Sacrotuberous Ligament Pain in Patients who Underwent Sacroiliac Joint Arthrodesis: Incidence and Management of Post-Surgical Lower-Buttock Pain

INTRODUCTION: Most sacroiliac joint (SIJ) disorders are conservatively treated; however, patients with severe pain occasionally require SIJ arthrodesis after failure of continuous conservative management for more than 6 months. We investigated the incidences of preoperative tenderness in the sacrotuberous ligament (STL) and postoperative lower-buttock pain originating from the STL to determine the best way to manage these symptoms to achieve good outcomes. METHODS: We retrospectively investigated 33 patients (14 men and 19 women) with a mean age of 47.7 years (range: 25-79 years) who underwent SIJ arthrodesis for severe pain confirmed using diagnostic SIJ injections between April 2009 and December 2019. We investigated the pain improvement at or around the posterior superior iliac spine (PSIS) pre- and postoperatively using the visual analogue scale (VAS) values, incidence of tenderness of the STL before surgery, rate of the persisting STL tenderness, incidence of new-onset STL pain, and treatment options for STL pain postoperatively. RESULTS: The mean VAS value at or around the PSIS was significantly relieved postoperatively from 85.6 to 31.5 mm (P<0.001). Preoperative tenderness of the STL was identified in 21 of 33 patients (63.6%). The STL tenderness resolved after surgery in 12 of these 21 patients (57.1%); however, it persisted in nine patients (42.9%), all of whom were women. Of the 12 patients who did not have preoperative STL tenderness, 4 (33.3%) developed lower-buttock pain and had STL tenderness. In total, 9 (27.3%) of the 33 patients whose progress could be followed up after SIJ arthrodesis had pain originating from the STL; the STL pain in 8 of the 9 patients was relieved after the STL injections and physical therapy. CONCLUSIONS: The STL pain can occur pre- and postoperatively, and management of both persisting and new-onset STL pain after SIJ arthrodesis should be considered to achieve better outcomes.