Incidence and determinants of anteflexion impairment after rotational acetabular osteotomy

This study aimed to identify the incidence of anteflexion impairment after rotational acetabular osteotomy based on patient-reported outcome measures, and the morphological factors and postoperative bony range of motion associated with anteflexion impairment at 2 years postoperatively. We analyzed 26 patients with developmental dysplasia of the hip who underwent rotational acetabular osteotomy at our institution. Using questionnaires, we defined anteflexion impairment as difficulty in clipping toenails and pulling up and removing socks. Morphological parameters and bony range of motion measured using a postoperative three-dimensional surface model, were compared between the subjects with and without anteflexion impairment. The incidence of anteflexion impairment was 69% at 6 months, 35% at 1 year, and 12% at 2 years after rotational acetabular osteotomy. The mean bony flexion angle was smaller in subjects with impairment than in those without impairment. The mean internal rotation (IR) angle at 90° of flexion was smaller in subjects with impairment than in those without impairment. The incidence of impairment was significantly higher in subjects with both less than or equal to 105° of bony flexion and less than or equal to 20° of IR at 90° of flexion than in the remaining subjects. No significant difference was observed in postoperative femoral head coverage and preoperative morphological parameters including spinal condition between the two groups. To prevent femoroacetabular impingement after rotational acetabular osteotomy, surgeons need to reorient the acetabulum to restore postoperative bony flexion to more than or equal to 105° and/or postoperative IR range of motion to more than or equal to 20° at 90° of flexion.