Abstract
There is ample data to confirm that Computer-assisted total knee replacement improves alignment of the limb when compared with the conventional technique. There is also published evidence that optimum alignment correlates with longevity of implants. CAS enables accurate component alignment of both femoral and tibial components. It enables accurate restoration of the posterior tibial slope which has important consequences for flexion range and stability of the component in flexion especially if mobile bearing implants are considered. CAS also aids in correctly orienting rotation of the femoral component; this has value in minimizing patellar maltracking. We will present our data showing accurate restoration of joint line and posterior femoral offset. As CAS ensures alignment, rotation, sizing and positioning of components, the surgeon is free to devote his efforts to ensuring soft-tissue balance and stability, since TKA is really a ‘soft-tissue’ operation.
How CAS is of immense value in deformity correction and soft-tissue balancing will be illustrated with examples. It helps in better understanding and quantification of the effects of soft-tissue release on flexion-extension gaps and this is of great value not only for minimal deformities (to minimise releases) but also for severe deformities (to ensure complete correction by adequate release). CAS is invaluable in helping equalize flexion-extension gaps; how it can help balance the flexion gap to the extension gap by ‘virtual surgery’ will be depicted with examples. It is particularly useful in presence of hardware in the femur or tibia and for concomitant extra-articular deformity.
We have also found a consistent improvement in recovery of functional milestones with CAS with similar results for both unilateral and bilateral TKAs. Furthermore, there is evidence to support that ensuring alignment has important benefits in improving functional and quality of life scores. In addition, those with alignment of mechanical axis within 3 degrees of normal have been shown to have a shorter stay in hospital by 2 days. Studies have shown reduced blood loss and incidence of emboli after CAS TKA.
Using CAS routinely for all cases, the author is ‘time neutral’. While there is always room for improvement with evolving technologies and CAS is no exception, it already has enormous benefits in the performance and outcome of TKA, and is an important part of the surgical armamentarium for a successful knee arthroplasty.
