Ch 46 - Principles of Angular Limb Deformity Correction Flashcards

1
Q

What are the two types of bone axis which can be used when calculating ALD

A

Anatomical and mechanical

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2
Q

How are joint orientation lines notated?

A
  • a or m for anatomical or mechanical
  • Cr/Ca or M/L
  • P/D for proximal or distal
  • F/H/R etc for femue/humerus/radius etc
  • A for angle

eg aMPTA = anatomical medial proximal tibial angle

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3
Q

What are the joint orientation line landmarks for the humerus?

A

Frontal:
- Proximal: best fit oval over humeral head
- DIstal: distolateral most to distomedial most aspecrt of humeral condyle

Sagittal
- Proximal: Best fit circle over humeral head
- Distal: Best fit circle over medial and lateral asepct of condyle so they overlap

mLDHA 86.9 +/- 1.24
mCdPHA 43.3 +/- 1.24
mCrDHA 71.86 +/- 3.97

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4
Q

What are the joint orientation line landmarks for the radius?

A

Frontal
- Proximal: Proximolateral aspect of radial head and medial portion of coronoid process
- Distal: Lateral and medial most aspect of articular surface

Sagittal
- Proximal: Most proximal extent of Cr and Ca aspect of radial head
- Distal: Cr and Ca aspect of radius articular surface

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5
Q

How do you measure procurvatum?

A

(90deg - aCdPRA) + (90deg - aCdDRA) + # = overall procurvatum

# is angle of intersection of the anatomical axis

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6
Q

What is the mean radius joint orientation angle and procurvatum angles?

A
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7
Q

What are the anatomical landmarks for joint orientation lines of the femur?

A

Frontal
- Proximal: Center of femoral head to proximal most aspect of greater trochanter
- Distal: Distal most aspect of lateral and medial condyles

Angle of inclination:
- Proximal femoral anatomic axis and line from from center of femoral head bisecting the neck. Coxa vara is increased angle, coxa valga is decreased angle

Anteversion Angle
- Transverse plane: Line across caudal most aspect of femoral condyles and a line bisecting femoral head and neck

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8
Q

What are the mean femoral orientation lines?

A
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9
Q

What is the mean femoral inclincation angle in Labs, Goldens, GSDs and Rottweilers?

A
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10
Q

What is the range of reported anteversion angles?

A
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11
Q

What are the anatomical landmarks for the joint orientation lines of the tibia?

A

Frontal
- Proximal: Most proximal point of subhondral bone concavities of medial and lateral condyle
- Distal: Most proximal points of the subhondral bone of the 2 archiform grooves of the cochlear tibiae

Sagittal
- Proximal: Cr and Ca aspect of medial tibial condyle
- Distal: Distal aspect of distal intermediate ridge of the tibia cr and ca

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12
Q

What are the mean tibial joint orientation angles?

A
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13
Q

How do torsional deformities effect surgical planning on radiographs?

A

Much more challenging
- Torsional deformity above 15deg results in greater than 5deg miscalculation of deformities in frontal plane

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14
Q

What are the steps to determining the three components of the CORA (location, plane and magnitude)

A
  • 1: Joint orientation lines, axes and intersecting angles measured for the normal limb
  • 2: Joint orientation lines determines for effected bone
  • 3: Axes are determined based off of joint orientation angles from normal limb or from reference library
  • 4: Intersection is determined within cortical confines, demarcating the CORA magnitude and location
  • 5: If angular deformity is present in both planes, then an oblique plane deformity is present and should be graphically interpreted/calculated
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15
Q

What is the direction of the CORA in relation to the deviation of the bone?

A

Plane of the CORA is always in the direction opposite to the direction that the bone is deviated

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16
Q

What is meant by a biapical, partially compensated deformity?

A

The effected bone has 2 CORAs in opposite planes

17
Q

How many antebrachial deformities are biapical in chondrodystrophic dogs as apposed to non-chondrodystrophic dogs?

A
  • 80% biapical and chondrodystropic dogs
  • 56% biapical in non-chondrodystrophic dogs

Biapical deformities are more likely to have pathology effecting the elbow, carpus or both

18
Q

How do you calculate oblique plane deformities?

A

Graphically!
- Draw a representation of the cross section of the bone at the CORA
- Vectors representing the magnitide and plane of the frontal and sagittal deformities are drawn, with deg changed to mm, originating in the centre of the bone
- Resolution of the vectors allows a derivation of the resulting vector whose angular position defines the plane and length represents the magnitude

19
Q

What are Paley’s rules os osteotomies?

A
  • Osteotomy rule 1: When osteotomy and ACA are based on the CORA, angular correction and colinearity are achieved
  • Osteotomy rule 2: When the ACA is based on the CORA but the osteotomy is executed at a level different from the ACA-CORA, translation is required to achieve angular correction and colinearity
  • Osteotomy rule 3: When osteotomy and ACA are completed at a level different from the CORA, angulation is corrected with undesireable translation. Should be avoided

ACA = angulation correction axis (“Hinge” point)

20
Q

What forms of osteotomies can be performed for ALD correction?

A
  • Opening wedge osteotomy
  • Closing wedge osteotomy
  • Radial (cylindrical) osteotomies
  • Dome osteotomies