Cementless total hip arthroplasty in rheumatoid arthritis: a systematic review of the literature.

BACKGROUND: Compromised rheumatic bone is a potential risk factor for mechanical complications in cementless total hip arthroplasty (THA) in cases of rheumatoid arthritis (RA). Increased rates of intra-operative fractures, component migration and (early) aseptic loosening are to be expected. Despite this, cementless THA is performed in cases of RA. METHODS: A literature search on cementless THA in RA was performed in EMBASE (1993-2011), Medline (1966-2011) and the Cochrane Library. A systematic review was conducted with a special emphasis on mechanical complications. RESULTS: Twenty-three case series and five studies of implant registries were included. Acetabular fractures and/or migration of the cup were reported in 9 out of 22 studies of the cup. Proximal femoral fractures and/or subsidence of the stem were reported in 14 out of 20 studies of the stem. Six studies compared failure rates of uncemented and cemented components due to aseptic loosening. The overall failure rate ratio (uncemented/cemented) for the cup was 0.6 (95% CI: 0.14-2.60) and for the stem 0.71 (95% CI: 0.06-8.55), both favoring uncemented fixation. The failure rates in case series without a control group were compared to the NICE criteria (failure rate/1). The overall failure rate for the cup was 0.97 (95% CI: 0.50-1.88) and for the stem 0.79 (95% CI: 0.44-1.41). Failure rates of aseptic loosening of higher than 1 (favoring cemented fixation) were reported in 6 out of 26 studies of the cup and in 2 out of 25 studies of the stem. In all these studies, the inferior implant designs were blamed, and not the type of fixation or the quality of the bone. CONCLUSIONS: Despite substantial rates of mechanical stem complications, no evidence was found to establish that cementless components perform less well than cemented components. The results justify the use of cementless THA in RA patients.

Primary total hip arthroplasty with a flattened press-fit acetabular component in osteoarthritis and inflammatory arthritis: a prospective study on 416 hips with 6-10 years follow-up.

INTRODUCTION: A flattened cup was designed to create a more physiological load transfer to the pelvic bone compared to hemispherical cups, and to allow more bone contact compared to low-profile' spherical cups. To investigate these theoretical advantages and the potential influence of the quality of the acetabular bone, a clinical study was performed in patients with osteoarthritis (OA) and inflammatory arthritis (IA). The aims of the study were (1) to evaluate the fixation of the cup, postoperatively and later when osseous integration should have taken place, (2) to assess perioperative complications such as acetabular fractures and (3) to monitor the polar gap, a potential risk factor for osteolysis. PATIENTS AND METHODS: A prospective study was performed on all consecutive OA and IA patients with an indication for primary total hip arthroplasty (THA). Three hundred and nine OA patients (340 hips) and 65 IA patients (76 hips) were included. The acetabular component was the flattened press-fit EPF-PLUS cup, the femoral component the tapered cementless Zweymueller SL-PLUS stem. All revisions and complications were recorded. Clinical and radiographical evaluation was performed on regular basis during 6-10 years. RESULTS: The incidence of early loosening of the cup was 0 out of 340 in the OA group and 1 out of 76 in the IA group. The incidence of acetabular fractures was 7 out of 340 in the OA group and 3 out of 76 in the IA group. Failure rate for the acetabular component due to aseptic loosening or osteolysis after 6-10 years was 0% in the OA group and 4.8% in the IA group. In all cases available for follow-up the polar gap had disappeared and full osseous integration had taken place in both the groups. INTERPRETATION: This study shows that the flattened press-fit acetabular component creates adequate initial mechanical stability to allow osseous integration and that the cup can be safely used in both OA and IA patients. However, after 6-10 years, in the IA group failure of the cup due to aseptic loosening occurred once and failure due to osteolysis occurred three times, while these type of failures did not occur in the OA group.

Increased risk of dislocation after primary total hip arthroplasty in inflammatory arthritis: a prospective observational study of 410 hips.

BACKGROUND: It is unclear whether patients with inflammatory arthritis have a higher risk of dislocation after hip replacement. PATIENTS AND MATERIAL: We carried out a prospective study assessing the incidence of dislocation within 2 years after surgery for patients diagnosed with inflammatory arthritis (IA) and osteoarthrosis (OA). One single type of prosthesis was implanted using a lateral approach. Both diagnostic groups were compared by univariate analysis with respect to dislocation, sex, age, diagnosis, prior hip surgery, experience of the surgeon and malposition of the acetabular component. In a multivariate logistic regression approach, the difference in dislocation incidence was assessed after adjusting for the effect of the potential confounders given above. Between 1996 and 1999, 410 THA were performed: 70 in IA and 340 in OA. After 2 years no patients were lost to follow-up, but 12 patients had died, and 5 revisions were carried out for reasons other than dislocation. RESULTS: The dislocation rate in patients with IA was higher than in patients with OA: 10% (7 hips) in the IA group and 3% (10 hips) in the OA group (p = 0.006). No significant differences were found among the risk factors for dislocation between the two groups. Multivariate logistic regression analysis showed that IA is an independent risk factor for dislocation (odds ratio (OR) 3.7, 95% CI 1.3-11), together with malposition of the cup in more than 55 degrees abduction (OR 7.7, CI 2.3-26) and increased anteversion (OR 7.6, CI 1.4-42.4). INTERPRETATION: Our findings clearly suggest that inflammatory arthritis has to be considered as an independent risk factor for dislocation after primary THA.