TKA ALIGNMENT — Hip & Knee Book | 合法醫療器材資訊網

2017年2月26日—TKAaimstorecreatethemechanicalaxisofthenativeleg, ...

The tibia is cut at 0°  (perpendicular to mechanical/anatomic axis), while the native tibia joint line is in slight varus (roughly 3°).  This means that we are over-resecting the lateral side (anatomically the lateral side is slightly higher giving that 3° varus, so with a cut at 0° you are resecting slightly more lateral tibia).    

Theoretically over resecting lateral tibial bone causes some varus laxity.  You can compensate by performing a medial release of soft tissue (such as taking down some of the deep MCL); or adjust the bony cuts on the femoral side by a) under-resect the lateral distal femur (decrease the valgus angle slightly to 6° based on the intramedullary femur guide... instead of cutting the femur at 9°) to reconcile the extension gap, and b) balance the flexion gap by adding 3° of external rotation (this technique was originally implemented to compensate fo...