[Osseointegration of ceramic cement-free acetabular cups]

A stable osseointegration of an alumina-matrix-composite-ceramic (AMC) could facilitate the use of a thin-walled monoblock acetabular cup for hip arthroplasty with large ball-heads providing advantages like reduced risk of dislocation. The aim of the pilot study was to examine the osseointegration of porous-coated alumina-matrix-composite-ceramic-monoblock cups after implantation in a sheep model.

The porous coated AMC-ceramic cups were taken out after a healing period of 8 and 52 weeks after unilateral implantation in 5 and 6 sheep, respectively. The osseointegration was analysed histomorphologically and histomorphometrically by representative serial sections after dying according to Masson-Goldner. The examination was stratified according the pole and the rim areas as a press-fit cup with an extended rim was used. Two animals had a hip dislocation after 8 weeks and these animals were excluded from the study and replaced.

The cups were appraised as stable in the bony bed. Histologically, the rim area of the acetabular cup showed a higher osseointegration rate than the pole area. The rate of osseointegration in total was 3% after 8 weeks and 7% after 52 weeks. The rim area furnished 5.1% after 8 and 8.6% after 52 weeks. At the pole the osseointegration was 1,2% after 8 and 5.5% after 52 weeks. No significant differences were seen between both assessed time periods regarding the osseointegration rates. The bone showed an interlocking aspect with the pores of the coating as bony tissue was determined in the pores.

The presented pilot study revealed a stable osseointegration of porous-coated AMC-ceramic monoblock cups one year after surgery in a weight-bearing animal model. Interlocking of bone and porous coating may provide a stable osseointegration in the presence of low osseointegration rates, whose enhancement seems to be preferable.