Final Femoral Rasp Predicts Intraoperative Stem Alignment in Primary Total Hip Arthroplasty Using a Cementless Triple-Tapered Stem

Background The final femoral rasp (FFR) serves as an intraoperative surrogate for positioning the final femoral implant (FFI) in total hip arthroplasty (THA), yet quantitative data on rasp–implant concordance for modern triple-tapered stems are limited. This study quantified positional differences between the final rasp and implant in primary cementless THA via the direct anterior approach (DAA). Methods This prospective study included 63 THA procedures using the DAA. Intraoperative fluoroscopic images of FFR and FFI were analyzed in coronal and axial projections, measuring from lateral shoulder to the greater trochanter tip and from osteotomy plane to taper apex in coronal view, as well as angular deviation between rasp/implant axis and proximal femoral shaft axis in both views. Positional differences (Δ = FFR − FFI) were assessed. Results The implant was positioned more proximally than the rasp (Δ greater trochanter–shoulder = 0.64 ± 2.51 mm, P = .048) and demonstrated valgus alignment relative to the rasp (Δ coronal angle=0.63° ± 1.38°, P < .001), whereas no differences were observed for the remaining parameters. Conclusions This intraoperative analysis demonstrated close positional agreement between FFR and FFI in a cementless, triple-tapered stem THA design implanted via the DAA. The FFI was positioned in valgus and at a more proximal level than the FFR. These differences were limited and likely attributable to minor intraoperative adjustment and design-related geometric differences. Overall, the findings support the reliability of the FFR as an intraoperative surrogate for implant positioning in cementless THA.