Purpose of the study: Recent years have seen an increase in cementless total hip endoprosthesis (THP) implantations. Easy radiological measurement of wear in cups coated with X-ray dense material, such as metal or ceramics, is not applicable. An alternative technique has thus been developed to radiographically measure wear on cementless spherical implants.
Material and methods: The authors present a method in which the center of the head of the prosthesis relative to the center of the cup was defined by graphical extrapolation. Changes between the two centers on subsequent images allowed the estimation of wear. Data from 148 randomly selected patients with cemented THP were compared with that from 50 with cementless THP (head diameter always 32 mm). RESULTS Within the cemented group metal heads showed significant more wear than ceramic heads (1.244 mm vs. 0.504 mm). However, calculating the wear rate per year showed no significant difference. No significant differences were observed comparing cemented and cementless group. A comparison of the own results with those of the literature revealed analogous values.
Discussion: Data of the cementless group were comparable with those obtained from conventional wear measurements on cemented hip cups thus validating the technique.
Conclusion: The method offers the potential to define wear of metal cups with a polyethylene inlay or with X-ray dense components such as ceramic or metal inlays.