Biomechanical Comparison of FiberLock Suspensionplasty and Flexor Carpi Radialis Ligament Reconstruction for Treatment of Thumb Carpometacarpal Osteoarthritis.

BACKGROUND: The purpose of this study was to compare the cyclic and load to failure characteristics of post-trapeziectomy suspensionplasty with the FiberLock Suspension System (FLSS; Arthrex Inc., Naples, Florida) to flexor carpi radialis ligament reconstruction (FCRLR). We hypothesized that the FLSS will have increased stiffness, yield, and ultimate load compared with FCRLR. METHODS: Ten matched pairs of cadaveric hands were used. One side of each pair was randomly assigned to receive the FCRLR or FLSS and the contralateral side received the other suspensionplasty. A complete trapeziectomy was performed followed by FLSS or FCRLR. Cyclic and load to failure characteristics were measured with loading in the distal to proximal direction. A preload of 1 N with 30 cycles of 1 N to 10 N was applied, followed by load to failure. A paired t test was used for statistical analysis (P < .05). RESULTS: The FLSS had significantly decreased nonrecoverable deformation and deformation at peak load during cyclic loading (P < .04). The FLSS also had significantly increased stiffness, yield load, ultimate load, and load and energy absorbed at 10 mm displacement compared with FCRLR (P < .04). All 10 FCRLR specimens failed with suture tearing through the tendon. Nine FLSS specimens failed due to suture slipping from the SwiveLock anchor (Arthrex Inc., Naples, Florida) and 1 failed due to the FiberTak anchor (Arthrex Inc., Naples, Florida) pulling through the index metacarpal. CONCLUSION: Suspensionplasty with the FLSS demonstrated greater structural integrity compared with FCRLR following trapeziectomy. The FLSS procedure may result in decreased thumb subsidence and decreased construct failure.

2022 Bernard Morrey Award: the elbow ulnar collateral ligament complex demonstrates region specific stretching and recovery characteristics with valgus loading.

BACKGROUND: The objective of this study was to quantify the valgus laxity and strain of the elbow ulnar collateral ligament (UCL) complex after repeated valgus stretching and subsequent recovery. Understanding these changes may have important implications in improving strategies for injury prevention and treatment. The hypothesis was that the UCL complex will demonstrate a permanent increase in valgus laxity and region-specific increase in strain as well as region-specific recovery characteristics. METHODS: Ten cadaveric elbows (7M, 3F, 61.7 ± 2.7 years) were used. Valgus angle and strain of the anterior and posterior bands of the anterior bundle and the posterior bundle were measured at 1 Nm, 2.5 Nm, 5 Nm, 7.5 Nm, and 10 Nm of valgus torque at 70° of flexion for: (1) intact UCL, (2) stretched UCL, and (3) rested UCL. To stretch the UCL, elbows were cycled with increasing valgus torque at 70° of flexion (10 Nm-20 Nm in 1 Nm increments) until the valgus angle increased 8° from the intact valgus angle measured at 1Nm. This position was held for 30 minutes. Specimens were then unloaded and rested for 2 hours. Linear mixed effects model with Tukey's post hoc test was used for statistical analysis. RESULTS: Stretching significantly increased valgus angle compared to the intact condition 3.2° ± 0.2° (P < .001). Strains of both the anterior and posterior bands of the anterior bundle were significantly increased from intact by 2.8% ± 0.9% (P = .015) and 3.1% ± 0.9% (P = .018), respectively at 10 Nm. Strain in the distal segment of the anterior band was significantly higher than the proximal segment with loads of 5 Nm and higher (P < .030). After resting, the valgus angle significantly decreased from the stretched condition by 1.0° ± 0.1° (P < .001) but failed to recover to intact levels (P < .004). After resting, the posterior band had a significantly increased strain compared to the intact state of 2.6% ± 1.4% (P = .049) while the anterior band was not significantly different from intact. CONCLUSION: After repeated valgus loading and subsequent resting, the UCL complex demonstrated permanent stretching with some recovery but not to intact levels. The anterior band demonstrated increased strain in the distal segment compared to the proximal segment with valgus loading. The anterior band was able to recover to strain levels similar to intact after resting, while the posterior band did not.

Latissimus dorsi and teres major tendon transfer for irreparable anterosuperior rotator cuff tear improves kinematics and internal rotation compared to latissimus dorsi tendon transfer.

INTRODUCTION: Latissimus dorsi and teres major (LDTM) tendon transfer has demonstrated better clinical outcomes compared to Latissimus dorsi (LD) transfer for irreparable anterosuperior cuff (subscapularis/supraspinatus) tears; however, the biomechanical effects of these procedures are unknown. Therefore, the objective of this study was to compare kinematics and internal rotation of LDTM transfer to LD transfer for anterosuperior cuff tear. METHODS: Eight cadaveric shoulders were tested in four conditions; (1) intact, (2) anterosuperior rotator cuff tear, (3) LDTM transfer, and (4) LD transfer. Glenohumeral kinematics and internal rotation at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane were measured. Muscle loading was applied based on physiological cross-sectional area ratios with three muscle loading conditions to simulate potentially increased tension due to the advanced insertion site of the transferred tendons. RESULTS: The anterosuperior rotator cuff tear leads to a significant superior shift of the humeral head compared to intact at 0° and 30° abduction (p < 0.039). Both the LDTM (p < 0.047) and LD transfers (p < 0.032) significantly shifted the humeral head inferiorly compared to the tear condition.; however, the LDTM transfer shifted the head in the anteroinferior direction compared to the LD transfer at 60° abduction and 30° ER (p < 0.045). Both LDTM and LD transfer significantly increased internal resting rotation (p < 0.008) and maximum internal rotation (p < 0.008) compared to anterosuperior rotator cuff tear and intact at 30° and 60° abduction. LDTM transfer resulted in a significant internal resting rotation compared with the LD transfer at 30° abduction with double muscle loading (p = 0.02). At 0° abduction, the LDTM transfer (p < 0.027) significantly increased maximum internal rotation compared to anterosuperior rotator cuff tear and intact. CONCLUSION: Although both LDTM and LD tendon transfer improved the abnormal humeral head apex position and internal rotation compared with the tear condition, the LDTM transfer was biomechanically superior to the LD transfer in a cadaveric model.

Biomechanical comparison of combined latissimus dorsi and teres major tendon transfer vs. latissimus dorsi tendon transfer in shoulders with irreparable anterosuperior rotator cuff tears.

BACKGROUND: Irreparable anterosuperior rotator cuff tears (IASRCTs) can result in a gradual loss of active elevation and internal rotation, superior and anterior translation of the humeral head, and cuff tear arthropathy. Joint-preserving treatment options for IASRCTs in young and high-demand elderly patients remain a subject of ongoing debate. The aim of the study was to evaluate the biomechanical efficacy of the combined latissimus dorsi and teres major tendon (LDTM) transfer and compare it to an isolated latissimus dorsi (LD) transfer in a cadaveric IASRCT model. METHODS: Eight cadaveric shoulders (mean age, 68.3 ± 5.2 years; range 58-71) were tested with a custom shoulder testing system. All specimens were tested at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane under 4 conditions: (1) intact, (2) IASRCT, (3) combined LDTM transfer, and (4) isolated LD transfer. The superior and anteroinferior translation and subacromial contact pressure were measured. The effects of 3 different LD and LDTM muscle loading conditions were investigated to determine the effectiveness of the muscle transfer conditions. A linear mixed effect model was used for statistical analysis, followed by a Tukey post hoc test. RESULTS: IASRCTs significantly increased superior translation, anteroinferior translation, and subacromial peak contact pressure. Combined LDTM transfer significantly decreased superior and anteroinferior translation compared with IASRCTs in all positions and muscle loadings. Isolated LD transfer did not significantly decrease superior (P > .115) and anteroinferior translation (P > .151) compared to IASRCT at any abduction and muscle loads except superior translation at 60° abduction and 90° of external rotation (ER) (P < .036). LDTM transfer also significantly decreased peak contact pressure from the IASRCT condition at every abduction angle (P < .046). However, isolated LD transfer significantly decreased subacromial peak contact pressure only at 30° abduction and 0° and 30° of ER with triple loading (P < .048), as well as at 60° abduction and 90° of ER (P < .003). CONCLUSIONS: Combined LDTM transfer decreased superior translation, anteroinferior translation, and subacromial contact pressure compared with the IASRCT condition. Isolated LD transfer did not improve glenohumeral translation and subacromial contact pressure. Combined LDTM transfer may be a more reliable treatment option than isolated LD transfer in patients with an IASRCT.