Total Hip Arthroplasty with the Circumferentially Porous-coated Femoral Stem in Osteonecrosis of the Femoral Head
BW Min, CS Kang
Keimyung University, Dongsan Medical Center, Department of Orthopaedic Surgery, Daegu, Korea

Total hip arthroplasty remains an effective tool for the treatment of patients with end-stage osteonecrosis with collapse of the femoral head, although there is an increased risk for failure. The aim of this study was to assess the clinical and radiographic outcome of the cementless femoral component with a circumferentially porous coated design. Sixty-four total hip arthroplasties in 53 patients with osteonecrosis of the femoral head were available for evaluation after a 5-10 year follow-up period (average, 7 years). The average age at surgery was 48.4 years (range, 25-66 years). Osteonecrosis etiology was alcohol induced in 31 hips, idiopathic in 21, steroid related in 5, and femoral neck fracture in 7. A cementless Harris-Galante II cup and Multilock cementless femoral stem with circumferentially porous coating in the proximal part were used in all patients. Average Harris hip scores improved from 51.6 points to 86.6 points. Thigh pain was noticed in 6 hips (9.4%) at the latest follow up. Most of thigh pain were related to the diffuse osteolysis with stem instability. At the latest follow up, 58 stems (90.6%) displayed stable bony fixation, one (1.6%) fibrous fixation, and five (7.8%) unstable fixation. Twenty-four hips (37.5%) revealed osteolysis mostly in Zones I and VII. Five hips (7.8%) exhibited distal osteolysis. Five hips (7.8%) exhibited mechanical failure of the stem usually associated with the diffuse osteolysis around the stem. We have also observed increased polyethylene line wear (annual wear rate = 0.39 mm / year) due to a weaker polyethylene interlocking mechanism of Harris-Galante II cup, young active age population of osteonecrosis, inadequate polyethylene liner thickness, and frequent sitting cross legged in non-western population. The midterm results using the circumferentially porous coated stem showed favorable bony ingrowth. Osteolytic lesions were primary limited to proximal Zones I and VII even with increased polyethylene wear particle formation and increased osteolytic lesions in Harris-Galante II cup designs. This may be due to the excellent circumferential osteointegration into the proximal part of the stem.