FP6.6 Risk Factors for Complications, secondary procedures and Conversion to THA following MIS-PAO

Abstract

Background: Minimally invasive Periacetabular osteotomy techniques MIS-PAO is becoming the standard for treating acetabular dysplasia. The lower complication rate and minimally invasive nature has encouraged high volume centres to expand their indications, including patients with higher BMI, older age group and higher Tonnis Grades. Quantifying the risk associated with these risk factors helps in patient education and decision making. We aim to examine binary clinical outcomes in consecutive MIS-PAOs in a tertiary referral centre perfromed by a single surgeon. Methods: All isolated PAOs with minimum follow-up 1 year on the local Hip Preservation Registry were identified. Independent variables as demographics, radiological parameters, diagnosis, and previous Surgery were collected from E-notes and Imaging. The outcome measures were complication rate, secondary procedures rate and conversion to Total hip arthroplasty THA. Independent variables were checked for correlation with outcome measures using multiple linear regression, with p value < 0.05 and survival analysis performed. Results: 513 PAOs were identified between Jan 2013 and October 2022. Mean follow-up was 5.18 years ± 2.42 SD. Mean age was 32.46 years ±9.86 SD. Mean BMI was 26.54± 4.35 SD. 18% were smokers. 12.3% were graded as Tonnis II. 32 patients sustained a complication(s) (6.2%) with most common being nonunion (4.3%). 10.9 % of patients required secondary procedures. 3.7% required conversion to THA with mean time to conversion 4.6 years ± 2.04 SD. The 5-year survival was 96.3 % (95% CI 93.9% to 97.8%) and 10-year survival was 92.7% (95% CI 86.7% to 96.0). Higher BMI, smoking, Tonnis Grade II and increasing age were identified as risk factors for any complication (p<0.05). Higher BMI correlated with the need for secondary surgery (p<0.05). Tonnis Grade II has 7.89 times the odds of conversion to THA compared to Tonnis grade 0 (p<0.05). Conclusion: MIS PAO can be performed safely with an acceptable complication and conversion rate at mid-term. We have identified age, BMI, smoking and Tonnis grade II as risk factors for inferior outcomes. Patient specific risk can be calculated using conditional probability. The patient specific rate of complications, secondary procedures and conversion can help guide the threshold for surgery, decision-making and surgical tactics.