Biomechanical Comparison of Open and Endoscopic Proximal Hamstring Repair Techniques
Authors: Ryan Michael K. , Crozier Matthew W. , Beason David P. , Emblom Benton A. 
Published: July 2018

Objectives: Proximal hamstring tendon avulsions are a rare subset of hamstring injuries, and surgical fixation has become standard, given superior outcomes compared to nonoperative treatment. Open surgical techniques employ a large incision near the gluteal crease and necessitate extensive retraction for optimal visualization, which may increase risk for infection, numbness and potential sciatic nerve injury. Recently described endoscopic repair techniques enable optimal visualization and access to the tendon and ischial tuberosity through several small incisions, potentially reducing risks associated with open repair. Prior cadaveric studies have evaluated biomechanical properties of open repair techniques. The purpose of this study was to compare the biomechanical properties of open and endoscopic suture anchor repair of proximal hamstring ruptures to validate the structural integrity of the endoscopic technique. Methods: Nine fresh-frozen cadaver pelvises (5 M, 4F) were randomly assigned open proximal hamstring repair, with subsequent contralateral endoscopic proximal hamstring repair. Laterality was evenly distributed. Open repair was performed after reflection of the gluteus maximus to optimize visualization and anchor placement during repair, while endoscopic repair was performed via four small incisions surrounding the ischial tuberosity. Proximal hamstring ruptures were simulated by subperiosteal dissection of the entire tendon from its insertion. Repairs were performed using two double-loaded 3.0 mm polyether ether ketone (PEEK) suture anchors and two 3.75 mm PEEK knotless screw-in anchors in a double-row configuration. After repair, the ischial tuberosity was harvested by cutting the inferior pubic ramus and superior aspect of the ischial tuberosity as far away from the repair site as possible. The bony inferior ramus and ischial tuberosity was potted into an acrylic cylinder using polymethylmethacrylate, while the musculotendinous junction was wrapped in gauze and clamped 3 cm from the insertion. Reference lines were marked at the insertion site and 1, 2, and 3 cm from the insertion to aid optical measurements. Potted specimens were mounted into an MTS 858 MiniBionix servohydraulic test frame and tested according to a previously established protocol. Each specimen was cycled 50 times within a pre-established range, with the range increased every 50 cycles until failure. Values were then compared using a paired t-test. Results: The open repair group failed at a mean of 119 cycles with an average displacement of 12.7 mm at a mean ultimate load of 574.5 N. The endoscopic repair group failed at a mean of 117 cycles with an average displacement of 14.9 mm at and mean ultimate load of 563.4 N. No statistically significant difference was noted among any of these parameters. Conclusion: This biomechanical analysis demonstrated no difference in the structural properties comparing open and endoscopic techniques. Endoscopic proximal hamstring repair is a viable option for surgical fixation of proximal hamstring avulsions, with the potential to decrease risks encountered using open techniques.