Cemented unipolar or modular bipolar hemiarthroplasty for femoral neck fractures in elderly patients - which is better?

Introduction: Hemiarthroplasty is considered to be the treatment of choice for femoral neck fractures in elderly, however there is no consensus to support the choice between unipolar or bipolar hemiarthroplasty. Several studies found that patients with bipolar hemiarthroplasty had a better outcome of pain, a higher rate of return to the pre-injury state, and a greater range of hip motion. Some studies have demonstrated equal hip functional outcome between unipolar and bipolar hemiarthroplasty, but unipolar hemiarthroplasty was favoured due to its lower cost. The purpose of this study was to compare the functional and radiological outcome of cemented unipolar vs modular bipolar hemiarthroplasty in displaced femoral neck fracture in elderly patient population.

Methods: It is a prospective randomized study, with 44 patients in each group. Elderly Patients (>60 years of age) with traumatic displaced femoral neck fractures were included in the study. Cemented unipolar or modular bipolar hemiarthroplasty was performed in the respective patient groups using posterior or anterolateral approach. Functional outcome evaluation was done by Harris Hip Score and radiological outcome evaluation was done for acetabular erosion. The data was entered in MS EXCEL spread sheet and analysis was done using Statistical Package for Social Sciences (SPSS) version 20.0 (IBM, Chicago).

Results: The mean age in the unipolar and bipolar group was 67.2 and 66.1 years respectively. The average follow-up period was 20.1 and 22.3 months in the unipolar and bipolar group respectively. Mean operating time was significantly more in the modular bipolar group (78.3 minutes) compared to the unipolar group (67.3 minutes). Two patients (4.5%) had acetabular erosion in each group. Mean Harris Hip score at 3 months follow-up was significantly higher (p value <0.05) in bipolar group (75.8±4.2) than the unipolar group (77.7±2.9). However, subsequent follow-ups at 6 months (80.9±2.8, 82.0±2.5, p value >0.05) 12 months (83.1±2.2, 83.2±1.2, p value >0.05) and 24 months (85.5±2.4, 85.2±2.8, p value >0.05) did not show any significant difference between the two groups. The incidence of general complications was 34% in bipolar and 20.4% in unipolar hemiarthroplasty group.

Conclusion: Functional outcome in terms of Harris Hip Score are better in the bipolar group at 3 months follow up but there was no significant difference in the functional outcome between the two groups at 6, 12 and 24 months follow up. The operative time for unipolar is lower and statistically significant compared to bipolar hemiarthroplasty of the hip.