Synchronisation of tibial rotational alignment with femoral component in total knee arthroplasty

Abstract

The rotational axis of the tibial component in total knee arthroplasty described by Insall is generally accepted, but rotational mismatch between the femoral and the tibial components can occur because the alignment of each component is determined separately. We developed a connecting instrument to synchronise the axis of the tibia to the axis of the femur. We compared the rotational axis of the tibial component using our method and medial one third of tibial tuberosity (Insall's reference) in 70 consecutive TKAs. The rotational axis of the tibial component from the femoro-tibial synchronisation was rotated internally 13.8°± 5.8°(range, 2°-24°) more than the axis of Insall's reference. Eighty three percent of patellae tracked centrally and the patellae tilt measured 2.2°on average. More attention should be given to the rotational congruency between the femorotibial components, because the recent prosthetic design has more conforming articular surfaces.Résumé La rotation axiale du composant tibial dans la prothèse totale du genou décrite par Insall est généralement acceptée mais elle peut poser problème lorsqu'il existe un trouble de rotation sur le composant fémoral et le composant tibial du fait d'une détermination séparée de la position de chaque composant au moment de l'implantation. Nous avons pour cela développé un instrument qui permet de synchroniser l'axe du tibia et l'axe du fémur. Nous avons comparé la rotation axiale du composant tibial en utilisant notre méthode à propos de 70 prothèses totales consécutives du genou. L'axe de rotation après synchronisation des deux composants a été noté en rotation interne. Cette rotation interne est plus importante que celle prévue par l'axe de référence d'Insall qui est représenté par le tiers interne de la tubérosité tibio-intérieure. 83% des rotules avaient une course normale et un accrochage rotulien a été noté dans 2,2% en moyenne. Une attention particulière doit être portée à la congruence en rotation des éléments fémoro-tibiaux pendant l'implantation d'une PTG d'autant que cette congruence est plus importante dans les nouveaux dessins de prothèses totales du genou récentes.

Easy Identification of Mechanical Axis during Total Knee Arthroplasty

“…Manipulation of hip and knee joint during operation cannot affect the alignment, and precision is increased and consistency can be maintained. In our cohort, outliers were less than 10%, making it vivid contrast to other conventional results with ranges of around 15-40% 7,10,16,23,26…”

“…In addition, the marker position could be mobilized due to hip and knee motion that is inevitable for the operation. Various methods using femoral head centers as a mechanical axis guider also suffer from delayed operation time or increased malalignment 1,10,13,16,25. Navigation, the developed version, also has the problems of low cost-effectiveness and protracted operation times 3,17,18,23,26…”

“…After soft tissue balancing, extramedullary technique was used to install distal femoral block. The connector to which proximal tibial resector was attached was inserted into distal femoral resector's slot, and then EM axis guider was used to adjust femur's coronal axis and sagittal alignment for synchronization 16. Proximal tibial cuts were made using an EM alignment guide (Linker®), an instrument that maintains a parallel status between the femoral and tibial mechanical axes 17,18.…”

“…As for extramedullary technique for the femoral bone resection, it relies on identifying the center of femoral head during surgical procedure. Although various techniques have been introduced such as the use of the pelvic anterior superior iliac spine or femoral artery as landmark to pinpoint femoral head center, these techniques have been abandoned because of increase in surgical times 1,16-18. In order to determine the femoral head center, it took much more complicated surgical procedure and increased cost with less accurate result of final lower limb alignment 1,10,17,18…”

Femoral and tibial component rotation in total knee arthroplasty

“…19,20 The third is to rotate the tibial component into alignment with the chosen femoral component rotation when the knee is moved into full extension. 6,21 Each of these methods has its advantages. Advocates of the anatomical method emphasise the advantage of maximally covering the cut tibial surface to facilitate component fixation, while avoiding the potential of component overhang and soft tissue impingement.…”