Ulnar Collateral Ligament Repair With Suture Tape Augmentation: Can You Overtighten?

BACKGROUND: There has been a renewed interest and, recently, wider implementation of ulnar collateral ligament (UCL) repair in throwing athletes because of improvement in ligament repair technology and corresponding outcome data. PURPOSE: To compare the biomechanical parameters and failure mode between 2 brace-tightening techniques for UCL repair. STUDY DESIGN: Controlled laboratory study. METHODS: Eleven matched pairs of cadaveric arms were procured. One limb from each pair underwent UCL repair with suture tape augmentation with either (1) attempted restoration of physiologic ligament tension or (2) maximal tension. Each specimen was subjected to 10 cycles of subfailure valgus torque at 90º of flexion in the intact state after UCL avulsion and then after UCL repair. Specimens were then torqued to failure. Articular contact mechanics, linear gap distance, angular displacement, failure torque, failure stiffness, and suture tape pull-through length were recorded. Two-way analysis of variance and paired t tests were used to test for statistical differences. RESULTS: There was a significant effect (P = .01) of tightening on joint contact area. There was a significant decrease in gap distance (P = .03) and angular displacement (P = .004) from the torn condition to the repaired condition for the maximum tension group, without a significant difference in gap distance from the intact condition. Failure torque and stiffness were not significantly different between groups, although there was a significant difference (P = .001) in the overall suture tape pull-through length. CONCLUSION: Although there are potential physiologic changes at time zero-including significant decreases in contact area, normalized gap distance, and normalized angular displacement with maximal tension repair-examination of failure biomechanics suggests that these effects may be mitigated over time within the construct by suture tape pull-through at the tape-anchor interface. Neither method of UCL repair with suture tape augmentation resulted in overconstraint of the elbow joint compared with the native ligament biomechanics. CLINICAL RELEVANCE: As more long-term outcome data from UCL repair with suture tape augmentation emerge, there will be wider implementation with various techniques to tension the suture tape. Examining the potential biomechanical sequelae of the UCL repair construct applied under maximal tension will help further refine recommendations for surgeons who utilize this technique for UCL repair.

Fixation strength in arthroscopic labral repair of the hip: A head-to-head comparison of the biomechanical performance of a biocompatible vs. all-suture anchor in the setting of acetabuloplasty.

Much is known about the biomechanical performance of various types of suture anchors commonly used for labral fixation in the shoulder; however, similar studies in the hip are less common. We sought to compare all-suture and polyether ether ketone small-diameter anchors in the setting of labral repair during hip arthroscopy, with and without acetabuloplasty. We hypothesized that the biomechanical properties of the all-suture group when compared to polyether ether ketone anchors would be similar amongst native acetabula and significantly less following acetabuloplasty and that pullout forces would be reduced in the anterior and inferior regions of the acetabulum compared to the superior region. Bone density was measured in nine matched pairs of fresh-frozen cadaveric acetabula in the superior, anterosuperior, and anterior regions. Acetabuloplasty was performed in all three regions, while the contralateral acetabulum was left in situ as a control. Suture anchors were placed such that one each of two different types was placed within each region. Specimens were tested in cyclic fatigue and loaded to failure. The all-suture group had significantly higher cyclic displacement compared to the polyether ether ketone, but there was no significant difference in ultimate load, regardless of acetabuloplasty. Amongst all non-resected specimens, the lowest bone density was observed consistently in the inferior region. Our results indicate that, with or without acetabuloplasty, a small-diameter polyether ether ketone anchor appears to be more stable than an all-suture anchor, which needs to be set first.

A Retrospective Case Series Study on a Minimally Invasive Ultrasound-Guided First Dorsal Compartment Release Technique for Refractory De Quervain Tenosynovitis.

OBJECTIVE: The aim of this study was to evaluate the outcomes of patients treated with a novel minimally invasive complete release of the first dorsal compartment percutaneously under ultrasound guidance using an 18-gauge needle with an 18 blade at the tip. DESIGN: This was a retrospective case series. Nine adults (ten wrists) were included in the study of this technique. All patients had failed conservative care and had tenderness to palpation over the first dorsal compartment, a positive Finklestein test, and confirmed tenosynovitis with ultrasound imaging before the procedure. The main outcome measures were reduction in pain as determined by the numeric rating scale and improvement of function determined by the Nirschl Phase scale at both short- and long-term follow-up. RESULTS: There was 100% follow-up, with mean (SD) follow-up occurring at 23.1 (9.8) mos (range, 9-42 mos). From preprocedure to follow-up, numeric rating scale pain decreased from 4.1 (SD, 2.5) to 0.0 (SD, 0.0) ( P < 0.001), and Nirschl phase improved from 2.5 (SD, 1.9) to 0.2 (SD, 0.4) ( P = 0.03). No patients required revision open-release surgery or suffered neurovascular complications. CONCLUSION: This technique resulted in significant improvement of pain and function for all patients and no short- or long-term neurovascular complications were seen.

Intersurgeon Consistency of Ulnar Collateral Ligament Repair With Internal Brace: A Biomechanical Analysis.

Background: Injury to the ulnar collateral ligament (UCL) of the medial elbow has been treated successfully with ligament repair augmented with internal brace. Previous work has shown that this procedure does not overconstrain the ulnohumeral joint; however, the procedures were conducted by a single surgeon, which controlled for anchor placement and graft tensioning. Purpose/Hypothesis: Our purpose was to evaluate the reproducibility of contact mechanics and joint torque after UCL repair with internal brace as performed by different surgeons compared with repair by a single surgeon. It was hypothesized that there would be no significant difference in elbow contact mechanics, valgus torque, or torsional stiffness between the 2 groups. Study Design: Controlled laboratory study. Methods: Nine pairs of fresh-frozen cadaveric elbows were tested biomechanically under 3 conditions: UCL-intact (UCL-I), UCL-deficient (UCL-D), and UCL-repaired with internal brace augmentation (UCLR-IB). For each pair, 1 elbow was repaired by a single surgeon, and the contralateral elbow was repaired by 1 of 9 other surgeons. Testing consisted of valgus torsion between 0° and 5° with the elbow positioned at 90° of flexion. Ulnohumeral contact mechanics and overall joint torque and stiffness were measured and compared between surgeon groups. Results: There were no statistically significant differences between the single-surgeon and multiple-surgeon groups regarding contact area (P = .83), contact force (P = .27), peak pressure (P = .26), or peak force (P = .30); however, contact pressure was significantly affected (P = .02) by surgeon group. Compared with UCL-I, both UCL-D and UCLR-IB conditions had a significant overall effect on contact area (P = .004) and contact force (P = .05); however, contact pressure (P = .56), peak pressure (P = .27), and peak force (P = .24) were not affected by injury condition. Measurements of elbow torque (P = .28) and stiffness (P = .98) were not significantly different between surgeon groups. Conclusion: UCL repair with internal brace provided consistent results among several surgeons when compared with a single surgeon. The procedure did not lead to joint overconstraint while also returning the ligament to near-intact levels of resisting valgus stress. Clinical Relevance: UCL repair with internal brace augmentation is a reproducible surgical technique that has good clinical outcomes in the literature.

Endoscopic Gluteus Medius Repair Replicates Open, Knotless Repair With Similar Cyclic Loading Properties: A Cadaveric Study.

Purpose: To compare the repair strength, gap formation, and mode of failure between endoscopic and open double-row gluteus medius repairs in a cadaveric model. Methods: Six pairs of fresh-frozen human cadavers were used in this study. Gluteus medius tears were created in an open fashion and then repaired with either open or endoscopic techniques. Specimens were manually preloaded to 5 N, then cycled between 20-50 N for 150 cycles s. Then, a ramp to/s. Specimens were then returned to 10 N and ramped to failure at 1 mm/s. Gap formation and strengths of the construct were compared for the 2 techniques. Results: Biomechanical testing resulted in no significant differences in ultimate load (P = .86) or gap formation (P > .10) between groups. Ninety-two percent of specimens failed near the muscle origin on the ilium. Conclusions: This study shows that both open and endoscopic gluteus medius repairs are stronger than the muscle-bone interface in a cadaveric model and loaded biomechanically in tension between the ilium origin and femoral insertion. Further, endoscopic technique is able to replicate open, knotless gluteus medius repair technique in terms of gap formation in physiologic (i.e., subfailure) cyclic loading. Clinical Relevance: Gluteus medius tendinopathy is an increasingly common recognized etiology of lateral hip pain. When tears occur, debate exists over whether open or endoscopic repair procedures are optimal. Double-row endoscopic gluteus medius repair with knotless suture anchors may be an alternative to open repair.

Biomechanical Evaluation of Anterolateral Ligament Repair Augmented with Internal Brace.

Injuries to the anterolateral ligament (ALL) of the knee are commonly associated with anterior cruciate ligament (ACL) ruptures. Biomechanical studies have demonstrated conflicting results with regard to the role of the ALL in limiting tibial internal rotation. Clinically, residual pivot shift following ACL reconstruction has been reported to occur up to 25% and has been correlated with poor outcomes. As such, surgical techniques have been developed to enhance rotational stability. Recent biomechanical studies have demonstrated restoration of internal rotational control following ALL reconstruction. The purpose of our study was to understand the biomechanical effects of ACL reconstruction with an ALL internal brace augmentation. We hypothesized that (1) sectioning of the ALL while preserving other lateral extra-articular structures would lead to significant internal rotation laxity and gap formation and (2) ALL repair with internal brace augmentation would lead to reduction in internal rotation instability and gap formation. In total, 10 fresh-frozen cadaveric knees were thawed and biomechanically tested in internal rotation for 10 cycles of normal physiologic torque in the intact, ACL-deficient, ACL/ALL-deficient, ACL-reconstructed, and ALL-repaired conditions. Each condition was tested at 30, 60, and 90 degrees of flexion. Following the final ALL-repaired condition, specimens were additionally subjected to a final internal rotation to failure at 1 degree at the last-tested degree of flexion. Kinematic measurements of angle and linear gap between the femur and tibia were calculated in addition to torsional stiffness and failure torque. As hypothesized, ALL repair with internal brace augmentation significantly reduced internal rotation angular motion and gap formation at flexion angles greater than 30 degrees. Additionally, ALL sectioning produced nonsignificant increases in internal rotation laxity and gap formation compared with ACL-deficient and ACL-reconstructed states, which did not support our other hypothesis.

In-line Pullout Strength of 2 Acetabular Fixation Methods for Ligamentum Teres Reconstruction of the Hip: A Cadaveric Study.

BACKGROUND: Ligamentum teres (LT) reconstruction is an appropriate alternative in select cases of LT full-thickness tears, resulting in hip micro- or macroinstability. Graft fixation at the acetabular fossa is critical to achieving the best functional results. PURPOSE: The purpose of this study is to compare the pullout strength of 2 graft fixation methods used for LT reconstruction of the hip. STUDY DESIGN: Controlled laboratory study. METHODS: In 7 cadaveric specimens, the acetabular socket was prepared after the native LT was transected and the femoral head was removed. Seven separate tibialis anterior grafts were then prepared by suturing a running-locking No. 2 suture on each tail of the graft. Three specimens had fixation of the graft to the acetabulum using an adjustable cortical suspension suture button; the remaining 4 were fixed to the acetabulum using a knotless suture anchor. Specimens were then mounted onto a custom jig within a mechanical test frame to allow for the in-line pull of the graft fixation construct. After a preload of 5 N, each specimen was loaded to failure at 0.5 mm/s. Stiffness and load to failure were measured for each specimen construct. RESULTS: Suture button fixation had a higher mean load to failure when compared with the knotless anchor fixation method (mean ± SD, 438.1 ± 114.3 vs 195.9 ± 50.0 N; P = .01). There was no significant difference in mean stiffness between the methods of fixation (24.5 ± 1.4 vs 26.5 ± 5.8 N/mm; P = .6). CONCLUSION: In this cadaveric study, the suture button fixation demonstrated greater load to failure than the knotless anchor fixation. CLINICAL RELEVANCE: Results of this study can guide surgical decision making when selecting an acetabular fixation method for LT reconstruction.

Increased Bite Distance From the Edge Lowers Risk of Pullout of Simple Sutures from Acellular Dermal Allograft.

PURPOSE: To investigate whether pullout strength in the acellular dermal allograft matrix (ADM) used for superior capsule reconstruction depends on the distance from the edge of the graft. METHODS: ADM used for superior capsule reconstruction was obtained and cut into 30 squares. Two sutures were placed through the center of each graft by using a loaded Keith needle and forming a simple stitch. The grafts were divided into 3 groups of 10 grafts with a distance of 5 mm, 10 mm or 15 mm from the closest edge of the graft, respectively. The grafts were then preloaded to 5 N and pulled to failure at a rate of 12 mm/s on an MTS 858 MiniBionix servohydraulic mechanical test frame. The load to failure was recorded as well as the stiffness of each graft. RESULTS: The mean load to failure was 34.5 N (SD 7.89) for the 5 mm grafts, 31.7 N (SD 5.99) for the 10 mm grafts, and 66.2 N (SD 18.4) for the 15 mm grafts. There was a significant difference (< 0.0001) between the large grafts (15 mm) and the 2 smaller grafts (10 mm, 5 mm). There was no significant difference in stiffness between the groups of graft (P 0.40). CONCLUSION: Placing the suture at least 15 mm from the edge of the graft increases the graft's ultimate yield strength to suture pullout. CLINICAL RELEVANCE: The depths of the suture in ADM could improve pullout strength for constructs of superior capsular reconstructions.

The Effect of Ulnar Collateral Ligament Repair With Internal Brace Augmentation on Articular Contact Mechanics: A Cadaveric Study.

BACKGROUND: There has been renewed interest in ulnar collateral ligament (UCL) repair in throwing athletes because of a greater understanding of UCL injuries, improvement in ligament repair technology, and potentially expedited rehabilitation time and return to play relative to UCL reconstruction. PURPOSE: To evaluate elbow articular contact and overall joint torque after UCL reconstruction and repair augmented with a collagen-coated fiber tape, InternalBrace. STUDY DESIGN: Controlled laboratory study. METHODS: Ten matched pairs of cadaveric arms (mean age, 41 ± 11 years) were dissected to expose the UCL. Each specimen was secured into a custom test fixture at 90°, and 1 specimen from each pair underwent either a modified Jobe UCL reconstruction or UCL repair with InternalBrace. Each specimen underwent 10 cycles of elbow valgus angular displacement between 0° and 5° at a rate of 1 deg/s in the intact state, after UCL avulsion, and then after UCL reconstruction or repair. Articular contact mechanics and overall joint torque and stiffness were recorded. RESULTS: Contact mechanics of reconstructed and repaired specimens were not significantly different. Both reconstruction and repair procedures returned the overall resistance of the joint to valgus torsion to near-intact levels. UCL repair tended to restore joint torque more closely to the intact state than did reconstruction, given that reconstruction showed a nonsignificant trend toward lower torque than the intact state (P = .07). CONCLUSION: Neither UCL reconstruction nor UCL repair with InternalBrace overconstrained the elbow joint, as both groups had similar contact pressures compared with the native joint. Both procedures also restored elbow joint torque and stiffness to levels not statistically different from the intact state. CLINICAL RELEVANCE: Given the sound biomechanical properties of UCL repair with InternalBrace, it may have a significant role as treatment for UCL injuries.

Collagen XII mediated cellular and extracellular mechanisms regulate establishment of tendon structure and function.

Tendons have a uniaxially aligned structure with a hierarchical organization of collagen fibrils crucial for tendon function. Collagen XII is expressed in tendons and has been implicated in the regulation of fibrillogenesis. It is a non-fibrillar collagen belonging to the Fibril-Associated Collagens with Interrupted Triple Helices (FACIT) family. Mutations in COL12A1 cause myopathic Ehlers Danlos Syndrome with a clinical phenotype involving both joints and tendons supporting critical role(s) for collagen XII in tendon development and function. Here we demonstrate the molecular function of collagen XII during tendon development using a Col12a1 null mouse model. Col12a1 deficiency altered tenocyte shape, formation of interacting cell processes, and organization resulting in impaired cell-cell communication and disruption of hierarchal structure as well as decreased tissue stiffness. Immuno-localization revealed that collagen XII accumulated on the tenocyte surface and connected adjacent tenocytes by building matrix bridges between the cells, suggesting that collagen XII regulates intercellular communication. In addition, there was a decrease in fibrillar collagen I in collagen XII deficient tenocyte cultures compared with controls suggesting collagen XII signaling specifically alters tenocyte biosynthesis. This suggests that collagen XII provides feedback to tenocytes regulating extracellular collagen I. Together, the data indicate dual roles for collagen XII in determination of tendon structure and function. Through association with fibrils it functions in fibril packing, fiber assembly and stability. In addition, collagen XII influences tenocyte organization required for assembly of higher order structure; intercellular communication necessary to coordinate long range order and feedback on tenocytes influencing collagen synthesis. Integration of both regulatory roles is required for the acquisition of hierarchal structure and mechanical properties.

Portal Placement and Biomechanical Performance of Endoscopic Proximal Hamstring Repair.

BACKGROUND: Proximal hamstring tendon avulsions are debilitating and commonly cause pain, weakness, and functional limitations. Open surgical repair has been the standard, but improved endoscopic techniques have enabled proximal hamstring fixation with decreased risk of infection and numbness, without the morbidity of a large incision. PURPOSE/HYPOTHESIS: The purpose was to (1) describe pertinent anatomy surrounding the proximal hamstring origin in relation to 4 endoscopic portal sites and (2) test for biomechanical differences between open and endoscopic repair. It was hypothesized that (1) endoscopic proximal hamstring repair is efficacious with respect to commonly used portals and (2) there is no biomechanical difference between open and endoscopic techniques. STUDY DESIGN: Descriptive and controlled laboratory study. METHODS: Proximal hamstring ruptures were simulated endoscopically in 10 fresh-frozen human cadaveric pelvis specimens. Endoscopic repair was then completed on 1 limb from each specimen through 4 portals. After repair, each specimen was dissected in layers and measurements from portal tracts to pertinent anatomy were obtained. Open repair was performed on all contralateral limbs, followed by cyclical biomechanical tensile testing to failure of both the open and endoscopically repaired hamstring tendons to assess failure load and local tissue strain. RESULTS: On average, no portal tract was closer than 2.0 cm to the sciatic nerve or inferior gluteal neurovascular bundle. Anatomic landmarks were identified that could improve the reproducibility and safety of the procedure. Biomechanical testing revealed no differences between the open and endoscopic repair techniques for any measured parameter. CONCLUSION: This study supports the safety and efficacy of endoscopic proximal hamstring repair through anatomic and biomechanical analyses and helps establish reproducible and recognizable landmarks that define a safe working zone. CLINICAL RELEVANCE: This study maps the anatomic landscape of the proximal hamstring as encountered endoscopically and demonstrates equivalent biomechanical strength of endoscopic proximal hamstring repair, supporting this technique's safety and efficacy.

The Effect of Humeral and Ulnar Bone Tunnel Placement on Achieving Ulnar Collateral Ligament Graft Isometry: A Cadaveric Study.

PURPOSE: To assess simulated ulnar collateral ligament (UCL) graft length change, using surgically dissected anatomic landmarks, between multiple combinations of humeral and ulnar bone tunnels. METHODS: Three equidistant humeral and ulnar tunnels were created at each UCL footprint of 10 cadaveric elbows. Suture was passed between 9 possible tunnel combinations for each elbow and affixed to an isometry gauge. Each elbow was moved through an arc of 0, 30, 60, 90, and 120° for each tunnel combination. Changes in isometry gauge spring displacement (and, in effect, tension) were recorded. RESULTS: There was an overall significant effect (P < .0001) of tunnel placement at all degrees of flexion. Pairwise comparisons revealed increases in displacement between the central and posterior tunnel positions of the medial epicondyle, with significant differences (P = .0009) occurring when paired with both the central and posterior aspect of the sublime tubercle. Significant differences (P < .0001) were noted between the anterior and posterior humeral tunnel positions. CONCLUSIONS: Simulated UCL graft isometry is dependent upon optimal bone tunnel placement. No significant differences were noted between ulnar tunnel locations when paired with any given humeral tunnel. Conversely, deviation anterior or posterior from the centroid of the UCL footprint on the medial epicondyle significantly affected isometry at all degrees of flexion recorded with the greatest amount of displacement occurring with pairi4ng of posterior tunnels on both the humeral and ulnar footprints. CLINICAL RELEVANCE: This anatomic study highlights the importance of medial elbow bone tunnel placement and its effect on simulated UCL graft isometry.

Biomechanical Comparison of 3 Syndesmosis Repair Techniques With Suture Button Implants.

BACKGROUND: Suture button fixation of syndesmotic injury is growing in popularity, as it has been shown to provide adequate stability in a more cost-effective manner than screw fixation while allowing more physiologic distal tibiofibular joint motion. However, the optimal repair technique and implant orientation have yet to be determined. PURPOSE/HYPOTHESIS: The purpose of this study was to biomechanically compare 3 suture button construct configurations/orientations for syndesmosis fixation: single, parallel, and divergent. The authors hypothesized that all 3 methods would provide adequate stabilization but that the divergent technique would be the most stable. STUDY DESIGN: Controlled laboratory study. METHODS: The fixation strengths of 3 stabilization techniques with suture button devices were compared with 10 cadaveric legs each (N = 30). Ankle motion under cyclic loading was measured in multiple planes: first in the intact state, then following simulated syndesmosis injury, and then following fixation with 1 of 3 randomly assigned constructs-1 suture button, 2 suture buttons in parallel, and 2 divergent suture buttons. Finally, axial loading with external rotation was applied to failure. RESULTS: All syndesmotic fixation methods provided stability to the torn state. There was no statistically significant difference among the 3 fixation techniques in biomechanical stability. Failure most commonly occurred through fibular fracture at supraphysiologic loads. CONCLUSION: Suture button implant fixation for syndesmotic injury appears to provide stability to the torn syndesmosis, and the configuration of the fixation does not appear to affect the strength or security of the stabilization. CLINICAL RELEVANCE: This study provides further insight into the biomechanics and optimal configuration of suture button fixation of the torn syndesmosis. Based on these results, the addition of a second suture button may not significantly contribute to immediate postoperative stability.

Ulnar Collateral Ligament Reconstruction Versus Repair With Internal Bracing: Comparison of Cyclic Fatigue Mechanics.

BACKGROUND: Ulnar collateral ligament (UCL) injuries have increased significantly in recent years, and reconstruction has become the preferred treatment for UCL injury over ligament repair. In a recent study, UCL repair with internal bracing demonstrated significantly greater resistance to gap formation in biomechanical tests, even at low cycles of valgus loading. PURPOSE/HYPOTHESIS: The purpose of this study was to compare the fatigue and failure mechanics of traditional UCL reconstruction with UCL repair and internal bracing. We hypothesized that repaired specimens would have less gap formation, closer return to native gap formation, and greater maximum torque to failure versus traditionally reconstructed specimens. STUDY DESIGN: Controlled laboratory study. METHODS: Ten matched pairs of cadaveric elbows were positioned at 90° of flexion and the native UCL subjected to 500 cycles of subfailure valgus loading. A simulated tear was created, and the 10 cycles were repeated. Each pair of specimens was next given repair with internal bracing on 1 side and a modified Jobe reconstruction on the contralateral side, followed by 100 manual cycles of flexion-extension, 500 cycles of valgus rotation, and, finally, rotation to failure. RESULTS: The specimens that received the repair unexpectedly experienced significantly less gapping in the torn state than did those in the reconstruction group. At the 10th cycle, repaired UCL injuries had significantly less gap formation than the reconstructed UCLs. At the 100th and 500th cycles, repaired UCL injuries continued to experience significantly less gap formation as compared with the reconstructed injuries. CONCLUSION: When compared with the gold standard reconstruction technique, UCL repair with internal bracing is more resistant to gap formation under fatigue loading. However, the unexpected early difference between the torn states may have confounded this finding. Time-zero failure properties of this repair technique are on par with those of traditional reconstruction, even after 500 cycles of valgus loading. CLINICAL RELEVANCE: UCL reconstruction has become a common procedure among adolescent and elite-level throwers. Recent data suggest that UCL repair may be a viable option for younger athletes with acute proximal or distal UCL tears, allowing a faster return to play.

Comparison of Anterior Cruciate Ligament Graft Isometry between Paired Femoral and Tibial Tunnels.

Accurate tunnel placement is important for a successful anterior cruciate ligament (ACL) reconstruction. Controversy exists concerning the preferred method of femoral tunnel preparation, with proponents of both medial portal and transtibial drilling techniques. Current ACL literature suggests that placement of the femoral ACL attachment site posterior or "low" in the ACL footprint leads to more anatomically correct ACL mechanics and better rotational control. There is limited literature focusing on ACL graft displacement through knee range of motion based on specific paired placement of femoral and tibial tunnels. Our purpose was to assess ACL isometry between multiple combinations of femoral and tibial tunnels. We hypothesized that placement of the graft at the posterior aspect of the ACL footprint on the femur would be significantly less isometric and lead to more graft displacement as compared with central or anterior placement. The ACL of matched pairs of cadaveric knees was arthroscopically debrided while leaving the soft tissue footprint on the femur and tibia intact. One knee from each pair underwent notchplasty. In all knees, three femoral and three tibial tunnels were created at the anterior, central, and posterior aspects of the ACL footprint. A suture was passed through each tunnel combination (nine potential pairs), and the change in isometry was measured throughout full knee range of motion. Placement of the femoral tunnel along the posterior aspect of the ACL footprint was less isometric compared with a central or anterior position in the femoral footprint. Placement of a posterior tibial tunnel also led to decreased isometry, but tibial tunnel placement affected isometry to a lesser extent than femoral tunnel placement. The combination of a posterior femoral and posterior tibial tunnel resulted in greater than 1 cm of graft excursion from full flexion to extension. Placement of ACL tunnels at anisometric sites may adversely affect the mechanical properties and behavior of the ACL graft, resulting in either graft laxity in flexion or overconstraint and loss of extension.

A Cadaveric Study Assessing the Accuracy of Ultrasound-Guided Sacroiliac Joint Injections.

BACKGROUND: Ultrasound guidance has been proposed as an alternative imaging modality for sacroiliac (SI) joint injections. Few studies have been published on the accuracy of this modality for the procedure. OBJECTIVE: The objective of this study was to determine the accuracy of ultrasound-guided SI joint injections using a cadaveric model. DESIGN: Controlled laboratory study. SETTING: The study was performed in the Skills Laboratory of the American Sports Medicine Institute in St. Vincent's Hospital, Birmingham, AL. METHODS: Seventeen cadaveric SI joints were injected under ultrasound guidance and dissected to determine the accuracy of intra-articular injections. MAIN OUTCOME MEASUREMENTS: The presence of intra-articular spread of a white paint marker in the SI joint after ultrasound-guided injection. RESULTS: Of 17 SI joints, 15 (88.2%) were accurately injected intra-articularly. One of the joints with no intra-articular spread was found to be partially frozen at the time of dissection, and the second joint was considered an unsuccessful injection before dissection due to difficulty entering the joint under ultrasound guidance because of marginal osteophytes at the joint line. Of the 15 joints with intra-articular placement, 5 joints (33.3%) showed partial extra-articular spread at the time of initial injection and required redirection of the needle under ultrasound guidance, and 3 joints (20%) had extra-articular spread that was not seen during ultrasound. CONCLUSION: Ultrasound allowed intra-articular injection in 88.2% of joints in this cadaveric study. Ultrasound does not expose the patient to radiation, as seen with fluoroscopic guidance, which is currently the gold standard for this injection. In addition, ultrasound may allow visualization of extra-articular spread when caused by extra-articular needle placement, which can allow for redirection of the needle to achieve intra-articular injection. LEVEL OF EVIDENCE: IV.

Mechanisms of mesenchymal stem cell correction of the impaired biomechanical properties of diabetic skin: The role of miR-29a.

Diabetic skin has impaired wound healing properties following injury. We have further shown that diabetic skin has weakened biomechanical properties at baseline. We hypothesize that the biomechanical properties of diabetic skin decline during the progression of the diabetic phenotype, and that this decline is due to the dysregulation of miR-29a, resulting in decreased collagen content. We further hypothesize that treatment with mesenchymal stem cells (MSCs) may improve diabetic wound healing by correction of the dysregulated miR-29a expression. We analyzed the biomechanical properties, collagen gene expression, collagen protein production, and miR-29a levels in skin harvested from 6 to 18 week old mice during the development of the diabetic phenotype. We also examined the correction of these impairments by both MSC treatment and the inhibition of miR-29a. Diabetic skin demonstrated a progressive impairment of biomechanical properties, decreased collagen content, and increased miR-29a levels during the development of the diabetic phenotype. MSC treatment decreased miR-29a levels, increased collagen content, and corrected the impaired biomechanical properties of diabetic skin. Additionally, direct inhibition of miR-29a also increased collagen content in diabetic skin. This decline in the biomechanical properties of diabetic skin during the progression of diabetes may increase the susceptibility of diabetic skin to injury and miR-29a appears to play a key role in this process.

Biomechanical Comparison of Ulnar Collateral Ligament Repair With Internal Bracing Versus Modified Jobe Reconstruction.

BACKGROUND: The number of throwing athletes with ulnar collateral ligament (UCL) injuries has increased recently, with a seemingly exponential increase of such injuries in adolescents. In cases of acute proximal or distal UCL insertion injuries or in partial-thickness injuries that do not respond to nonoperative management, UCL repair and augmentation rather than reconstruction may be a viable option. PURPOSE/HYPOTHESIS: The purpose of this study was to biomechanically compare a new technique of augmented UCL repair versus a typical modified Jobe UCL reconstruction technique. The hypotheses were that (1) the repaired specimens would have less gap formation and a higher maximal torque to failure compared with the reconstruction group, and (2) while both groups would show an increase in gap formation after the simulated tear, the repair group would return closer to the native values compared with the reconstruction group. STUDY DESIGN: Controlled laboratory study. METHODS: Nine matched pairs of cadaveric arms were dissected to expose the UCL. Each elbow was mounted on a test frame at 90° of flexion. A cyclic valgus rotational torque was applied to the humerus with the UCL in its intact state and repeated in its surgically torn state. Finally, each specimen received either an augmented repair or reconstruction and was again put through the cyclic protocol, followed by a torque to failure. RESULTS: Gap formation (0.51 ± 0.22 mm) in the torn state for the repair group was significantly higher (P = .04) than in the intact state (0.33 ± 0.12 mm). After the procedures, the repair group (0.35 ± 0.16 mm) showed greater resistance to gapping (P = .03) compared with the reconstruction group (0.53 ± 0.23 mm). No statistical differences were found for the maximum torque at failure, torsional stiffness, or gap formation during the failure test. CONCLUSION: The current study shows that this novel technique of augmented UCL repair replicates the time-zero failure strength of traditional graft reconstruction and appears to be more resistant to gapping at low cyclic loads. CLINICAL RELEVANCE: This study demonstrates that this novel technique has important biomechanical properties, including time-zero strength and ultimate failure load, compared with the gold standard of UCL reconstruction. In some throwing athletes, this technique may supplant standard UCL reconstruction as the procedure of choice.

Injury response of geriatric mouse patellar tendons.

Injury adversely impacts the structure and mechanical properties of a tendon, thus causing pain and disability. Previously, we demonstrated that patellar tendons in mature (P150) and aged (P300) mice do not recover original functionality, even 6 weeks after injury, and that uninjured geriatric tendons (P570) are functionally inferior to uninjured mature tendons. In this study, we hypothesized that the repair response in injured geriatric mice would be further compromised, thus undermining patellar tendon function post-injury. Patellar tendons from wild-type mice were injured at 540 days. At 3 and 6 weeks post-surgery, structural, mechanical, and biochemical analyses were performed and compared to uninjured controls. Mechanical properties of geriatric tendons failed to improve after injury. When compared to mature and aged tendons post-injury, it was determined that at no age was there a suitable repair response. In previous studies, we were able to associate the absence of SLRPs with phenotypic changes both early and late in repair. Here we found that SLRPs were significantly decreased after injury, thus offering a possible explanation for why geriatric tendons were unable to mount an adequate repair response. Thus, we conclude that regardless of age after maturity, tendon healing ultimately results in a substandard outcome. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1256-1263, 2016.

Torsional Fracture of the Humerus after Subpectoral Biceps Tenodesis with an Interference Screw: A Biomechanical Cadaveric Study.

BACKGROUND: Humeral fracture following subpectoral biceps tenodesis has been previously reported; however, there are no published biomechanical studies reporting the resulting torsional strength of the humerus. Our purpose was to determine if there is an increased risk of humerus fracture after subpectoral biceps tenodesis with an interference screw and to determine if screw size is also a factor. We hypothesized that limbs receiving the procedure would have reduced failure torque and rotation under external rotation compared to untreated controls and that the larger screw size would result in inferior mechanical properties compared to the smaller. METHODS: Twenty matched pairs of embalmed cadaveric humeri were subjected to subpectoral biceps tenodesis using either a 6.25 or 8.0mm interference screw, with the untreated contralateral limb serving as a control. Each humerus was mechanically tested in torsional external rotation to failure. FINDINGS: Maximum torque and rotation to failure were reduced in the tenodesis group compared to controls; however, there was no difference between screw sizes. When both screw sizes were combined into a single group, paired t-tests also showed similar differences. INTERPRETATION: Based on our experiment, there is an increased risk for humerus spiral fracture when subjected to torsional external rotation after subpectoral biceps tenodesis with an interference screw compared to an intact humerus; however, there is not a significant difference between a 6.25mm and 8.0mm screw. Surgeons may elect to use alternative fixation methods in patients at high risk (e.g., overhead throwing athletes, etc.) for torsional loads and fracture.