David P. Beason

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.

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.

Evaluation and Comparison of Femoral Tunnel Placement During Anterior Cruciate Ligament Reconstruction Using 3-Dimensional Computed Tomography: Effect of Notchplasty on Transtibial and Medial Portal Drilling.

Background: Advocates of medial portal drilling claim that the transtibial technique results in a more vertical positioning of the graft, which could lead to subsequent failure and/or a residual pivot shift on postoperative examination. However, advocates of transtibial drilling state that with appropriate placement and adequate notchplasty, their technique places the graft in a more anatomically correct position on the wall, negating the resultant potential for pivot shift and early postoperative failure. Hypothesis: Transtibial femoral drilling can adequately reproduce the femoral origin of the anterior cruciate ligament (ACL) and place the graft in an anatomical position equivalent to medial portal drilling. Study Design: Controlled laboratory study. Methods: Ten matched-pair cadaveric knees (N = 20) were scanned using computed tomography (CT), and 3-dimensional images of the native ACL origin were reconstructed. The matched pairs were then randomized into transtibial and medial portal groups. The femoral tunnel was drilled in each knee according to group. A bamboo skewer was placed in the femoral tunnel, and the knees underwent a second CT scan. Arthroscopic notchplasty was performed, and the femoral tunnels were redrilled. Radiographs confirmed placement, and the post-notchplasty tunnel was reamed with a 4-mm reamer. The knees underwent a third CT scan. CT scans compared femoral tunnel placement with the native ACL footprint before and after notchplasty. Results: The post-notchplasty transtibial group revealed an average of 68.3% coverage of the native ACL femoral origin. The medial portal group revealed an average of 60.8% coverage, with 1 instance of perforation of the posterior cortex. There were no instances of perforation in the transtibial group. Conclusion: Both drilling techniques place the graft in an anatomically correct position. Clinical Relevance: Transtibial drilling of the femur can adequately place the entry tunnel at the origin of the ACL’s native footprint.

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

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.

Tibiofemoral contact biomechanics following meniscocapsular separation and repair.

Meniscocapsular separations are often seen in knees with other intra-articular pathology. The consequences of these tears with regard to knee contact mechanics are currently unknown, and the biomechanical advantages of repair have not been measured. We hypothesize that tears to the meniscocapsular junction will cause an increase in tibiofemoral contact pressure and a decrease in contact area, with a return to more normal conditions after repair. 10 fresh-frozen cadaver knees each underwent 10 cycles of axial compressive loading in full extension under three different testing conditions: intact, meniscocapsular separation, and repair. A pressure sensor matrix was inserted into the medial joint space and used to measure magnitude and location of contact pressure and area. Mean contact pressure increased from 0.80±0.17 MPa in the intact knee to 0.88±0.19 MPa with separation, with a decrease to 0.78±0.14 MPa following repair. Peak pressures followed a similar trend with 2.59±0.41, 3.03±0.48, and 2.84±0.40 MPa for the same three groups, respectively. While none of the changes seen was statistically significant, even these small changes would potentially create degenerative changes at the articular surface over prolonged (i. e., months or years) standing, walking, and activity in the unrepaired state.

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.

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.

Comparison of Cyclic Fatigue Mechanics between UCL Repair with Internal Bracing and UCL Reconstruction

Objectives: UCL reconstruction has become the preferred treatment for UCL injury in elite throwers desiring a return to throwing. Prior reports of UCL repair demonstrated poor results in professional pitchers, with rate of return to the same or higher level pitching between 0% and 63%. 1,3,6,9,11 However, in young athletes without chronic attritional UCL damage, recent data shows reliable and rapid return to sport with primary UCL repair.2,12,14 We previously introduced a novel UCL repair technique consisting of primary UCL repair, augmented with a spanning tape anchored at either end of the native ligament. Compared to UCL reconstruction, this construct demonstrated significantly greater resistance to gap formation, even at low cycles of valgus loading.8 The purpose of the current study was to compare the high-cycle fatigue mechanics of augmented UCL repair versus modified Jobe UCL reconstruction. We hypothesized that the repaired specimens would have less gap formation compared to the reconstruction group after 10, 100, and 500 cycles of valgus loading. Methods: Twenty fresh-frozen cadaveric upper extremities (10 matched pairs) were dissected to expose the anterior band of the UCL.3 The humeral and ulnar insertions of the UCL were identified and marked to measure ligament displacement.7 Each specimen was potted and mounted on a mechanical test frame.4,5,8,10,13 A 2 N-m valgus preload was applied to the native elbow followed by a 60 s hold and 500 cycles of valgus loading between 2 N-m and 10 N-m. A longitudinal split in the anterior band was created and the distal attachment of the sublime tubercle was released, simulating a distal avulsion tear of the UCL. Ten cycles were repeated in this torn state. Each pair was randomly separated into either a repair or a reconstruction group (Fig 1). Each specimen was then manually subjected to 100 cycles of flexion-extension range of motion to simulate early rehabilitation protocols. The specimens were again loaded for 500 cycles between 2 N-m and 10 N-m, followed by a ramp to failure at a rate of 1°/s. Torque and rotation were recorded in addition to gap measurements for the 10th, 100th, and 500th cycle of the intact and repair/reconstruction conditions. Gaps were measured optically8 as the change in distance of the two anatomical landmarks between the pre-cycling hold and the peak of the cycle of interest. A two-way ANOVA with repeated measures was used to detect overall differences in addition to post-hoc t-tests and Tukey’s HSD for between the two procedures and three conditions, respectively. Significance was set at p ≤ 0.05. Results: The repair group showed greater resistance to gapping compared to reconstruction after 10 (p=0.008), 100 (p=0.02), and 500 (p=0.004) cycles (Fig. 2) of valgus motion. There was no difference in the intact state; however, the repair group did exhibit a reduction (p=0.007) in gap in the torn state after 10 cycles. Conclusion: In this preliminary report, UCL repair using internal bracing is more resistant to gap formation under fatigue loading than the gold standard reconstruction technique. The time-zero failure properties of this repair technique are on par with those of traditional reconstruction, although similar differences also seen in the torn state at early cycles may act as a confounding factor. In young throwers with insertional UCL injuries, our UCL repair technique may provide a suitable alternative to reconstruction with similar biomechanical properties and faster return to sport.

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

&NA; 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.