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.

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.

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.

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.

The effect of insulin dependent diabetes on bone metabolism and growth after spinal fusion.

STUDY DESIGN: Experimental animal model. OBJECTIVE: The purpose of this study was to evaluate the hypothesis that insulin dependent diabetes mellitus (IDDM) will inhibit the formation of a solid bony union after spinal fusion surgery via an alteration of the microenvironment at the fusion site in a rat model. SUMMARY OF BACKGROUND DATA: Previous studies report diabetes mellitus (DM) and specifically IDDM as a risk factor for complications and poor surgical outcomes following spinal fusion. METHODS: Twenty control and 22 diabetic rats were obtained at 5 weeks of age. At 20 weeks of age, all animals underwent posterolateral lumbar fusion surgery using a tailbone autograft with diabetic rats receiving an implantable time release insulin pellet. A subset of rats was sacrificed 1-week postsurgery for growth factor (PDGF, IGF-I, TGF-ß, and VEGF) and proinflammatory cytokine ELISA analysis. All other rats were sacrificed 3-months postsurgery for fusion evaluation via manual palpation and micro CT. Glycated hemoglobin (HbA1c) was measured at surgery and sacrifice on all animals. RESULTS: Compared with healthy rats undergoing spinal fusion, rats with IDDM demonstrated a significant reduction in manual palpation fusion rates (16.7% vs. 43%, p<.05). Average bone mineral density, bone volume, and bone volume fraction were also significantly reduced and negatively correlated to blood glucose levels. IL-1B, IL-5, IL-10, TNF-α, and KC/GRO were significantly elevated in fusion beds of IDDM rats. CONCLUSIONS: This study demonstrates that rats with IDDM demonstrate a reduced rate and quality of spinal fusion with increased local levels of inflammatory cytokines. Targeted modalities are required to improve bone healing in this growing, high-risk population. CLINICAL SIGNIFICANCE: This is the first translational animal model of IDDM to evaluate the rate and quality of spinal fusion while controlling for other surgical and patient-related risk factors. Our findings demonstrate the complex nature by which IDDM impairs bone healing and highlight the need for additional basic science research to further elucidate this mechanism in order to develop more effective therapeutic interventions.

Infraspinatus Tenotomy Improves Glenoid Visualization With the Modified Judet Approach.

OBJECTIVES: To determine if the addition of an infraspinatus tenotomy to the modified Judet approach (MJA) improves glenoid visualization. METHODS: We performed an MJA on 14 human cadaveric shoulders. After exposing the glenoid, the boundary of the visualized glenoid surface was marked with a 1.8- and 2.0-mm drill bit before and after performing an infraspinatus tenotomy, respectively. The humerus was disarticulated, and the pre- and post-tenotomy drill marks were verified. The area of the entire glenoid, and each of the 4 quadrants [anterior-superior (AS), anterior-inferior (AI), posterior-superior (PS), and posterior-inferior (PI)] were analyzed using a custom image-processing program. The amount of glenoid exposure and percentage of area visualized before and after the tenotomy were compared. RESULTS: Adding an infraspinatus tenotomy to the MJA significantly increased total glenoid area (cm) exposure by 33%, P < 0.0001. Three of 4 glenoid quadrants (PS, AS, and AI) had a significant increase in glenoid visualization, with the AS quadrant having the most substantial improvement after the tenotomy (+67%), P < 0.0001. CONCLUSIONS: The results provide the percentage of glenoid fossa that can be seen using an MJA and demonstrate that visualization significantly improves after adding an infraspinatus tenotomy.

Anatomic and Biomechanical Evaluation of Ulnar Tunnel Position in Medial Ulnar Collateral Ligament Reconstruction.

BACKGROUND: Although numerous techniques of reconstruction of the medial ulnar collateral ligament (mUCL) have been described, limited evidence exists on the biomechanical implication of changing the ulnar tunnel position despite the fact that more recent literature has clarified that the ulnar footprint extends more distally than was appreciated in the past. PURPOSE: To evaluate the size and location of the native ulnar footprint and assess valgus stability of the medial elbow after UCL reconstruction at 3 ulnar tunnel locations. STUDY DESIGN: Controlled laboratory study. METHODS: Eighteen fresh-frozen cadaveric elbows were dissected to expose the mUCL. The anatomic footprint of the ulnar attachment of the mUCL was measured with a digitizing probe. The area of the ulnar footprint and midpoint relative to the joint line were determined. Medial elbow stability was tested with the mUCL in an intact, deficient, and reconstructed state after the docking technique, with ulnar tunnels placed at 5, 10, or 15 mm from the ulnotrochlear joint line. 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: The mean ± SD length of the mUCL ulnar footprint was 27.4 ± 3.3 mm. The midpoint of the anatomic footprint was located between the 10- and 15-mm tunnels across all specimens at a mean 13.6 mm from the joint line. Sectioning of the mUCL increased elbow valgus rotation throughout all flexion angles and was statistically significant from 30° to 100° of flexion as compared with the intact elbow (P < .05). mUCL reconstruction at all 3 tunnel locations restored stability to near intact levels with no significant differences among the 3 ulnar tunnel locations at any flexion angle. CONCLUSION: Positioning the ulnar graft fixation site up to 15 mm from the ulnotrochlear joint line does not significantly increase valgus rotation in the elbow. CLINICAL RELEVANCE: A more distal ulnar tunnel may be a viable option to accommodate individual variation in morphology of the proximal ulna or in a revision setting.

Biomechanical Comparison of Achilles Tendon Pullout Strength Following Midline Tendon-Splitting and Endoscopic Approaches for Calcaneoplasty.

BACKGROUND: Calcaneoplasty is a common procedure performed for the management of Haglund's syndrome when nonoperative management fails. Midline tendon-splitting and endoscopy are 2 common approaches to calcaneoplasty. Studies have suggested that an endoscopic approach may allow earlier return to activity and superior outcomes, but there are no biomechanical or clinical studies to validate these claims. The goal of this study was to quantify and compare Achilles tendon pullout strength following midline tendon-splitting and endoscopic calcaneoplasty in cadaveric specimens. METHODS: Twelve match-paired cadaveric specimens were randomly divided into 2 groups: endoscopic and midline tendon-split. Following calcaneoplasty, fluoroscopy was used to match bone resection and the Achilles was loaded to failure in a mechanical testing system. A paired-samples t test was conducted to compare bone resection height, bone resection angle, load to failure, and mode of failure. RESULTS: The endoscopic approach yielded a 204% greater postsurgical pullout strength for the Achilles tendon than the midline tendon-split (1368 ± 370 N vs 450 ± 192 N, respectively) (P < .05). There were no differences in resection angle or resection height. All specimens failed due to bone or tendon avulsion. CONCLUSION: Endoscopic calcaneoplasty had more than 3 times greater pullout strength than the midline tendon-splitting approach. CLINICAL RELEVANCE: This may allow earlier return to functional rehabilitation following endoscopic calcaneoplasty, but further studies are needed to determine if these differences are clinically significant. Further understanding of the time-zero biomechanics following calcaneoplasty may provide guidance regarding postoperative management with respect to surgical approach.

The impact of type 2 diabetes on bone metabolism and growth after spinal fusion.

BACKGROUND CONTEXT: Some clinical reports suggest diabetes may have a negative effect on spinal fusion outcomes, although no conclusive experimental research has been conducted to investigate the causality, impact, and inherent risks of this growing patient population. PURPOSE: To analyze the hypothesis that type 2 diabetes (T2DM) inhibits the formation of a solid bony union after spinal fusion surgery by altering the local microenvironment at the fusion site through a reduction in growth factors critical for bone formation. STUDY DESIGN/SETTING: In vivo rodent model of type 2 diabetes. METHODS: Twenty control (Sprague Dawley, SD) and 30 diabetic (Zucker Diabetic Sprague Dawley, ZDSD) rats underwent posterolateral and laminar fusion surgery using a tailbone autograft implanted onto the L4/L5 transverse processes. A subset of animals was sacrificed 1-week postsurgery for growth factor analysis. Remaining rats were sacrificed 3-month postsurgery for fusion evaluation via manual palpation, micro-CT, and histology. RESULTS: There was no significant difference in the manual palpation fusion rate between ZDSD rats and SD control rats. Growth factor assay of fusion site explants at early sacrifice demonstrated PDGF was upregulated in the ZDSD rats. TGFB, IGF, and VEGF were not statistically different between groups. Bone mineral density as determined by micro-CT was significantly lower in ZDSD rats compared to SD controls and was a significant function of HbA1c. CONCLUSIONS: Data generated in this in vivo rat model of T2DM demonstrate that the metabolic dysregulation associated with the diabetic condition negatively impacts the quality and density of the formed fusion mass. Increased measures of diabetic status, as determined by blood glucose and HbA1c, were correlated with decreased quality of formed fusion, highlighting the importance of diabetic status monitoring and regulation to bone health, particularly during bone healing. CLINICAL RELEVANCE: T2DM rats demonstrated increased rates of infection, metabolic dysregulation, and a reduction in spinal fusion consolidation. Clinicians should consider these negative effects during preoperative care and treatment of this growing patient population.

Achilles Pullout Strength After Open Calcaneoplasty for Haglund's Syndrome.

BACKGROUND: Haglund's syndrome involves a prominent posterior superior prominence of the calcaneus. If nonoperative management fails, operative management with calcaneoplasty is often needed. No study has assessed Achilles tendon pullout strength after an open calcaneoplasty for Haglund's syndrome. The purpose of this study was to investigate those changes in a cadaveric model and provide objective data upon which to base postoperative recovery. METHODS: Seven matched pairs of cadaveric specimens (mid-tibia to toes) were divided into 2 cohorts: (1) intact/untreated and (2) open resection. The open resection group was treated with an open calcaneoplasty through a posterior approach using a microsagittal saw. We compared Achilles pullout strength between the 2 groups through the use of a mechanical testing system. Specimens were then loaded to failure. Lateral radiographs were obtained before and after surgery to quantify bone removal. Outcome measures included height of bony resection, angle of bone resection, and load to failure. RESULTS: The mean maximum pullout strength was significantly higher in the intact specimens (1300 ± 500 N) compared to the open resection group (740 ± 180 N) ( P < .01), representing a 45% reduction in pullout force in the open resection group. Pullout force was significantly correlated to bone mineral density (BMD) ( P < .05). Pullout force was negatively correlated to both radiographic measures of resection level, angle, and height, but neither of these were significant. CONCLUSION: Open calcaneoplasty demonstrated a significant weakness of the Achilles tendon insertion. Pullout strength of the Achilles was also positively correlated with BMD. CLINICAL RELEVANCE: Biomechanical evidence presented above supports the practice of protected weightbearing and cautious return to activity after open calcaneoplasty for Haglund's syndrome.