Abstract
Purpose
Patients with femoroacetabular impingement (FAI) frequently experience sacroiliac joint (SIJ) pain. This study aimed to investigate whether SIJ stress in patients with FAI changes depending on posture or cam resection.
Methods
Preoperative and postoperative computed tomography (CT) scans were analyzed in 31 patients with FAI who underwent cam resection. We created CT models of the lumbar spine, pelvis, and hip joints, including the SIJ cartilage and surrounding ligaments. For both pre- and post-operative conditions, we constructed models of standing, sitting, and sitting with a 10° posterior pelvic tilt positions and measured the equivalent stress in the anterior, superior-posterior, and inferior-posterior regions of the SIJ under a 600 N load.
Results
Preoperatively, the equivalent stress in the posterior-inferior SIJ region was generally higher in the sitting than in the standing position (up to 2.87-fold, p<0.0001), whereas there was no significant difference between standing and sitting with a 10° posterior pelvic tilt position. After cam resection, the equivalent stress in the lower portion of the SIJ during sitting generally decreased (p<0.0001). A positive correlation was observed between the preoperative posterior-inferior SIJ equivalent stress in the sitting position and preoperative α angle (r=0.40).
Conclusions
In patients with FAI, the equivalent stress in the lower portion of the SIJ generally increased in the sitting posture. Cam resection decreased the equivalent stress in the posterior-inferior SIJ region in the sitting posture to a level similar to that observed with a 10° posterior pelvic tilt before surgery. These findings suggest that optimizing pelvic posture and appropriate cam resection may help mitigate SIJ-related pain in FAI patients, providing valuable insights for surgical planning and rehabilitation strategies.