Collared Cementless Femoral Components Reduce the Revision Rates in Primary Total Hip Arthroplasty Using the Direct Anterior Approach: An Australian Orthopaedic Association National Joint Replacement Registry Study

BackgroundAn increased risk of periprosthetic fracture and aseptic loosening is reported when the direct anterior approach (DAA) is used for total hip arthroplasty (THA), especially with cementless implants. We assessed the rate of revision comparing collared and collarless femoral stems when using the DAA for THA.MethodsWe used data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) for primary THA for osteoarthritis inserted with the DAA between January 2015 and December 2022. There were 48,567 THAs that used the DAA (26,690 collarless cementless, 10,161 collared cementless, and 11,716 cemented). Cumulative percent revision (CPR) was calculated for all-cause revision, revision for periprosthetic femoral fractures, and aseptic femoral stem loosening. Cox proportional hazard ratios were used to compare the revision of collared and collarless cementless stems. We also compared collared cementless stems and cemented stems.ResultsA higher rate of all-cause revision within three months of surgery was observed with collarless compared to collared cementless implants (HR [hazard ratio]: 1.99 [95% CI (confidence interval), 1.56 to 2.54]; P < 0.001). Similarly, collarless cementless implants were associated with a greater rate of revision for fracture in the first six months (HR: 2.90 [95% CI, 1.89 to 4.45]; P < 0.001) and after 6 months (HR 10.04 [95% CI 1.38 to 73.21]; P = 0.02), as well as an increased rate of revision for aseptic loosening after two years (HR: 5.76 [95% CI, 1.81 to 18.28], P = 0.003). Collared cementless and cemented stems performed similarly.ConclusionCollared stems were associated with a reduced rate of all-cause revision for cementless THA performed via the DAA. The reduction in risk may be due to protection from periprosthetic femoral fracture and aseptic loosening.