Hip arthroscopy leaves femoral head position unchanged on 3D CT analysis

Arthroscopic surgery for cam-type femoroacetabular impingement (FAI) involves reshaping the bone at the femoral head-neck junction and managing the joint capsule, both of which could in principle shift the resting position of the femoral head inside the socket. A new study set out to measure whether that actually happens, using three-dimensional computed tomography (CT) reconstructions from before and after surgery.

Researchers retrospectively reviewed CT scans of 22 patients with FAI, 14 with the cam type and 8 with the mixed type, who underwent hip arthroscopy. Using patient-specific pre- and postoperative 3D CT data, they computed the distances between the femoral head center and the acetabular center and compared the femoral head position before and after surgery. Net changes in the femoral head center were evaluated in the mediolateral and anteroposterior directions.

The results showed no significant change in the femoral head center in either direction. In the mediolateral direction the mean change was −0.08 millimeters, with a standard deviation of 1.49 millimeters, and in the anteroposterior direction the mean change was 0.22 millimeters, with a standard deviation of 1.12 millimeters. There was also no significant difference in these values when compared with the non-operated contralateral side, providing an internal reference for what an unaltered hip looks like on the same imaging protocol.

The authors frame the findings cautiously. In this exploratory cohort, no statistically significant pre- to postoperative difference in the resting femoral head position was detected on supine CT after arthroscopic cam resection with capsular repair. Importantly, they note that these findings should not be interpreted as evidence of preserved dynamic hip stability, because the measurements were taken on static, supine scans rather than during movement or loading.

The study suggests that, at least in terms of static bony geometry measured on CT, arthroscopic cam resection combined with capsular repair did not measurably displace the femoral head center relative to the acetabulum in this patient group. The authors conclude that further research incorporating dynamic analysis is necessary to evaluate functional joint stability, since a resting position captured on a supine scan cannot capture how the hip behaves under the loads and motions of daily activity.

Subject of Research: Three-dimensional CT assessment of femoral head center position before and after arthroscopic surgery for femoroacetabular impingement

Article Title: Evaluation of the three-dimensional position of the femoral head center after arthroscopic surgery for femoroacetabular impingement

Article References: Higashihira, S., Iwanaga, D., Yukizawa, Y., Kumagai, K., Inoue, Y., Choe, H., Ike, H., Inaba, Y., & Kobayashi, N. (2026). Evaluation of the three-dimensional position of the femoral head center after arthroscopic surgery for femoroacetabular impingement. BMC Musculoskeletal Disorders. https://doi.org/10.1186/s12891-026-10683-6

Image Credits: AI Generated

DOI: 10.1186/s12891-026-10683-6

Keywords: femoroacetabular impingement, hip arthroscopy, femoral head center, 3D CT, cam resection, capsular repair, hip stability, orthopedic surgery, musculoskeletal imaging, retrospective study, Evaluation, three-dimensional