Prediction of clinical outcome of THR from migration measurements on standard radiographs. A study of cemented Charnley and Stanmore femoral stems

Walker, P. S. and Mai, S. F. and Cobb, A. G. and Bentley, G. and Hua, Jia (1995) Prediction of clinical outcome of THR from migration measurements on standard radiographs. A study of cemented Charnley and Stanmore femoral stems. Journal of Bone and Joint Surgery, British Volume, 77-B (5). pp. 705-714. ISSN 0301-620X

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Abstract

We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs.

Item Type: Article
Research Areas: A. > School of Science and Technology > Natural Sciences > Biophysics and Bioengineering group
Item ID: 16598
Useful Links:
Depositing User: Jia Hua
Date Deposited: 29 May 2015 14:26
Last Modified: 21 Jun 2018 17:42
URI: http://eprints.mdx.ac.uk/id/eprint/16598

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