In the native hip, the hip capsular ligaments tighten at the limits of range of hip motion and may provide a passive stabilizing force to protect the hip against edge loading. In this study we quantified the stabilizing force vectors generated by capsular ligaments at extreme range of motion (ROM), and examined their ability to prevent edge loading. Torque-rotation curves were obtained from nine cadaveric hips to define the rotational restraint contributions of the capsular ligaments in 36 positions. A ligament model was developed to determine the line-of-action and effective moment arms of the medial/lateral iliofemoral, ischiofemoral, and pubofemoral ligaments in all positions. The functioning ligament forces and stiffness were determined at 5 Nm rotational restraint. In each position, the contribution of engaged capsular ligaments to the joint reaction force was used to evaluate the net force vector generated by the capsule.Aims
Methods
Over an eight-month period we prospectively enrolled 122 patients who underwent arthroscopic surgery of the hip for femoroacetabular impingement and met the inclusion criteria for this study. Patients with bilateral hip arthroscopy, avascular necrosis and previous hip surgery were excluded. Ten patients refused to participate leaving 112 in the study. There were 62 women and 50 men. The mean age of the patients was 40.6 yrs (95% confidence interval (CI) 37.7 to 43.5). At arthroscopy, 23 patients underwent osteoplasty only for cam impingement, three underwent rim trimming only for pincer impingement, and 86 underwent both procedures for mixed-type impingement. The mean follow-up was 2.3 years (2.0 to 2.9). The mean modified Harris hip score (HHS) improved from 58 to 84 (mean difference = 24 (95% CI 19 to 28)) and the median patient satisfaction was 9 (1 to 10). Ten patients underwent total hip replacement at a mean of 16 months (8 to 26) after arthroscopy. The predictors of a better outcome were the pre-operative modified HHS (p = 0.018), joint space narrowing ≥ 2 mm (p = 0.005), and repair of labral pathology instead of debridement (p = 0.032). Hip arthroscopy for femoroacetabular impingement, accompanied by suitable rehabilitation, gives a good short-term outcome and high patient satisfaction.
