Die Bedeutung der dynamischen Beinachse: biomechanische Einflüsse auf Knie-Totalendoprothesen und Gelenkbelastung

Zusammenfassung

Im klinischen Alltag hat sich zur Beurteilung der Beinachse in der Frontalebene die statische Röntgenaufnahme etabliert. Mit vermehrtem Einsatz von funktionellen Analysen wie der Bewegungsanalyse rückt die Betrachtung der dynamischen Beinachse zunehmend in den Fokus. Die dynamische Achse des Kniegelenks spielt eine entscheidende Rolle für den Verschleiß von Knie-Totalendoprothesen (K-TEP), da sie die Belastungsverteilung und Bewegungsmuster im femorotibialen Gelenk beeinflusst. Insbesondere das Knieadduktionsmoment (KAM) wirkt sich bei medialen Belastungen auf das Inlay aus, das bei hohen Belastungsfrequenzen Verschleiß zeigt. Studien zeigen, dass das KAM bei Varusausrichtung steigt, was zu einer ungleichmäßigen Lastverteilung und einer erhöhten Belastung des medialen Kompartiments führt. In-vitro- und Post-mortem-Analysen quantifizieren den jährlichen Materialverlust im Inlay, wobei Design und Ausrichtung der Prothese die Verschleißrate beeinflussen. Die dynamische Beinachse und das Gangbild können den Verschleiß weiter modifizieren; ein „Toe-in“-Gangmuster etwa senkt das KAM signifikant und könnte somit eine nichtoperative Option zur Verschleißminderung darstellen. Neuere Ansätze, wie das kinematische Alignment, streben eine natürliche Positionierung der Prothese an, was den Verschleiß nicht zwingend erhöht, jedoch im Vergleich zur mechanischen Ausrichtung eine präarthrotische Varus- oder Valgusachse belassen kann. Zusammenfassend könnte eine dynamische Bewertung der Beinachse zur präoperativen Planung und zur Verschleißreduktion bei K-TEP beitragen, wobei die statische radiologische Achsbestimmung klinisch relevant bleiben wird.

Abstract

In routine clinical practice, static radiographic imaging has become the standard method for assessing the leg axis in the frontal plane. With increasing use of functional analyses, such as motion analysis, the focus is shifting more towards the dynamic leg axis. The dynamic axis of the knee joint plays a critical role in the wear of total knee arthroplasty (TKA) components, as it influences load distribution and movement patterns in the femorotibial joint. In particular, the knee adduction moment (KAM) affects the inlay during medial loading, which exhibits wear at high loading frequencies. Studies indicate that KAM increases with varus alignment, leading to uneven load distribution and greater stress on the medial compartment. In-vitro and post-mortem analyses quantify the annual material loss in the inlay, with prosthesis design and alignment influencing wear rates. The dynamic leg axis and gait patterns can further modify wear; for example, a “toe-in” gait pattern significantly reduces KAM and may therefore represent a non-surgical option to mitigate wear. More recent approaches, such as kinematic alignment, aim for a more natural positioning of the prosthesis, which does not necessarily increase wear but, compared with mechanical alignment, may preserve a pre-arthritic varus or valgus axis. In summary, a dynamic evaluation of the leg axis may contribute to preoperative planning and wear reduction in TKA, while static radiological axis assessment will remain clinically relevant.

Schlüsselwörter

Biomechanik - Knie-Totalendoprothetik - Gelenkbelastung - Beinachse

Keywords

biomechanics - total knee arthroplasty - joint load - leg axis

Publication History

Received: 17 March 2025

Accepted after revision: 04 December 2025

Article published online:
12 February 2026

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