Kinematic Alignment Technique for Medial Unicompartmental Knee Arthroplasty

Abstract

The kinematic alignment (KA) technique for unicompartmental knee arthroplasty (UKA) is a simple, safe, more anatomical, more physiological and probably clinically advantageous method compared to traditional mechanical alignment. The KA technique for UKA aims to produce “true” joint surfacing by restoring the level and three-dimensional orientation of the native joint space in the implanted knee compartment. It is biomechanically healthy and conserves ligament balance, knee kinematics and transmission of stresses to the metaphyseal bone. The KA technique for UKA is likely to better reproduce natural frontal alignment of the limb when the knee is flexed due to conservation of the posterior tibial slope. It may reduce the risk of fracture and secondary residual pain in remodelling metaphyseal bone. KA-UKA enables optimal dynamic interaction of prosthetic components, reduces risks of overlap and underdimensioning, and is biomechanically healthy. Studies have reported good long-term results, with acceptable lifespan, high functional performance, and high patient satisfaction. KA for UKA is a technique with independent sectioning that can be performed with manual instrumentation, measuring the thickness of bone resection with vernier callipers, and using three-dimensional planning. Tibial resection for medial Oxford^® UKA involves assessing the posterior slope and anteroposterior and mediolateral dimensions, and measuring the thickness of the Oxford^® tibial implant. Femoral resection for medial Oxford^® UKA involves axial and frontal rotations, frontal alignment, thickness verification, and distal femoral reaming. The kinematic alignment technique for UKA is a simple, safe, more anatomical, physiological and clinically advantageous method.