Contributions of the Abductor Muscles to Rotational and Distractive Stability of the Hip in a Biomechanical Cadaveric Model.

Background: The gluteus minimus (GMin) and gluteus medius (GMed) are important dynamic stabilizers of the hip, but quantitative data on their biomechanical roles in stabilizing the hip are currently lacking. Purpose: To (1) establish a reproducible biomechanical cadaveric model of the hip abductor complex and (2) characterize the effects of loading the GMin and GMed on extraneous femoral rotation and distraction. Study Design: Controlled laboratory study. Methods: A total of 10 hemipelvises were tested in 4 muscle loading states: (1) unloaded, (2) the GMin loaded, (3) the GMed loaded, and (4) both the GMin and GMed loaded. Muscle loads were applied via cables, pulleys, and weights attached to the tendons to replicate the anatomic lines of action. Specimens were tested under internal rotation; external rotation; and axial traction forces at 0°, 15°, 30°, 60°, and 90° of hip flexion. Results: When loaded together, the GMin and GMed reduced internal rotation motion at all hip flexion angles (P < .05) except 60° and reduced external rotation motion at all hip flexion angles (P < .05) except 0°. Likewise, when both the GMin and GMed were loaded, femoral distraction was decreased at all angles of hip flexion (P < .05). Conclusion: The results of this study demonstrated that the GMin and GMed provide stability against rotational torques and distractive forces and that the amount of contribution depends on the degree of hip flexion. Clinical Relevance: Improved understanding of the roles of the GMin and GMed in preventing rotational and distractive instability of the hip will better guide treatment of hip pathologies and optimize nonoperative and operative therapies.

Suture Tape Augmentation Increases the Time-Zero Stiffness and Strength of Anterior Cruciate Ligament Grafts: A Cadaveric Study.

Purpose: To determine the postsurgical strength and stiffness of anterior cruciate ligament (ACL) reconstructions with (ACLR-SA) and without suture tape augmentation (ACLR) in a human cadaveric model. Methods: Eight matched pairs of cadaveric knees were tested intact and after bone-patellar tendon-bone ACL reconstruction. Specimens were potted and loaded onto a mechanical testing system, and an anterior drawer force of 88N was applied at 0°, 15°, 30°, 60°, and 90° of flexion. Specimens were then loaded to failure, with clinical failure defined as anterior translation greater than 10 mm. Results: ACL-intact knees translated an average of 4.99 ± 0.28 mm across all flexion angles when an 88N anterior load was applied. ACLR knees had significantly greater translation compared to intact specimens. ACLRs with suture augmentation had less of an increase (0.67 mm, 95% confidence interval [CI]: 0.20, 1.14, P < .01) than those without suture augmentation (1.42 mm, 95% CI: 0.95, 1.89, P < .001). ACLR-SA required greater anterior load (170.4 ± 38.1 N) to reach clinical failure compared to ACLR alone (141.8 ± 51.2 N), P = .042. In addition, stiffness of ACLR-SA constructs (23.5 ± 3.3) were significantly greater than ACLR alone (20.3 ± 3.9), P = .003. Conclusion: Augmentation of ACLR with suture tape allowed full range of motion with improved graft stiffness and increased failure load compared to unaugmented ACLR in this time-zero study. Clinical Relevance: Internal bracing may help reinforce ACLR grafts and allow for acceleration of rehabilitation protocols and earlier return to activity.

Comparable Torque to Failure Using the Simple Stich Versus the Figure-of-Eight Configuration for Hip Capsular Closure Following an Interportal Capsulotomy: A Cadaveric Study.

PURPOSE: To measure and compare the torque to failure and stiffness of the capsular repair construct consisting of four-suture simple stitches to a two-figure of eight stitches repair construct in external rotation following an interportal capsulotomy. METHODS: Six pairs of fresh-frozen cadaveric hemipelves were divided into two capsular repair groups. All hips underwent a 40-mm interportal capsulotomy from the 12 o'clock position to the 3 o'clock position. Capsular closure was performed using either the two stitches in a figure of eight or with four simple stitches. Afterward, each hemipelvis was securely fixed to the frame of a mechanical testing system with the hip in 10° of extension and externally rotated to failure. Significance was set at P < .05. RESULTS: The average failure torque was 86.2 ± 18.9 N·m and 81.5 ± 8.9 N·m (P = .57) for the two stitches in a figure of eight and the four simple stitches, respectively. Failure stiffness was also not statistically different between groups and both capsular closure techniques failed at similar degrees of rotation (P = .65). CONCLUSION: Hip capsular repair using either the four simple stitch or two-figure of eight configurations following interportal capsulotomy demonstrated comparable failure torques and similar stiffness in a cadaveric model. CLINICAL RELEVANCE: Adequate and comprehensive capsular management in hip arthroscopy is critical. Capsular repair following capsulotomy in femoroacetabular impingement surgery has been associated with higher patient-reported outcomes when compared to capsulotomy without repair. Therefore, determining which capsular closure construct provides the higher failure torque is important.

An Increased Allograft Width for Circumferential Labral Reconstruction Better Restores Distractive Stability of the Hip: A Cadaveric Biomechanical Analysis.

BACKGROUND: Questions remain about whether circumferential labral reconstruction (CLR) using an iliotibial band (ITB) allograft can effectively restore the labral suction seal of the hip. HYPOTHESES: (1) CLR with an ITB allograft >6.5 mm would restore distractive stability force to that of the intact labrum. (2) CLR with an ITB allograft >6.5 mm would achieve significantly superior distractive stability force compared with CLR with an ITB allograft <6.5 mm. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 6 fresh-frozen pelves with attached femurs (n = 12 matched hemipelves) from male donors were procured and dissected free of all soft tissue, including the hip capsule but preserving the native labrum, transverse acetabular ligament, and ligamentum teres. Potted hemipelves were placed in a saline bath and securely fixed to the frame of a hydraulic testing system. A 500-N compressive load was applied, followed by femoral distraction at a rate of 5.0 mm/s until the suction seal ruptured. Force and femoral displacement were continually recorded. Force versus displacement curves were plotted, the maximum force was recorded, and the amount of femoral distraction to rupture the suction seal was determined. After intact testing, the labrum was excised, and specimens were retested using the same protocol. CLR was subsequently performed twice in a randomized fashion using (1) an ITB allograft with a width >6.5 mm (7.5-9.0 mm) and (2) an ITB allograft with a width <6.5 mm (4.5-6.0 mm). Specimens were retested after each CLR procedure. Force (in Newtons) and femoral distraction (in millimeters) required to rupture the suction seal were measured and compared between the 4 testing states (intact, deficient, CLR <6.5 mm, and CLR >6.5 mm) using repeated-measures analysis of variance. RESULTS: On average, intact specimens required 148.4 ± 33.1 N of force to rupture the hip suction seal, which significantly decreased to 44.3 N in the deficient state (P < .001). CLR with ITB allografts <6.5 mm did not improve the maximum force (63 ± 62 N) from the deficient state (P = .42) and remained significantly lower than the intact state (P < .01). CLR with ITB allografts >6.5 mm recorded significantly greater force to rupture the suction seal (135.8 ± 44.6 N) compared with both the deficient and CLR <6.5 mm states (P < .01), with a mean force comparable with the intact labrum (P = .59). The amount of femoral distraction to rupture the suction seal demonstrated similar findings. CONCLUSION: In a cadaveric model, CLR using ITB allografts >6.5 mm restored the distractive force and distance to the suction seal rupture to values comparable with hips with an intact labrum. CLR using ITB allografts >6.5 mm outperformed CLR with ITB allografts <6.5 mm, demonstrated by a significantly higher force to rupture the suction seal and increased distraction before the rupture. CLINICAL RELEVANCE: The results of this cadaveric investigation suggest that using wider labral allografts during CLR will provide the distractive force required to rupture the suction seal and immediate postoperative stability of the hip, although further studies are required to determine if these results translate to improved clinical outcomes.

Biomechanical Comparison of Ulnar Collateral Ligament Reconstruction With and Without Suture Augmentation.

BACKGROUND: A common concern associated with elbow ulnar collateral ligament (UCL) reconstruction is the amount of time required for recovery and rehabilitation. For example, for Major League Baseball pitchers, the average time to return to competition ranges from 13.8 to 20.5 months. Suture tape augmentation has shown the ability to provide additional soft tissue stability across other joints in the body. By providing an additional checkrein to the UCL reconstruction while the graft is healing, it may be possible to accelerate the rehabilitation process in overhead athletes and thus effect a quicker return to sports. PURPOSE: To compare elbow valgus stability and load to failure between UCL reconstruction with and without suture tape augmentation. STUDY DESIGN: Controlled laboratory study. METHODS: Fresh-frozen cadaveric elbows (N = 24) were dissected to expose the UCL. Medial elbow stability was tested with the UCL intact, deficient, and reconstructed utilizing the 3-strand docking technique with or without suture augmentation. A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion-tracking cameras as the elbow was cycled through a full range of motion. After kinematic testing, reconstructed specimens were loaded to failure at 70° of elbow flexion. RESULTS: UCL-deficient elbows demonstrated significantly greater valgus rotation when compared with intact and internally braced reconstructed elbows at every angle of flexion tested and when compared with unbraced UCL-reconstructed elbows at 50° to 120° of flexion (P < .05). There were no significant differences between intact and UCL-reconstructed elbows with and without suture augmentation at any flexion angle tested. When loaded to failure, unbraced reconstructed elbows failed at a significantly lower torque as compared with elbows with UCL reconstruction with suture tape augmentation (P < .01). CONCLUSION: In this cadaveric model, 3-strand UCL reconstruction with suture augmentation did not overconstrain the elbow throughout all flexion angles when compared with the native state and UCL reconstruction alone, while providing greater load to failure. CLINICAL RELEVANCE: Suture tape augmentation may provide the additional strength necessary to accelerate rehabilitation after UCL reconstruction.

Proximal Overresection During Femoral Osteochondroplasty Negatively Affects the Distractive Stability of the Hip Joint: A Cadaver Study.

BACKGROUND: Contact between the acetabular labrum and articular cartilage of the femoral head creates a suction seal that helps maintain stability of the femoral head in the acetabulum. A femoral osteochodroplasty may occasionally extend proximally into the femoral head, diminishing the articular surface area available for sealing contact. PURPOSE: To determine whether proximal overresection decreases the rotational and distractive stability of the hip joint. STUDY DESIGN: Controlled laboratory study. METHODS: Six hemipelvises in the following conditions were tested: intact, T-capsulotomy, osteochondroplasty to the physeal scar, and 5- and 10-mm proximal extension. The pelvis was secured to a metal plate, and the femur was potted and attached to a multiaxial hip jig. Specimens were axially distracted using a load from 0 to 150 N. For rotational stability testing, 5 N·m of internal and external torque was applied. Both tests were performed at different angles of flexion (0°, 15°, 30°, 60°, 90°). Displacement and rotation were recorded using a 3-dimensional motion tracking system. RESULTS: The T-capsulotomy decreased the distractive stability of the hip joint. A femoral osteochondroplasty up to the physeal scar did not seem to affect the distractive stability. However, a proximal extension of the resection by 5 and 10 mm increased axial instability at every angle of flexion tested, with the greatest increase observed at larger angles of flexion (P < .01). External rotation increased significantly after T-capsulotomy in smaller angles of flexion (0°, P = .01; 15°, P = .01; 30°, P = .03). Femoral osteochondroplasty did not create further external rotational instability, except when the resection was extended 10 mm proximally and the hip was in 90° of flexion (P = .04). CONCLUSION: This cadaveric study demonstrated that proximal extension of osteochondroplasty into the femoral head compromises the distractive stability of the hip joint but does not affect hip rotational stability. CLINICAL RELEVANCE: Clinically, this study highlights the importance of accuracy when performing femoral osteochondroplasty to minimize proximal extension that may increase iatrogenic instability of the hip joint.

Posterior Lateral Meniscal Root Tears Increase Strain on the Reconstructed Anterior Cruciate Ligament: A Cadaveric Study.

PURPOSE: To quantify the amount of strain across an anterior cruciate ligament reconstruction (ACLR) before and after a lateral meniscus (LM) posterior root complex tear and determine whether a meniscal root repair effectively protects the ACLR against excessive strain. METHODS: Fresh-frozen cadaveric knees were tested with an 88-N anterior drawer force and an internal and external torque of 5-Nm applied at 0°, 15°, 30°, 60°, and 90° of flexion. A simulated pivot shift was also applied at 0, 15, and 30° of flexion. Rotation and translation of the tibia, and strain across the ACL graft were recorded. Testing was repeated for the following four conditions: ACL-intact, ACLR with intact LM, ACLR with LM posterior root complex tear, and ACLR with root repair. RESULTS: The kinematic data from 12 fresh frozen cadaveric knees underwent analysis. Only 11 specimens had usable strain data. Sectioning the meniscofemoral ligaments and the LM posterior root increased rotational and translational laxity at 30° of knee flexion. ACLR graft strain significantly increased when an anterior load and internal torque were applied. Repair of the LM posterior root reduced strain when the knee was internally rotated but was unable to normalize strain when an anterior force was applied. CONCLUSIONS: This cadaveric biomechanical study suggests injury to the LM posterior root complex increases rotational and anterior laxity of the knee and places increased strain across reconstructed ACL grafts. Subsequent root repair did not result in a statistically significant reduction in strain. CLINICAL RELEVANCE: This study provides quantitative data on the implications of a LM posterior root injury in the setting of an ACL reconstruction to help guide clinical decision-making.

Pie-Crusting Capsulotomy Provides Similar Visualization With Increased Repair Stiffness Compared With a T-Capsulotomy: A Biomechanical Study.

PURPOSE: To compare the area of visualization, capsular stiffness, and strength between the pie-crusting capsulotomy technique and the T-capsulotomy technique following repair. METHODS: Eight matched pairs of fresh-frozen cadaveric hips (n = 16) were divided to either T-capsulotomy or pie-crusting capsulotomy followed by subsequent repair. The area of visualization was measured for all capsulotomy states using a digitizing probe. Hips were then distracted along the iliofemoral ligament in the intact, extended capsulotomy, and repair states. Afterwards, specimens were externally rotated to failure. RESULTS: An average force of 250.1 ± 16.1 N was required to distract intact hips to 6 mm. Both extended capsulotomy techniques reduced the force required to distract the hip 6 mm with no statistical difference between the two (T-capsulotomy [T-cap] = 114.3 ± 63.4 N vs pie-capsulotomy [Pie-cap] = 170.1 ± 38.8 N), P = .07. Subsequent repair of the extended capsulotomies demonstrated the pie-crust capsulotomy required significantly greater force to reach 6 mm of distraction than those with a repaired T-capsulotomy (T-cap = 165.04 ± 40.43N vs Pie-cap = 204.43 ± 10.13N), P = .03. There was no significant difference in ultimate torque to failure between the 2 techniques (T-cap = 22.0 ± 7.41 N·m vs Pie-cap = 27.01 ± 11.13 N·m), P = .28. Visualization significantly increased with each extended capsulotomy, with an average increase of 62% (P < .001) and 48% (P < .001) for the pie- and T-capsulotomies, respectively. CONCLUSIONS: The pie-crusting technique maintained similar strength and increased stiffness to the T-capsulotomy following repair while using less suture. Both techniques provided similar visualization. Clinically, the pie-crusting technique provides an alternative to the T-capsulotomy with similar biomechanical and visual outcomes. CLINICAL RELEVANCE: Visualization during hip arthroscopy can be difficult with large cam morphology. Techniques to improve visualization while restoring the native biomechanics of the hip as best as possible are important.

Neural crest-derived mesenchymal progenitor cells enhance cranial allograft integration.

Replacement of lost cranial bone (partly mesodermal and partly neural crest-derived) is challenging and includes the use of nonviable allografts. To revitalize allografts, bone marrow-derived mesenchymal stromal cells (mesoderm-derived BM-MSCs) have been used with limited success. We hypothesize that coating of allografts with induced neural crest cell-mesenchymal progenitor cells (iNCC-MPCs) improves implant-to-bone integration in mouse cranial defects. Human induced pluripotent stem cells were reprogramed from dermal fibroblasts, differentiated to iNCCs and then to iNCC-MPCs. BM-MSCs were used as reference. Cells were labeled with luciferase (Luc2) and characterized for MSC consensus markers expression, differentiation, and risk of cellular transformation. A calvarial defect was created in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice and allografts were implanted, with or without cell coating. Bioluminescence imaging (BLI), microcomputed tomography (µCT), histology, immunofluorescence, and biomechanical tests were performed. Characterization of iNCC-MPC-Luc2 vs BM-MSC-Luc2 showed no difference in MSC markers expression and differentiation in vitro. In vivo, BLI indicated survival of both cell types for at least 8 weeks. At week 8, µCT analysis showed enhanced structural parameters in the iNCC-MPC-Luc2 group and increased bone volume in the BM-MSC-Luc2 group compared to controls. Histology demonstrated improved integration of iNCC-MPC-Luc2 allografts compared to BM-MSC-Luc2 group and controls. Human osteocalcin and collagen type 1 were detected at the allograft-host interphase in cell-seeded groups. The iNCC-MPC-Luc2 group also demonstrated improved biomechanical properties compared to BM-MSC-Luc2 implants and cell-free controls. Our results show an improved integration of iNCC-MPC-Luc2-coated allografts compared to BM-MSC-Luc2 and controls, suggesting the use of iNCC-MPCs as potential cell source for cranial bone repair.

Biomechanical Comparison of UCL Repair Using Suspensory Fixation Versus UCL Reconstruction.

BACKGROUND: Medial ulnar collateral ligament (mUCL) repair is growing in popularity as a treatment for younger athletes with mUCL tears. One of the most recent techniques utilizes a collagen-coated suture tape to augment the repair. The most popular repair technique uses a screw for proximal fixation in the humerus. We present an alternative technique that uses suspensory fixation in the proximal humerus. PURPOSE: To biomechanically compare elbow valgus stability and load to failure of a novel alternative repair technique with suspensory fixation to an mUCL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: Eighteen fresh-frozen cadaveric elbows were dissected to expose the mUCL. Medial elbow stability was tested with the mUCL in an intact, deficient-either repaired or reconstructed-state. The repair technique used a suspensory fixation with suture augmentation, and the docking technique was used on all reconstructions. A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion tracking cameras as the elbow was cycled through a full range of motion. After kinematic testing, specimens were loaded to failure at 70° of elbow flexion. RESULTS: Both ulnar collateral ligament reconstruction and repair restored valgus stability to levels that were not statistically different from intact at all angles of flexion. There was no significant difference in the ultimate torque to failure between repaired and reconstructed mUCLs. CONCLUSION: There was no significant difference in the valgus strength between the mUCL repair with suspensory fixation and the mUCL reconstruction. CLINICAL RELEVANCE: Suspensory fixation is an alternative method for proximal fixation in the mUCL without compromising the strength of the construct.

Assessing the Resident Progenitor Cell Population and the Vascularity of the Adult Human Meniscus.

PURPOSE: To identify, characterize, and compare the resident progenitor cell populations within the red-red, red-white, and white-white (WW) zones of freshly harvested human cadaver menisci and to characterize the vascularity of human menisci using immunofluorescence and 3-dimensional (3D) imaging. METHODS: Fresh adult human menisci were harvested from healthy donors. Menisci were enzymatically digested, mononuclear cells isolated, and characterized using flow cytometry with antibodies against mesenchymal stem cell surface markers (CD105, CD90, CD44, and CD29). Cells were expanded in culture, characterized, and compared with bone marrow-derived mesenchymal stem cells. Trilineage differentiation potential of cultured cells was determined. Vasculature of menisci was mapped in 3D using a modified uDisco clearing and immunofluorescence against vascular markers CD31, lectin, and alpha smooth muscle actin. RESULTS: There were no significant differences in the clonogenicity of isolated cells between the 3 zones. Flow cytometry showed presence of CD44+CD105+CD29+CD90+ cells in all 3 zones with high prevalence in the WW zone. Progenitors from all zones were found to be potent to differentiate to mesenchymal lineages. Larger vessels in the red-red zone of meniscus were observed spanning toward red-white, sprouting to smaller arterioles and venules. CD31+ cells were identified in all zones using the 3D imaging and co-localization of additional markers of vasculature (lectin and alpha smooth muscle actin) was observed. CONCLUSIONS: The presence of resident mesenchymal progenitors was evident in all 3 meniscal zones of healthy adult donors without injury. In addition, our results demonstrate the presence of vascularization in the WW zone. CLINICAL RELEVANCE: The existence of progenitors and presence of microvasculature in the WW zone of the meniscus suggests the potential for repair and biologic augmentation strategies in that zone of the meniscus in young healthy adults. Further research is necessary to fully define the functionality of the meniscal blood supply and its implications for repair.

Comparative Analysis of Sagittal-Plane Radiographic Landmarks Used to Identify the Femoral Attachments of Lateral Knee Structures.

PURPOSE: To compare previously described radiographic parameters for the localization of the lateral knee (LK) structures, including the popliteal tendon (Pop), anterolateral ligament (ALL), and lateral collateral ligament (LCL), to determine which method best estimates the femoral attachment of each LK structure. METHODS: Twenty-nine human cadaveric knee specimens were carefully dissected to identify the LCL, ALL, and Pop. The femoral attachment for each structure was labeled with a radiopaque bead. LK radiographic images were obtained using fluoroscopy. Two radiographic approaches were used to identify each LK structure (Pop-A, Pop-B, LCL-A, LCL-B, ALL-A, and ALL-B) via previously published methods based on radiographic landmarks including the posterior femoral cortex and the Blumensaat line. The identification of radiographic landmarks was performed at 2 different time points by 2 different surgeons to determine the Pearson correlation between values, as well as interobserver and intraobserver reliability and reproducibility. The paired t test was conducted to compare the distance between the actual attachment site (as determined by the bead location) and the 2 radiographically identified estimations of attachment locations. RESULTS: For the LCL, the mean difference between the actual location and the estimated location via application of the LCL-B method (5.0 ± 2.4 mm) was significantly less than that estimated using the LCL-A method (8.2 ± 3.3 mm, P < .0001). Likewise, the Pop-B (5.7 ± 2.0 mm) and ALL-B (9.3 ± 4.5 mm) methods were shown to have smaller differences between the actual and estimated femoral attachment sites of the Pop insertion and ALL insertion, respectively (P < .0001). Methods for estimating the ALL femoral origin were the worst among the LK structures analyzed, with 90% of estimated values greater than 5 mm from the anatomic origin. Interobserver and intraobserver intraclass correlation coefficients were 0.785 or higher. CONCLUSIONS: Previously described radiographic methods for localization of the femoral attachment sites of the LK structures resulted in estimated locations that were significantly different from the locations of the radiographic beads placed at the anatomic femoral attachment sites of these structures. Therefore, radiographic methods used to localize the femoral attachments of the LK structures may not be reliable. CLINICAL RELEVANCE: This study shows the variability of the anatomy of the LK structures and the lack of reproducible radiographic criteria to identify these structures. As a result, there will be decreased reliance on radiographic landmarks to identify the placement of femoral grafts and fixation when reconstructing these structures.

A Comparison of 3 Fixation Strategies in the Treatment of Neer Type IIB Distal Clavicle Fractures.

OBJECTIVES: To compare the stability of NT2B clavicle fractures fixed with either a hook plating (HP), Superior Plating with Suture Augmentation (SPSA), or dual orthogonal plating (DP) with the hypothesis that DP would provide increased multiplanar stability across NT2B fractures. METHODS: NT2B distal clavicle fractures were created in cadaveric specimens and fixed using (1) HP, (2) SPSA, or (3) DP. Specimens were cyclically loaded in 3 different planes of motion: (1) anteroposterior (AP), (2) superior-inferior, and (3) axial rotation while displacement was continually recorded. Afterward, a superiorly directed load was applied to the clavicle. Load to failure, stiffness, and mode of failure were recorded. RESULTS: During AP loading, clavicles fixed with a DP had significantly lower mean posterior displacement compared to those fixed with SPSA at every 100-cycle interval of testing, P < 0.01. During inferior-superior loading, specimens fixed with a DP had less superior displacement than specimens fixed with an HP and SPSA, reaching significance at the 500-700 cycles of testing. There was no significant difference in axial rotation stability or load to failure between the 3 fixation techniques. CONCLUSIONS: Orthogonally placed minifragment plates provide improved stability against anterior displacement with no significant difference in superior stability, axial rotational stability, stiffness, or load to failure. Further clinical studies are needed to confirm the long-term stability of dual plating and determine the risks and benefits of this novel method of distal clavicle fixation.

Biomechanical evaluation of PCL reconstruction with suture augmentation.

PURPOSE: The purpose of this study was to compare kinematics and patellofemoral contact pressures of all inside and transtibial single bundle PCL reconstructions and determine if suture augmentation further improves the biomechanics of either technique. METHODS: Cadaveric knees were tested with a posterior drawer force, and varus, valgus, internal and external moments at 30, 60, 90, and 120° of flexion. Displacement, rotation, and patellofemoral contact pressures were compared between: Intact, PCL-deficient, All-Inside PCL reconstruction with (AI-SA) and without (AI) suture augmentation, and transtibial PCL reconstruction with (TT-SA) and without (TT) suture augmentation. RESULTS: Sectioning the PCL increased posterior tibial translation (PTT) from intact at 60° to 120° of flexion, p < 0.001. AI PCL reconstruction improved stability from the deficient-state but had greater PTT than intact at 90° of flexion, p < 0.05. Adding suture augmentation to the AI reconstruction further reduced PTT to levels that were not statistically different from intact at all flexion angles. TT reconstructed knees had greater PTT than intact knees at 60, 90, and 120° of flexion, p < 0.01. Adding suture augmentation (TT-SA) improved posterior stability to PTT levels that were not statistically different from intact knees at 30, 60, and 120° of flexion. Patellofemoral pressures were highest in PCL-deficient knees at increased angles of flexion and were reduced after reconstruction, but this was not significant. CONCLUSION: In this time-zero study, both the all-inside and transtibial single bundle PCL reconstructions effectively reduce posterior translation from the deficient-PCL state. In addition, suture augmentation of both techniques provided further anterior-posterior stability.

Extensor Tendon Transfers for Treatment of Foot Drop in Charcot-Marie-Tooth Disease: A Biomechanical Evaluation.

BACKGROUND: In Charcot-Marie-Tooth (CMT) disease, selective weakness of the tibialis anterior muscle often leads to recruitment of the long toe extensors as secondary dorsiflexors, with subsequent clawing of the toes. Extensor hallucis longus (EHL) and extensor digitorum longus (EDL) tendon transfers offer the ability to augment ankle dorsiflexion and minimize claw toe deformity. The preferred site for tendon transfer remains unknown. Our goal was to quantify ankle dorsiflexion in the "intact" native tendon state, compared with tendon transfers to the metatarsal necks or the cuneiforms. We hypothesized that EHL and EDL transfers would improve ankle dorsiflexion as compared with the intact state and would produce similar motion when anchored at the metatarsal necks or cuneiforms. METHODS: Eight fresh-frozen cadaveric specimens transected at the midtibia were mounted into a specialized jig with the ankle held in 20 degrees of plantarflexion. The EHL and EDL tendons were isolated and connected to linear actuators with suture. Diodes secured on the first metatarsal, fifth metatarsal, and tibia provided optical data for tibiopedal position in 3 dimensions. After preloading, the tendons were tested at 25%, 50%, 75%, and 100% of maximal physiologic force for the EHL and EDL muscles, individually and combined. RESULTS: Transfers to metatarsal and cuneiform locations significantly improved ankle dorsiflexion compared with the intact state. No difference was observed between these transfer sites. Following transfer, only 25% of maximal force by combined EHL and EDL was required to achieve a neutral foot position. CONCLUSION: Transfer of the long toe extensors, into either the metatarsals or cuneiforms, significantly increased dorsiflexion of the ankle. CLINICAL RELEVANCE: The transferred extensors can serve a primary role in treating foot drop in CMT disease, irrespective of the presence of clawed toes. This biomechanical study supports tendon transfers into the cuneiforms, which involves less time, fewer steps, and easier tendon balancing without compromising dorsiflexion power.

Knot of Henry Variation and the Effect on Plantar Flexion Strength.

BACKGROUND: The flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons are commonly used for tendon transfer in reconstructive foot and ankle procedures. Some patients experience great toe weakness and loss of push-off strength. The objective of this biomechanical study was to quantify plantarflexion force after FHL and FDL harvest and correlate it to variations in tendon crossover patterns at the knot of Henry to determine if specific patterns have an increased tendency toward forefoot weakness. METHODS: Simulated loads through the Achilles, FHL, and FDL were applied to cadaveric specimens while plantarflexion force was measured using a pressure mapping system. Force was recorded with the FDL and FHL unloaded to simulate tendon transfer. Afterward, specimens were dissected to classify the tendinous slips between the FHL and FDL based on a previously determined system. Functional and anatomical relationships between the classification type and loading patterns were analyzed. RESULTS: There were no statistical differences between the tendon crossover patterns in forefoot force reduction after FHL or FDL harvest. Average decrease in great toe and total forefoot pressure after FHL harvest was 31% and 22%, respectively. Average decrease in lesser toe and total forefoot push-off force after FDL harvest was 23% and 9%, respectively. CONCLUSION: This study quantified loss of plantarflexion force after simulated FHL and FDL harvest and correlated these losses to variations in anatomic crossover patterns at the knot of Henry. Variations at the knot of Henry do not contribute to differences in forefoot weakness. CLINICAL RELEVANCE: The decrease in forefoot pressure seen here would help explain the clinical scenario where a patient does note a loss of great toe strength after FHL transfer.

Anterior cruciate ligament repair versus reconstruction: A kinematic analysis.

BACKGROUND: The purpose of this study was to compare the biomechanical properties of an anterior cruciate ligament (ACL) anatomic repair of a true femoral avulsion to an anatomic ACL reconstruction. It was hypothesized that the ACL repair and ACL reconstruction would have comparable biomechanical behavior when compared to the native knee. METHODS: Ten paired fresh-frozen cadaveric knees (n = 20) were used to investigate knee kinematics when an anterior drawer force, varus, valgus, internal, and external rotational moment were applied at 0, 15, 30, 45, 60, and 90 degrees of flexion. Displacement and rotation were recorded in the following conditions: ACL-intact, ACL-deficient, and ACL-repaired vs reconstructed. RESULTS: Sectioning of the ACL significantly increased anterior tibial translation (0°, 15°, 30° and 45°) compared to the intact state. The mean anterior displacement difference from intact was lower in the ACL-repaired knees compared to reconstructed knees at 30° and 90°. There were no significant differences between conditions in varus, valgus, internal, or external rotations. CONCLUSION: ACL repair and ACL reconstruction procedures restored knee anterior tibial translation in matched paired specimens. There were no differences in valgus, varus, internal, or external rotation. Although, ACL-repaired knees (avulsion model) demonstrated less anterior tibial translation when compared to ACL-reconstructed knees, this difference was less than one millimeter. Based on the findings of this study, repair and reconstruction procedures both restored anterior tibial translation in matched-pair specimens. This suggests that the initial functionality of both techniques is similar and that further clinical studies are needed to compare the long-term stability.

Biomechanical Evaluation of Pediatric Anterior Cruciate Ligament (ACL) Reconstruction Techniques With and Without the Anterolateral Ligament (ALL).

BACKGROUND: Two popular physeal-sparing procedures used in the management of anterior cruciate ligament (ACL) injuries in skeletally immature patients are the iliotibial band (ITB) ACL reconstruction (ACLR) and the all-epiphyseal (AE) ACLR. Although there has been concern for overconstraint of the lateral compartment of the knee with the ITB ACLR technique, rotational stability, as provided by the anterolateral ligament (ALL) and ACL, has not been assessed in the setting of pediatric ACLR techniques. Our hypothesis is that the ITB ACLR and AE ACLR with ALL reconstruction (ALLR) will best replicate the biomechanical profile of the intact ACL that is lost with transection of the ACL and ALL. METHODS: Eight cadaveric legs were statically loaded with an anterior drawer force and varus, valgus, internal and external rotational moments at 0, 30, 60, and 90 degrees of flexion. Displacement and rotation were recorded in the following conditions: intact ACL/intact ALL, ACL-deficient/intact ALL, ITB ACLR/intact ALL, ITB ACLR/ALL-deficient, ACL-deficient/ALL-deficient, AE ACLR/ALL-deficient, AE ACLR/ALLR. RESULTS: Both ACLR techniques reduced anterior tibial translation from the ACL-deficient state, but neither restored it to the intact state (P<0.05), except in full extension. ALL deficiency increased anterior tibial translation in the ACL-deficient state (P<0.05). In rotational testing, no significant increase was seen with transection of the ACL, but the ACL-deficient/ALL-deficient state had a significant increase in internal rotation (P<0.05). This was significantly restored to the intact state at most flexion angles with the ITB ACLR without rotational overconstraint of the lateral compartment. The AE ACLR/ALL-deficient state and AE ACLR/ALLR improved rotational stability at lower flexion angles, but not at 60 and 90 degrees. There were no significant changes in varus/valgus moments. CONCLUSIONS: In this model, the ITB ACLR provided the superior biomechanical profile between our tested reconstructions. It best corrected both AP and rotatory stability without overconstraining the knee. The AE ACLR and AE ACLR/ALLR improved both parameters but not at all flexion angles and not as robustly. ACL deficiency in the knee increased anterior tibial translation, but did not affect rotatory stability. ALL deficiency in the knee increased anterior displacement and rotational moments in the ACL-deficient state. CLINICAL RELEVANCE: Cadaveric Laboratory Study. The ITB ACLR seems to be the biomechanically superior pediatric ACLR technique to regain translational and rotational stability.