Bipolar versus monopolar hemiarthroplasty for displaced femur neck fractures: a meta-analysis study.

Hemiarthroplasty is commonly performed to treat femoral neck fractures. Still, there is a lack of consensus concerning the best component for hemiarthroplasty: unipolar and bipolar implants. Last meta-analysis on this topic is outdated, and an update of current evidences is required. The purpose of this study is to conduct a meta-analysis comparing the unipolar versus bipolar implants for hemiarthroplasty, focusing on the clinical scores, perioperative data, further complications and mortality rate. In September 2019, the main databases were accessed: all the clinical trials comparing unipolar versus bipolar hemiarthroplasty for displaced femoral neck fractures were considered for inclusion. For the methodological quality assessment, we referred to the PEDro score. For the statistical analysis, we referred to the Review Manager 5.3 (The Nordic Cochrane Collaboration, Copenhagen). For implant survivorship, we referred to the STATA/MP software version 14.1 (StataCorp, College Station, Texas). A total of 27 articles were considered for inclusion, consisting of 16 randomized and 11 non-randomized clinical trials. A total of 4511 patients were enrolled, undergoing a mean 21.26 months follow-up. A statistically significant reduction in the acetabular erosion was observed in the bipolar group (OR 3.16, P < 0.0001). Although statistically insignificant, the bipolar group reported a reduction in the mean Harris hip score, reduced surgical duration and hospitalization, reduced dislocation and revisions rate. Concerning the mortality, a reduction across all the follow-ups in favor of the bipolar group was detected, but without statistically significance. This meta-analysis evidenced a reduction in the acetabular erosion after bipolar hemiarthroplasty compared to the unipolar implants. Any statistically significant difference concerning the other endpoints of interest was detected. Current evidence concerning this topic are controversial, and further randomized clinical trials are required.