Description
【Purpose】
Accurate osteotomy and evaluation of intraoperative soft tissue balance are possible in robotic assisted TKA. However, there were some cases in which there was a gap between the predicted soft tissue balance and the results. The accuracy has not been adequately studied. The purpose of this study is to be discussed about the gap of soft tissue balance between intraoperative final prediction and after implant placement and the factor related to it.
【Method】
We examined 15-knees operated TKA with Bi-Cruciate Retaining(BCR-TKA) and 123-knees operated TKA with Bi-Cruciate Stabilized(BCS-TKA) using a surgical assist robot(Navio/CORI). We evaluated soft tissue balance in full range of motion with varus and valgus stress before osteotomy after resecting osteophyte as much as possible and after implant placement. We compared the balance and considered the factors affected of the gap between final prediction and results.
【Result】
The gap of soft tissue balance between the predictions and the results of BCR-TKA were 0.2mm on the inside, -0.1mm on the outside in extension position, 0.5mm on the inside and 0.2mm on the outside in 90°flexion position on average. On the other hand, the gap of BCS-TKA were 2.9mm on the inside, 0.5mm on the outside in extension position, 3.1mm on the inside and 2.0mm on the outside in 90° flexion position on average. Significant correlations were found in the amount of the gap between preoperative alignment and the result of inside in extension position with BCS-TKA.
【Discussion】
We considered that accuracy of the final prediction of the soft tissue balance was highly in the less deformed case because the soft tissue balance of BCR-TKA turned out to be generally just as predicted. On the other hand, when we operate with BCS-TKA, it is needed to consider preoperative plan with the amount of change, because the intraoperative prediction contains osteophyte with difficulty to resect at the time of evaluation and the gap makes more bigger after cutting cruciate ligament. The date makes gap slightly depending on the measurement and between examiners, so it is necessary to choice the reproductive and objective evaluation methods.
【Conclusion】
Evaluation of the soft tissue balance using a surgical assist robot has less accuracy compared with evaluation of balance after osteotomy, but we can predict the balance to some extent before osteotomy and adjust placement position with reference to the effect, so surgical assist robot contributes to achieve suited soft tissue balance.
