Summary
Optimal total knee arthroplasty balance is achieved 98.5% of the time when the tibia is cut first, osteophytes are removed, and a ligament tensor is used.
Abstract
Purpose
This study assesses total knee arthroplasty (TKA) balance using four different alignment and balancing techniques.
Methods
A prospective cohort of 400 patients undergoing primary robotic-assisted cruciate-retaining TKA performed by one surgeon was analyzed. The VELYS image-free robotic system collects a balance curve that enables the surgeon to intra-operatively analyze the balance consequence of a mechanical (MA), kinematic (KA), functional (FA) from a KA starting point and tibia first, ligament guided (TFLG) TKA.
FA TKA was determined by starting with KA position then making small positional implant changes to balance the TKA with equal extension gaps, equal medial gaps, and 2 mm more laxity laterally in flexion. Balance was determined as +/- 2mm from optimal.
The tibia was then cut robotically, and the ACL, menisci, and osteophytes were resected. A ligament tensor was inserted, and the knee was placed through a ROM to determine the balance consequence of FA TKA. The femoral component position was then adjusted as required to balance the TKA optimally. The TFLG TKA position was then blindly evaluated to determine the balance consequence of this technique.
Results
A total of 400 consecutive patients (188 women, 212 men) with a mean age of 67 ± 9 years were included. The proportion of overall balanced knees was 17% with MA, 38% with KA, 29% with FA, and 98.5% with TFLG (P < .05). KA showed significantly better balance than MA in all gap measurements (P < .05). FA achieved balance in 80%, 69%, 56%, and 53% in extension, flexion, medial, and lateral gaps, respectively. TFLG TKA balance was 100%, 100%, 100%, and 98.5 % in extension, flexion, medial, and lateral gaps, respectively. There was no statistically significant difference between overall balanced valgus and varus knees in MA, KA, FA, and TFLG, respectively (P > .05).
Conclusion
Functional alignment failed to achieve better ligament balance than kinematic alignment, which showed poor but better balance than mechanical alignment. Optimal TKA balance is achieved 98.5% of the time when the tibia is cut first, osteophytes are removed, and a ligament tensor is used.