A 14-year-old boy has a femoral shaft deformity with 22° anterior bow and valgus alignment following malunited fracture. The CORA (centre of rotation of angulation) technique is used to plan the corrective osteotomy. What does CORA represent?
- A The geometric centre of the femoral head, used for biomechanical axis calculations
- B The intersection of the mechanical axes of the two bone segments proximal and distal to the deformity, defining the apex of the angulation ✓
- C The point along the bone where hardware stress is maximal during weight-bearing
- D The midpoint between the level of angular correction and the desired resultant axis
Correct answer: B. The intersection of the mechanical axes of the two bone segments proximal and distal to the deformity, defining the apex of the angulation
Explanation
CORA is the intersection point of the mechanical/anatomical axes of the proximal and distal bone segments; it identifies the apex of the deformity in the true deformity plane. Performing the osteotomy directly at the CORA produces pure angular correction without translation. If the osteotomy is placed away from the CORA, secondary translation is required to realign the mechanical axis, making CORA-based planning fundamental to precise deformity correction.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.