Abstract
Utilising a new implant design and improved alumina ceramic materials, 514 hips were implanted in a US IDE prospective, randomised study. All patients received the same press-fit hydroxylapatite (HA) coated femoral stem. Two-thirds (349 hips) received alumina ceramic bearings, and one-third (165 hips) received CoCr heads on polyethylene liners. The alumina group was further divided. Approximately one-half (172 hips – System I) received a porous-coated titanium shell and an alumina insert, and one-half (177 hips – System II ) received a HA-coated, arc-deposited titanium shell and an alumina insert. System III (the control) consisted of a porous-coated titanium shell and a polyethylene insert. External geometry of all shells was identical.
An independent orthopaedic surgeon who did not participate in the study reviewed all radiographs. At latest follow-up, (minimum 2 years; range 2-4 years), differences were noted in the developmental pattern of the radiolucent line around the acetabular component. Radiolucent lines were most often noted with System I and System III (porous acetabular shells) in De Lee and Charnley Zone 3 and were absent in System II (arc-deposited titanium with HA) (p=0.001). Other standard radiographic parameters evaluated were found to be comparable, with one exception: In 10 cases in the control group, the development of a small erosive lesion (scalloping) in femoral Gruen Zone 8 was observed on the lateral film. This compares to two cases in System I, and no cases in System II (p=0.001).
Dislocation rates were comparable for all three Systems. Seven acetabular components were revised: one in System I, three in System II and System III. The two revisions for aseptic loosening were both in the control group.
The abstracts were prepared by Nico Verdoschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, Universitair Medisch Centrum, Orthopaedie / CSS1, Huispost 800, Postbus 9101, 6500 HB Nijmegen, Th. Craanenlaan 7, 6525 GH Nijmegen, The Netherlands.
