Abstract
Our objective was to assess and validate low-dose computed tomography (CT) scanogram as a post-operative imaging modality to measure the mechanical axis after navigated total knee replacement. A prospective study was performed to compare intra-operative and post-operative mechanical axis after navigated total knee replacements. All consecutive patients who underwent navigated total knee replacement between May and December 2006 were included. The intra-operative final axis was recorded, and post-operatively a CT scanogram of lower limbs was performed. The mechanical axis was measured and compared against the intra-operative measurement. There were 15 patients ranging in age from 57 to 80 (average 70) years. The average final intra-operative axis was 0.56° varus (4° varus to 1.5° valgus) and post-operative CT scanogram axis was 0.52° varus (3.1° varus to 1.8° valgus). The average deviation from final axes to CT scanogram axes was 0.12° valgus with a correlation coefficient of 0.9. Our study suggests that CT scanogram is an imaging modality with reasonable accuracy for measuring mechanical axis despite significantly low radiation. It also confirms a high level of correlation between intra-operative and post-operative mechanical axis after navigated total knee replacement.
Résumé
Cette étude a pour but d’analyser et d’évaluer les images scanner et les modalités des clichés post-opératoires après prothèse totale du genou implantée avec navigation.
Matériel et méthode: une étude prospective a été réalisée pour comparer les axes mesurés en per et post-opératoire, après navigation, chez les patients ayant bénéficié d’une prothèse totale du genou avec navigation et inclus de mai à décembre 2006. Les axes per et post-opératoires ont été rapportés et comparés avec l’axe mécanique obtenu et mesuré en per-opératoire.
Résultats: 15 patients d’âge moyen de 70 ans (57 – 80 ans) ont été analysés. L’axe final per-opératoire a été de 0.52° varus (4° à 1,5°) et, l’axe post-opératoire mesuré par scanner a été de 0.52° varus (3,1° à 1,8°). La déviation axiale médiane est de 0.12° valgus avec un coefficient de corrélation de 0,9.
En conclusion, notre étude permet de penser que le scanner est une modalité d’évaluation raisonnable de mesure de l’axe mécanique en dépit d’une irradiation significative mais néanmoins assez basse. Cette étude permet également de confirmer un haut niveau de corrélation entre la mesure de l’axe per-opératoire et la mesure de l’axe post-opératoire dans les prothèses totales du genou avec navigation.
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Mohanlal, P., Jain, S. Assessment and validation of CT scanogram to compare per-operative and post-operative mechanical axis after navigated total knee replacement. International Orthopaedics (SICOT) 33, 437–439 (2009). https://doi.org/10.1007/s00264-008-0639-3
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DOI: https://doi.org/10.1007/s00264-008-0639-3