Functional acetabular retroversion syndrome: description of a specific sub-type of FAI and results of treatment with minimally invasive PAO.

Introduction: Acetabular retroversion syndrome is associated with pincer-type femoroacetabular impingement (FAI) and results, theoretically, from an externally rotated hemipelvis. The purpose of this study was to examine our surgical experience and the clinical results of functional acetabular retroversion syndrome treated with minimally-invasive periacetabular osteotomy (PAO).
Methods: We performed a retrospective cohort study of prospectively collected data in consecutive patients who had an anteverting PAO from 01 November 2010 to 31 December 2015. All patients were followed up clinically and radiologically.Functional scores were ascertained using pre- and postoperative iHOT-12 and EQ-5D. The effect of hypermobility, smoking status and body mass index (BMI) on outcome measures was evaluated.
Results: 31 anteverting PAOs were performed on 27 consecutive patients. All patients were female. The mean age was 26.7 years (SD 6.7). The mean BMI was 25.8 kg/m ² (SD 5.1). 5 patients were smokers (16.1%) and 11 exhibited signs of generalised joint laxity. 23 hips had undergone prior hip arthroscopy and 1 patient had previous open FAI surgery. The minimum clinical follow-up was 2 years (mean 3.4 years; range 2-7 years). A crossover sign was present in all cases. The mean iHOT-12 score improved from 19.5 to 51 at 6 months, 64.5 at 1 year and 48 at 2 years following surgery ( p < 0.05) EQ-5D improved from 0.42 preoperatively to 0.76 at 6 months and 0.69 at 1 year following surgery ( p < 0.05).
Conclusions: We have characterised functional acetabular retroversion syndrome (FARS) as a condition affecting young, active females which severe symptoms out of proportion to demonstrable radiographic pathology.