Tibia‐first, gap‐balanced patient‐specific alignment in total knee arthroplasty achieves better ligament balance than mechanical, kinematic and functional alignment strategies
Guido Wierer, Mark ClatworthyAbstract
Purpose
This study evaluates four different alignment techniques to assess total knee arthroplasty (TKA) balance.
Methods
A prospective cohort of 400 patients undergoing primary robotic‐assisted cruciate‐retaining TKA was analysed. The Velys TKA robotic system collects a balance curve that enables the surgeon to intraoperatively analyse the balance consequence of a mechanical alignment (MA), kinematic alignment (KA), functional alignment (FA) and patient‐specific alignment (PSA) TKA. FA was determined by starting from the KA position and then making positional implant changes to balance the TKA with equal extension gaps, equal medial gaps, and 2 mm more laxity laterally in flexion. The tibia was then cut robotically, and a ligament tensor was inserted to determine the balance consequence of FA. For PSA, the femoral component position was further adjusted, if necessary, to achieve optimal balance. Finally, the femur was resected robotically, and the balance outcome of PSA was assessed in a blinded manner. Balance was determined as ±2 mm from optimal.
Results
A total of 400 consecutive patients (188 women, 212 men) with a mean age of 67 ± 9 years were included. The proportion of balanced TKAs was 17% with MA, 38% with KA, 29% with FA and 98% with PSA ( p < 0.05). The proportion of potentially correctable TKAs was 33% for MA; thus, MA achieved balanced TKA in 50% of cases overall. For KA, 11% of TKAs were potentially correctable, resulting in an overall balancing rate of 49%. For FA, the planned preresection gaps differed significantly after tibial resection ( p > 0.05), and 44% of TKAs were potentially correctable. Thus, FA achieved balanced TKA in 73% of cases.
Conclusion
Optimal TKA balance is achieved with a tibia‐first, gap‐balanced PSA technique.
Level of Evidence
Level II, prospective comparative study.