Good Mid- to Long-Term THA Outcomes with a Modified Cementless Rectangular Biconical Stem Design

Abstract

Purpose Second- and third-generation cementless Zweymüller stems have achieved good long-term outcomes in total hip arthroplasty (THA). The PPF cementless proximal press-fit femoral stem (Biomet Inc.) is based on the Zweymüller stem, with some prominent design differences. This study was designed to assess its performance in terms of survivorship, clinical function, and radiographic outcomes. Methods We retrospectively analysed 250 patients (303 hips) who underwent THA between 1998 and 2011. Patients attended a follow-up visit a mean 10.9 ± 2.6 years after the procedure. All patients underwent radiographic examination and were clinically assessed for Forgotten Joint Score (FJS) and pain visual analogue scale (VAS). Survivorship was calculated using Kaplan-Meier analysis. Results Clinical data were available for 142 patients (192 hips) and radiographic data for 79 patients (109 hips). Stem survival was 99.1% (95% confidence interval [CI] 96.6%-99.8%) at 10 years and 95.6% (95% CI 96.6%-99.8%) at 15 years. The median postoperative FJS was 91 (interquartile range [IQR], 75-100). The median VAS score was 0 (IQR, 0-2). Radiolucent lines were observed in 47 hips (43.1%). 25 hips (22.9%) had Grade I ossification, 17 (15.6%) Grade II, and 2 (1.8%) Grade III. 12 hips (11.0%) had osteolysis in at least 1 femoral zone. Conclusions The cementless proximal press-fit femoral stem was associated with good mid- to long-term survival and functional outcomes. The current design can be considered equivalent to the second- and third-generation Zweymüller stems.