Session V - Geriatrics

Unipolar vs. Bipolar Prosthesis: A Prospective Evaluation of Long-Term Functional Outcome following Femoral Neck Fracture

Stephen G. Maurer, MD; Kenneth A. Egol, MD; Philip R. Wolinsky, MD; Kenneth J. Koval, MD, New York University - Hospital for Joint Diseases, Dept. of Orthopaedic Surgery, New York, NY

Introduction: This study sought to compare the effect of unipolar vs. bipolar hemiarthroplasty on functional recovery 4-5 years following hip fracture.

Methods: Between July 1987 and December 1993, 213 community-dwelling patients age >65 years (mean 80 years) with a displaced femoral neck fracture underwent primary prosthetic replacement and were prospectively followed. Prior to January 1990, a cemented bipolar endoprosthesis was used for all cases (n = 99); from that date forward, a cemented modular unipolar endoprosthesis was used in all cases (n = 114). Because the prosthesis was changed as a matter of department policy, indications for primary prosthetic replacement and the surgeons performing the procedure were essentially identical throughout the study. Prefracture characteristics (age, sex, medical comorbidities, and walking ability) were comparable for the unipolar (UP) and bipolar (BP) groups. Data were analyzed using contingency table methods (chi-square); to determine the simultaneous effects of covariates (age, sex, comorbidities), multiple logistic regression methods were used.

Results: Seven patients died during hospitalization, and 59 more patients died prior to 4-year follow-up. 113 patients (47 BP, 66 UP) were available for follow-up. An in-depth functional evaluation was obtained, including ambulation, basic activities of daily living (feeding, bathing, dressing, toileting), and instrumental activities of daily living (food shopping, food preparation, banking, laundry, housework, public transportation). At 4- and 5-year follow-up, there were no functional differences identified between the UP and BP groups. Furthermore, at latest follow-up there were no significant differences between the two groups with regard to rate of infection, prosthetic dislocation, or mortality.

Discussion/Conclusion: This study suggests that there is no advantage to using bipolar endoprostheses in treating femoral neck fractures in the elderly patient. Furthermore, the lower cost of modular unipolar endoprostheses compared with bipolar endoprostheses provides additional support for use of the former.