Inverted T-capsulotomy of the iliofemoral ligament restores capsular-mediated loss of internal rotation after periacetabular osteotomy: a cadaveric study

Abstract Periacetabular osteotomy (PAO) surgically corrects hip dysplasia, restoring hip function by optimizing acetabular coverage. Changes in acetabular positioning may alter tension forces on capsular ligaments, causing range of motion (ROM) constraints, independent of acetabular orientation. Capsulotomy’s role in restoring capsular mechanics following PAO has not yet been investigated. We aimed to assess how distal iliofemoral ligament (IFL) capsulotomy post-PAO affects hip ROM. Radiographic markers were implanted into the IFL in six cadaveric hip joints. External rotation (ER) and internal rotation (IR) were assessed at 90° of hip flexion. Each hip underwent PAO and was re-tested, with intact capsule. Post-PAO, stepwise capsulotomy was performed. ROM was reassessed and marker displacement analyzed radiographically. Paired t-tests compared ROM in experimental settings (CI = 95%). Capsular tightening from PAO significantly restricted IR, independent of bony corrections. IR decreased by 12° after PAO (P = .0039). Inverted T-capsulotomy restored IR losses (P = .0341). ER and flexion demonstrated non-significant changes pre- to post-capsulotomy interventions (P .05). Full capsulectomy increased IR (20 ± 3.2°, P = .0028), ER (50 ± 3.2°, P = .0031), and flexion (111.25 ± 8.3°, P = .006), but compromised stability. Radiographically, PAO shifted the hip center inferomedially, tensioning the posterior capsule and impairing IR. After PAO, intracapsular markers displaced superolaterally with minimal anteroinferior movement. Capsular ligament reorientation constrained functional motion in cadaveric specimens. Inverted T-capsulotomy restored hip ROM, specifically IR, and may present a valuable tool in addressing functional limitations after PAO.