Bone landmarks are more reliable than tensioned gaps in TKA component alignment

Abstract

Two distinct techniques have been used to achieve alignment and ligament balance in TKA. We hypothesized a bone landmark technique would result in normal alignment, stability, and load-bearing characteristics and that the tensioned gap technique results in malalignment. We studied 12 normal cadaveric knees (six with each technique) for stability, alignment, load-bearing stress transfer characteristics, and patellar groove position after TKA. The tensioned gap technique used tensioners to establish equal loads in the medial and lateral ligaments at 90 degrees flexion and to resect the posterior femoral surfaces parallel to the cut tibial surfaces. The bone landmarks technique aligns the anterior and posterior femoral cuts perpendicular to the median sagittal plane as defined by the anteroposterior axis and then resects bone to match implant thickness. The tensioned gap technique maintained nearly equal laxity medially and laterally but the knee shifted into varus malalignment in flexion. Compressive stress in the knee shifted medially in flexion, and the patellar groove shifted laterally. The bone landmarks technique produced near normal varus and valgus and rotational stability; alignment, patellar groove position, and load transfer characteristics remained near normal throughout flexion.