High subsidence rate in primary total hip arthroplasty with a taper wedge stem featuring a three-dimensionally...

Femoral stem subsidence (FSS) following total hip arthroplasty (THA) can lead to complications such as aseptic loosening and early implant failure. This study evaluated the subsidence and clinical outcomes of the GS-Taper stem, a taper wedge stem using a three-dimensional (3D)-printed porous structure, in primary THA cases.

This retrospective analysis was conducted in 112 hips that underwent THA using the GS-Taper stem between October 2020 and May 2023, with follow-up at 1 year postoperatively. The primary outcome was the evaluation of FSS and its relationship with neck length, canal fill ratio, and stem alignment. Secondary outcomes included clinical scores assessed using the modified Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles activity scores, as well as radiographic findings such as periprosthetic bone reactions, including stress shielding, radiolucent lines, and spot welds.

The mean subsidence at 1 year postoperatively was 3.4 ± 3.0 mm, with 55 hips showing subsidence ≥ 3 mm (FSS group) and 57 hips showing subsidence < 3 mm (non-FSS group). The FSS group demonstrated significantly shorter neck length, lower canal fill ratio, valgus positioning, and a higher proportion of medial gaps compared to the non-FSS group. Radiographic analysis revealed increased radiolucent lines and stress shielding in Gruen zone 1 in the FSS group. The FSS group had significantly worse clinical outcomes and a higher incidence of thigh pain than the non-FSS group.

The GS-Taper stem exhibited a high rate of subsidence, potentially due to its 3D-printed porous structure and micro-spike configuration. These findings highlight the need for design modifications to improve initial stability and biological fixation.