Prevalence of Saphenous Nerve Injury After Autogenous Hamstring Harvest: An Anatomic and Clinical Study of Sartorial Branch Injury

PURPOSE: Injury to the sartorial (terminal) branch of the saphenous nerve (SBSN) has received little attention in the literature, despite its anatomic proximity to the hamstring tendons during autogenous harvesting. This study aims to define the prevalence of saphenous nerve injury after anterior cruciate ligament (ACL) reconstruction with autogenous hamstrings and define clinically relevant anatomy that may contribute to nerve injury. METHODS: Surveys regarding the presence and duration of sensory changes in the infrapatellar branch of the saphenous nerve (IPBSN) and SBSN were retrospectively sent to 164 patients who had undergone arthroscopically assisted ACL reconstruction with hamstring autograft over a 4-year period. Eleven cadavers were then dissected to identify the relation of the saphenous nerve to the hamstring tendons and accessory insertions. RESULTS: Postoperative sensory disturbance was present in 74% of patients surveyed. Concomitant injuries to both the SBSN and IPBSN occurred in 32% of patients, whereas isolated paresthesias in the SBSN and IPBSN distribution affected 23% and 19%, respectively. The saphenous nerve was intimately associated with the gracilis for 4.6 cm in the distal thigh, from 7.2 cm (range, 6.4 to 9.3 cm) to 11.8 cm (range, 7 to 13.2 cm) proximal to its insertion. Accessory hamstring insertions were present distal to the point where the sartorial branch became extrafascial. CONCLUSIONS: The SBSN is at higher risk of injury during hamstring ACL reconstruction than has been previously reported. The saphenous nerve is intimately involved with the gracilis tendon for a portion of its course in the distal thigh, likely predisposing it to damage during passage of the tendon stripper. LEVEL OF EVIDENCE: Level IV.