Suture Anchor Repair of Complete Proximal Hamstring Ruptures: A Cadaveric Biomechanical Evaluation

摘要

Background: Few studies have examined the importance of suture anchor size, quantity, or configuration on the initial biomechanical strength of proximal hamstring repair.Hypothesis: An anatomic repair with 5.5 mm suture anchors will be biomechanically superior to a similarly configured repair with 2.8 mm suture anchors, with a 3-anchor repair providing a biomechanically superior construct compared to a 5-anchor "X configuration" repair. Methods: Twenty-one fresh-frozen human pelvis to mid-femoral shaft specimens were dissected isolating the proximal hamstrings and their origins from the ischial tu-berosity. Specimens were mounted to a custom jig, and the hamstring tendons were secured to a MTS machine load cell distal to the musculotendinous junction. Native intact specimens (Group 1: control) were loaded to failure at a rate of 33 mm/sec to simulate rapid eccentric contraction. Experimental complete ruptures of the proximal hamstrings were created and repaired using four different configurations, including 2.8 mm suture anchors in a 3-anchor repair configuration (Group 2); 2.8 mm suture anchors in a 5-an-chor ("X") repair configuration (Group 3); 5.5 mm suture anchors in a 3-anchor configuration (Group 4); and 5.5 mm suture anchors in a 5-anchor ("X") configuration (Group 5). Repairs were tested with cyclic axial loading between 150 and 350 Newtons (N) at a frequency of 1 Hz for up to 500 cycles. Gap formation was assessed using digital photography and Image-J analysis after the initial 250 N load was applied and again at the conclusion of cyclic loading. Specimens were then loaded to failure at 33 mm/sec. Load to failure and mode of failure were recorded for each specimen. Comparisons were made between the treatment groups with respect to gap formation and ultimate load to failure. Statistical significance level was p < 0.05. Results: All suture anchor repairs failed at the tendon-bone interface. There was a significant difference in cycles to gap formation, with all 2.8 mm repairs gapping after the placement of the initial 250 N load versus the 5.5 mm repairs demonstrating initial gap formation after 58 and 110 cycles for groups 4 and 5, respectively. Mean initial gap formation was significantly less in the 5.5 mm repair groups (Group 4: 0.60 mm and Group 5: 0.44 mm versus Group 2: 3.29 mm and Group 3: 3.27 mm). The 5.5 mm anchor repairs had significantly greater ultimate loads to failure compared to repairs using 2.8 mm anchors (Group 4: 502.4 N and Group 5: 490.8 N versus Group 2: 284.7 N and Group 3: 183.3 N) with no significant difference compared to intact controls (Group 1: 501.8 N). Conclusion: The use of 5.5 mm anchors resulted in a significantly greater ultimate load to failure and significantly less gap formation than that seen following repairs with 2.8 mm anchors. With an initial fixation strength that is similar to intact controls and no difference between 3- and 5-anchor repairs, our data supports the use of three large suture anchors in the surgical management of complete proximal hamstring ruptures potentially allowing for earlier active rehabilitation.