Biomechanical comparison of composite and cadaveric humeri models in experiments on operated humeral shaft fractures.

A study was undertaken to determine how well contacting fracture fragments of composite bone replicated the behavior of fracture fragments in real bone. Ten composite and ten real humeral diaphyses were transected and reconstructed with limited-contact dynamic-compression plates. Two screws were placed on each side of the transection site and a calibrated electronic sensor sheet was placed between the imitated fracture fragments. After insertion of the distal screws, pressure measurements were made during insertion of the first proximal screw in compression mode, during insertion of the second screw in compression mode after loosening the first screw, and finally after retightening the first screw. The process was repeated after bending the plate. The contact area, the net compression force and the average compressive stress were computed and statistically compared. The composite bone and cadaveric bone differed in contact area and compressive stress but not in net compressive force. Plate bending did not produce a significant difference between composite and cadaveric bone. The results indicate that composite bone does not reproduce all the local fracture fragment conditions so that hardware testing in composite bone should proceed carefully. A gap between fracture fragments as is often used in comminuted fracture tests may remain as the most appropriate situation for fracture hardware testing.

The impact of intersectional racial and gender biases on minority female leadership over two centuries.

This study scrutinizes the enduring effects of racial and gender biases that contribute to the consistent underrepresentation of minority women in leadership roles within American private, public, and third sector organizations. We adopt a behavioural data science approach, merging psychological schema theory with sociological intersectionality theory, to evaluate the enduring implications of these biases on female leadership development using mixed methods including machine learning and econometric analysis. Our examination is concentrated on Black female leaders, employing an extensive analysis of leadership rhetoric data spanning 200 years across the aforementioned sectors. We shed light on the continued scarcity of minority female representation in leadership roles, highlighting the role of intersectionality dynamics. Despite Black female leaders frequently embracing higher risks to counter intersectional invisibility compared to their White counterparts, their aspirations are not realized and problems not solved generation after generation, forcing Black female leaders to concentrate on the same issues for dozens and, sometimes, hundreds of years. Our findings suggest that the compound influence of racial and gender biases hinders the advancement of minority female leadership by perpetuating stereotypical behavioral schemas, leading to persistent discriminatory outcomes. We argue for the necessity of organizations to initiate a cultural transformation that fosters positive experiences for future generations of female leaders, recommending a shift in focus from improving outcomes for specific groups to creating an inclusive leadership culture.

"Safe dissection parameters of the anconeus rotational flap for soft tissue coverage at the elbow".

Background: The anconeus is a small muscle located on the posterior elbow originating on the lateral epicondyle and inserting onto the proximal-lateral ulna that functions as an elbow extensor as well as dynamic stabilizer. The blood supply is tri-fold: medial/middle collateral artery (MCA), recurrent posterior interosseous artery (RPIA), and less commonly found, the posterior branch of the radial collateral artery. The anconeus has become a popular option for local soft tissue coverage about the elbow (distal triceps, olecranon, proximal forearm). The average defect size for consideration of local anconeus flap coverage is 5-7cm2. The aim of the study was to determine safe dissection parameters of the anconeus as well as map arterial pedicles to achieve successful local harvest of the muscle without devascularization. Materials and Methods: 8 fresh frozen cadaveric arms (all male, average age 63 years - 4 left arms, 4 right arms) from scapula to fingertip were obtained. First, the radial, ulnar and axillary arteries were dissected and isolated. The radial and ulnar arteries were transected. 100cc normal saline was injected through the axillary artery, sequentially clamping the radial followed by the ulnar artery so that adequate flow could be seen through all vessels. 100cc mixture of Biodür and hardener (10:1) was mixed and injected into the axillary artery. We first allowed free flow through both the ulnar and radial vessels followed by clamping of these vessels. This allowed the pressure to build up and fill the smaller vessels in the arms. After injection, the axillary artery was then clamped and the specimens were left to harden for 24-48 h. After hardening, dissection was performed by making a curvilinear incision centred over the lateral epicondyle. The anconeus was identified and the interval between the anconeus and ECU was then confirmed. Measurements of the anconeus muscle were taken. Blunt dissection was carried between anconeus and ECU until the RPIA was identified and protected. We isolated the MCA by dissecting proximally. This was found to run with the nerve to the anconeus. Once this vessel had been protected, the muscle reflected from distal to proximal staying along its ulnar border. The branches of the RPIA were ligated and the dissection was continued proximally. Measurements of the distances of the RPIA, MCA were taken. Results: The average distance of olecranon to muscle tip was 95.0mm. The average distance of lateral epicondyle (LE) to muscle tip was 90.8mm. The average distance of LE to olecranon was 49.8mm. The average location of the RPIA was 63.mm when measuring LE to vessel, 68.3mm when measuring olecranon to vessel, 18.3mm when measuring RPIA to muscle tip. The average RPIA diameter was 1.1mm and length was 36.4mm from the initial branching of the posterior interosseous artery. The average MCA diameter was 0.7mm. The posterior branch of the radial collateral artery was only found in 3/8 specimens. The RPIA and MCA were constant in all specimens. Dissection was safely carried to the border of the LE and olecranon without disruption of the MCA. CONCLUSIONS: Our conclusions determined that if dissection of the anconeus is undertaken, the RPIA remains constant between the interval of the ECU as well as anconeus at an average distance of 18.3mm from the tip of the muscle measuring proximally; moreover, the MCA was constant in all specimens found directly between the LE and olecranon always running with the nerve to the anconeus. When dissecting and mobilizing to ensure preservation of the MCA, dissection should be taken from distal to proximal as well as dissecting along the ulnar border of the anconeus. Proximal dissection can be taken as proximal as the border of the LE and olecranon as that did not disrupt MCA blood supply.

Digital medicine: the next big leap advancing cardiovascular science.

Solid clinical and academic leadership remains necessary to ensure that healthcare based on digital technologies is relevant, meaningful, and stands on the best possible evidence. This compendium accompanying the "Digital Technologies in Cardiovascular Disorders" article collection in BMC Cardiovascular Disorders summarizes recent knowledge about robust and advanced digital tools for preventing, monitoring, diagnosing, and treating cardiovascular diseases.

Biomechanical Analysis of Ideal Knee Flexion Angle for ACL Graft Tensioning Utilizing Multiple Femoral and Tibial Tunnel Locations.

Anterior cruciate ligament (ACL) graft failure rate has been reported to be greater than 5% at 5 years. Our study evaluated ACL excursion with anatomic and nonanatomic femoral and tibial tunnels to determine optimal flexion angle to tension the ACL to minimize excursion. Ten cadaveric knee specimens were used. The ACL was sectioned and the femoral and tibial attachments were marked. A 1/16-inch drill created a tunnel in the center of the ACL footprint on the tibia and femur and additional tunnels were made 5 mm from this. A suture was passed through each tunnel combination and attached to a string potentiometer. The knee was ranged from full extension to 120 degrees of flexion for 10 cycles while mounted in a custom fixture. The change in length (excursion) of the suture during movement was recorded for each combination of femoral and tibial tunnels. Anatomic reconstruction of the ACL with tunnel placement in the center of the femoral and tibial footprint did not result in an isometric graft, with excursion of the ACL during knee motion of 7.46 mm (standard deviation [SD]: 2.7mm), greatest at 2.84 degrees of flexion (SD: 4.22). The tunnel combination that resulted in the least excursion was a femoral footprint 5 mm anterior to the femoral and 5 mm posterior to the tibial footprint (4. 2mm, SD: 1.37 mm). The tunnel combination that resulted in the most excursion utilized femoral footprint 5 mm proximal to the femoral and 5 mm posterior to the tibial footprint (9.81 mm, SD: 2.68 mm). Anatomic ACL reconstruction results in significant excursion of the ACL throughout motion. If not tensioned properly, the ACL can stretch during range of motion, potentially leading to rerupture. To prevent stretching of the graft, the current biomechanical study recommends tensioning an anatomic ACL reconstruction at its point of maximal excursion, or between 0 and 5 degrees of flexion. The level of evidence is IV.

Stability, deformity, and fixation of the floating shoulder: a cadaveric biomechanical study.

BACKGROUND: Floating shoulder injuries cause instability and deformity due to disruptions of the scapula, clavicle, and superior shoulder suspensory complex ligaments (SSSC). Resulting deformity of the glenopolar angle (GPA) has not previously been established, nor has the impact on stability and deformity when surgical fixation is performed. This study sought to quantify stability and deformity for multiple injury patterns and the improvement to these parameters provided by clavicle and coracoclavicular (CC) ligament fixation. METHODS: Fourteen cadaveric specimen upper extremities were used, which included the entire upper extremity, scapula, clavicle, and cranial-most ribs. After being mounted upright, a scapular neck fracture was created, followed by either a midshaft clavicle fracture or sectioning of the acromioclavicular and coracoacromial ligaments. Subsequent sectioning of the other structure(s) followed by the CC ligaments was then performed. In all specimens, the clavicle was then plated, followed by a CC ligament repair. At each step, a radiograph in the AP plane of the scapula was taken to measure GPA and displacement of the glenoid fragment using radiopaque markers placed in the scapula. These radiographs were taken both unloaded and with a 100-N applied medializing force. RESULTS: When evaluating deformity related to sectioning, the GPA was reduced when the CC ligaments were sectioned compared to an isolated scapula fracture (P = .022) and compared to a combined scapula and clavicle fracture (P = .037). For stability, displacement with a 100-N force was significantly increased when the CC ligaments were sectioned compared to an isolated scapula fracture (P = .027). In cases of an ipsilateral scapula neck and clavicle fracture with intact ligaments, fixation of the clavicle alone provided a statistically significant improvement in the GPA (P = .002); but not in reduction of displacement (P = .061). In cases of an ipsilateral scapula neck and clavicle fracture with concomitant disruption of the coracoacromial, acromioclavicular, and CC ligaments, the GPA was improved by clavicle fixation (P < .001) and increasingly so by subsequent CC ligament repair (P < .001). Displacement was also improved in these 2 states (P < .001, P = .008, respectively). DISCUSSION: This biomechanical study confirmed the importance of the acromioclavicular, coracoacromial, and CC ligaments in conferring stability in SSSC injuries. Disruption of the CC ligaments created significant deformity of the GPA and instability with a medializing force. Clinical treatment should consider the integrity of these ligaments and their repair in conjunction with clavicle fixation, knowing that this combination should restore a biomechanical state equivalent to an isolated scapula fracture.

A biomechanical comparison of superior ramus plating versus intramedullary screw fixation for unstable lateral compression pelvic ring injuries,,.

INTRODUCTION: Management of the anterior component of unstable lateral compression (LC) pelvic ring injuries remains controversial. Common internal fixation options include plating and superior pubic ramus screws. These constructs have been evaluated in anterior-posterior compression (APC) fracture patterns, but no study has compared the two for unstable LC patterns, which is the purpose of this study. METHODS: A rotationally unstable LC pelvic ring injury was modeled in 10 fresh frozen cadaver specimens by creating a complete sacral fracture, disruption of posterior ligaments, and ipsilateral superior and inferior rami osteotomies. All specimens were repaired posteriorly with two fully threaded 7 mm cannulated transiliac-transsacral screws through the S1 and S2 corridors. The superior ramus was repaired with either a 3.5 mm pelvic reconstruction plate (n = 5) or a bicortical 5.5 mm cannulated retrograde superior ramus screw (n = 5). Specimens were loaded axially in single leg support for 1000 cycles at 400 N followed by an additional 3 cycles at 800 N. Displacement and angulation of the superior and inferior rami osteotomies were measured with a three-dimensional (3D) motion tracker. The two fixation methods were then compared with Mann-Whitney U-Tests. RESULTS: Retrograde superior ramus screw fixation had lower average displacement and angulation than plate fixation in all categories, with the motion at the inferior ramus at 800 N of loading showing a statistically significant difference in angulation. CONCLUSION: Although management of the anterior ring in unstable LC injuries remains controversial, indications for fixation are becoming more defined over time. In this study, the 5.5 mm cannulated retrograde superior ramus screw significantly outperformed the 3.5 mm reconstruction plate in angulation of the inferior ramus fracture at 800 N. No other significance was found, however the ramus screw demonstrated lower average displacements and angulations in all categories for both the inferior and superior ramus fractures.

Biomechanical analysis of stability of joint depression calcaneal fractures: Fixation with locking compression plate alone compared with addition of supplemental oblique screw.

Purpose: The standard treatment of calcaneus fractures is a lateral plate and screw construct. Patients at our institution have been treated with a lateral locking plate combined with one retrograde screw inserted in the oblique plane to allow immediate weight bearing. The purpose of this study was to determine whether addition of a oblique screw to a lateral plate construct increases stability. Methods: A Sanders 2B fracture (AO/OTA 83-C2) was created in 8 pairs (16 total specimens) of cadaveric feet. All were repaired using a lateral locking plate/screws construct. One specimen in each pair was chosen randomly to receive an additional oblique screw. The specimens were tested with cyclic load of up to 800 N. Movement at the fracture sites and subsidence of the talus were tracked with a three-dimensional video analysis system. Results: Talar subsidence was not significantly affected by the presence of the additional oblique screw (p = 0.22). The sustentaculum fragment in the case of the screw repair moved 0.39 mm while the same fragment without the additional screw repair displaced 0.12 mm (p < 0.01). Two repairs with and one repair without the additional screw failed during longer-term cyclic loading. Conclusion: The two repair types were not statistically different in regards to talar subsidence. While statistical significance resulted in the comparison of sustentaculum fragment movement, the amount of movement did not reach a level of clinical relevance. This study demonstrated immediate stability and durability of the additional screw construct with high volume weight bearing loads.

Conduit/Wrap Repairs to Digital Nerves Provide Residual Strength After Peak Loading.

BACKGROUND: Many techniques are used for digital nerve repair, most commonly coaptation by sutures. Nerve repairs must be strong while offering an environment for nerve regeneration. Sutures can damage the nerve and thereby limit growth and regeneration. Sutures can rip and cause sudden catastrophic failure. Fibrin glue and conduit-wraps allow a good environment for growth, but neither provides much strength. A benefit to conduit repair would arise if the repair maintained integrity after the peak load so that the path for regrowth stayed in place. The goal for this study was to determine whether conduit with glue provides continued strength after a maximum load is reached. METHODS: Digital cadaveric nerves were harvested and repaired with 2 epineurial sutures, conduit, and fibrin glue in all combinations. Tests to failure were performed, gap displacement between nerve ends recorded, and the postpeak load energy to dissociation of the nerve and conduit was calculated. RESULTS: Conduit with glue and 2 sutures at the end had the greatest energy and displacement after the peak load but was not significantly different than conduit with glue and 1 suture. Conduit with glue alone obtained statistically the same displacement as conduit with glue and 2 sutures. Conduit, with or without glue, and 2 sutures was statistically the same as suture only repair for peak load. CONCLUSION: Conduit/wrap maintains a load capacity and a path for nerve regeneration after the peak. Suture at the ends of conduit, not at the coaptation site, reduces damage at the point of injury.

Valgus fatigue and nonlinear damage accretion of the anterior bundle of the elbow medial collateral ligament (AMCL).

Failure by fatigue is one mechanism by which ligaments can rupture, with the accumulation of damage gradually degrading the ligament strength. Baseball pitchers who perform repeated high-level throwing continuously subject the medial ligament complex of the elbow to extreme levels of loading, which can lead to fatigue and eventual rupture. This study sought to investigate this behavior and quantify the fatigue properties of the anterior bundle of the medial collateral ligament (AMCL) with respect to valgus elbow torque. Eleven pairs of cadaveric elbow specimens were used for this study. One side of each pair was tested in vertical elongation at four flexion angles and then tested to failure at 90° of flexion. The contralateral specimens were tested in valgus fatigue at 90° of flexion using a specialized apparatus with application of known moments based on the elongation failure load. The average tensile failure load for the AMCL was 595.3 ± 201.9 N. During cycling, the average increase in the maximum valgus rotation angle was 4.77° ± 2.82°. The average maximum stretch of the AMCL middle band increased from 1.066 ± 0.017 to 1.076 ± 0.018 near the time of fatigue failure. The average cycles to failure for specimens tested at 90% and 80% of the estimated failure torque were 3211 ± 4721.33 and 25063 ± 30487.58, respectively. The nonlinear non-dimensional fatigue life and damage accretion results work in conjunction to predict the fatigue properties for a valgus elbow motion of arbitrary torque magnitude at 90° of elbow flexion.

Fibrin Glue and Conduit Form a Composite Structure in Digital Nerve Repair.

Repair of severed nerves without autograft or allograft has included suture, suture with glue alone, suture with conduit and suture with glue augmentation to conduit, where use of conduit is considered for separation of the nerve ends from 5 mm to 3 cm. Repairs must not only serve acutely to provide apposition of nerve ends but must enable the healing of the nerve. Using biological conduit can place suture at the ends of the conduit while fibrin glue alone eliminates suture but with limited strength. The combination of conduit and glue offers the growth guidance of conduit with sufficient strength from the glue to maintain the nerve within the conduit. The role of fibrin glue in the integrity of the repair remains an open question, however. We sought to determine the factors in the strength of a glue-conduit-nerve construct and include consideration of standard suture repair. Fresh-frozen cadaveric digital nerves were repaired with suture alone, with glue alone or with suture and glue together and then loaded to failure. Previously tested specimens with conduit, suture and glue were considered for comparison. The suture alone (2.02 N) and suture with glue (2.24 N) were not statistically different from each other but were statistically stronger than glue alone (0.15 N). When compared to the earlier results of the strength of conduit with glue (0.65 N), these simple results show that the glue and conduit act together. The increased area over which the glue adheres to the nerve and conduit creates a composite structure stronger than either alone.

Avoiding the blood supply to the femoral head during cannulated screw fixation: A comparison of two techniques.

OBJECTIVES: To compare the strength of the inverted triangle (IT) versus the L-shaped cannulated screw fixation technique for stabilizing a Pauwels 2 femoral neck fracture. To demonstrate the risk to the blood supply to the femoral head from a posterior-superior screw. METHODS: The IT construct was compared with the L-shaped design in 10 composite femurs. A Pauwels 2 fracture was made with a 5 mm gap. Each specimen was loaded over 5000 cycles, measuring angular/shear displacement then loaded to failure. The data were analyzed using Mann-Whitney U test. Three separate fresh frozen cadavers were injected with low-viscosity epoxy. The intraosseous bloody supply was inspected in each femoral head (no fixation, IT, L-shaped). RESULTS: There was no difference in angular (P = .3) or shear displacement (P = .99) between either screw design after cyclical loading. Also, there was not statistical difference in load to failure testing between either construct (P = .99). The average load to failure in the IT group was 3204.4 N. The average was 3180.2 N in the L-shaped design. We demonstrated the presence of the intraosseous portion of the lateral epiphyseal vessel in the specimen without screw fixation. This was preserved in the specimen with the L-shaped design but absent in the specimen following IT fixation. CONCLUSIONS: The strength of the L-shaped construct was not statistically different than the strength of the IT design. The posterior-superior screw may put the main blood supply to the femoral head at risk and should be avoided.

Smart City Data Sensing during COVID-19: Public Reaction to Accelerating Digital Transformation.

The article presents the results of the analysis of the adaptation of metropolis IT technologies to solve operational problems in extreme conditions during the COVID-19 pandemic. The material for the study was Russian-language data from social networks, microblogging, blogs, instant messengers, forums, reviews, video hosting services, thematic portals, online media, print media and TV related to the first wave of the COVID-19 pandemic in Russia. The data were collected between 1 March 2020 and 1 June 2020. The database size includes 85,493,717 characters. To analyze the content of social media, a multimodal approach was used involving neural network technologies, text analysis, sentiment-analysis and analysis of lexical associations. The transformation of old digital services and applications, as well as the emergence of new ones were analyzed in terms of the perception of digital communications by actors.

Measurements of Tendon Movement Within the Bicipital Groove After Suprapectoral Intra-articular Biceps Tenodesis in a Cadaveric Model.

BACKGROUND: Lesions of the long head of the biceps can be successfully treated with biceps tenotomy or tenodesis when surgical management is elected. The advantage of a tenodesis is that it prevents the potential development of a cosmetic deformity or cramping muscle pain. Proponents of a subpectoral tenodesis believe that "groove pain" may remain a problem after suprapectoral tenodesis as a result of persistent motion of the tendon within the bicipital groove. PURPOSE/HYPOTHESIS: To evaluate the motion of the biceps tendon within the bicipital groove before and after a suprapectoral intra-articular tenodesis. The hypothesis was that there would be minimal to no motion of the biceps tendon within the bicipital groove after tenodesis. STUDY DESIGN: Controlled laboratory study. METHODS: Six fresh-frozen cadaveric arms were dissected to expose the long head of the biceps tendon as well as the bicipital groove. Inclinometers and fiducials (optical markers) were used to measure the motions of the scapula, forearm, and biceps tendon through a full range of shoulder and elbow motions. A suprapectoral biceps tenodesis was then performed, and the motions were repeated. The motion of the biceps tendon was quantified as a function of scapular or forearm motion in each plane, both before and after the tenodesis. RESULTS: There was minimal motion of the native biceps tendon during elbow flexion and extension but significant motion during all planes of scapular motion before tenodesis, with the most motion occurring during shoulder flexion-extension (20.73 ± 8.21 mm). The motion of the biceps tendon after tenodesis was significantly reduced during every plane of scapular motion compared with the native state (P < .01 in all planes of motion), with a maximum motion of only 1.57 mm. CONCLUSION: There was a statistically significant reduction in motion of the biceps tendon in all planes of scapular motion after the intra-articular biceps tenodesis. The motion of the biceps tendon within the bicipital groove was essentially eliminated after the suprapectoral biceps tenodesis. CLINICAL RELEVANCE: This arthroscopic suprapectoral tenodesis technique can significantly reduce motion of the biceps tendon within the groove in this cadaveric study, possibly reducing the likelihood of groove pain in the clinical setting.

Closed cranial window rodent model for investigating hemodynamic response to elevated intracranial pressure.

Background: Elevated intracranial pressure (ICP) occurs in several physiological and pathological conditions, yet long-term sequellae are not common, which implies that blood flow is preserved above ischemic thresholds. Methods: This pilot study sought to confirm this hypothesis using a closed cranial window model in a rat in which ICP was elevated to 120 mmHg for 12 min, and superficial cortical perfusion was measured by laser Doppler flowmetry and laser speckle flowmetry. Results: Following a transient increase, cortical blood flow decreased to between 25% and 75% of baseline. These levels correspond to disrupted metabolism and decreased protein synthesis but did not exceed thresholds for electrical signaling or membrane integrity. This may partially explain how some episodes of elevated ICP remain benign. Conclusion: The closed cranial window model provides a platform for prospective study of physiologic responses to artificially elevated ICP during neurosurgery to promote hemostasis.

Biomechanical Testing of a Transmetatarsal Base Screw in Lisfranc Injuries.

OBJECTIVES: To compare displacement between the cuneiforms and metatarsals for a typical Lisfranc screw and a transmetatarsal base screw under biomechanical loading. METHODS: Eight pairs of cadaveric feet (16 total) were evaluated. The Lisfranc ligamentous structures were transected in all specimens. All feet were repaired with screws traversing the first and second tarsometatarsal joints. A Lisfranc screw was placed from the first cuneiform to the second metatarsal in 8 specimens. A transmetatarsal base screw from the first metatarsal to the second metatarsal was placed in the remaining 8 corresponding feet. The repairs were randomized by side. Markers were placed on the dorsum of the midfoot for optical tracking. The feet were mounted into a load frame and loaded on the plantar forefoot to 100, 400, 800, and 1100 N. Displacement was measured and recorded using 3D camera tracking. RESULTS: Displacement between the first cuneiform and second metatarsal base was found to be significantly less (P = 0.02) with the transmetatarsal screw than the Lisfranc screw. There were no significant differences between displacements at any other articulations. CONCLUSIONS: This study demonstrates biomechanical superiority using a modified transmetatarsal base screw compared with the highly used Lisfranc screw for fixation of ligamentous Lisfranc injuries.

Medial Plating of Pauwels Type III Femoral Neck Fractures Decreases Shear and Angular Displacement Compared with a Derotational Screw.

OBJECTIVES: The purpose of this mechanical study was to compare 2 methods of augmented stabilization of Pauwels type III femoral neck fractures. METHODS: Ten matched pairs of young cadaveric femurs were cut 22 cm distal to the lesser trochanter. All specimens received a 70-degree osteotomy, which was stabilized with a 135-degree sliding hip screw. One of each pair received augmented fixation with a 6.5 mm fully threaded cannulated screw. The other specimen in the matched pair had additional fixation with a 3.5 mm 5-hole tubular plate placed at the inferior-medial femoral neck. Each specimen was tested under cyclic axial loading conditions (5000 cycles between 200 and 1400 N at 2 cycles/sec) and subsequently loaded to failure. The angular displacement (varus), interfragmentary (shear) displacement, and failure loads were calculated. RESULTS: In the augmented plate group, 7 specimens failed by angular displacement and 3 failed by shear displacement. In the augmented screw group, 8 specimens failed by angular displacement and 2 by shear displacement. The plate group was found to have significantly less angular displacement, regardless of completed cycles, than the augmented screw group (0.75 ± 0.35 degrees vs. 2.15 ± 1.99 degrees averaged across completed cycles, P < 0.01). Similarly, the plate group was found to have significantly less shear displacement, regardless of completed cycles, than the augmented screw group (0.77 ± 0.70 mm vs. 1.22 ± 0.92 mm averaged across completed cycles, P = 0.01). The average failure load of the plate group (4930 ± 1578 N) was also larger but not significantly different from the screw group (3824 ± 2140 N), P = 0.12. CONCLUSIONS: Augmenting sliding hip screw stabilization of a Pauwels type III fracture with a medial plate applied to the femoral neck significantly decreases angular displacement and shear displacement compared with augmentation with a derotational screw.

The moving valgus stress test produces more ulnar collateral ligament change in length during extension than during flexion: a biomechanical study.

HYPOTHESIS AND BACKGROUND: Injuries to the elbow medial ulnar collateral ligament (mUCL) pose a diagnostic challenge, with the moving valgus stress test (MVST) currently accepted as the gold-standard clinical test. This study sought to biomechanically evaluate the change in length of the ulnar collateral ligament (UCL) during flexion-extension using a null hypothesis that the mUCL will not experience a greater change in length with movement than with static loading. METHODS: Seven fresh-frozen human cadaveric elbows were tested with static and dynamic valgus stress. We measured (1) ligament length with a multi-camera optical system, (2) elbow flexion with an incremental encoder, and (3) valgus deviation with an electronic inclinometer. With a force applied to the wrist to simulate a clinical stress examination, the elbow was flexed and extended in a physiological elbow simulator to mimic the flexion and extension of the MVST. RESULTS: The simulated MVST produced more elongation of the UCL compared with static stress testing (P < .001). Ninety degrees of flexion produced the highest mean change, and the anterior and posterior bands demonstrated different length change characteristics. Comparison of dynamic flexion and extension showed a statistically significant difference in change in length: The mUCL reached the greatest change during extension, with the greatest changes during extension near 90° of flexion. DISCUSSION AND CONCLUSION: The MVST produces significantly more elongation of the mUCL than either a static test or a moving test in flexion. This study provides biomechanical evidence of the validity of the MVST as a superior examination technique for injuries to the UCL.

Biomechanical Response to Distraction of Hip Capsular Reconstruction With Human Acellular Dermal Patch Graft.

PURPOSE: To quantify the biomechanical properties of the hip capsule with human dermal allograft reconstruction to determine whether a dermal patch restored capsular resistance to distraction. METHODS: Nine cadaveric hip specimens were dissected until capsule and bony structures remained and were then mounted in a testing fixture in neutral flexion and abduction. Four states of the hip capsule were sequentially tested under axial distraction of 5 mm measured with video analysis and with resultant force measurement: (1) intact hip capsule, (2) interportal capsulotomy, (3) capsulectomy to the zona orbicularis, and (4) capsular reconstruction with human dermal allograft using acetabular anchors and capsule-to-patch sutures. RESULTS: Capsulectomy was different from intact (P = .036), capsulotomy differed from capsulectomy (P = .012), and the repair was statistically significantly different from capsulectomy (P = .042); intact and reconstructed cases were not statistically significantly different. The force required for 5 mm of distraction decreased after interportal capsulotomy by an average of 9% compared with the intact state and further decreased after capsulectomy by 30% compared with the intact state. After capsular reconstruction using dermal allograft, force requirements increased by an average of 36% from the capsulectomy state, only 5% below the intact state. CONCLUSIONS: Human dermal allograft tissue graft provides restoration of distractive strength for use during hip capsule reconstruction with acetabular anchor fixation and distal soft-tissue fixation after capsulectomy in a cadaveric model. CLINICAL RELEVANCE: Capsular repair or reconstruction with a dermal patch offers time-zero restoration of function; intact and reconstructed cases showed no difference, and reconstruction restored a capsulectomy to a biomechanical equivalent of the intact case when distraction was applied.