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

Introduction. Acetabular cup positioning has been linked to dislocation and increased bearing surface wear. A previous study found correlations between patient and surgical factors and acetabular component position. The purpose of this study was to determine if acetabular cup positioning improves when surgeons receive feedback on their performance. Methods. Post-op anteroposterior (AP) pelvis and cross-table lateral radiographs were previously obtained for 2061 patients who received a total hip arthroplasty (THA) or hip resurfacing from 2004–2008. The surgeries were performed by 7 surgeons. AP radiographs were measured using Hip Analysis Suite to calculate the cup inclination and version angles. Acceptable ranges were defined for abduction (30–45 °) and version (5–25 °). The same surgeons performed a THA or hip resurfacing on 385 patients from January 2009 through June 2010. Cup inclination and version angles for this set of surgeries were compared to surgeries from 2004–2008 to determine if cup inclination and version angles improved in response to previous acetabular cup positioning studies. Improvement in accuracy was assessed by the chi-square test. Results. Time 1, from 2004 through 2008, had 1952 qualifying hips with 1845 having both version and abduction, and Time 2, from 2009 through June 2010, had 385 qualifying hips, all of which had both version and abduction angles. For Time 1, 1192 (62%) acetabular cups were within the abduction range, 1422 (79%) were within the version range, and 908 (49%) were within the range for both. For Time 2, 276 (72%) acetabular cups were within the abduction range, 250 (65%) were within the version range, and 217 (56%) were within the ranges for both. Accuracy of abduction angle improved (p<0.01) while accuracy of version angle decreased (p<0.01). Accuracy of acetabular cup positioning being within range for both abduction angle and version angle improved significantly (p=0.01), by 7%. Conclusions. Increased awareness and feedback on the resulting abduction and version measurements from THA surgery over time improves the positioning of the acetabular component. A system where objective measurements are presented to the surgeon can significantly improve cup placement which could improve the clinical outcome of THR patients