INTRODUCTION: Acetabular retroversion (AR) is a variant of hip dysplasia,1 enhancing the risk of pincer-morphology femoroacetabular impingement syndrome (FAIS).2 FAIS is associated with pain,3 reduced level of function,4 decreased health-related quality of life,5 and early development of hip osteoarthritis (OA).6, 7 Symptoms may be exacerbated by anterior pelvic tilt (APT)8 as it functionally increases anterosuperior femoral head cover.1, 9, 10 Currently, the standard treatment for symptomatic AR is an invasive anteverting periacetabular osteotomy.11 Exercise aiming at reducing APT may be a less-invasive alternative treatment strategy. However, the impact of a targeted exercise intervention in patients with symptomatic AR, and excessive APT is unknown.
RESEARCH QUESTION: What is the change in patient-reported symptoms and pelvic tilt in patients with AR and excessive APT of an 8-week targeted progressive home-based exercise intervention compared with a prior control period?
METHODS: The sample size was n=36 patients (age 18-40 years) not eligible for surgery, with radiographic signs of AR on an anterior/posterior radiograph in standing position. Patients were recruited from Odense University Hospital outpatient clinic (Denmark) from November 2018 to December 2019. Exclusion criteria were; pelvic-tilt-ratio greater than 0.512 (the height of the obturator foramen divided by the height of the lesser pelvis) indicating posterior pelvic tilt, radiographic sign of hip OA, related surgery, and a body mass index (BMI) above 35. The intervention consisted of education, activity modification, stretching for posterior pelvic tilt mobility, strengthening muscles for tilting the pelvis posteriorly, improving body core stability, and pelvic movement control three times per week. The primary outcome was change in the Copenhagen Hip and Groin Outcome Score (HAGOS) pain subscale. Secondary outcomes included change in pelvic tilt in standing position measured by EOS® scanning, as the angle between a horizontal line and a line connecting the upper border of the symphysis with the sacral promontory.13
RESULTS: Forty-two patients (39 women) (median [interquartile range], 20.5 [19 – 25 years] were included. Three patients were lost to follow-up. Between-period mean change scores were 5.2 points (95% confidence interval [CI]: [-0.3 – 10.6]), for the HAGOS-PAIN subscale and -1.6 degrees [-3.9 – 0.7] of anterior pelvic tilt.
DISCUSSION: No statistical or clinically relevant changes in self-reported hip-related pain and APT were found. However, post-hoc responder analysis revealed that patients with moderate pain at baseline benefited from exercise. Patients had an excessive APT of 74° ±8 (mean ±SD) at baseline, which is 14° more than the defined neutral pelvic tilt.13 The current study is limited by a short and unsupervised training period, and measuring static pelvic tilt only. Future results from three-dimensional gait analysis will provide answers to whether patients' ability to dynamically tilt their pelvis posteriorly has changed.

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