The Coronal Plane Alignment of the Knee Classification May be Unreliable With Advanced Knee Arthritis

Area of Science:

• Orthopedic surgery
• Biomechanical analysis
• Radiographic assessment

Background:

• Kinematic alignment (KA) aims to replicate native knee alignment, including arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO).
• Severe osteoarthritis can distort these parameters through bone erosion or collapse, potentially misrepresenting the native coronal plane alignment of the knee (CPAK) phenotype.
• Evaluating CPAK phenotype concordance between arthritic and healthy knees is crucial for accurate surgical planning.

Purpose of the Study:

• To assess the concordance of CPAK phenotype parameters between severely arthritic knees and contralateral healthy knees.
• To determine if advanced osteoarthritis alters measurable knee alignment parameters.
• To inform the application of kinematic alignment in total knee arthroplasty.

Main Methods:

• Radiographic review of 578 patients with bilateral weight-bearing long-leg radiographs.
• Inclusion criteria: Kellgren-Lawrence grade 4 arthritic knee and grade 0-1 contralateral healthy knee.
• Calculation of absolute side-to-side differences for aHKA, JLO, medial proximal tibial angle, and lateral distal femoral angle.

Main Results:

• Ninety patients met inclusion criteria.
• Mean absolute differences between healthy and arthritic knees: 3.5° for aHKA, 2.3° for JLO, 2.4° for medial proximal tibial angle, 1.7° for lateral distal femoral angle.
• Limited CPAK concordance: 41% for medial arthritis, 50% for lateral arthritis.

Conclusions:

• Advanced knee osteoarthritis can cause permanent bony changes that alter measured CPAK phenotype.
• Replicating pathologic alignment in kinematic alignment total knee arthroplasty may lead to component malposition.
• Preoperative radiographic assessment is essential to identify and account for alignment deformities.