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.