Cutting to the Truth: Are We Measuring Osteotomy Parameters Correctly?

Purpose Traditional lower limb deformity analysis in pediatrics and adults centers on the anatomical center of the knee. However, in high tibial osteotomy (HTO) for medial compartment knee osteoarthritis (KOA), the surgical goal is often valgus overcorrection toward a lateral weight-bearing point. This study quantified the effect of using a lateral weight-bearing point versus the center of the knee on lower-limb alignment parameters and assessed how these differences may influence surgical decision-making. Methods A retrospective radiographic study was conducted in 20 patients with unicompartmental KOA who underwent HTO. Alignment was measured using 2 methods: the anatomical center of the knee and a 62.5% lateral weight-bearing point as the lateral weight-bearing reference point. Measured parameters included the mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal tibial angle (mLDTA), and mechanical hip-knee-ankle angle (mHKAA). Methods were compared using paired t tests. Results Using a 62.5% lateral weight-bearing point altered all alignment parameters. Compared with knee-centered measurements, mLDFA increased by 1.52° (more varus), mMPTA decreased by 1.84° (more varus), and mLDTA decreased by 1.85° (more valgus) (all P < 0.001). These changes altered deformity classification, with femora classified as varus increasing from 4 to 10 and tibiae from 8 to 13. Conclusion Using a lateral weight-bearing point for deformity analysis produces predictable changes in alignment measurements that frequently alter deformity classification. This approach may reveal occult femoral deformities underestimated by traditional methods and may provide a more biomechanically relevant framework for osteotomy planning.