotational stabilization. The proposed anatomic repair improved posterior rotational stability but did not improve anterior rotational stability as compared with the combined deltotrapezial defect; however, neither was restored to native stability. Clinical Relevance: Traumatic or iatrogenic damage to the deltotrapezial fascia and the inability to restore anatomic deltotrapezial attachments to the acromioclavicular joint may contribute to rotational instability. Limiting damage and improving the repair of these muscles should be a consideration during AC reconstruction.

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Feng, Jie, Xuguang Wang y Jonathan Poterjoy. "A Comparison of Two Local Moment-Matching Nonlinear Filters: Local Particle Filter (LPF) and Local Nonlinear Ensemble Transform Filter (LNETF)". Monthly Weather Review 148, n.º 11 (noviembre de 2020): 4377–95. http://dx.doi.org/10.1175/mwr-d-19-0368.1.

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AbstractThe local particle filter (LPF) and the local nonlinear ensemble transform filter (LNETF) are two moment-matching nonlinear filters to approximate the classical particle filter (PF). They adopt different strategies to alleviate filter degeneracy. LPF and LNETF localize observational impact but use different localization functions. They assimilate observations in a partially sequential and a simultaneous manner, respectively. In addition, LPF applies the resampling step, whereas LNETF applies the deterministic square root transformation to update particles. Both methods preserve the posterior mean and variance of the PF. LNETF additionally preserves the posterior correlation of the PF for state variables within a local volume. These differences lead to their differing performance in filter stability and posterior moment estimation. LPF and LNETF are systematically compared and analyzed here through a set of experiments with a Lorenz model. Strategies to improve the LNETF are proposed. The original LNETF is inferior to the original LPF in filter stability and analysis accuracy, particularly for small particle numbers. This is attributed to both the localization function and particle update differences. The LNETF localization function imposes a stronger observation impact than the LPF for remote grids and thus is more susceptible to filter degeneracy. The LNETF update causes an overall narrower range of posteriors that excludes true states more frequently. After applying the same localization function as the LPF and additional posterior inflation to the LNETF, the two filters reach similar filter stability and analysis accuracy for all particle numbers. The improved LNETF shows more accurate posterior probability distribution but slightly worse spatial correlation of posteriors than the LPF.

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Doğan, Şeref, Seungwon Baek, Volker K. H. Sonntag y Neil R. Crawford. "Biomechanical Consequences of Cervical Spondylectomy Versus Corpectomy". Operative Neurosurgery 63, suppl_4 (1 de octubre de 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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Basu, Sanjib. "Uniform stability of posteriors". Statistics & Probability Letters 46, n.º 1 (enero de 2000): 53–58. http://dx.doi.org/10.1016/s0167-7152(99)00086-3.

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Almeida, Renato Rodrigues de, Marcio Rodrigues de Almeida, Paula Vanessa Pedron Oltramari-Navarro, Ana Cláudia de Castro Ferreira Conti, Ricardo de Lima Navarro y Henry Victor Alves Marques. "Posterior crossbite - treatment and stability". Journal of Applied Oral Science 20, n.º 2 (abril de 2012): 286–94. http://dx.doi.org/10.1590/s1678-77572012000200026.

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Ayanbayev, Birzhan, Ilja Klebanov, Han Cheng Lie y T. J. Sullivan. "Γ -convergence of Onsager–Machlup functionals: I. With applications to maximum a posteriori estimation in Bayesian inverse problems". Inverse Problems 38, n.º 2 (28 de diciembre de 2021): 025005. http://dx.doi.org/10.1088/1361-6420/ac3f81.

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Abstract The Bayesian solution to a statistical inverse problem can be summarised by a mode of the posterior distribution, i.e. a maximum a posteriori (MAP) estimator. The MAP estimator essentially coincides with the (regularised) variational solution to the inverse problem, seen as minimisation of the Onsager–Machlup (OM) functional of the posterior measure. An open problem in the stability analysis of inverse problems is to establish a relationship between the convergence properties of solutions obtained by the variational approach and by the Bayesian approach. To address this problem, we propose a general convergence theory for modes that is based on the Γ-convergence of OM functionals, and apply this theory to Bayesian inverse problems with Gaussian and edge-preserving Besov priors. Part II of this paper considers more general prior distributions.

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Chang, Hsuan-Sung, Jen-Suh Chern y Chi-Wen Long. "P-27 THE EFFECTS OF ANTERIOR AND POSTERIOR ANKLE-FOOT-ORTHOSIS ON POSTURAL STABILITY IN HEMIPLEGIC PATIENTS". Proceedings of the Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2007.3 (2007): S115. http://dx.doi.org/10.1299/jsmeapbio.2007.3.s115.

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Basu, Sanjib, Sreenivasa Rao Jammalamadaka y Wei Liu. "Stability and infinitesimal robustness of posterior distributions and posterior quantities". Journal of Statistical Planning and Inference 71, n.º 1-2 (agosto de 1998): 151–62. http://dx.doi.org/10.1016/s0378-3758(98)00090-1.

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Inoue, Jumpei, Tetsuya Takenaga, Atsushi Tsuchiya, Norio Okubo, Satoshi Takeuchi, Keishi Takaba, Masahiro Nozaki et al. "Ultrasonographic Assessment of Glenohumeral Joint Stability Immediately After Arthroscopic Bankart-Bristow Procedure". Orthopaedic Journal of Sports Medicine 10, n.º 11 (1 de noviembre de 2022): 232596712211316. http://dx.doi.org/10.1177/23259671221131600.

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Background: The changes in glenohumeral joint stability after surgery in a clinical setting are yet unknown. Purpose/Hypothesis: This study aimed to compare the anterior humeral head translation between pre- and postsurgical conditions using ultrasonography. It was hypothesized that ultrasonographic assessment would reveal decreased anterior translation. Study Design: Case series; Level of evidence, 4. Methods: A total of 27 patients (24 male, 3 female; mean age, 24.1 ± 9.7 years) with anterior shoulder instability were studied prospectively. All the patients underwent the arthroscopic Bankart-Bristow procedure under general anesthesia, and ultrasonographic evaluation was performed before and immediately after surgery. The forearm was fixed with an arm positioner in the beach-chair position, and the ultrasonographic transducer was located at the posterior part of the shoulder to visualize the humeral head and glenoid rim at the level of interval between the infraspinatus tendon and teres minor tendon. The upper arm was drawn anteriorly with a 40-N force at 0°, 45°, and 90° of shoulder abduction with neutral rotation. The distance from the posterior edge of the glenoid to that of the humeral head was measured using ultrasonography with and without anterior force. Anterior translation was defined by subtracting the distance with anterior force from the distance without anterior force. Results: The humeral head position was translated posteriorly immediately after surgery in all patients. Anterior translation decreased significantly after surgery at 45° (7.7 ± 4.3 vs 5.8 ± 2.0 mm; P = .031) and 90° (8.9 ± 3.4 vs 6.1 ± 2.2 mm; P < .001) of abduction, whereas there was no difference between pre- and postsurgical translation at 0° of abduction (4.9 ± 2.3 vs 4.0 ± 2.1 mm, P = .089). Conclusion: Ultrasonographic assessment immediately after a Bankart-Bristow procedure showed the humeral head was translated posteriorly relative to the glenoid at 0°, 45°, and 90° of abduction. The surgery also decreased anterior translation in response to an anteriorly directed force at 45° and 90° of abduction.

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Jee, Govind Mohan y Nitin Kumar. "Surgical treatment of acetabular fracture". Indian Journal of Orthopaedics Surgery 8, n.º 1 (15 de marzo de 2022): 67–71. http://dx.doi.org/10.18231/j.ijos.2022.012.

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The kocher -Langenbeck approach is the best suited approach for reduction and fixation of acetabular fracture that require fixation through posterior approach and provides sufficient access to the majority of posterior based acetabular fracture. Accuracy of fracture reduction is the strongest predictor of clinical outcome in acetabular fixation surgery.Twenty four patients with posteriorly based acetabular fracture were treated with open reduction and internal fixation using Kocher- Langenbeck incision. In our series, there were 11 posterior wall, 3 posterior column, 5 transverse, 2 posterior column and posterior wall and 3 transverse and posterior wall fractures. All the patients were in the age group of 30 to 45 years (mean age 38.5 years). Males dominated our series (n=18 i.e. 75%) and right side was more commonly involved in both the sexes (n=14 i.e. 58.33%). Road traffic accident was the leading cause (n=19 i.e. 79.16%). All the patients were operated achieving adequate stability and with utmost soft tissue care. Follow up radiograph were graded according to criteria developed by Matta J et al. A minimum follow up was two years. Patient with accurate reconstruction (n =21 i.e. 87.50%) had good or excellent functional outcome while two patients (08.33%) with inaccurate reduction and one patient (04.16%) with poor reduction had fair and poor outcome respectively. Despite relatively large number of possible complications Kocher–Langenbeck Approach is the best suited approach for posterior acetabular fracture.

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Rahimizadeh, Abolfazl, Naser Asgari, Walter L. Williamson y Shaghayegh Rahimizadeh. "Congenital cervical isthmic spondylolisthesis: A case report". Surgical Neurology International 10 (24 de abril de 2019): 57. http://dx.doi.org/10.25259/sni-92-2019.

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Background: There are only 20 reported cases of cervical isthmic spondylolisthesis in literature that have been surgically managed either anteriorly or posteriorly. Herein, we report such a case managed with circumferential fusion. Case Description: A 27-year-old male became progressively quadriparetic due to cervical isthmic spondylolisthesis at the C6–C7 level. Removal of the posterior arch of C6 with subsequent C5–C7 pedicle screw/rod fixation and anterior interbody fusion resulted in marked recovery and adequate cervical realignment. Conclusion: For patients with cervical isthmic spondylolisthesis, circumferential fusion provides the best surgical option to achieve stability and sagittal balance.

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Geisler, Fred H., Charles Cheng, Attila Poka y Robert J. Brumback. "Anterior Screw Fixation of Posteriorly Displaced Type II Odontoid Fractures". Neurosurgery 25, n.º 1 (1 de julio de 1989): 30–38. http://dx.doi.org/10.1227/00006123-198907000-00006.

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Abstract Posteriorly displaced Type II odontoid fractures (Type II-P) are difficult to stabilize in an anatomic position with accepted methods of posterior atlantoaxial arthrodesis. Nine patients with Type II-P odontoid fractures with 4 to 15 mm displacement were treated with anterior odontoid screw stabilization. Seven of these patients had associated fractures or defects of the posterior arch of the first cervical vertebra (C1). Atlantoaxial posterior arthrodesis in these patients would not have been possible initially because of the lack of structural integrity of the posterior arch of C1. Two patients, later in the study, had no injury to the ring of C1. The odontoid fractures were stabilized with two 4.0-mm cancellous screws inserted through an anterior approach to the neck under fluoroscopic control with the skin incision at the C5 level. Preoperative reduction of the displaced odontoid process and immediate operative stability of the atlantoaxial complex were obtained in each case. No neurological complications related to the procedure occurred. Two patients died of causes unrelated to their cervical fracture surgery. The 7 patients who survived were followed for a minimum of 6 months. Fracture union and cervical stability were demonstrated in each of the surviving patients, without evidence of screw loosening or loss of fixation. Normal range of motion of the neck was documented at follow-up in all surviving patients. Although this series represents a limited experience with this treatment technique, anterior odontoid screw fixation has significant advantages over accepted methods of cervical stabilization for Type II-P odontoid fractures. Immediate cervical stabilization is obtained, with a predictably high rate of fracture union and preservation of atlantoaxial motion. We believe this technique to be the treatment method of choice for Type II-P odontoid fractures displaced 4 mm or more accompanied by fractures of the posterior arch of the first cervical vertebra.

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Yoon, Kyoung Ho, Sung Woo Park, Sang Hak Lee, Man Ho Kim, Soo Yeon Park y Hoon Oh. "Does Cast Immobilization Contribute to Posterior Stability After Posterior Cruciate Ligament Reconstruction?" Arthroscopy: The Journal of Arthroscopic & Related Surgery 29, n.º 3 (marzo de 2013): 500–506. http://dx.doi.org/10.1016/j.arthro.2012.10.019.

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Firoozabadi, Reza, Clay Spitler, Calvin Schlepp, Benjamin Hamilton, Julie Agel, Milton “Chip Routt y Paul Tornetta. "Determining Stability in Posterior Wall Acetabular Fractures". Journal of Orthopaedic Trauma 29, n.º 10 (octubre de 2015): 465–69. http://dx.doi.org/10.1097/bot.0000000000000354.

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Miller, Matthew A., Tyler C. McDonald, Matthew L. Graves, Clay A. Spitler, George V. Russell, LaRita C. Jones, William Replogle, Jeremy A. Wise, Josie Hydrick y Patrick F. Bergin. "Stability of the Syndesmosis After Posterior Malleolar Fracture Fixation". Foot & Ankle International 39, n.º 1 (23 de octubre de 2017): 99–104. http://dx.doi.org/10.1177/1071100717735839.

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Background: We sought to define the rate of syndesmotic instability after anatomic reduction of the posterior malleolus when posterior stabilization of a trimalleolar or trimalleolar equivalent ankle fracture was chosen vs when a supine position and initially conservative management of the posterior elements was chosen. Methods: The types of syndesmotic and posterior malleolar fixation used to treat adult patients with ankle fractures involving the posterior malleolus at our level I trauma center were retrospectively assessed (N = 198). Specifically, both bimalleolar and trimalleolar fractures were included. Exclusion criteria included pilon fractures, trimalleolar fractures with Chaput fragments, and neurologic injury. Demographics, fracture classification, initial operative position, medial clear space, and posterior malleolar fragment size were recorded for each fracture. Results: In total, 151 patients (76.3%) were initially positioned supine, 27.2% of whom had syndesmotic instability requiring operative stabilization. Almost 25% of supine patients also underwent posterior malleolar stabilization for posterior instability. Overall, 73 (48.3%) patients who were initially treated in the supine position needed some form of additional stabilization. Forty-seven patients (23.7%) were initially positioned prone. Syndesmotic stability was restored in 97.9% of these patients. This 2.1% rate of instability vastly differs from the 13-fold higher syndesmotic instability rate observed in the supine group ( P < .001). Conclusion: Our data demonstrate that the rate of syndesmotic instability was reduced in trimalleolar and trimalleolar equivalent fractures when prone positioning and direct fixation of the posterior malleolus were first performed. Using traditional preoperative estimates of posterior stability to determine the need for posterior malleolar fixation may be inadequate since almost a quarter of patients treated supine received posterior stabilization. Level of Evidence: Level III, retrospective comparative series.

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Thongtrangan, Issada, Raju S. V. Balabhadra y Daniel H. Kim. "Management of strut graft failure in anterior cervical spine surgery". Neurosurgical Focus 15, n.º 3 (septiembre de 2003): 1–8. http://dx.doi.org/10.3171/foc.2003.15.3.4.

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Although successfully used, long strut grafts are vulnerable to dislodgment, displacement, fracture, and nonunion, which can require revision surgery; thus, meticulous preparation of the vertebral endplate along with exact sizing and harvesting of the bone graft with plating are essential for successful outcomes. Biomechanical data and previous clinical studies support the addition of posterior fusion and fixation following multilevel (more than two-level) corpectomy. The additional posterior instrumentation moves the instantaneous axis of rotation posteriorly, thus approximating its normal location in the posterior vertebral body (VB). Biomechanically, this protects the graft from excessive loads while in extension and explains the clinical success of circumferential instrumentation for long-segment corpectomy reconstructions. If strut fracture occurs with minimal displacement and the graft position is still satisfactory, application of a halo vest and judicious observation are recommended. Significant displacement, kyphosis, or loss of contact of the graft and VB require revision surgery. In patients requiring revision surgery for nonunion, placement of fibular autograft or allograft with use of bone morphogenetic protein is likely to be beneficial. If questions remain regarding bone quality or construct stability, the supplemental use of posterior stabilization is recommended. Various surgical approaches have been advocated for treatment of symptomatic anterior cervical pseudarthroses or nonunion. It remains controversial as to whether the anterior or posterior approach is best. Adequate understanding of the graft and implant biomechanics are essential for a successful outcome.

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Miller, Mark D., Michael S. Laidlaw y Kadir Buyukdogan. "Anterior versus Posterior Tibial Tunnel Placement in ACL Reconstruction". Orthopaedic Journal of Sports Medicine 6, n.º 3_suppl (1 de marzo de 2018): 2325967118S0000. http://dx.doi.org/10.1177/2325967118s00001.

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Objectives: Previously, we reported that the use of the posterior border of the anterior horn of the lateral meniscus as a landmark for tibial tunnel placement during anatomic ACL reconstruction resulted in a wide variation of tunnel location in the sagittal plane. The effects of such tibial tunnel variations on functional outcomes have not been previously reported. Hypothesis: Anteriorly placed tibial tunnels lead to better anterior knee stability than posteriorly placed tunnels. Study Design: Cohort study, Level of evidence 3. Methods: 71 patients (aged 18-55) underwent isolated unilateral anatomic single bundle primary ACL reconstruction with quadrupled hamstring tendons or bone patellar tendon bone autografts between March 2013 and June 2014 by the same surgeon using an accessory medial portal technique. All guide pins for the tibial tunnel were placed using a 55-degree guide using the posterior border of the anterior horn of the lateral meniscus as a landmark. Following pin placement, a true lateral fluoroscopic image was obtained and these were digitally analyzed to measure the location of the pin along the length of the tibial plateau using the method described by Amis and Jakob. The patients were divided into two groups—one anterior and the other posterior to 40% of the tibial plateau length. Side-to-side difference in anterior knee translation (KT-1000), thigh circumference, range of motion, IKDC and Marx activity scale were evaluated and compared between the groups at a minimum of 2 years following ACL reconstructive surgery. Results: 50 patients (26 in the anterior group and 24 in the posterior group) were avaliable for follow-up at a mean of 2.5 years. There was no difference in the terms of age, sex, BMI, loss of extension, graft type (Hams-BPTB) and size (mm) between the groups (p>.05). In terms of stability, the mean side-to-side difference was 0.19±1.3 mm for anterior group and 1.27 ±1.3 mm for posterior group based on KT-1000 measurements (P<.005). The IKDC (75.1±4.1 vs 79.2±2.8) and Marx activity (6.6±1.05 vs 8.3±1.04) scores were similar in both groups. No difference in thigh circumference was found between the involved and uninvolved extremities of the both groups (-1.48±1.41 vs -1.52±1.17). Conclusion: Using the posterior border of the anterior horn of the lateral meniscus as a landmark yields a wide range of tibial tunnel locations along the tibial plateau. Anterior placement of the tibial tunnel leads to better anterior knee stability than posterior placement does.

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Gibreel, Mona, Mohammed Fouad, Fatma El-Waseef, Nesma El-Amier y Hamdy Marzook. "Clips vs Resilient Liners Used With Bilateral Posterior Prefabricated Bars for Retaining Four Implant-Supported Mandibular Overdentures". Journal of Oral Implantology 43, n.º 4 (1 de agosto de 2017): 273–81. http://dx.doi.org/10.1563/aaid-joi-d-16-00148.

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The objective of this research was to clinically compare peri-implant tissue health of bar-clips vs silicone-resilient liners used with bilateral posterior bars for retaining 4 implant-supported mandibular overdentures. Thirty completely edentulous male patients (mean age, 65 years) were randomly assigned into 2 equal groups. Each patient received 4 implants in the canine and first molar regions of the mandible using a flapless surgical technique. Mandibular overdentures were immediately connected to the implants with bilateral prefabricated instant adjusting bars. According to the method of retention to the bar, 1 group was retained with clips (GI), whereas the other group was retained with a silicone-resilient soft liner (GII). Peri-implant tissue health was evaluated clinically in terms of plaque scores (MPI), bleeding scores (MBI), probing depth (PD), and implant stability (IS). MPI, MBI, and PD were measured at mesial, distal, buccal, and lingual surfaces of each implant. Evaluations were performed 2 weeks (T0), 6 months (T6), and 12 months (T12) after overdenture insertion. Implants of GI with clips demonstrated significant increase in plaque, bleeding, and PD scores compared with those of GII with silicone-resilient liner at all observation times. Implants in GI demonstrated a significant decrease in implant stability compared with those of GII at T6 and T12 anteriorly and at T12 posteriorly. Resilient liners are considered better than bar-clips when used with bilateral posterior bars for retaining implant-supported mandibular overdentures in terms of peri-implant soft tissue health. Bilateral posterior ready-made bars cannot be proposed as a promising design for supporting implant-assisted mandibular overdentures.

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Lampridis, Vasileios, Nikolaos Gougoulias y Anthony Sakellariou. "Stability in ankle fractures". EFORT Open Reviews 3, n.º 5 (mayo de 2018): 294–303. http://dx.doi.org/10.1302/2058-5241.3.170057.

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Medial column (deltoid ligament) integrity is of key importance when considering the stability of isolated lateral malleolus ankle fractures. Weight-bearing radiographs are the best method of evaluating stability of isolated distal fibula fractures. Computed tomography (CT) scanning is mandatory for the assessment of complex ankle fractures, especially those involving the posterior malleolus. Most isolated trans-syndesmotic fibular fractures (Weber-B, SER, AO 44-B) are stable and can safely be treated non-operatively. Posterior malleolus fractures, regardless of size, should be considered for surgical fixation to restore stability, reduce the need for syndesmosis fixation, and improve contact pressure distribution. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170057

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23

Cagini, Carlo, Marco Messina, Marco Lupidi, Francesco Piccinelli, Tito Fiore, Daniela Fruttini y Leopoldo Spadea. "Posterior Corneal Surface Stability after Femtosecond Laser-Assisted Keratomileusis". Journal of Ophthalmology 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/184850.

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The purpose of this study was to evaluate posterior corneal surface variation after femtosecond laser-assisted keratomileusis in patients with myopia and myopic astigmatism. Patients were evaluated by corneal tomography preoperatively and at 1, 6, and 12 months. We analyzed changes in the posterior corneal curvature, posterior corneal elevation, and anterior chamber depth. Moreover, we explored correlation between corneal ablation depth, residual corneal thickness, percentage of ablated corneal tissue, and preoperative corneal thickness. During follow-up, the posterior corneal surface did not have a significant forward corneal shift: no significant linear relationships emerged between the anterior displacement of the posterior corneal surface and corneal ablation depth, residual corneal thickness, or percentage of ablated corneal tissue.

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Morikawa, Daichi, Joel B. Huleatt, Lukas N. Muench, Cameron Kia, Daniel P. Berthold, Mark P. Cote, Elifho Obopilwe, Denis Kelolli, Bastian Scheiderer y Augustus D. Mazzocca. "Posterior Rotational and Translational Stability in Acromioclavicular Ligament Complex Reconstruction: A Comparative Biomechanical Analysis in Cadaveric Specimens". American Journal of Sports Medicine 48, n.º 10 (21 de julio de 2020): 2525–33. http://dx.doi.org/10.1177/0363546520939882.

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Background: Persistent posterior instability of the acromioclavicular (AC) joint is a reported complication after isolated coracoclavicular (CC) reconstruction. Thus, multiple techniques have been proposed attempting to restore biomechanics of the AC ligament complex (ACLC). Purpose/Hypothesis: The purpose was to evaluate the posterior translational and rotational stability of an ACLC reconstruction with a dermal allograft (ACLC patch) as compared with 3 suture brace constructs. It was hypothesized that the ACLC patch would better restore AC joint posterior stability. Study Design: Controlled laboratory study. Methods: A total of 28 cadaveric shoulders (mean ± SD age, 57.6 ± 8.3 years) were randomly assigned to 1 of 4 surgical techniques: ACLC patch, oblique brace, anterior brace, and x-frame brace. The force and torque to achieve 10 mm of posterior translation and 20° of posterior rotation of the AC joint were recorded in the following conditions: intact, transected ACLC, ACLC patch/brace repair, ACLC patch/brace repair with dissected CC ligaments, and ACLC patch/brace repair with CC ligament repair. Results: For posterior translation, transection of the ACLC reduced resistance to 16.7% of the native. With the native CC ligaments intact, the ACLC patch (59.1%), oblique brace (54.1%), and anterior brace (60.7%) provided significantly greater stability than the x-frame brace (33.2%; P < .001, P = .008, P < .001, respectively). ACLC patch, oblique brace, and anterior brace continued to have significantly higher posterior translational resistance than the x-frame (35.1%; P < .001, P = .003, P < .001) after transection and subsequent CC ligament repair. For posterior rotation, transection of the ACLC decreased the resistance to 5.4% of the intact state. With the CC ligaments intact, the ACLC patch (77.1%) better restored posterior rotational stability than the oblique (35.3%), anterior (48.5%), and x-frame (23.0%) brace repairs ( P < .001, P = .002, P < .001). CC ligament transection and subsequent repair demonstrated the ACLC patch (41.0%) to have improved stability when compared with the oblique (16.0%), anterior (14.0%), and x-frame (12.7%) repairs ( P = .006, P = .003, P = .002). Conclusion: ACLC reconstruction with a dermal allograft better restored native posterior rotational stability than other brace constructs, with translational stability similar to the oblique and anterior brace technique at the time of surgery. Clinical Relevance: Horizontal stability of the AC joint is primarily controlled by the ACLC. Inability to restore AC joint biomechanics can result in persistent posterior instability and lead to functional impairment.

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Harper, Marion C. "Posterior Instability of the Talus: An Anatomic Evaluation". Foot & Ankle 10, n.º 1 (agosto de 1989): 36–39. http://dx.doi.org/10.1177/107110078901000107.

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A cadaver study was conducted to evaluate the role of the posterior tibial margin or posterior malleolus, as well as medial and lateral supporting structures, in providing posterior stability for the talus. Posterior malleolar fractures consisting of approximately 30%, 40%, and 50% of the articular margin on the lateral radiograph were created in specimens that were then subjected to posterior stressing. No posterior talar subluxation was noted in any specimen. Repeat stressing following removal of the medial malleolus again revealed no subluxation in any specimen. The lateral supporting structures, primarily the posterior fibulotalar and fibulocalcaneal ligaments, appeared to be the key structures providing posterior talar stability. If the fibula is stable in an anatomic position, feared posterior instability of the talus would not appear to be an indication for internal fixation of posterior malleolar fractures.

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Singh, Harshpal, Scott Y. Rahimi, David J. Yeh y David Floyd. "History of posterior thoracic instrumentation". Neurosurgical Focus 16, n.º 1 (enero de 2004): 1–4. http://dx.doi.org/10.3171/foc.2004.16.1.12.

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The term “backbone” appears in many expressions used in modern day society. In any scenario, it has one central meaning: stability. Best defined as a foundation that is able to sustain multiple stressors without adversely affecting integrity, the commonly and appropriately termed backbone of humans is the spinal column. As the central focus of stability in our species, the spine is subject to a great degree of trauma and mechanical forces. A variety of methods have been developed throughout history in the treatment of spinal column injury. Initial treatment involved the use of simple traction devices for the reduction of spinal fractures; these have evolved to include the current insertion of spinal instrumentation. The authors review the historical treatment and development of posterior instrumentation for thoracic spinal injury.

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Bartzela, Theodosia y Irmtrud Jonas. "Long-term Stability of Unilateral Posterior Crossbite Correction". Angle Orthodontist 77, n.º 2 (marzo de 2007): 237–43. http://dx.doi.org/10.2319/0003-3219(2007)077[0237:lsoupc]2.0.co;2.

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Bussey, M., S. Milosavljevic y D. Aldabe. "Increased postural stability in posterior pelvic girdle pain". Physiotherapy 101 (mayo de 2015): e191-e192. http://dx.doi.org/10.1016/j.physio.2015.03.352.

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Hoshijima, Kazuo, Roger W. Nightingale, Jim R. Yu, William J. Richardson, Kristine D. Harper, Hiroshi Yamamoto y Barry S. Myers. "Strength and Stability of Posterior Lumbar Interbody Fusion". Spine 22, n.º 11 (junio de 1997): 1181–88. http://dx.doi.org/10.1097/00007632-199706010-00002.

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Arno, Sally, Scott Hadley, Kirk A. Campbell, Christopher P. Bell, Michael Hall, Luis S. Beltran, Michael P. Recht, Orrin H. Sherman y Peter S. Walker. "The Effect of Arthroscopic Partial Medial Meniscectomy on Tibiofemoral Stability". American Journal of Sports Medicine 41, n.º 1 (13 de noviembre de 2012): 73–79. http://dx.doi.org/10.1177/0363546512464482.

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Background: There is still little known regarding the effects of meniscus resection size on tibiofemoral stability. Purpose: To determine if partial medial meniscectomy of the posterior horn significantly alters tibiofemoral stability as measured by the anterior-posterior (AP) position and laxity of the medial femoral condyle. Study Design: Controlled laboratory study. Methods: Five cadaveric knees were dissected to the capsule, preserving all ligaments and the quadriceps tendon. Each specimen was first tested on a rig where the AP position and laxity of the medial femoral condyle were measured while a range of forces was applied from full extension to 90° of flexion. Magnetic resonance imaging (MRI) at 3 tesla was then performed for baseline measurements of the meniscus before partial meniscectomy. Arthroscopic partial medial meniscectomy aimed at 30% of the posterior horn was then performed, followed by repeat mechanical testing and MRI. The sequence was then repeated for arthroscopic partial meniscectomy aimed at 60% and 100% of the posterior horn of the medial meniscus. Results: The MRI analysis demonstrated that 22% ± 9% of the original width of the posterior horn was removed at the first resection, 46% ± 11% was removed at the second resection, and the third resection was 100% removal of the posterior horn for all specimens. After 22% resection, no significant difference in AP laxity was observed. A statistically significant increase in AP laxity was observed with 46% resection under a 500-N compressive load compared with the intact meniscus. After full resection, significant increases in AP laxity were observed under a 50-N compressive load compared with the intact and 22% and 46% resections. The 22% resection had similar AP positions as the intact knee, whereas the 46% resection and 100% removal of the posterior horn had statistically further posterior AP positions than the intact knee. Conclusion: Partial medial meniscectomy with ≥46% resection of the original width of the posterior horn significantly altered the AP position of the medial femoral condyle and also increased laxity. Clinical Relevance: These mechanical changes may lead to abnormal cartilage loading and early osteoarthritis.

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Rauck, Ryan, Amir Jahandar, Andreas Kontaxis, David Dines, Russell Warren, Lawrence Gulotta y Samuel Taylor. "Paper 05: The Role of the Long Head of the Biceps Tendon in Posterior Shoulder Stabilization during Forward Flexion". Orthopaedic Journal of Sports Medicine 10, n.º 7_suppl5 (1 de julio de 2022): 2325967121S0056. http://dx.doi.org/10.1177/2325967121s00569.

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Objectives: The incidence of long head of the biceps tendon (LHBT) procedures is increasing, yet the role of the LHBT in glenohumeral stability is not fully understood. People lift most objects in the sagittal plane with forward flexion, which stresses the posterior aspect of the unconstrained glenohumeral joint. Determining the mechanism by which the shoulder maintains stability with functional motions is important to understanding the pathoanatomy of degenerative shoulders. We hypothesize that the LHBT resists posterior translation of the humeral head (HH) during forward flexion by tensioning the posterior capsuloligamentous complex. Methods: Ten fresh-frozen cadaveric shoulders were tested using an established shoulder simulator, which loads the rotator cuff, deltoid and LHB tendons through a system of pulleys and weights. A motion tracking system recorded glenohumeral translations with an accuracy of ±0.2mm. In each subject, the scapula was fixed and the humerus was tested in 6 positions: 30 and 60 degrees of glenohumeral forward flexion at i) maximum internal rotation (IR), ii) neutral rotation and iii) maximum external rotation (ER) (Figure 1). The deltoid was loaded with 100N, and the infraspinatus and subscapularis were loaded with 22N each. The difference in glenohumeral translation was calculated at each position comparing the LHBT loaded with 45N or unloaded. Results: When comparing the two states of LHBT loading vs unloading, unloading the LHBT led to an overall increase in posterior and superior translation of the humeral head (Figure 2) in all tested positions (neutral, maximum internal rotation, maximum external rotation in both 30 and 60 degrees of forward flexion). At 30 degrees of glenohumeral forward flexion, unloading the LHBT increased HH posterior translation by 2.46mm (±0.92mm) (p<0.001), 1.71mm (±1.02mm) (p<0.001) and 1.02mm (±0.88mm) (p=0.014) at maximum ER, neutral rotation, and maximum IR, respectively (Figure 3). At 60 degrees of glenohumeral forward flexion, unloading the LHBT increased HH posterior translation by 2.77mm (±1.16mm) (p<0.001), 2.43mm (±1.56mm) (p<0.001) and 1.66mm (±1.42mm) (p<0.001) at maximum ER, neutral rotation and maximum IR, respectively (Figure 4). Unloading the LHBT led to more posterior translation at 60 degrees of glenohumeral forward flexion compared to 30 degrees (p=0.013). Conclusions: LHBT loading resists posterior translation of the humeral head during forward flexion. This data supports the role of the LHBT as a posterior stabilizer of the shoulder, specifically when a person is carrying objects in front of them. Biceps tenotomy or tenodesis may contribute to microinstability of the glenohumeral joint and shift contact pressure posteriorly. Further work is needed to determine if unloading the LHBT, as is done with biceps tenotomy or tenodesis, may eventually contribute to the posterior glenoid wear seen with osteoarthritis.

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Bansal, Tungish, Mandeep S. Dhillon, y Kamal Dureja,. "How We do It. Trimalleolar Fractures: Fixing the Posterior Malleolus by Posterolateral Approach". Journal of Foot and Ankle Surgery (Asia Pacific) 4, n.º 2 (2017): 63–68. http://dx.doi.org/10.5005/jp-journals-10040-1073.

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ABSTRACT The understanding of trimalleolar fractures and, in particular, the posterior malleolus fragment has drastically evolved over the last decade. There has been a tilt in favor of fixing almost all posterior malleolus fragment in contrast to the old school thought of the 20th century. The concept of stability offered by posterior malleolus fixation to the syndesmotic stability is well understood now. Posterolateral approach has almost evolved as a gold standard approach for posterior malleolus fixation. How to cite this article Dhillon MS, Dureja K, Patel S, Bansal T. How We do It. Trimalleolar Fractures: Fixing the Posterior Malleolus by Posterolateral Approach. J Foot Ankle Surg (Asia-Pacific) 2017;4(2):63-68.

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Traynelis, Vincent C., Paul A. Donaher, Robert M. Roach, H. Kojimoto y Vijay K. Goel. "Biomechanical comparison of anterior Caspar plate and three-level posterior fixation techniques in a human cadaveric model". Journal of Neurosurgery 79, n.º 1 (julio de 1993): 96–103. http://dx.doi.org/10.3171/jns.1993.79.1.0096.

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✓ Traumatic cervical spine injuries have been successfully stabilized with plates applied to the anterior vertebral bodies. Previous biomechanical studies suggest, however, that these devices may not provide adequate stability if the posterior ligaments are disrupted. To study this problem, the authors simulated a C-5 teardrop fracture with posterior ligamentous instability in human cadaveric spines. This model was used to compare the immediate biomechanical stability of anterior cervical plating, from C-4 to C-6, to that provided by a posterior wiring construct over the same levels. Stability was tested in six modes of motion: flexion, extension, right and left lateral bending, and right and left axial rotation. The injured/plate-stabilized spines were more stable than the intact specimens in all modes of testing. The injured/posterior-wired specimens were more stable than the intact spines in axial rotation and flexion. They were not as stable as the intact specimens in the lateral bending or extension testing modes. The data were normalized with respect to the motion of the uninjured spine and compared using repeated measures of analysis of variance, the results of which indicate that anterior plating provides significantly more stability in extension and lateral bending than does posterior wiring. The plate was more stable than the posterior construct in flexion loading; however, the difference was not statistically significant. The two constructs provide similar stability in axial rotation. This study provides biomechanical support for the continued use of bicortical anterior plate fixation in the setting of traumatic cervical spine instability.

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Nahi Hamdi, Dr Ali y Dr Shehab Ahmed Hemd. "Comparison between Osseo densification burs and osteotome technique for closed sinus lift in partially edentulous maxilla (clinical and radiological study)". Journal of University of Shanghai for Science and Technology 23, n.º 05 (22 de mayo de 2021): 392–411. http://dx.doi.org/10.51201/jusst/21/05164.

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Dental implants are considered the first choice to replace lost or non-restorable teeth. However, the posterior maxilla remains a challenge in its management because of the quality of bone in the posterior maxilla. Osseo densification (OD) concept has been proposed in the literature to improve primary implant stability, which is an important aspect of osseointegration. Densah bur is novel drills specially designed to enhance a bone density by Osseo densification, which in turn increases primary stability. This present study was conducted to assess crestal sinus floor elevation by osteotome in comparison to Densah bur in the posterior atrophic maxilla. This was a randomized controlled clinical trial conducted on 20 patients to evaluate available crestal bone height loss, implant stability after implant placement in healed posterior maxillary alveolar ridge, whole bone height, Schneiderian membrane trauma, and post-operative complication.

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Bishop, Frank S., Mical M. Samuelson, Michael A. Finn, Kent N. Bachus, Darrel S. Brodke y Meic H. Schmidt. "The biomechanical contribution of varying posterior constructs following anterior thoracolumbar corpectomy and reconstruction". Journal of Neurosurgery: Spine 13, n.º 2 (agosto de 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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Bryniarski, Anna, Alex Brady, Jon Miles, Grant Dornan, Jan Radsen, Bradley Fossum, C. Thomas Haytmanek, Elisabeth Husebye, Thomas Clanton y Ingrid Stake. "Poster 267: The Impact of Posterior Malleolar Fixation on Syndesmotic Stability". Orthopaedic Journal of Sports Medicine 10, n.º 7_suppl5 (1 de julio de 2022): 2325967121S0082. http://dx.doi.org/10.1177/2325967121s00828.

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Objectives: Trans-syndesmotic fixation with suture buttons, posterior malleolar fixation (PMF) with screws and anterior inferior tibiofibular ligament (AITFL) augmentation with suture tape have all been suggested as potential treatments in the setting of a malleolar fracture. However, there is no consensus on the optimal treatment for small vs. large malleolar fractures. The purpose of this study was to determine which combination of: 1) posterior malleolar screw fixation, 2) syndesmotic fixation with suture button (SB), and 3) AITFL augmentation with suture tape (ST) best restored native tibio-fibular and ankle joint kinematics following a small and large posterior malleolar fracture. Methods: Twenty fresh frozen cadaveric lower leg specimens were divided into two groups and underwent biomechanical testing using a 6-degrees-of-freedom robotic arm in 7 states: 1) Native, 2) Syndesmosis Injury + Malleolar Fracture (Group 1: small fracture, Group 2: large fracture) 3) Screw fixation, 4) Screw + Suture Tape Augmentation, 5) Screw + Suture Tape Augmentation + Suture Button, 6) Suture Button + Suture Tape Augmentation, 7) Suture Button. Four biomechanical tests were performed at neutral and at 30 degrees of plantarflexion: 1) Internal Rotation, 2) External Rotation, 3) Lateral Drawer, 4) Posterior Drawer. The position of the tibia, fibula and talus were continuously recorded using a 5-camera motion capture system. Results: No differences were found in the efficacy of treatments between the small fracture and large fracture groups. In the external rotation test, screws with ST augmentation resulted in best stability of the fibula and ankle joint. In the internal rotation test, all repairs that included posterior malleolar screws stabilized the fibula and ankle. Posterior and lateral drawer of the foot resulted in only small differences between the intact and malleolar fracture states. Conclusions: Posterior malleolar fixation resulted in higher syndesmotic stability compared to trans-syndesmotic fixation with SBs. AITFL augmentation with ST provided additional external rotation stability when combined with screw fixation. Posterior malleolar screw fixation with AITFL augmentation using ST may be the preferred surgical method when treating patients with acute ankle injury involving an unstable syndesmosis injury and a posterior malleolar fragment. [Figure: see text][Figure: see text]

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Cho, Heon Jae. "Long-Term Stability of Surgical Mandibular Setback". Angle Orthodontist 77, n.º 5 (1 de septiembre de 2007): 851–56. http://dx.doi.org/10.2319/052306-209.1.

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Abstract Objective: To test the relationship between positional changes of the proximal segments during surgery and the positional rebound of the mandible during the postsurgical period of orthodontic treatment. Materials and Methods: The sample included records for 34 patients who had received sagittal split surgery for the correction of mandibular prognathism. Data were collected from standardized cephalometric radiographs taken immediately prior to surgery (T2), immediately following surgery (T3), and following the completion of orthodontic treatment (T4). Linear and angular changes in the orientation of the posterior border of the ascending ramus between time points T2, T3, and T4 were measured relative to superimposition on the anterior cranial base. In addition, linear changes in the position of pogonion between T3 and T4 were measured. Results: The magnitude of linear displacement of the posterior border of the proximal segment during surgery (T2 to T3) was statistically significantly correlated (r = .61) with the magnitude of linear displacement of pogonion during the postsurgical phase of orthodontic treatment (T3 to T4). There was a strong relationship between the magnitude of angular (r = .67) displacement of the posterior border of the proximal segments during surgery (T2 to T3) and the magnitude of angular rebound of the posterior border of the proximal segments that occurred during the postsurgical phase of orthodontic treatment (T3 to T4). Conclusions: When rigid fixation procedures alter the position of the proximal segments during sagittal split osteotomy of the mandible, the proximal segments tend to go back toward their presurgical positions following surgery.

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Erbulut, D. U., I. Zafarparandeh, A. F. Ozer y V. K. Goel. "Biomechanics of Posterior Dynamic Stabilization Systems". Advances in Orthopedics 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/451956.

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Spinal rigid instrumentations have been used to fuse and stabilize spinal segments as a surgical treatment for various spinal disorders to date. This technology provides immediate stability after surgery until the natural fusion mass develops. At present, rigid fixation is the current gold standard in surgical treatment of chronic back pain spinal disorders. However, such systems have several drawbacks such as higher mechanical stress on the adjacent segment, leading to long-term degenerative changes and hypermobility that often necessitate additional fusion surgery. Dynamic stabilization systems have been suggested to address adjacent segment degeneration, which is considered to be a fusion-associated phenomenon. Dynamic stabilization systems are designed to preserve segmental stability, to keep the treated segment mobile, and to reduce or eliminate degenerative effects on adjacent segments. This paper aimed to describe the biomechanical aspect of dynamic stabilization systems as an alternative treatment to fusion for certain patients.

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Zita Gomes, Raquel, Mario Ramalho de Vasconcelos, Isabel Maria Lopes Guerra, Rute Alexandra Borges de Almeida y Antonio Cabral de Campos Felino. "Implant Stability in the Posterior Maxilla: A Controlled Clinical Trial". BioMed Research International 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/6825213.

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Aim. To evaluate the primary and secondary stability of implants in the posterior maxilla. Methods. Patients were allocated into three groups: (A) native bone, (B) partially regenerated bone, and (C) nearly totally regenerated bone. Insertion torque (IT) and implant stability quotient (ISQ) were measured at placement, to evaluate whether satisfactory high primary stability (IT ≥ 45 N/cm; ISQ ≥ 60) was achieved; ISQ was measured 15, 30, 45, and 60 days after placement, to investigate the evolution to secondary stability. Results. 133 implants (Anyridge®, Megagen) were installed in 59 patients: 55 fixtures were placed in Group A, 57 in Group B, and 21 in Group C. Fifty-two implants had satisfactory high primary stability (IT ≥ 45 N/cm; ISQ ≥ 60). A positive correlation was found between all variables (IT, ISQ at t = 0, t = 60), and statistically higher IT and ISQ values were found for implants with satisfactory high primary stability. Significant differences were found for IT and ISQ between the groups (A, B, and C); however, no drops were reported in the median ISQ values during the healing period. Conclusions. The evaluation of the primary and secondary implant stability may contribute to higher implant survival/success rates in critical areas, such as the regenerated posterior maxilla. The present study is registered in the ISRCTN registry with ID ISRCTN33469250.

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Li, G., E. Most, L. E. DeFrate, J. F. Suggs, T. J. Gill y H. E. Rubash. "Effect of the posterior cruciate ligament on posterior stability of the knee in high flexion". Journal of Biomechanics 37, n.º 5 (mayo de 2004): 779–83. http://dx.doi.org/10.1016/j.jbiomech.2003.09.031.

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Spadea, Leopoldo, Marco Messina, Carlo Cagini, Marco Lupidi, Francesco Piccinelli, Tito Fiore y Daniela Fruttini. "Posterior Corneal Surface Stability after Femtosecond Laser-Assisted Keratomileusis". Highlights of Ophthalmology 44, n.º 2ENG (2016): 2–5. http://dx.doi.org/10.5005/highlights-44-2-2.

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Gardner, Michael J., Adam Brodsky, Stephen M. Briggs, Jason H. Nielson y Dean G. Lorich. "Fixation of Posterior Malleolar Fractures Provides Greater Syndesmotic Stability". Clinical Orthopaedics and Related Research 447 (junio de 2006): 165–71. http://dx.doi.org/10.1097/01.blo.0000203489.21206.a9.

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Walker, Peter S., M. S. Ambarek, Joanne R. Morris, Kola Olanlokun y Andrew Cobb. "Anterior-Posterior Stability in Partially Conforming Condylar Knee Replacement". Clinical Orthopaedics and Related Research &NA;, n.º 310 (enero de 1995): 87???97. http://dx.doi.org/10.1097/00003086-199501000-00016.

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Kane, Steven y Gibran Syed Khurshid. "Haptic stability of intrascleral fixated posterior chamber intraocular lenses". Journal of Cataract & Refractive Surgery 41, n.º 9 (septiembre de 2015): 2034. http://dx.doi.org/10.1016/j.jcrs.2015.09.012.

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Tenke, Craig E., Jürgen Kayser, Jorge E. Alvarenga, Karen S. Abraham, Virginia Warner, Ardesheer Talati, Myrna M. Weissman y Gerard E. Bruder. "Temporal stability of posterior EEG alpha over twelve years". Clinical Neurophysiology 129, n.º 7 (julio de 2018): 1410–17. http://dx.doi.org/10.1016/j.clinph.2018.03.037.

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Schuster, A. J., A. L. von Roll, D. Pfluger y T. Wyss. "Anteroposterior stability after posterior cruciate-retaining total knee arthroplasty". Knee Surgery, Sports Traumatology, Arthroscopy 19, n.º 7 (14 de enero de 2011): 1113–20. http://dx.doi.org/10.1007/s00167-010-1364-1.

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WHITESIDE, LEO A. y DAVID D. AMADOR. "Rotational Stability of a Posterior Stabilized Total Knee Arthroplasty". Clinical Orthopaedics and Related Research &NA;, n.º 242 (mayo de 1989): 241???246. http://dx.doi.org/10.1097/00003086-198905000-00024.

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WHITEHILL, RICHARD, C. E. WILHELM, J. T. MOSKAL, S. J. KRAMER y WOLFGANG W. RUCH. "Posterior Strut Fusions to Enhance Immediate Postoperative Cervical Stability". Spine 11, n.º 1 (enero de 1986): 6–13. http://dx.doi.org/10.1097/00007632-198601000-00003.

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Choma, Theodore, Ferris Pfeiffer, Santaram Vallurupalli, Irene Mannering y Youngju Pak. "Segmental Stiffness Achieved by Three Types of Fixation for Unstable Lumbar Spondylolytic Motion Segments". Global Spine Journal 2, n.º 2 (junio de 2012): 079–86. http://dx.doi.org/10.1055/s-0032-1319773.

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Objective The objective of this study was to compare the relative stability in lumbar spondylolysis (SP) of a rigid anterior plate (with a novel compression slot) versus traditional posterior pedicle screw (PS) fixation. Summary of Background Data Arthrodesis has been a mainstay of treatment for symptomatic isthmic spondylolisthesis in adults. Posterior PS fixation has become a commonly used adjunct. Some have advocated anterior lumbar interbody fixation (ALIF) plate as an alternative. The relative stability afforded by ALIF in SP has not been well characterized, nor has the contribution afforded by a compression screw slot in an ALIF plate. Methods Calf spine segments were characterized in the normal state, after sectioning the pars (SP model), then after reconstruction with an interbody spacer and either PS/rods, or an ALIF plate, or both. Results ALIF plate conferred stability on the spondylolytic segment only comparable to that of the normal functional spinal unit (FSU). Posterior fixation was more stable than anterior fixation in all testing modes. Addition of an ALIF plate conferred a significant additional stability in those that already had posterior fixation. The utilization of an anterior compression screw conferred additional stability in extension testing only. Conclusions ALIF plate reconstruction in the setting of SP may not confer enough segmental stability to predictably encourage fusion beyond that of the uninstrumented intact FSU. The utilization of an integral compression screw in an ALIF plate may not confer clinically significant additional construct stability in SP.

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Lee, Jin-Ah, Yong-Gon Koh, Paul Shinil Kim, Ki Won Kang, Yoon Hae Kwak y Kyoung-Tak Kang. "Biomechanical effect of tibial slope on the stability of medial unicompartmental knee arthroplasty in posterior cruciate ligament-deficient knees". Bone & Joint Research 9, n.º 9 (1 de septiembre de 2020): 593–600. http://dx.doi.org/10.1302/2046-3758.99.bjr-2020-0128.r1.

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Aims Unicompartmental knee arthroplasty (UKA) has become a popular method of treating knee localized osteoarthritis (OA). Additionally, the posterior cruciate ligament (PCL) is essential to maintaining the physiological kinematics and functions of the knee joint. Considering these factors, the purpose of this study was to investigate the biomechanical effects on PCL-deficient knees in medial UKA. Methods Computational simulations of five subject-specific models were performed for intact and PCL-deficient UKA with tibial slopes. Anteroposterior (AP) kinematics and contact stresses of the patellofemoral (PF) joint and the articular cartilage were evaluated under the deep-knee-bend condition. Results As compared to intact UKA, there was no significant difference in AP translation in PCL-deficient UKA with a low flexion angle, but AP translation significantly increased in the PCL-deficient UKA with high flexion angles. Additionally, the increased AP translation became decreased as the posterior tibial slope increased. The contact stress in the PF joint and the articular cartilage significantly increased in the PCL-deficient UKA, as compared to the intact UKA. Additionally, the increased posterior tibial slope resulted in a significant decrease in the contact stress on PF joint but significantly increased the contact stresses on the articular cartilage. Conclusion Our results showed that the posterior stability for low flexion activities in PCL-deficient UKA remained unaffected; however, the posterior stability for high flexion activities was affected. This indicates that a functional PCL is required to ensure normal stability in UKA. Additionally, posterior stability and PF joint may reduce the overall risk of progressive OA by increasing the posterior tibial slope. However, the excessive posterior tibial slope must be avoided. Cite this article: Bone Joint Res 2020;9(9):593–600.

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