Collared fully hydroxyapatite-coated femoral components reduce early periprosthetic femoral fractures in total hip arthroplasty with the direct anterior approach

Aims The purpose of this study was to investigate the difference in the incidence of early postoperative periprosthetic femoral fracture (POPFF) between flat-tapered wedge and collared fully hydroxyapatite (HA)-coated femoral components performed through the direct anterior approach (DAA). Methods This was a retrospective comparative study of 4,511 primary total hip arthroplasties (THAs), including 1,842 flat-tapered wedge and 2,669 collared fully HA-coated components, conducted by a single surgeon at a single institution using the DAA from August 2009 to June 2023. Propensity score matching was used to control confounding factors related to POPFF. After matching, 1,804 cases were selected for each group, and the incidence of early POPFF was compared between the two implant designs. An early POPFF was defined as a periprosthetic fracture undetected intraoperatively and on immediate postoperative radiographs that occurred within 90 days. The incidence of intraoperative periprosthetic femoral fracture (IOPFF) was also evaluated and compared between the two groups. Results Early POPFF was significantly less frequent in the collared fully HA-coated designs (0.11%; n = 2) than in the flat-tapered wedge designs (0.72%; n = 13; p = 0.007). Regarding the details of early POPFFs, the median time to fracture was ten days and an injury mechanism was absent in 73% (n = 11). According to the Vancouver classification, two were fracture type A(G) and one was A(L), while B1 and B2 fractures comprised 33% (n = 5) and 47% (n = 7), respectively. Treatment methods included conservative management in 33% (n = 5), osteosynthesis in 53% (n = 8), and revision surgery in 13% (n = 2). IOPFF was significantly more frequent in the collared fully HA-coated designs (3.49%; n = 63) than in the flat-tapered wedge designs (2.00%; n = 36; p = 0.008). Conclusion The results of this large-scale, propensity score-matched study implied that the incidence of early POPFFs with collared fully HA-coated femoral components was lower than flat-tapered wedge designs. However, the incidence of IOPFFs was higher with collared fully HA-coated femoral components. These findings highlight the importance of femoral component design, including broaching, in THA implant selection for POPFF and IOPFF. Cite this article: Bone Joint J 2025;107-B(10):1011–1019.