Abstract
Femoral malrotation in total knee arthroplasty causes flexion gap instability. Conventional instruments mostly reference the posterior condylar angle (PCA). The aim of this study was to verify whether the computer-navigated flexion gap (GAP) method produces a rectangular flexion gap and if a balanced flexion gap could also be achieved by referencing the PCA. A total of 100 knee prostheses were analysed using the navigated GAP method, and flexion gap symmetry along with femoral rotation were recorded. The GAP technique resulted in a rectangular flexion gap with adequate femoral rotational alignment. If the PCA technique had been used, only 51% of the femoral components would have been implanted in correct femoral rotation; the remaining 49% would have implanted with flexion gap instability. The GAP technique produces a rectangular flexion gap. The referencing of the PCA was shown to be less reliable. Thus, modern knee prosthesis instrumentation should not base femoral rotation solely on the PCA.
Résumé
Les anomalies de rotations fémorales peuvent être à l’origine d’instabilité dans les prothèses totales du genou. Le matériel ancillaire conventionnel a pour référence l’angle postérieur des condyles (PCA). Le but de cette étude est de vérifier grâce à la navigation (GAP) si l’on peut avoir une meilleure balance ligamentaire et un meilleur équilibrage qu’en faisant référence à la PCA. Matériel et méthode: 100 prothèses de genou ont été analysées en utilisant la navigation de type GAP et les anomalies de l’espace en flexion et rotation ont été rapportées. Résultats: la technique utilisant la navigation de type GAP permet d’avoir un bon alignement en rotation alors que la technique conventionnelle faisant référence au condyle postérieur ne permet d’avoir une bonne implantation que dans 34% des cas, les 66% de cas restant présentent une instabilité. En conclusion: la technique avec navigation permet d’avoir un espace en flexion parfaitement rectangulaire, la référence au condyle postérieur est moins fiable. Le matériel ancillaire moderne des prothèses du genou ne doit plus se baser uniquement sur les condyles postérieurs en flexion.
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Schnurr, C., Nessler, J. & König, D.P. Is referencing the posterior condyles sufficient to achieve a rectangular flexion gap in total knee arthroplasty?. International Orthopaedics (SICOT) 33, 1561–1565 (2009). https://doi.org/10.1007/s00264-008-0656-2
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DOI: https://doi.org/10.1007/s00264-008-0656-2