O1494 INCREASED RISK OF EARLY DISLOCATION AFTER PRIMARY TOTAL HIP ARTHROPLASTY IN INFLAMMATORY ARTHRITIS

Abstract

Aims: Patient-related risk factors of dislocation after total hip arthroplasty (THA) that have been identified are previous hip surgery, old age and female gender. However, there have been no prospective reports whether inflammatory arthritis (IA) is an independent risk factor. Methods: Prospective evaluation of the incidence of early (< 2 year post-surgery) dislocation in a consecutive series of primary THA. From January 1996 to December 1999 341 THAs in 311 patients with osteoarthrosis (OA) and 69 THAs in 59 patients with IA (mainly rheumatoid arthritis) were included in this study. One type of prosthesis having a 28 mm. ball head was implanted in every hip through an anterior appoach. Results: Both groups were comparable with respect to the following risk factors: gender, position of the acetabular component and experience of the surgeon. Average age was lower in the IA group than in the OA group: 61.0 vs 68.1 years. Furthermore, the incidence of previous hip surgery was higher in the OA group. Despite the presence of these risk factors in the OA group, the incidence of dislocation was higher in IA than in OA: 10.1% vs. 2.9% (p=0.006). All dislocations in IA where posterior, in OA 5 were posterior and 4 were anterior (1 unknown). No other mechanical factors leading to an increased instability of the hip in IA, such as trochanteric fractures, could be identified. Conclusions: Inflammatory arthritis is an independent risk factor of dislocation after THA. Both the polyarticular impairments and the lower quality of the soft tissues in IA could explain this increased risk.