Neutral boundary alignment in total knee arthroplasty: a novel concept

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Biomedical Engineering

Background:

• Total knee arthroplasty (TKA) aims to restore knee function and stability.
• Existing alignment philosophies include mechanical alignment (MA), kinematic alignment (KA), and anatomical alignment (AA).
• Functional alignment (FA) is a recent concept in TKA.

Purpose of the Study:

• To introduce and describe a novel TKA approach termed Neutral Boundary Alignment (NBA).
• To propose hypotheses regarding joint line orientation, stability criteria, and bone resection accuracy in NBA.
• To restore a native-like knee from an arthritic state by aligning the joint line parallel to the ground.

Main Methods:

• Description of the NBA approach for TKA.
• Development of an iterative algorithm for structural layout patterns of truss.
• Formulation of three key hypotheses regarding NBA principles.

Main Results:

• Hypothesis 1: A ground-parallel joint line during midstance is crucial for gait stability.
• Hypothesis 2: NBA stability is achieved when gravity aligns with hip, knee, and ankle, consistent with MA's Varus/Valgus envelope.
• Hypothesis 3: Parallel bone resections in NBA remain within 1.5 degrees of traditional MA resections.

Conclusions:

• NBA provides a conceptual framework for achieving a stable and functional knee joint post-TKA.
• The proposed alignment strategy aims to optimize limb alignment with gravity during gait.
• NBA demonstrates potential for accurate bone resections, comparable to established MA techniques.