Scandinavian multicenter porous coated anatomic total hip arthroplasty study. Clinical and radiographic results with 7- to 10-year follow-up evaluation.

Four hundred ninety-four patients (539 hips) with a mean age of 50.1 (SD, 9.7) years entered a prospective, multicenter study of the Porous Coated Anatomic (Howmedica, Rutherford, NJ) total hip arthroplasty. The preoperative diagnoses were primary osteoarthrosis (297 hips), secondary osteoarthrosis to childhood diseases (88 hips), fracture (73 hips), inflammatory arthritis (26 hips), idiopathic avascular necrosis (28), and miscellaneous (27 hips). After a mean follow-up period of 6 years and 10 months, 71 hips had been revised. The mean Harris hip score increased from 43 (15.7) to 94 (7.4) at the last follow-up evaluation, without any deterioration with time. After 7 years, the combined survival rate for the cup and/or stem using revision as endpoint was 92.2%. Radiographic failure, defined as migration of either component more than 5 min and/or focal osteolysis, was registered in 72 stems and 96 cups. The combined clinical (revision) and radiographic 7-year survival rates were 61.1 (+/-5.2) and 59.7 (+/-5.3) for the stem and cup, respectively. Statistical analysis revealed that young age and poor fill rate influenced the rate of stem failure, whereas cup failure was difficult to predict. Four variables were associated with stem subsidence: loosening of beads, pedestal formation, sclerotic lines in Gruen zone 7, and acetabular granuloma. According to our findings, the 5- to 10-year complication rate with this implant is high. Therefore, continuous radiographic follow-up evaluation of these cases is strongly recommended, to enable revision before severe destruction of bone or catastrophic clinical failure has occurred.