DISLOCATION OF TOTAL HIP REPLACEMENT IN PATIENTS WITH FRACTURES OF THE FEMORAL NECKA PROSPECTIVE COHORT STUDY ON 532 CONSECUTIVE HIPS

Abstract

Background: Total hip arthroplasty (THR) is a commonly performed procedure to treat displaced fractures of the femoral neck, either as a primary procedure, or as a secondary procedure after failed healing of internal fixation. Dislocation of the prosthesis remains as a problem, and controversies still exist regarding the optimal surgical approach and its influence on stability of the THR. The main issue is whether to use an anterolateral or a posterolateral surgical approach. Repair of the posterior soft tissue structures when performing a posterolateral approach has been proposed to increase the stability. Other factors such as age, gender, indication for surgery (primary, secondary), caput size and the experience of the surgeon may also influence the stability, but are not well documented.

Material and Methods: Between January 1 1999, and December 31 2005, 532 consecutive THR’s in 523 patients were performed at our institution as a primary, or a secondary, procedure after fracture of the femoral neck. The patients have been followed with a prospective 6 week questionnaire, and after that via the clinics journal database. Finally, thanks to the Swedish personal identification number, a search has been done in a national registry by the Swedish National Board of Health and Welfare. For all patients, all dislocations and related reoperations until December 31 2006, or death, were registered and analyzed. Logistic regression analyse was performed in order to evaluate factors associated with prosthetic dislocation. Age, gender, indication for surgery, the surgeon’s experience, caput size and surgical approach were tested as independent variables in the model.

Results: Dislocation of the THR occurred in 27 patients. In the multivariate regression analyze the posterolateral surgical approach performed without posterior repair was associated with a significant higher risk of dislocation compared with the anterolateral approach (OR 4.7, 95% CI 1.1–19.6). The 28 mm caput size was associated with a significant lower risk of dislocation compared with the 22 mm (OR 0.3, 95% CI 0.1–0.99). There was a strong, but not significant, trend of higher risk for dislocation with a posterolateral approach performed with posterior repair compared with the anterolateral approach (OR 3.3, 95% CI 0.9–11.4). Age, gender, indication for surgery or the experience of the surgeon did not affect the risk for dislocation.

Interpretations: We recommend the anterolateral surgical approach and 28 mm caput size for THR after femoral neck fracture.