Multi-center study of use of the Exeter stem in Japan: evaluation of 1000 primary THA

The Exeter stem was introduced to the Japanese market in 1996. Since then, owing to excellent clinical results, the number of stems used has increased year by year and more than 2000 stems were implanted in 2009. The objective of this study was to prove the efficacy of the Exeter stem for Japanese patients by evaluating the short-term results of four major dedicated hip centers. We performed a retrospective study of clinical and radiographic results of 1000 primary total hip arthroplasties (THA) performed using the Exeter stem on 881 patients who were followed-up for at least 2 years after surgery. The average age of the patients at operation was 62.3 years (range 23-89 years). Mean postoperative follow-up period was 4.0 (range 2-9) years. Thirty postoperative complications were observed, including 9 infections, 14 dislocations, 5 cases of deep vein thrombosis, and 2 cases of sciatic nerve palsy. No symptomatic pulmonary embolization or femoral fractures were observed. Re-operations for infection and dislocation were performed in 8 and 6 hips, respectively. According to Barrack's classification, the postoperative cementing grade was judged as A for 735 hips, B for 246 hips, and C for 4 hips. At final follow-up, no radiolucent line was observed at the bone-cement interface. Cortical hypertrophy was observed in 9.5 % of cases in Gruen zones 2-6. Kaplan-Meier survival analysis predicted 100 % survival at 5 years when a radiolucent line at the bone-cement interface of the femur was used as the endpoint, 98.8 % when re-operation was required for any reason. This study revealed that excellent short-term results were achieved by fixing the Exeter stem with modern cementing techniques for primary THA in Japanese patients.