Abstract
Introduction & Aims
The traditional method of soft-tissue balancing during TKA is subjective in nature, and stiffness and instability are common indications for revision, suggesting that TKA balancing by subjective assessment is suboptimal. This study examines the intraoperative mediolateral loads measured with a nanosensor-enabled tibial insert trial and the sequential balancing steps used to achieve quantitative balance. Data obtained from a prospective multicenter study was assessed to determine the effect of targeted ligament release on intra-articular loading, and to understand which types of releases are necessary to achieve quantified ligament balance.
Methods
A group of 129 patients received sensor-assisted TKA, as part of a prospective multicenter study. Medial and lateral loading data were collected pre-release, during any sequential releases, and post-release. All data were collected at 10, 45, and 90 degrees during range of motion testing. Ligament release type, release technique type, and resultant loading were collected.
Results
Measured loads consistently decreased after soft-tissue release or bony re-cut and the relative mediolateral loading became more symmetric. The average change in loading values were approximately the same whether release or pie-crusting techniques were employed. In order to achieve balance, exhibited through the range of motion, the medial compartment required, on average, over double the release to loading (lbf.) than the lateral compartment. Structural changes that contributed significantly to changes in loading were: Release of the anterior and posterior bands of the MCL, pes anserine release, and recutting the tibia. On average, 2 or 3 structural corrections were performed to achieve balance.
Conclusions
The use of quantitative sensor data during TKA balancing enables targeted corrections to the soft-tissue envelope in order to correct intercompartmental load differential. 2–3 steps are needed on average to achieve soft tissue balance.
