Extra-articular deformity is always correctable intra-articularly: to the contrary

Area of Science:

• Orthopedic Surgery
• Biomechanical Analysis

Background:

• Debates persist regarding the optimal surgical correction for knee deformities.
• Extra-articular correction is sometimes indicated but requires careful patient selection.

Observation:

• Four key factors guide the decision for extra-articular correction: deformity magnitude, proximity to the knee, varus/valgus nature, and bone involvement (femur/tibia).
• Large deformities remote from the knee have minimal impact.
• Varus and valgus deformities necessitate intra-articular overresection, potentially causing instability.

Findings:

• Lateral instability, often resulting from valgus correction, is better tolerated than medial instability.
• Templating the knee's mechanical axis helps quantify overresection and assess the need for extra-articular correction.
• This templating method aids in identifying cases where extra-articular correction offers advantages.

Implications:

• This analysis provides a framework for surgeons to determine the suitability of extra-articular correction.
• Improved patient selection can lead to better outcomes and reduced complications in knee deformity correction.
• Understanding the biomechanics of malalignment is crucial for surgical planning.