The outcomes of conversion of hemiarthroplasty to total hip arthroplasty, a systematic review and meta-analysis

Introduction Acetabular erosion is an important complication in hemiarthroplasty and may lead to total hip arthroplasty as a conversion. The results of total hip arthroplasty as a conversion remain unclear. We performed a systematic review and meta-analysis to compare the outcome of total hip arthroplasty as a conversion with primary total hip arthroplasty. Materials and methods PRISMA guidelines were used and Pubmed, Embase and the Cochrane libraries were searched. Both, studies comparing the outcome of total hip arthroplasty as a conversion with the outcome of primary total hip arthroplasty and the outcome of cohort studies limited to total hip arthroplasty as a conversion, were included. Risk of bias was assessed using the Methodological Index for Non Randomized Studies checklist. Meta-analysis was performed concerning pooled annual revision, dislocation and infection rates. Results A total of 27 studies were available for analysis; four comparative studies and 23 cohort studies. Comparative studies were defined as high quality and cohort studies as medium quality. Analysis revealed a significantly higher overall revision risk (Hazard Ratio 1.72, 95% confidence interval 1.39 to 2.14) after total hip arthroplasty as a conversion compared to primary total hip arthroplasty. The annual revision rate of total hip arthroplasty as a conversion was 1.63% (95% confidence interval 1.14 to 2.33) in the comparative studies and 1.40% (95% confidence interval 1.17 to 1.66) in the cohort studies. A pooled infection rate of 4.34% (95% confidence interval 2.66 to 7.01) and dislocation rate of 4.79% (95% confidence interval 3.02 to 7.53), was found. Conclusions Literature concerning the results of total hip arthroplasty as a conversion is limited. The risk of revision after conversion of hemiarthroplasty is higher compared to primary total hip arthroplasty.