Lower Rates of Femoral Fracture and Subsidence with a Morphometric Stem in Cementless Total Hip Arthroplasty.

Abstract

A "morphometric" tapered femoral stem with size-specific medial curvatures and proportional neck lengths was introduced, attempting to improve fixation and biomechanics in cementless total hip arthroplasty (THA) across a range of femoral sizes and morphotypes. We investigated whether this design reduced complications and better restored anatomy (e.g., limb length and offset) compared to a traditional tapered stem with consistent neck lengths across sizes. We reviewed 389 THAs (340 patients) performed using either of two cementless femoral implants. Records were reviewed for demographics, surgical details, complications, and reoperations. Radiographs were examined for subsidence, biologic fixation, leg lengths, offset, and proximal femoral morphology. The intraoperative fracture rate was lower with this morphometric stem compared to this traditional stem (0 vs. 3.4%), as was the incidence of postoperative subsidence ≥3mm (4.7 vs. 19.2%). With the numbers available, no differences were identified regarding rates of reoperation for periprosthetic femur fracture (0 vs. 1.0%) and femoral fixation failure without fracture (1.1 vs. 0%), or all-cause reoperations (2.7 vs. 2.4%). Limb length and offset restoration were similar with the two implants, but the shortest available femoral head was used less frequently with this morphometric stem compared to this traditional stem (22 vs. 54%). This morphometric stem was associated with decreased rates of intraoperative fracture and postoperative subsidence, along with decreased use of the shortest available head. Nevertheless, both implants demonstrated clinical success, allowing reconstruction of limb length and offset with low rates of femoral fixation failure.