Clinical outcomes of bipolar hemiarthroplasty for femoral neck fracture: a nationwide, multicenter, prospective observational study

Purpose Femoral neck fractures (FNFs) are common among elderly patients, and bipolar hemiarthroplasty (BHA) is widely performed in Japan. This nationwide, multicenter, prospective study assessed clinical and radiological outcomes following BHA using representative cemented and cementless stems. Methods The Japanese Outcome in Neck Fracture (JOIN) study prospectively enrolled 951 patients who underwent primary BHA at 32 institutions between August 2015 and March 2019. Of these, 722 patients (mean age 81.3 ± 7.9 years; 78.4% female) with a mean follow-up of 1.1 ± 1.0 years were analyzed. Cemented Exeter stems were used in 244 patients, while cementless Accolade II stems were used in 478 patients. Outcomes assessed included peri-operative complications, death, revision surgery, Japanese Orthopaedic Association (JOA) hip score, EuroQol measures (EQ-5D and EQ-VAS), and radiographic findings. Results Complication rates were low, with femoral fractures occurring in 0.7% of patients, dislocation in 0.6%, and infection in 0.6%. Two patients required stem revision. One year mortality was 4.4% and cumulative mortality at final follow-up was 7.8%, with no significant difference between fixation types. The EQ-5D utility score improved from 0.62 ± 0.38 pre-injury to 0.72 ± 0.20 at follow-up, whereas the JOA hip score showed a modest decline from 88.7 ± 15.8 to 76.7 ± 17.4. Radiographs demonstrated stable fixation in all but one case. Conclusions BHA for FNF demonstrated favorable short-term outcomes with low complication, revision, and mortality rates. Although hip function declined modestly from pre-injury levels, patient-reported quality of life was maintained or improved. Both cemented and cementless BHA remain viable options for elderly patients with FNF. Clinical trial registration number: UMIN000019328.