Abstract
Introduction and Aims: To determine whether polyethylene wear is different comparing cemented polyethylene cups with metal-backed cups and a polyethylene insert.
Method: A sample of patients who had hip replacements between February 1995 and July 2002 have been studied. They were randomly allocated to either a cemented polyethylene cup or a metal-backed press-fit cup and polyethylene insert. All patients had a cemented stem and a 28mm ceramic head inserted. Ninety-one patients were treated, and 83 are available for analysis. The pre-operative diagnosis in all was unilateral osteoarthritis. The trial is a prospective randomised one and patients have been assessed clinically and radiologically annually. Twenty-eight patients with cemented polyethylene cups and 55 patients with uncemented metal-backed cups have been analysed. The polyethylene thickness of the cemented cups is 9.6mm on average, and the metal-backed cups had an average liner thickness of 8.9mm. Wear measurements were done using the Martell computer system.
Results: Based on measurements done on acetabular cups with the longest follow-up, the metal-backed cups have an average wear of 0.65mm, with an annual wear rate of 0.14mm. The cemented cups have an average wear of 0.64mm, with an annual average of 0.12mm. The study is ongoing and data will be updated.
Conclusion: Wear measurements were done using the three-month post-operative x-ray as the baseline and the most recent follow-up x-ray. Based on measurements done on cups with the longest follow-up, there is very little difference between the two groups. The study is ongoing and data will be updated.
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.
At least one of the authors is receiving or has received material benefits or support from a commercial source.
