HYDROXYAPATITE-COATED IMPLANTS - TOTAL HIP-ARTHROPLASTY IN THE YOUNG PATIENT AND PATIENTS WITH AVASCULAR NECROSIS

Two high risk groups for total hip arthroplasty, 136 patients (155 hip s) younger than 50 years of age (average age, 38 years) and 44 patient s (53 hips) with the diagnosis of avascular necrosis, have a minimum f ollowup of 5 years and a mean followup of 6.8 years, The average Harri s Hip Score at last followup totaled 93 and 90, respectively, and thig h pain was reported in 1.3% and 3.8%, respectively, All patients in bo th groups received the same hydroxyapatite coated femoral stem and the mechanical failure was 0%, No stem was revised for aseptic loosening, 100% of stems were bony stable by radiographic criteria, new bone for mation was progressive about the femoral stem, and 0% endosteal lysis was found, The acetabular components had a mechanical failure rate of 10% and 7.5%, respectively, without osteolysis, and an additional 7% a nd 7.5% failure as a direct result of progressive osteolysis, The resu lts with the porous press fit and hydroxyapatite threaded sockets were far superior to that of the smooth hydroxyapatite press fit sockets a nd socket failure was associated with thin polyethylene liners and the use of 32-mm head diameters, These findings show a high success rate with a nonporous hydroxyapatite coated titanium femoral stem, However, hydroxyapatite on a smooth acetabular component yielded less predicta ble results indicating that for long term fixation of the acetabulum a n interlock of bone is preferred.