HYDROXY APATITE CERAMIC HIP SURVEY CERAMIC/CERAMIC BEARINGS

Abstract

Aims Osteolysis from polythene debris contributes to loosening of total hip components. Will ceramic/ceramic bearings in conjunction with Hydroxyapatite Ceramic Coated Hips (HAC) survive any better?

Material. Hydroxyapatite Ceramic Coated Hips were first used in Sunderland, U.K. in May 1988. More than 2400 HAC hips have been inserted.

There are 521 hips in 441 patients with ceramic/ceramic bearings. I am reporting this consecutive series.

These hips are generally inserted into patients with a 20+ year life expectancy. This ranges from 18 to 74. Mean age is 52.4 years. These young patients are mostly active and many are working.

Amongst the indications were osteoarthritis 297, hip dysplasia 76, and ankylosing spondylitis 18. Thirty eight had had previous childhood hip disorders, and 19 had rheumatoid arthritis. The series also includes 43 with AVN and 7 revisions from cemented hip replacement

All the patients are assessed using the Harris Hip Score before and after surgery. They are assessed annually. Post operative scores show 22 patients with Harris Hip Scores of less than 80, but only 9 patients have problems attributable to HAC hip surgery. These include 2 patients with infection, 3 fractured ceramic acetabular liners, two broken heads and 2 patients with loose cups, one from aseptic loosening. Apart from this one case, aseptic loosening has not been a problem.

Discussion. The results have been rewarding. There are 2400+ HAC hips in the whole series. This sub group of 521 ceramic/ceramic HAC hips is small with a maximum follow up of 14 years. However, there have been few failures which could be attributed to the HA coated device. The broken ceramic components are a concern. It is probable that third body inclusions between the modular components led to stress concentrations. It is also possible that acetabular impingement was a problem and the hips may have been subluxing a few microns with every step and not just gliding with every step. This might overload the alumina implants leading to their failure. All the earlier prostheses are alumina/alumina but 55 hips inserted since august, 2005 have an alumina/zirconia compound head (Biolox Delta®). There have been no cases of periprosthetic osteolysis.

Conclusions. Hydroxy Apatite bony bonding secures the implants. No cement or polyethylene is used which can contribute to osteolysis.

Wear in ceramic bearings will be negligible. Third body inclusions must be avoided to prevent wear or fracture.

The femoral spigot must not impinge on the acetabular margin causing subluxation which may lead to fracture.

The ceramic material has to be supported to prevent fracture.

The outcome of the patients in this sub-group has been rewarding. Alumina/alumina hip arthroplasty should be considered where life expectancy is substantial.