Principles of ALD Correction Flashcards
What are the two types of bone axis which can be used when calculating ALD
Anatomical and mechanical
How are joint orientation lines notated?
- 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
What are the joint orientation line landmarks for the humerus?
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
What are the joint orientation line landmarks for the radius?
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 aspectf of radius articular surface
How do you measure procurvatum?
(90deg - aCdPRA) + (90deg - aCdDRA) + # = overall procurvatum
# is angle of intersection of the anatomical axis
What is the mean radius joint orientation angle and procurvatum angles?
What are the anatomical landmarks for joint orientation lines of the femur?
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
What are the mean femoral orientation lines?
What is the mean femoral inclincation angle in Labs, Goldens, GSDs and Rottweilers?
What is the range of reported anteversion angles?
What are the anatomical landmarks for the joint orientation lines of the tibia?
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
What are the mean tibial joint orientation angles?
How do torsional deformities effect surgical planning on radiographs?
Much more challenging
- Torsional deformity above 15deg results in greater than 5deg miscalculation of deformities in frontal plane
What are the steps to determining the three components of the CORA (location, plane and magnitude)
- 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
What is the direction of the CORA in relation to the deviation of the bone?
Plane of the CORA is always in the direction opposite to the direction that the bone is deviated
How do you calculate oblique plane deformities?
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
What are Paley’s rules os osteotomies?
- 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)
