A patient with post-traumatic malunion of the tibia with a combined angulatory and translational deformity requires correction. The center of rotation and angulation (CORA) method is used to plan osteotomy. If the osteotomy is performed at a site away from the CORA, which secondary deformity results?

• A Increased angulation
• B Rotational deformity
• C Shortening only
• D Translation deformity (secondary translation at the osteotomy site) ✓

Explanation

The CORA (center of rotation of angulation) is the apex of the deformity where the mechanical axes of the proximal and distal bone segments intersect. Performing an osteotomy at the CORA corrects both angulation and translation simultaneously. If the osteotomy is performed away from the CORA (at a different level), angulation is corrected but a secondary translation deformity is created at the osteotomy site, creating a new deformity. This principle guides proper surgical planning in deformity correction surgery.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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