LAUSR

Objectives: Hamstring injuries commonly cause pain, weakness and functional limitations. While most hamstring injuries involve the musculotendinous junction or muscle belly, proximal hamstring tendon avulsions are a subset of hamstring injuries that are frequently more debilitating. Nonoperative treatment has demonstrated poor outcomes, thus surgical repair has become the mainstay. 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, posterior incision. Prior anatomic studies described relevant anatomy near the proximal hamstring origin at the ischial tuberosity in the setting of an open repair, but literature describing pertinent anatomy during endoscopic repair is sparse. This cadaveric study enhances knowledge and safety of endoscopic proximal hamstring repair by describing pertinent anatomy surrounding four commonly used endoscopic portals. Methods: Ten fresh-frozen pelvis specimens (5 M, 5F) underwent endoscopic proximal hamstring repair and dissection with evenly distributed laterality (5 R, 5 L). Proximal hamstring ruptures were simulated endoscopically with an arthroscopic knife. Endoscopic repair was then completed on each specimen through four endoscopic portals (Inferolateral, Medial, Superolateral and Accessory Superior) using two double-loaded 3.0 mm polyether ether ketone (PEEK) suture anchors and two 3.75 mm PEEK knotless screw-in anchors. After repair, portal tracts were maintained by inserting four 2.0 mm k-wires through cannulas placed through the portals, securing the wires in bone in the ischial tuberosity beyond the zone of repair. The specimen was dissected in layers around the wires, and measurements from portal tracts to nine pertinent anatomic structures were obtained using a digital caliper. Each measurement was repeated three times, then averaged to obtain a composite mean. Measurements were statistically verified with an intraclass correlation coefficient (ICC), all but two of which were above 0.90. Results: Ten cadaveric specimens demonstrated a mean age and BMI of 45.4 and 27.3, respectively. With respect to anatomic measurements, on average no portal tract was closer than 2.0 cm to the sciatic nerve, inferior gluteal neurovascular bundle or posterior cutaneous nerve, and all double-row repairs were easily completed with good fixation through these four portals (Table 1). Additional anatomic landmarks surrounding the hamstring origin were identified endoscopically, and when routinely located, each landmark helped improve reproducibility and safety of endoscopic proximal hamstring repair (Figure 1). Conclusion: This cadaveric study of the proximal hamstring origin maps the anatomic landscape encountered endoscopically, and supports the efficacy and safety of endoscopic proximal hamstring repair. Average distances (cm) from endoscopic portal sites to nine anatomic structures. Inferolateral Medial Superolateral Accessory Superior Inferior Border Gluteus Maximus 2.49 1.57 4.15 3.95 Adductor Magnus 0.69 0.88 1.80 2.95 Conjoint Hamstring Tendon 0.80 1.25 0.60 1.27 Tip of Ischial Tuberosity 1.15 1.27 2.36 3.39 Sacrotuberous Ligament 2.59 2.23 1.81 1.04 Sciatic Nerve 2.91 3.97 2.37 3.04 Short External Rotators 3.41 3.46 1.89 1.25 Posterior Cutaneous Nerve 3.34 4.54 2.55 3.22 Inferior Gluteal Neurovascular Bundle 5.82 5.96 4.27 3.65 Figure 1. Endoscopic view of a left hip from the medial portal. The intact hamstring tendon is in the center of the image, with pertinent surrounding anatomy. 1. The sacrotuberous ligament. 2. The adductor magnus tendon and muscle fibers. 3. The lateral edge of the ischial tuberosity (with the fibers of the quadratus femoris just lateral to it). 4. The inferior fibers of the inferior gemellus muscle.