Adjustment of stem anteversion using tapered cone stem in total hip arthroplasty.

Aims: The aim of this study was to evaluate the suitability of the tapered cone stem in total hip arthroplasty (THA) in patients with excessive femoral anteversion and after femoral osteotomy.
Methods: We included patients who underwent THA using Wagner Cone due to proximal femur anatomical abnormalities between August 2014 and January 2019 at a single institution. We investigated implant survival time using the endpoint of dislocation and revision, and compared the prevalence of prosthetic impingements between the Wagner Cone, a tapered cone stem, and the Taperloc, a tapered wedge stem, through simulation. We also collected Oxford Hip Score (OHS), visual analogue scale (VAS) satisfaction, and VAS pain by postal survey in August 2023 and explored variables associated with those scores.
Results: Of the 58 patients (62 hips), two (two hips) presented with dislocation or reoperation, and Kaplan-Meier analysis indicated a five-year survival rate of 96.7% (95% CI 92.4 to 100). Mean stem anteversion was 35.2° (SD 18.2°) for the Taperloc stem and 29.8° (SD 7.9°) for the Wagner Cone stem; mean reduction from Taperloc to Wagner Cone was 5.4° (SD 18.8°). Overall, 55 hips (52 patients) were simulated, and the prevalence of prosthetic impingement was lower for the Wagner Cone (5.5%, 3/55) compared with the Taperloc (20.0%, 11/55) stem, with an odds ratio of 0.20 (p = 0.038). Among the 33 respondents to the postal survey (36 hips), the mean scores were VAS pain 10.9, VAS satisfaction 86.9, and OHS 44.7. A multivariable analysis revealed that reduction of stem anteversion from Taperloc to Wagner Cone was more favourable for VAS pain (p = 0.029) and VAS satisfaction (p = 0.002).
Conclusion: The mid-term survival rate for THA using the Wagner Cone stem was high, which may be supported by a reduction in prosthetic impingement. The reduction in excessive stem anteversion by using a tapered cone stem was associated with reduced pain and increased patient satisfaction.
Competing Interests: S. Hamai reports payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Stryker, Johnson & Johnson, Japan MDM, Kaken Pharmaceutical, and Ayumi Pharnmaceutical, unrelated to this study. D. Hara reports grants from Shimazu Science Foundation, the Founation for the Promotion of Clinical Medicine, Kyocera, JPJS Kakenhi, and a 2021 grant from the Clinical Research Promotion Foundation. Y. Nakashima received research grants from Chugai Pharmaceutica, AYUMI Pharmaceutical, EA Pharma, KYOCERA, and Zimmer Biomet, all unrelated to this study. Y. Nakashima is also President of the Japanese Orthopaedic Association. All other authors have no conflicts of interest to disclose.
(© 2024 Yamate et al.)