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

21. THANK YOU