Abstract
Aim: The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components.
Our hypothesis was that the surface finish of the femoral components deteriorated in accordance with the duration of implantation
Materials and method: 22 femoral components (all Freeman-Samuelson prostheses) were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. The surfaces of femoral components & polyethylene inserts were inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a stylus profilometer. The surface roughness was characterised by measuring Ra (micron-meter), which is the mean of the measured height deviations within the evaluation area. The articulating surface on both condyles was examined seperately. Ra measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK)
Results: The mean CAK was 7.2° ± 1°. Parallel scratching and burnishing were the main modes of damage on the surface in the articulating areas. Inspection of polyethylene inserts failed to find embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components.
The mean Ra values were:
Control: Mean-0.0230 mm, SD- 0.00821.
Medial Femoral condyle (0 – 60) = 0.0225 mm, SD – 0.00797
Medial Femoral Condyle (61 – 120) = 0.0244 mm, SD – 0.00532
Lateral Femoral condyle (0 – 60) = 0.0263 mm, SD – 0.00694
Lateral Femoral Condyle (61 – 120) = 0.0253 mm, SD – 0.00758
No statistically significant difference was seen in the mean-Ra of the femoral condyles compared to that of the control (P less than 0.05).
Conclusion: The surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
