The CORA (Center of Rotation of Angulation) concept is fundamental to deformity correction osteotomies. If an osteotomy is performed at a level other than the CORA, which deformity will result after correction?

• A Residual angular deformity at the osteotomy site
• B Rotational deformity of the distal segment
• C Translational deformity (secondary translation) at the osteotomy site ✓
• D Limb lengthening rather than angular correction

Explanation

The Center of Rotation of Angulation (CORA) is the apex of angular deformity where the mechanical and anatomic axes of proximal and distal bone segments intersect. Performing an osteotomy exactly at the CORA and rotating around it corrects angular deformity without creating secondary translation. If the osteotomy is performed at a level different from the CORA, angular correction will be achieved but a translational offset (secondary deformity) is created at the osteotomy site. This secondary translation must then be corrected by intentional translation of the distal fragment, a principle exploited in 'oblique plane analysis' of deformity. Understanding CORA is essential for planning osteotomies.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.