Computer navigation of soft tissues in total knee replacement

Following the success of computer navigation in producing consistently accurate alignment, the focus has shifted to use of these techniques for soft tissue assessment during total knee replacement (TKR). We undertook a prospectively randomized clinical study to compare two methods of tissue balancing in TKR. One method, called bone referencing (BR) employed independent cutting of the femur and tibia followed by subjective assessment with trial prostheses and soft tissue release as deemed necessary. The other method, termed ligament balancing (LB), involved cutting the tibia first and titration of tissue balance and alignment parameters to guide femoral cuts. Our total sample comprised 77 subjects with 80% statistical power. To assess tissue balance we used (a) coronal laxity testing and (b) computer navigation generated passive knee range of movement graphs. The graphical assessment was validated with coronal laxity testing. There was no difference between the resultant tissue balances achieved. However, correlation with preoperative status revealed the LB technique to show better results in a smaller subgroup of knees with greater preoperative tissue imbalance. We advocate variation of tissue balancing technique to suit the individual knee, based on preoperative assessment, to achieve an optimal result in all TKR.