What level of pain reduction can be expected up to two years after periacetabular osteotomy? A prospective cohort study of 146 patients.

Periacetabular osteotomy (PAO) corrects underlying anatomical anomalies, reduces pain and may postpone or even prevent osteoarthritis onset in patients with symptomatic acetabular dysplasia. Current evidence is based on immediate post-operative pain levels, but knowledge on pain levels in the period after PAO is scarce, and the association between pain score and acetabular angles at PAO is unknown. This study had two aims. First, we studied pain level and patient-reported outcome scores pre- and postoperatively; second, we analysed the association between acetabular angles and pain level. From our database, 426 patients operated from June 2012 to November 2015 were analysed; 127 were exduded. Patients were invited to complete standardized questionnaires preoperatively and postoperatively at 6 and 24 months. Pain was measured using visual analogue scale (VAS). Multiple regression analysis was used to investigate the association between change in centre edge (CE) and acetabular index (AI) angle and pre/postoperative pain levels. Mean (standard deviation, SD) VAS pain at rest before surgery and at the 6- and 24-month follow-up were 35 (24), 14 (20) and 14 (19), respectively. Mean (SD) VAS pain at activity were 69 (22), 41 (29) and 41 (30), respectively. Both VAS pain at rest and at activity fell from the preoperative level to 6 months post-surgery with no further change at 24 months. Patients reported significant improvement in outcomes after 6 months and no further change at the 24-month follow-up. There was no significant association between change in CE/Al angles and VAS pain, either during rest or activity.