Functional alignment achieves soft-tissue balance in total knee arthroplasty as measured with quantitative sensor-guided technology

Aims Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology. Methods This prospective study included 30 consecutive patients undergoing robotic-assisted TKA using the Stryker PS Triathlon implant with functional alignment. Intraoperative soft-tissue balance was assessed using sensor-guided technology after definitive component implantation; soft-tissue balance was defined as intercompartmental pressure difference (ICPD) of < 15 psi. Medial and lateral compartment pressures were recorded at 10 degrees, 45 degrees, and 90 degrees of knee flexion. This study included 18 females (60%) and 12 males (40%) with a mean age of 65.2 years (SD 9.3). Mean preoperative hip-knee-ankle deformity was 6.3 degrees varus (SD 2.7 degrees). Results TKA with functional alignment achieved balanced medial and lateral compartment pressures at 10 degrees (25.0 psi (SD 6.1) vs 23.1 psi (SD 6.7), respectively; p = 0.140), 45 degrees (21.4 psi (SD 5.9) vs 20.6 psi (SD 5.9), respectively; p = 0.510), and 90 degrees (21.2 psi (SD 7.1) vs 21.6 psi (SD 9.0), respectively; p = 0.800) of knee flexion. Mean ICPD was 6.1 psi (SD 4.5; 0 to 14) at 10 degrees, 5.4 psi (SD 3.9; 0 to 12) at 45 degrees, and 4.9 psi (SD 4.45; 0 to 15) at 90 degrees of knee flexion. Mean postoperative limb alignment was 2.2 degrees varus (SD 1.0 degrees). Conclusion TKA using the functional alignment achieves balanced mediolateral soft-tissue tension through the arc of knee flexion as assessed using intraoperative pressure-sensor technology. Further clinical trials are required to determine if TKA with functional alignment translates to improvements in patient satisfaction and outcomes compared to conventional alignment techniques.