Boundaries in Kinematic Alignment: Why, When, and How

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Biomechanics

Background:

• Patient dissatisfaction with total knee arthroplasty (TKA) outcomes, often linked to suboptimal alignment, has driven interest in alternative surgical techniques.
• Kinematic alignment (KA) is an increasingly popular approach in TKA, aiming to restore the knee's native axes and potentially improve patient-reported outcome measures (PROMs).
• Traditional TKA alignment principles emphasize achieving a neutral hip-knee-ankle (HKA) axis, but newer classifications of knee anatomy challenge this dogma.

Purpose of the Study:

• To review the existing literature on alignment strategies in TKA.
• To evaluate the evidence supporting the establishment of alignment boundaries within kinematic alignment.
• To determine a safe range for reproducing constitutional knee anatomy in TKA.

Main Methods:

• Literature review of studies on TKA alignment, kinematic alignment, and patient outcomes.
• Analysis of research investigating the relationship between TKA alignment, knee biomechanics, and implant survivorship.
• Examination of proposed classifications for preoperative limb deformity and their implications for surgical planning.

Main Results:

• Many patients remain dissatisfied with TKA outcomes, highlighting the need for patient-centered alignment techniques.
• Pure kinematic alignment aims to preserve native knee joint axes, potentially enhancing patient satisfaction.
• Reproducing atypical anatomies without considering alignment boundaries may compromise TKA biomechanics and implant longevity.

Conclusions:

• Setting appropriate alignment boundaries in TKA is crucial when aiming to replicate a patient's natural knee anatomy.
• Balancing the reproduction of constitutional knee anatomy with established biomechanical principles is essential for successful TKA outcomes.
• Further research is needed to define optimal alignment ranges that ensure both patient satisfaction and implant survivorship in TKA.