Cementless porous-coated anatomic medullary locking total hip prostheses.

Abstract

The authors studied 50 consecutive and nonselected patients (52 hips) who were followed for a minimum of 7 years (range, 84-89 months) after they had a primary total hip arthroplasty with an uncemented Anatomic Medullary Locking (DePuy, Warsaw, IN) hip system. The average age of the patients at operation was 47.6 years (range, 19-88 years). The operative diagnoses were: avascular necrosis of the femoral head in 18 hips (34%), osteoarthritis in 16 (31%), fracture of the femoral neck in 14 (27%), and miscellaneous in 4 (8%). The average preoperative Harris hip score was 59 points (range, 6-67 points) that improved to 91 points (range, 69-100 points) at the 7-year follow-up examination. To assess the adequacy of intramedullary fit, the fit of the stem at the proximal canal and isthmus level was evaluated. Forty-one hips (79%) had a good press-fit at both the proximal canal and isthmus level, five hips (10%) had a good press-fit at the proximal canal only, and the remaining six hips (11%) had a poor fit at both the proximal canal and isthmus level. Of the 46 hips that had a good press-fit at the proximal canal and/or isthmus level or proximal canal only, 32 (70%) had bone ingrowth and 14 (30%) had stable fibrous tissue ingrowth. Of the remaining six hips with a poor press-fit at both the proximal canal and isthmus level, three (6%) had stable fibrous tissue ingrowth and another three (6%) were unstable. Of the three hips (6%) with femoral component loosening, one was revised and the other two were asymptomatic. There was an alarmingly high incidence of perioprosthetic osteolysis in our series: 16 hips (31%) had acetabular and femoral osteolysis and 13 hips (25%) had femoral osteolysis only. Also, there was a strikingly high incidence of polyethylene-liner wear (12 hips or 23%). Although the incidence of component loosening was low, a high incidence of periprosthetic osteolysis and excessive wear in the polyethylene linear remain challenging problems after insertion of the cementless Anatomic Medullary Locking prosthesis.