[Total hip replacement for acetabular protrusion in patients with osteoarthritis].

Background: Total hip replacement (THR) is at present an accepted treatment in patients with severe deformity of the hip and acetabular protrusion. The aim of this paper is to evaluate the results of THR in patients suffering from acetabular protrusion, operated from 1991 to 2006 in the Orthopaedic and Traumatologic Department of Poznan University of Medical Sciences.

Material: Material included 36 patients, 34 females and 2 males, on whom 51 THR were performed, lateral approach was used in all cases. At the time of operation, the age of patients ranged from 41 to 78 years (mean 63). Follow-up ranged from 4 to 19 years (mean 9.9 years). The operative treatment was a multistage process (during one operation only one joint was replaced). Cemented total hip arthroplasty was used during 28 of the THR, 22 of them were cementless and 1 as a hybrid.

Method: The patients were clinically and radiologically evaluated preoperatively, postoperatively, and at final examination. The clinical state was evaluated with Harris hip score and WOMAC scale. We based our radiological examination on Hip Society system.

Results: The average preoperative Harris score for the group of patients was 29, WOMAC score 77. After an average of 9 years follow-up all hips were considered excellent, with average Harris score of 90, WOMAC Score of 6. All patients had increased function and decreased pain. The radiograms of all patients revealed that the acetabular and femoral components were correctly positioned with no radiographic evidence of loosening in the last examination. The inclination angle of the acetabular component was 30-55 degrees (mean: 40 degrees) and the acetabular opening angle was 2-15 (mean: 4 degrees). The stem was valgus-oriented in 8 hips, varus-oriented in 13 hips and neutral-oriented in 30 hips. No ectopic ossification concentrations were found.

Conclusion: Clinical and radiological evaluation of our material showed that total hip replacement in the treatment of severe deformity of the hip caused by osteoarthritis with acetabular protrusion allows regaining good lower limb function, which helps the patients staying less dependant on the surrounding environment. The results of THR are good regardless of the type of prosthesis and the type of fixation. Ectopic ossification is not the clinical problem during THR in patients who suffer from acetabular protrusion. We found a significant acetabular remodeling with the decreasing of the protrusion after THR.