Angular limb deformity

Question 1

Define anatomic axis

Answer 1

line that passes through the center, or mid-diaphysis, of the bone in the frontal or sagittal plane. Best used with straight bones. If the bone is curved more than one line may be used to resolve the curved anatomic axis (think radius pro-curvatum)

Question 2

Define mechanical axis

Answer 2

A straight line connecting the center points of the joints proximal and distal to the bone in the frontal or sagittal plane. It is always a straight line and represents the weight bearing axis of the bone

Question 3

Define joint orientation angle

Answer 3

The intersection of a joint orientation line and a bone axis

Question 4

How are joint orientation angles named (labeled)

Answer 4

Axis first (so a or m), then cranial/caudal or medial/lateral,
then proximal or distal and finally the bone.  mMPTA

Question 5

Define inclination angle

Answer 5

Measured in the frontal plane. Its the intersection of the proximal femoral anatomic axis and a line originating at the center of the femoral head that bisects the femoral neck

Question 6

Define coxa vara using inclination angle

Answer 6

This is a deceased angle of inclination

Question 7

Define coxa valga using the inclination angle

Answer 7

This an increased angle of inclination

Question 8

Anteversion angle

Answer 8

Measured in the transverse plane and is the angle between the femoral neck and the frontal plane of the femur as described by the caudal aspect of the femoral condyles

Question 9

Define CORA

Answer 9

Center of rotation of angulation (essentially the apex of the deformity). A bone can have more than one

Question 10

What three things does every CORA posses

Answer 10

A location, a magnitude and a plane. The plane is always directed opposite the way the bone is deviated

Question 11

What is meant by an opening CORA

Answer 11

A CORA on the convex side of the transverse bisecting line with respect to the neutral CORA

Question 12

What is meant by a closing CORA

Answer 12

A CORA on the concave side of the transverse bisecting line with respect to the neutral CORA

Question 13

Angular limb deformity with a single CORA (the anatomic axes of the bone intersect within the cortical confines of the bone)

Answer 13

Uniapical deformity

Question 14

Angular limb deformity with two CORA

Answer 14

biapical deformity

Question 15

Angular limb deformity with more than 2 CORA

Answer 15

multiapical deformity

Question 16

Angular limb deformity with 2 CORA whose planes lie in opposite directions

Answer 16

Biapical partially compensated

Question 17

Angular limb deformity with 2 CORA whose planes lie in the same direction

Answer 17

Biapical non-compensated

Question 18

What happens if your osteotomy and the ACA (angular correction axis) is placed at the CORA

Answer 18

Angular correction and co-linearity of the axis are achieved

Question 19

What happens when your ACA (angular correction axis) is based at the CORA and the osteotomy is located somewhere other than the CORA

Answer 19

Appropriate realignment occurs through angulation AND translation

Question 20

What happens when the osteotomy and the ACA occur at a level different from the CORA

Answer 20

Co-linearity of the segments does not occur and iatrogenic translation results (avoid this)