Four-year results of summit stems for total hip arthroplasty in Japanese patients

Purpose: A retrospective study to evaluate the clinical and radiographic outcome of the Summit primary total hip arthroplasty (THA) at a minimum follow-up of 4 years. Methods: 87 hips in 84 Japanese patients underwent THA using Summit stems. 3 patients were lost to follow-up, and 4 patients were excluded because a Summit stem was judged to be inappropriate for their narrow femoral canals. The remaining 80 hips in 77 patients were evaluated. Mean age was 66 years (range, 33-86 y). Mean postoperative follow-up period was 52 months (range, 48-66 m). Results: There was no early stem subsidence after surgery. Of the 80 hips, 60 (75%) showed radiographic signs of stem osseointegration including zones 3 and 5 at final follow-up. Stress shielding occurred in 50 hips (62.5%), and third-degree stress shielding was observed in 12 hips (15%). 3 patients experienced postoperative thigh pain due to distal fixation. Conclusions: These short-term results indicate that the Summit stem achieved good initial fixation, although there were some cases of distal fixation. Careful long-term follow-up and observation will be necessary for hips in which stress shielding occurs.