Neutral mechanical alignment: a requirement for successful TKA: affirms

Abstract

Restoration of an overall neutral mechanical axis has been a long-held tenet in total knee arthroplasty (TKA). Numerous biomechanical, finite element, and clinical studies have demonstrated that coronal malalignment, particularly varus, is associated with increased strain, higher failure rates, and, in some cases, poorer outcomes. With advances in computer-assisted navigation, 3-dimensional imaging, and patient-specific positioning guides, the potential for greater precision in bone resection and component positioning has rekindled interest in this important issue. Several recently published studies demonstrating no difference in survivorship for malaligned TKAs have challenged the concept of an alignment safe zone. Some surgeons have discussed a paradigm shift in defining optimal alignment. While we agree that compared to several decades ago, there is greater understanding of TKA kinematics and that broad targets for alignment may not impart significant benefit as a dichotomous variable, there are multiple reasons why neutral alignment and classic bone cuts remain valid and important in delivering a successful TKA. In comparison to the preponderance of evidence advocating a neutral mechanical axis and approximately 5° to 7° valgus anatomic alignment, there is insufficient support for reasonably choosing any other target. Although technology has improved surgical precision, it has not eliminated the human factor, and aiming for neutral provides the safest margin for error. The foremost objective of TKA is a durable and well-functioning joint, not necessarily one that replicates normal or the patient's native condition. While the latter goal is certainly desirable, the priority of the former should never be overlooked.