Cora

Center of rotation of angulation and basic osteotomy rules

1. CORA PRAVEEN KUMAR T S JUNIOR RESIDENT DEPARTMENT OF ORTHOPEDICS MCH TRIVANDRUM

2. WHAT IS CORA? The point at which the proximal and distal axis lines of a deformed bone intersect is called CORA- Center of rotation of Angulation

3. CORA It is the point about which a deformity may be rotated to achieve correction

4. CORA The angle formed by the two axes at the CORA is a measure of angular deformity in that plane

5. HOW TO MARK CORA Draw axis of proximal segment Draw axis of distal segment For diaphyseal deformity, the anatomic axis are more convenient For metaphyseal and epiphyseal deformity, mechanical axis is more convenient The intersecting point is the CORA

6. IMPORTANCE OF CORA CORA helps to measure the magnitude of angular deformity Helps to plan the operative correction of angular deformities It indicates where an angulation correction axis-ACA should be placed

7. IMPORTANCE OF CORA If the CORA lies at the point of obvious deformity in the bone, the deformity is UNIAPICAL ANGULAR DEFORMITY in the respective plane If the CORA does not corresponds to obvious deformity, there is more than one angular deformity present- MULTIAPICAL ANGULAR DEFORMITY or there is a translational deformity

8. BISECTOR The BISECTOR is a line that passes through the CORA and bisects the angle formed by the proximal and distal axes

9. BISECTOR Angular correction along the bisector results in complete deformity correction without any translational deformity

10. ANGULATION CORRECTION AXIS(ACA) Angulation correction axis or ACA is an imaginary line in space perpendicular to the plane of deformity Deformity correction is performed around this line It is axis around which a bony segment is rotated to achieve correction

11. ANGULAR CORRECTION AXIS(ACA) ACA can be a line anywhere in the space perpendicular to the plane of deformity, But when ACA is on a point on the BISECTOR there will be complete correction of deformity There will be collinear realignment of proximal and distal axis when ACA is a point on bisector Thus CORA can also be defined as any point that will leads collinear realignment of proximal and distal axis of deformed bone when the ACA passes through it.

12. ACA - CORA

13. CORA AND OSTEOTOMY An osteotomy is used to correct the alignment of a deformed bone The ability of an osteotomy to restore alignment depends on Location of CORA Location of ACA Location of Osteotomy Three possibilities Realignment through angulation alone Realignment through angulation and translation Realignment through angulation and translation with an iatrogenic translational deformity

14. CORA AND OSTEOTOMY RULE 1 When the CORA , Correction axis and osteotomy lie at the same location ,the bone will realign through angulation alone, without translation .

15. RULE 2 When the CORA and correction axis are at the same location but osteotomy is made proximal or distal to that location ,the bone realign through both angulation and translation

16. RULE 3 When CORA lies at one location and the correction axis and osteotomy lie in a different location , correction of angulation results in an iatrogenic translational deformity

17. WEDGE OSTEOTOMY OPENING WEDGE OSTEOTOMY The CORA and correction axis lie on the convex side of the deformity Correction produces a wedge shaped defect with a base on concave side Opening wedge osteotomy increases the final bone length.

18. WEDGE OSTEOTOMY CLOSING WEDGE OSTEOTOMY CORA and correction axis lie on concave side of deformity A wedge of bone is removed with a base on convex side Decreases the bone length

19. WEDGE OSTEOTOMY NEUTRAL WEDGE OSTEOTOMY CORA and correction axis lie at middle of bone A bone wedge is removed from the convex side With correction the convex side is compressed and concave side is distracted No effect on bone length

20. DOME OSTEOTOMY OPENING DOME CLOSING DOME NEUTRAL DOME

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