A novel fragment specific classification of complex olecranon fractures: 3-dimensional model design, radiological validation, and proposed surgical algorithm.

BACKGROUND: Current classifications for proximal ulna fracture patterns rely on qualitative data and cannot inform surgical planning. We propose a new classification system based on a biological and anatomical stress analysis. Our hypothesis is that fragment types in complex fractures can be predicted by the tendon and ligament attachments on the proximal ulna. METHODS: First, we completed a literature review to identify quantitative data on proximal ulna soft tissue attachments. On this basis, we created a 3-dimensional model of ulnar anatomy with SliceOMatic and Catia V5R20 software and determined likely locations for fragments and fracture lines. The second part of the study was a retrospective radiological study. A level-1 trauma radiological database was used to identify computed tomography scans of multifragmentary olecranon fractures from 2009 to 2021. These were reviewed and classified according to the "fragment specific" classification and compared to the Mayo and the Schatzker classifications. RESULTS: Twelve articles (134 elbows) met the inclusion criteria and 7 potential fracture fragments were identified. The radiological study included 67 preoperative computed tomography scans (mean 55 years). The fragments identified were the following: posterior (40%), intermediate (42%), tricipital (100%), supinator crest (25%), coronoid (18%), sublime tubercle (12%), and anteromedial facet (18%). Eighteen cases (27%) were classified as Schatzker D (comminutive) and 21 (31%) Mayo 2B (stable comminutive). Inter-rater correlation coefficient was 0.71 among 3 observers. CONCLUSION: This proposed classification system is anatomically based and considers the deforming forces from ligaments and tendons. Having a more comprehensive understanding of complex proximal ulna fractures would lead to more accurate fracture evaluation and surgical planning.

Optoelectronic Pressure Sensor Based on the Bending Loss of Plastic Optical Fibers Embedded in Stretchable Polydimethylsiloxane.

We report the design and testing of a sensor pad based on optical and flexible materials for the development of pressure monitoring devices. This project aims to create a flexible and low-cost pressure sensor based on a two-dimensional grid of plastic optical fibers embedded in a pad of flexible and stretchable polydimethylsiloxane (PDMS). The opposite ends of each fiber are connected to an LED and a photodiode, respectively, to excite and measure light intensity changes due to the local bending of the pressure points on the PDMS pad. Tests were performed in order to study the sensitivity and repeatability of the designed flexible pressure sensor.

Numerical Investigation of Spinal Cord Injury After Flexion-Distraction Injuries at the Cervical Spine.

Flexion-distraction injuries frequently cause traumatic cervical spinal cord injury (SCI). Post-traumatic instability can cause aggravation of the secondary SCI during patient care. However, there is little information on how the pattern of disco-ligamentous injury affects the SCI severity and mechanism. This study objective was to analyze how posterior disco-ligamentous injuries affect spinal cord compression and stress and strain patterns in the spinal cord during post-traumatic flexion and extension. A cervical spine finite element model including the spinal cord was used and different combinations of partial or complete intervertebral disc (IVD) rupture and disruption of various posterior ligaments were modeled at C4-C5, C5-C6, or C6-C7. In flexion, complete IVD rupture combined with posterior ligamentous complex rupture was the most severe injury leading to the highest von Mises stress (47-66 kPa), principal strains p1 (0.32-0.41 in white matter) and p3 (-0.78 to -0.96 in white matter) in the spinal cord and the highest spinal cord compression (35-48%). The main post-trauma SCI mechanism was identified as the compression of the anterior white matter at the injured level combined with distraction of the posterior spinal cord during flexion. There was also a concentration of the maximum stresses in the gray matter during post-traumatic flexion. Finally, in extension, the injuries tested had little impact on the spinal cord. The capsular ligament was the most important structure to protect the spinal cord. Its status should be carefully examined during the patient's management.

A Sensitive and Fast Fiber Bragg Grating-Based Investigation of the Biomechanical Dynamics of In Vitro Spinal Cord Injuries.

To better understand the real-time biomechanics of soft tissues under sudden mechanical loads such as traumatic spinal cord injury (SCI), it is important to improve in vitro models. During a traumatic SCI, the spinal cord suffers high-velocity compression. The evaluation of spinal canal occlusion with a sensor is required in order to investigate the degree of spinal compression and the fast biomechanical processes involved. Unfortunately, available techniques suffer with drawbacks such as the inability to measure transverse compression and impractically large response times. In this work, an optical pressure sensing scheme based on a fiber Bragg grating and a narrow-band filter was designed to detect and demonstrate the transverse compression inside a spinal cord surrogate in real-time. The response time of the proposed scheme was 20 microseconds; a five orders of magnitude enhancement over comparable schemes that depend on costly and slower optical spectral analyzers. We further showed that this improvement in speed comes with a negligible loss in sensitivity. This study is another step towards better understanding the complex biomechanics involved during a traumatic SCI, using a method capable of probing the related internal strains with high-spatiotemporal resolution.

Biomechanical evaluation of bovine stifles stabilized with an innovative braided superelastic nitinol prosthesis after transection of the cranial cruciate ligament.

OBJECTIVE: To determine the stability bovine stifles stabilized with nylon or nitinol superelastic prostheses after transection of the cranial cruciate ligament (CCL). STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Stifles (n = 15) harvested from adult bovine cadavers. METHODS: The stifles were randomly assigned pairwise to a ligament reconstruction technique (n = 5): (1) and (2) Hamilton's technique using a prosthesis made of 24 nitinol strands (0.39 mm) braided at 40°or single 600-lb test nylon implant, and (3) nitinol prosthesis placed in femoral and tibial bone tunnels (bone-to-bone). Craniocaudal tibial translation at ±2000 N was applied to the tibia, and mediolateral angular displacement via measured under torsional tibial loading at ±60 Nm on three occasions: intact CCL, transected, and stabilized. Outcomes were evaluated with a mixed effect linear model for repeated measures. RESULTS: Bone-to-bone using nitinol was the only repair that decreased tibial translation after CCL transection (p = .001) with a 23% change magnitude compared with intact CCL. Hamilton was the only stabilization reestablishing angular displacement, similar to intact CCL (p = .109 and .134 for nitinol and nylon). Bone-to-bone nitinol stabilization decreased angular displacement after CCL-transection with an 8% change magnitude (p = .040) without returning to normal values. CONCLUSION: CCL replacement with nylon did restore joint stability. Nitinol prostheses passed through single femoral and tibial bone tunnels (bone-to-bone) were the only techniques reducing tibial translation. CLINICAL SIGNIFICANCE/IMPACT: Bone-to-bone stabilization with a nitinol prosthesis may be considered as an alternative to nylon for CCL replacement in cattle. These results provide evidence to justify clinical evaluation in cattle undergoing CCL replacement.

Morphological features of thoracolumbar burst fractures associated with neurological outcome in thoracolumbar traumatic spinal cord injury.

PURPOSE: To identify specific morphological characteristics in thoracolumbar burst fractures associated with neurological outcome after severe traumatic spinal cord injury (TSCI). METHODS: We retrospectively analyzed the clinical and radiological (CT scan morphological characteristics) data of 25 consecutive patients admitted for TSCI secondary to a burst fracture at levels from T11 to L2 between 2010 and 2017 in single level-1 trauma center. We included severe TSCI, defined as American Spinal Injury Association Impairment Scale (AIS) grade A, B or C. RESULTS: Among the 25 patients with severe TSCI, 14 were AIS A, 5 were AIS B, and 6 were AIS C upon initial preoperative neurological evaluation. The AIS grade and the burden of associated injuries (Injury Severity Score, ISS) were the only clinical factors significantly associated with poor neurological recovery. The trauma level of energy was not associated with neurological outcome. Several fractures parameters were independently related to neurological recovery: the postero-inferior corner translation, presence of retropulsed fragment comminution and complete lamina fracture. The magnitude of sagittal kyphosis angle, vertebral kyphosis index and vertebral body comminution were not associated with the neurological outcome. CONCLUSIONS: Morphological features of the bony structures involving the spinal canal in thoracolumbar burst fractures with severe TSCI are associated with the chronic neurological outcome and could provide more insight than the AIS clinical grading. The fracture pattern may better reflect the actual level of energy transferred to the spinal cord than distinguishing between low- and high-energy trauma.

Quantitative localization of the entry point of the lateral ascending branch of the anterior circumflex humeral artery: a high definition CT-scan radiological study.

PURPOSE: To define the localization of the entry point of the lateral ascending branch of the anterior circumflex humeral artery (LACHA) for better surgical management and prevention of injury to this important vessel. The hypothesis is that the insertion point of the artery will be constant in subjects. METHODS: A retrospective study of 27 tomographic images was conducted to generate a three-dimensional (3D) model and localize the entry point of the LACHA. Using a coordinate system consisting of three axes: the proximal-distal axis (PDA), the anterior-posterior axis (APA) and the medial-lateral axis (MLA), the position of a foramen located in the superior portion of the bicipital groove and representing the entry point of LACHA was measured on each reconstructed model. RESULTS: On average, the foramen was located 10.0 mm distal along the PDA from the most proximal point of the greater tuberosity (GT). Along the MLA and with respect to the most medial portion of the GT, the foramen was located 3.4 mm medially, on average. No significant differences between men and women or between sides for foramen position measurements were found. CONCLUSION: Unnecessary procedures to the proximal biceps, aiming to prevent chronic pain, should be avoided in fracture fixation as they would affect a significant source of blood supply to the humeral head. These findings could help surgeons protect the only vascular supply they can during the fixation of proximal humeral fractures, when using the anterior or antero-lateral approaches.

Traumatic Spinal Cord Injuries with Fractures in a Québec Level I Trauma Center.

BACKGROUND: Traumatic spinal cord injuries (TSCI) have devastating consequences on patients' quality of life. More specifically, TSCI with spinal fractures (TSCIF) have the most severe neurological impairment, although limited data are available. This study aimed at providing data and analyzing TSCIF in a level I trauma center in the province of Québec, Canada. METHODS: Two hundred eighty-two TSCIF were reviewed. Spinal injuries and neurological impairment were assessed with AO classification and AIS, respectively. Variables included age, sex, cause, location, mechanism of injury (MOI), and severity of TSCIF. Chi-squared Pearson determined significant associations (p < 0.05). RESULTS: Male-to-female ratio was 3.21:1. Patients were 42.5 ± 18.7 years. The leading causes of TSCIF were high-energy falls (28.4%), cars (26.2%) and vehicle without restraint system (motorcycle, all-terrain vehicle, snowmobile, and bicycle) (21.3%). Vehicle collisions, pooling cars and unrestrained vehicles, mostly affected the 20-49-year population (62.2%). The main MOI was distraction in males (47.9%), and axial compression in females (44.8%). There were significant associations between causes and injured spinal level, as well as between MOI and injured spinal level, sex, and TSCIF severity. Most patients involved in unrestrained vehicle accidents sustained a thoracolumbar spine distraction with complete motor deficit. A severe neurologic deficit affected most patients following car accidents that caused cervical spine distraction or axial torsion. CONCLUSIONS: In Québec, most TSCIF caused by vehicle collisions affect a young population and have severe neurological impairments. Future efforts should focus on better understanding accidents involving the unrestrained vehicle category to further improve preventive measures.

Des lésions traumatiques de la moelle épinière associées à des fractures dans le cadre d'un centre de traumatologie de niveau 1 du Québec Contexte: Les lésions traumatiques de la moelle épinière (LTME) ont des conséquences catastrophiques sur la qualité de vie des patients qui en sont victimes. De façon plus particulière, il faut savoir que les LTME associées à des fractures vertébrales sont celles qui entraînent, bien que les données à ce sujet soient limitées, les déficiences neurologiques les plus graves. Cette étude vise à collecter des données et à analyser les LTME associées à des fractures vertébrales dans un centre de traumatologie de niveau 1 situé au Québec (Canada). Méthodes: Au total, nous avons examiné 282 cas de LTME associés à des fractures vertébrales. Pour ce faire, nous avons évalué ces fractures au moyen de la classification Müller AO ; quant au niveau de déficience neurologique, nous l'avons évalué au moyen de l'échelle ASIA. Parmi les variables incluses dans cette étude, mentionnons l'âge, le sexe, la cause, l'endroit de l'incident, le mécanisme de blessure (mechanism of injury) ainsi que la gravité des LMTE associées à des fractures vertébrales. Enfin, c'est au moyen du test du X2 de Pearson qu'on a pu déterminer des associations statistiques valables (p < 0,05). Résultats: Le rapport hommes/femmes était de 3,2 :1. En moyenne, les patients étaient âgés de 42,5 ans ± 18,7 ans. Les principales causes de LMTE associées à des fractures vertébrales se sont révélées être des chutes à haut transfert d'énergie (28,4 %), des accidents de la route impliquant des automobiles (26,2 %) et des accidents impliquant des moyens de transport (motocyclettes, VTT, motoneiges et vélos) dépourvus d'un dispositif de retenue (21,3 %). Tant les collisions à bord d'une automobile que celles impliquant un moyen de transport sans dispositif de retenue ont surtout affecté la population des 20 à 49 ans (62,2 %). Chez les hommes, le principal mécanisme de blessure était la distraction de la colonne (47,9%) alors que chez la femme, c'était la compression axiale (44,8%). Des associations significatives sont apparues entre les causes énumérées ci-dessus et la gravité des blessures à la colonne vertébrale de même qu'entre le mécanisme de blessure et la gravité des blessures à la colonne vertébrale, le sexe des patients et la gravité des LMTE associées à des fractures vertébrales. La plupart des patients victimes d'un accident sur un véhicule sans dispositif de retenue ont subi une distraction thoraco-lombaire de la colonne vertébrale jumelée à un déficit moteur complet. Enfin, un déficit neurologique marqué a affecté la plupart des patients victimes d'un accident de la route ayant subi une distraction cervicale et une torsion axiale. Conclusions: Au Québec, la plupart des LMTE associées à des fractures vertébrales et causées par des accidents de la route affectent une population plus jeune et entraînent de graves déficits neurologiques. À l'avenir, on devrait tenter de mieux comprendre les accidents impliquant des moyens de transport dépourvus de dispositif de retenue afin d'améliorer davantage les mesures préventives.

Teaching simulated arthroscopic Bankart repair: residents' assessment at the Annual Shoulder Course

Background: This study's aim was to evaluate the performance of senior orthopedic residents during simulated arthroscopic anterior stabilization (Bankart repair) before and after a national shoulder review course. Methods: Participants were assessed before and after the Annual Shoulder Review Course over a 3-day period, using a multiple-choice examination and surgery performance assessment. The surgical evaluation was completed by fellowship-trained surgeons using a standardized procedure checklist and a global rating scale. All Canadian senior orthopedic residents were invited to participate in the course. Results: The 57 participants showed improvement following the course. The written knowledge evaluation mean score increased, and all 3 surgical performance measurements improved: surgical task time improved from 4:40 min to 2:53 min (p < 0.001), surgical technique evaluation increased from 56% to 67% after the procedure checklist (p < 0.001), and anchor placement improved for all 3 aspects. Anchor entry point was the sole measure not to improve enough to reach statistical significance (p = 0.37). Conclusion: Our data support the inclusion of dry model surgical simulation as part of a surgical skills course for both training and assessment of orthopedic surgery residents.

Contexte: Le but de cette étude était d'évaluer le rendement des résidents seniors en orthopédie durant une simulation de stabilisation arthroscopique antérieure (intervention de Bankart) avant et après un cours de révision national sur l'articulation de l'épaule. Méthodes: Les participants ont été évalués avant et après l'Annual Shoulder Review Course sur une période de 3 jours, à l'aide d'un examen à choix multiples et d'une épreuve chirurgicale pratique. L'évaluation chirurgicale était effectuée par des chirurgiens spécialisés, à l'aide d'une liste de vérification normalisée des procédures et d'une échelle d'évaluation globale. Tous les résidents séniors canadiens en orthopédie étaient invités à participer au cours. Résultats: Les 57 participants ont montré une amélioration après le cours. Lesrésultats à l'examen écrit ont augmenté, tout comme ceux des 3 évaluations chirurgicales : le temps chirurgical a diminué, passant de 4:40 min à 2:53 min (p < 0,001), l'évaluation de la technique chirurgicale a augmenté de 56 % à 67 % selon la liste de vérification (p < 0,001) et le positionnement des ancres s'est aussi amélioré pour les 3 positionnements. Le point d'entrée des ancres a été la seule mesure à ne pas s'améliorer suffisamment pour atteindre une portée statistique (p = 0,37). Conclusion: Nos données appuient l'inclusion d'un modèle de simulation sec pour la formation et l'évaluation des résidents en chirurgie orthopédique.

Suture bridge transosseous equivalent repair is stronger than transosseous tied braided-tape.

BACKGROUND: This study biomechanically compares two methods of supraspinatus repair: single row transosseous braided-tape (BT) and suture bridge transosseous equivalent (SBTE) with 2 medial anchors and 2 lateral anchors. The purpose is to test the hypothesis that BT provides superior or equal biomechanical strength compared to SBTE. METHODS: Nine pairs of frozen cadaveric shoulders were selected and both repair techniques were tested on each pair, using a biomechanical testing unit to measure cyclic loading and ultimate load to failure. Moreover, tendon displacement was measured using the percentage of footprint exposed during the cyclic loading phase. RESULTS: Mean specimen age was 71 years (6 males, 3 females), and mean volumetric bone mineral density was 134 mg/cm3. BT mean ultimate load was 266 ± 81 Newton (N) compared to 398 ± 69 N for SBTE and this difference of 131 N was statistically significant p = 0.025. There was a strong positive correlation between bone mineral density and SBTE construct ultimate load. The difference between the percentage of footprint exposed after cyclic loading of the two repairs was statistically significant with the exception of the 10-80 N load (p < 0.05). The failure mode was suture cutout through the tendon in 88% (7/8) of specimens for both techniques. CONCLUSION: SBTE repair with bone anchors provides superior biomechanical strength compared to BT repair in terms of ultimate load and cyclic loading. The tendon-suture junction is the weakness of both methods. These models simulate a complete tear with total loss of contact with rotator interval and infraspinatus. Future studies could focus on a more isolated physiologic supraspinatus tear pattern. LEVEL OF EVIDENCE: Basic science study (Level II).

Comparison of Pedicle Screw Loosening Mechanisms and the Effect on Fixation Strength.

Screw loosening is a common complication in spinal fixation using pedicle screws which may lead to loss of correction and revision surgery. The mechanisms of pedicle screw loosening are not well understood. The purpose of this study was to compare the pedicle screw pullout force and stiffness subsequent or not to multidirectional cyclic bending load (toggling). Pedicle screws inserted into porcine lumbar vertebrae underwent toggling in craniocaudal (CC), mediolateral (ML) directions, and no toggling (NT) before pullout. This study suggests that toggling and in particular CC toggling should be included in biomechanical evaluation of pedicle screw fixation strength.

The relevance of sacral and sacro-pelvic morphology in developmental lumbosacral spondylolisthesis: are they equally important?

STUDY DESIGN: Retrospective study of the importance of sacral and sacro-pelvic morphology in developmental L5-S1 spondylolisthesis. OBJECTIVES: To determine and compare the importance of sacral and sacro-pelvic morphology in developmental L5-S1 spondylolisthesis. Recent studies have shown abnormalities in sacral and sacro-pelvic morphology in spondylolisthesis. However, it is still unclear if sacral and sacro-pelvic morphology are correlated and if they are equally important in the progression of spondylolisthesis. METHODS: Lateral radiographs of 120 controls and 131 subjects with developmental L5-S1 spondylolisthesis were analyzed. Sacral table angle (STA) and pelvic incidence (PI) were compared using Student t tests. The relationship between STA and PI was assessed separately in the control and spondylolisthesis groups using Pearson's coefficients. The proportion of subjects with high PI but average STA was compared to the proportion of subjects with low STA but average PI using χ (2) tests. RESULTS: STA was significantly lower and PI was significantly higher in the spondylolisthesis group. STA was statistically related to PI in both control (r = -0.43) and spondylolisthesis (r = -0.57) groups. In the spondylolisthesis group, STA (r = -0.45) and PI (r = 0.35) were significantly related to slip percentage. STA remained statistically related to slip when controlling for PI. A significantly greater proportion of subjects in the spondylolisthesis group had average STA and high PI, rather than average PI and low STA. CONCLUSION: The significant relationship between PI and STA validates that geometrically sacral morphology depends on sacro-pelvic morphology. This study failed to demonstrate a clear predominant role of either STA or PI in the presence of spondylolisthesis.

The influence of proximal anchors on the risk of proximal junctional fracture in the osteoporotic spine: biomechanical comparison between pedicle screws and transverse process hooks.

STUDY DESIGN: Biomechanical comparison of the risk of proximal junctional fracture (PJF) after multilevel spinal instrumentation using pedicle screws or transverse process hooks on the top of a pedicle screw construct. OBJECTIVE: To compare the loads leading to PJF when using pedicle screws or transverse process hooks at the proximal level after multilevel spinal instrumentation using pedicle screws. SUMMARY OF BACKGROUND DATA: With stronger spinal fixation techniques, there is increased risk of PJF, especially in the osteoporotic spine. The use of transverse process hooks over pedicle screws at the proximal level of multilevel pedicle screw constructs has been proposed to decrease the incidence of PJF. However, there is no biomechanical study evaluating this concept. METHODS: Twenty-four segments of 4 vertebrae from 6 human cadaveric spines were evaluated after instrumentation of the distal 3 vertebrae using pedicle screws, except at the top of the construct where either pedicle screws (AP group) or transverse process hooks (PTPH group) were placed. The proximal vertebra was left uninstrumented. Quantitative computed tomography scan was used before instrumentation in order to assess the bone density for each specimen. Cyclic compression loading between 50 and 1000 N at 1 Hz was applied to each of 24 instrumented spinal segments until obtaining a PJF. RESULTS: Bone density was similar between the AP and PTPH groups. A PJF occurred in 22 of 24 tested specimens. The number of cycles required to produce the PJF ranged between 2 and 1002. The number of cycles required to produce the PJF was similar between the AP construct group (median: 3; interquartile range: 3-7) and the PTPH construct group (median: 4; interquartile range: 3-5). CONCLUSIONS: The current study failed to observe a significant impact of using transverse process hooks over pedicle screws on top of multilevel pedicle screw construct to decrease the risk of PJF.

Three-dimensional finite element modeling of the human external ear: simulation study of the bone conduction occlusion effect.

A linear three-dimensional (3D) elasto-acoustic finite element model was used to simulate the occlusion effect following mechanical vibration at the mastoid process. The ear canal and the surrounding soft and bony tissues were reconstructed using images of a female cadaver head (Visible Human Project(®)). The geometrical model was coupled to a 3D earplug model and imported into comsol Multiphysics (COMSOL(®), Sweden). The software was used to solve for the sound pressure at the eardrum. Finite element modeling of the human external ear and of the occlusion effect has several qualities that can complement existing measuring and modeling techniques. First, geometrically complex structures such as the external ear can be reconstructed. Second, various material behavioral laws and complex loading can be accounted for. Last, 3D analyses of external ear substructures are possible allowing for the computation of a broad range of acoustic indicators. The model simulates consistent occlusion effects (e.g., insertion depth variability). Comparison with an experimental dataset, kindly provided by Stenfelt and Reinfeldt [Int. J. Audiol. 46, 595-608 (2007)], further demonstrates the model's accuracy. Power balances were used to analyze occlusion effect differences obtained for a silicone earplug and to examine the increase in sound energy when the ear canal is occluded (e.g., high-pass filter removal).

Quantitative validation of two model-based methods for the correction of probe pressure deformation in ultrasound.

PURPOSE: The acquisition of good quality ultrasound (US) images requires good acoustic coupling between the ultrasound probe and the patient's skin. In practice, this good coupling is achieved by the operator applying a force to the skin through the probe. This force induces a deformation of the tissues underlying the probe. The distorted images deteriorate the quality of the reconstructed 3D US image. METHODS: In this work, we propose two methods to correct these deformations. These methods are based on the construction of a biomechanical model to predict the mechanical behavior of the imaged soft tissues. The originality of the methods is that they do not use external information (force or position value from sensors, or elasticity value from the literature). The model is parameterized thanks to the information contained in the image. This is allowed thanks to the optimization of two key parameters for the model which are the indentation d and the elasticity ratio α. RESULTS: The validation is performed on real images acquired on a gelatin-based phantom using an ultrasound probe inducing an increasing vertical indentation using a step motor. The results showed a good correction of the two methods for indentations less than 4 mm. For larger indentations, one of the two methods (guided by the similarity score) provides a better quality of correction, presenting a Euclidean distance between the contours of the reference image and the corrected image of 0.71 mm. CONCLUSION: The proposed methods ensured the correction of the deformed images induced by a linear probe pressure without using any information coming from sensors (force or position), or generic information about the mechanical parameters. The corrected images can be used to obtain a corrected 3D US image.

Optimization of S2-alar-iliac screw (S2AI) fixation in adult spine deformity using a comprehensive genetic algorithm and finite element model personalized to patient geometry and bone mechanical properties.

PURPOSE: To optimize the biomechanical performance of S2AI screw fixation using a genetic algorithm (GA) and patient-specific finite element analysis integrating bone mechanical properties. METHODS: Patient-specific pelvic finite element models (FEM), including one normal and one osteoporotic model, were created from bi-planar multi-energy X-rays (BMEXs). The genetic algorithm (GA) optimized screw parameters based on bone mass quality (BM method) while a comparative optimization method maximized the screw corridor radius (GEO method). Biomechanical performance was evaluated through simulations, comparing both methods using pullout and toggle tests. RESULTS: The optimal screw trajectory using the BM method was more lateral and caudal with insertion angles ranging from 49° to 66° (sagittal plane) and 29° to 35° (transverse plane). In comparison, the GEO method had ranges of 44° to 54° and 24° to 30° respectively. Pullout forces (PF) using the BM method ranged from 5 to 18.4 kN, which were 2.4 times higher than the GEO method (2.1-7.7 kN). Toggle loading generated failure forces between 0.8 and 10.1 kN (BM method) and 0.9-2.9 kN (GEO method). The bone mass surrounding the screw representing the fitness score and PF of the osteoporotic case were correlated (R2 > 0.8). CONCLUSION: Our study proposed a patient-specific FEM to optimize the S2AI screw size and trajectory using a robust BM approach with GA. This approach considers surgical constraints and consistently improves fixation performance.

Does radiographic beam angle affect the radiocapitellar ratio measurement of subluxation in the elbow?

BACKGROUND: Radial head alignment is the key to determine elbow reduction after treatment of subluxations or Monteggia fractures. The radiocapitellar ratio (RCR) quantifies the degree of subluxation, by evaluating radial head alignment with the capitellum of the humerus; this ratio is reproducible when measured on true lateral radiographs of nonsubluxated elbows. However, the impact of beam angulation on RCR measurement is unknown. QUESTIONS/PURPOSES: Our hypotheses were that the RCR of the nonsubluxated elbow would remain in the normal range as the beam angle changed and that the RCR variability would increase for the subluxated elbow with small deviations in the beam angle. METHODS: Radiographs were taken of six healthy cadaveric extremities using beam angles ranging from -20° to 20° along the inferosuperior axis and from -20° to 20° along the dorsoventral axis. The same views then were taken of the six arms with anterior radiocapitellum subluxation followed by posterior radiocapitellum subluxation. RCRs were measured by one observer. As a reference value, the RCR was measured in the 0° to 0° position and the difference between each RCR in a nonreference position was subtracted from each RCR reference to obtain the delta-RCR. An ANOVA was performed to assess the main and interactive effects on the RCR measured in each C-arm position compared with the RCR measured on a true lateral radiograph. RESULTS: The RCR remained in the normal range even as the beam angle of the C-arm varied between -20° and 20°. The position of the beam did not affect the RCR in anteriorly subluxated elbows (p = 0.777), whereas RCR variation increased especially in the presence of posterior radial head subluxation when the C-arm position was 10° or more out of plane (p = 0.006). The inferosuperior malposition of the C-arm had a greater impact on quantification of radial head alignment measurement. Despite that, the RCR measurement is reliable in reduced and subluxated elbows on lateral radiographs with a C-arm position deviation of as much as 20°. CONCLUSIONS: Identification of a subluxated elbow could be made on any lateral radiograph with a beam angulation deviation of as much as 20°. This suggests that the RCR is a useful diagnostic tool for clinical and research purposes, although for subluxated elbows, it is important to pay careful attention to the inferosuperior position of the C-arm.

Compressive loading of the spine may affect the spinal canal encroachment of burst fractures.

STUDY DESIGN: Spinal canal encroachment of burst fractures under different compressive loading. OBJECTIVE: To assess whether the application of different compressive loads affect the spinal canal encroachment (SCE) of thoracolumbar burst fractures and to relate any significant encroachment differences to the fracture morphology. SUMMARY OF BACKGROUND DATA: The SCE is an important part of the evaluation process of thoracolumbar burst fractures. It is, however, not well understood how a variation in spinal internal loads resulting from a change in patient posture may affect the SCE after a burst fracture. The application of a compressive load on fractured vertebrae may displace bony fragments further into the canal and increase the encroachment. METHODS: Ten thoracolumbar functional spinal units harvested from mature minipigs and compressed to create burst fractures were imaged by computed tomography under 3 loading conditions: without compressive force and with 2 compressive forces analogous to the load expected in vivo. SCE were measured for all loading cases and compared with each other to identify whether they systematically changed between loading cases and to discriminate which specimens were affected by an increase in the loading. RESULTS: The application of a compressive loading did not systematically increase the SCE. However, specimens with a large bony fragment originating from the superior and posterior aspect of the vertebral body with a centrifugal orientation had a significant increase of SCE when loaded. CONCLUSIONS: An increase in spinal internal loads resulting from a change in the patient posture may increase the SCE of burst fracture. Measurement of the SCE should take into account the bony fragment distribution of burst fracture.

Demographic and anthropometric factors affecting elbow range of motion in healthy adults.

BACKGROUND: To use elbow range of motion routinely as a diagnostic index, it is important to explain the normal variability among the population. Consequently, this study assessed the possible associations between age, sex, laterality, body mass index, joint laxity, level of physical activities, upper limb dimensions, and the elbow range of motion in flexion/extension. MATERIALS AND METHODS: Maximal flexion and extension were measured on the lateral radiographs of 102 elbows of 51 volunteers. The difference of range of motion regarding sex and laterality was assessed with Student t tests. The Pearson correlation coefficient was used to evaluate the relationship between elbow mobility and the other factors, and a stepwise multiple regression analysis was performed. RESULTS: Among the 51 volunteers, a correlation was found between flexion and body mass index, age, and midbrachial and forearm circumferences (r = -0.234 to -0.594). Age (r = 0.268) and hyperlaxity (r = -0.323) were the only factors associated with a change in elbow extension. No correlation was found between the level of physical activity or with the laterality and changes in elbow mobility. Finally, women presented with more flexion and total elbow range of motion than men. CONCLUSIONS: This study confirms the association between various demographic and anthropometric factors and elbow range of motion in healthy adults. Among these, the body mass index and forearm circumference are the most likely responsible for mobility variations among the population.

Initial tension loss in cerclage cables.

Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure tension during insertion. Significant tension loss was observed with crimping for all cables (P<0.05). Removing the tensioner led to an additional unexpected tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent tension loss.