The centre of rotation of angulation (CORA) concept in deformity analysis is used to determine the apex of a bone deformity. When a closing-wedge osteotomy is performed exactly at the CORA, which residual deformity is expected?

• A No angular or translational deformity — perfect anatomical correction is achieved ✓
• B Translational deformity (offset) will remain at the osteotomy site
• C Residual angulation in the coronal plane remains
• D Osteotomy at the CORA always requires bone grafting to prevent translational offset

Explanation

The CORA (center of rotation of angulation) is the intersection of the proximal and distal mechanical axis lines of a deformed bone segment. An osteotomy performed EXACTLY at the CORA and rotated around this point corrects both the angular deformity AND any translation simultaneously — no residual angular or translational deformity remains. If the osteotomy is placed away from the CORA (a common practical necessity), correction of angulation introduces secondary translation (offset), which must be accounted for. The CORA principle, described by Paley, is fundamental to preoperative deformity planning.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.