Cementless Tapered Wedge Femoral Stems Decrease Subsidence in Obese Patients Compared to Traditional Fit-and-Fill...

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical imaging

Background:

• Femoral component stability is crucial for osseointegration and clinical success in cementless total hip arthroplasty.
• Evaluating component fit and subsidence is key to understanding long-term implant performance.
• Modern cementless femoral components aim to optimize stability and minimize micromotion.

Purpose of the Study:

• To radiographically compare the anatomic fit and subsidence of two distinct cementless femoral component designs.
• To assess the performance of proximally tapered, porous-coated femoral stems.
• To determine if stem design influences stability and resistance to subsidence.

Main Methods:

• Retrospective cohort study of 126 cementless total hip arthroplasties.
• Comparison between traditional fit-and-fill stems (n=61) and morphometric tapered wedge stems (n=65).
• Radiographic assessment of canal flare index, canal fill, stem alignment, and subsidence.

Main Results:

• The tapered wedge stem demonstrated greater femoral canal fill (P=.001).
• Significantly less subsidence was observed with the tapered wedge design (0.3 mm) versus the fit-and-fill design (1.1 mm) (P=.001).
• Subsidence increased with higher BMI in fit-and-fill stems, but not in tapered wedge stems (P=.013).

Conclusions:

• The morphometric tapered wedge femoral stem offers superior axial stability and reduced subsidence compared to fit-and-fill stems.
• The tapered wedge design's inherent stability may make it optimal for obese patients, mitigating BMI-related subsidence.
• Anatomical stem design is critical for enhancing implant stability and patient outcomes in total hip arthroplasty.