Abstract
When a total knee arthroplasty (TKA) is implanted using the traditional mechanical
alignment technique, this typically results in a straight leg, independently of pre-operative
or even pre-arthrotic varus or valgus alignment. With mechanical alignment, we distinguish
between 2 different alignment techniques: ligament balancing and bony referencing
according to bony skeletal landmarks. In ligament balanced technique beside the straight
mechanical axis, the prosthesis is implanted at 90° to the latter. The rotational
alignment of the femur is set according to the ligament tension. In the skeletal referenced
technique, the rotation of the femur is also set according to bony skeletal landmarks.
As a variation of this technique, the prosthesis can be implanted with anatomical
alignment. In this technique, the medial slope of the joint line of 3° in the frontal
plane is respected during the implantation of TKA. Both techniques result in comparable
long-term results with
survival rates of almost 80% after 25 years. On the other hand, 15 – 20% of TKA
patients report dissatisfaction with their clinical result. For more than 10 years
now, the kinematic TKA alignment concept has been developed with the goal to achieve
implantation that is adapted to the individual anatomy of the patient. The advocates
of this technique expect better function of TKA. This strategy aims to reconstruct
the pre-arthrotic anatomy of a given patient while preserving the existing joint line
and the mechanical axis without performing ligamentary release. Studies have shown
that the function of the prothesis is at least that good as in the conventional techniques.
Long-term results are still sparse, but initial studies show that TKA implanted using
the kinematic alignment technique exhibit comparable 10-year-survival rates to those
implanted using the traditional mechanical alignment technique. Future studies need
to show the limitations of this new technique and to
identify patients who will or will not significantly benefit from this technique.
Key words
knee arthroplasty - mechanical alignment - gap balancing - measured resection - kinematic
alignment
