Inverse kinematic alignment accommodates native coronal knee alignment better in comparison to adjusted mechanical...

Area of Science:

• Orthopedic surgery
• Biomechanical analysis
• Knee arthroplasty

Background:

• Native knee coronal alignment exhibits significant variability.
• Accurate alignment is crucial for total knee arthroplasty (TKA) outcomes.
• Current alignment methods (aMA, rKA) may not fully accommodate natural knee anatomy.

Purpose of the Study:

• To determine the proportion of native non-arthritic knees fitting within aMA, rKA, and iKA target zones.
• To estimate necessary coronal alignment adjustments for outlier knees.
• To test the hypothesis that iKA accommodates a higher proportion of native knees.

Main Methods:

• Analysis of CT scans from 972 healthy knees (SOMA database).
• Measurement of Hip Knee Ankle (HKA), Medial Proximal Tibial Angle (MPTA), and Lateral Distal Femoral Angle (LDFA).
• Calculation of native alignment proportions within target zones and theoretical adjustments for outliers.

Main Results:

• Inverse kinematic alignment (iKA) accommodated 74% of native knees, compared to 55% for restricted kinematic alignment (rKA) and 8% for adjusted mechanical alignment (aMA).
• Adjustments required for outlier knees were lowest for iKA (25% MPTA, 23% LDFA, 7% HKA).
• rKA required 45% MPTA, 28% LDFA, and 25% HKA adjustments.

Conclusions:

• Considerable variability exists in native knee coronal alignment.
• iKA accommodates a greater proportion of native limb alignment compared to aMA and rKA.
• iKA may provide a more patient-specific approach for TKA by accommodating natural alignment variations.