Despite the recognized importance of proper soft tissue balancing during a total knee arthroplasty, instability remains a major cause for revision surgery. During surgery, indicators such as joint space are used to help achieve a balanced knee, and a subjective manual check of stability is performed after trial components are in place. This contrasts with biomechanics researchers who use complex devices to apply known loads and measure resultant motions to find stability. However, none of these devices are appropriate for use during a total knee arthroplasty to provide surgeons with immediate feedback.
I created a novel device to help surgeons apply known loads, intra-operatively, for varus/valgus, internal/external, and anterior/posterior stability tests. The device employs a load cell and surgical navigation system. Validation of the device showed high accuracy and error standard deviations of no greater than 2.50 Nm varus/valgus moment, 1.38 Nm internal/external moment, and 5.45 N anterior/posterior force.