Abstract
Introduction and Aims: Polyethylene wear after total hip arthroplasty with an uncemented titanium coated non-modular acetabular component was measured using a computer-assisted technique and correlated with clinical outcomes. Polyethylene wear measurements using post-operative radiographs and recent supine and standing radiographs were compared to see if there was a difference. To date, there is no definitive evidence in the literature that indicates a difference.
Method: Fifty-five patients who had total hip arthroplasties using a non-modular titanium-backed Mathys (Protec, Switzerland) press-fit acetabular component in 1992–1993 were included in this study. Patients who had a revision were excluded. The patients were contacted and reviewed in clinic. Each patient completed an Oxford Hip Score. They also had a cross-table lateral, supine and standing AP radiographs. The radiographs were digitised and analysed using a computer-assisted method (PolyWare) of measuring polyethylene wear. Correlations were sought between the rate of polyethylene wear and clinical outcome using the Oxford Hip Score. Polyethylene wear measurements using supine and standing radiographs were also compared to determine if there was a significant difference.
Results: Early results showed a trend indicating a difference in measured polyethylene wear rates comparing supine and standing radiographs. Previous experience at this institution measuring polyethylene wear using the same computer-assisted technique has shown that leg position has an effect on polyethylene wear measurements; weightbearing radiographs with the leg maximally internally and externally rotated resulted in an increase in polyethylene wear calculation of volumetric wear by 35% as compared to calculations with supine radiographs. A non-cylindrical wear tract was proposed to be the reason for the difference. There is no definitive answer in the literature as to the significance of the effect of supine versus standing radiographs on the measurement of polyethylene wear. Polyethylene wear rate did not seem to be related to clinical outcome as detected by the Oxford hip score.
Conclusion: Early results indicate a difference in polyethylene wear measurement comparing standing and supine radiographs. Polyethylene wear rates using the Mathys acetabular component do not seem to be related to clinical symptoms as detected by the Oxford Hip Score.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
One or more of the listed authors are receiving or have received benefits or support from a recognised academic body for the pursuance of the study.
