Abstract
Introduction
Proper cup positioning is a critical component in the success of total hip arthroplasty surgery. A multicenter study has been initiated to study a new type of highly cross-linked polyethylene. This study provides a unique opportunity to a review the acetabular cup placement of over 500 patients implanted in the past 2 years from 13 medical centers from the U.S., Mexico, and Europe.
Methods
482 patients have received primary total hip arthroplasty using components from a single manufacturer in 5 centers in the US and Mexico and 7 centers in Europe. The acetabular anteversion and inclination were measured in post-operative radiographs. An acceptable window of cup position is defined at 5–25° of anteversion and 30–45° of inclination.
Results
The measured cup anteversion and inclination averaged 15.89° ± 8.91° (0.00–42.25°) and 43.27° ± 7.17° (23.46–67.79°), respectively. Of the patient radiographs read, 71% were within the acceptable range of anteversion, 55% were in the acceptable range of inclination, and 41% satisfied both criteria. The best performing center had 86% of patients within the acceptable range of anteversion, 63% in the acceptable range of inclination, and 57% satisfied both criteria. The worst performing center had 54% within the acceptable range of anteversion, 29% in the acceptable range of inclination, and 17% satisfied both criteria.
Conclusion
A significant variation in acetabular cup anteversion and inclination exists in this study both within and between the participating high volume centers. Correlation to mid- and long-term clinical outcome will show the clinical relevance of the finding, but liner designs with unsupported polyethylene should be used with caution.
