Porous coated anatomic total hip arthroplasty: 5- to 10-year follow up

We report the medium term results of a study of patients with noncemented total hip arthroplasty (THA) using a first generation porous coated anatomic (PCA) prosthesis.

We reviewed 161 primary uncemented PCA THAs performed in 141 patients from November 1985 through March 1989 in our hospital. Subjects were followed up for a minimum of 5 years or until revision. Most common indicators for THA were osteoarthritis in 81 hips (50.3%) and avascular necrosis in 64 hips (39.8%). The average age at operation was 48.2 years. The average follow-up period was 6.9 years in patients without revision.

The average modified d'Aubigne and Postel hip scores improved from 10.9 points preoperatively to 17.4 points at the final postoperative evaluation. Results were rated as good to excellent in 146 hips (90.7%). Twelve (7.4%) hips received revision arthroplasty, 8 because of cup loosening, one because of polyethylene wear, and 3 hips because of stem loosening. Prostheses were removed in 2 hips, one due to tuberculosis and the other due to infection. Other complications included focal osteolysis in 54 hips (33.5%), posterior dislocation in 3 hips (1.9%), and lesser trochanter fracture in one hip. Thigh pain occurred in 30 hips (18.6%). In 114 hips, the roentgenograms were used to assess polyethylene wear. The average wear rate was 0.11 +/- 0.15 mm/year. Excessive wear rate (> 0.2 mm/year) occurred in 28 hips (24.6%). Factors contributing to higher wear rate included young age, cup inclination angle beyond the range of 35-55 degrees, and thin polyethylene liner.

The high rate of osteolysis and thigh pain in these patients should alert surgeons to be cautious in using this type of prosthesis.