Chapter 47 Principles of Angular Limb Deformity Flashcards
CORA
Center of rotation of angulation. A method of planning and correcting deformities. Also creates a library of normal values, but do not apply to all breeds.
joint orientation angle
the intersection of an axis and a joint orientation line. Defines the relationship of the joint to the rest of the bone.
deformities can occur in one of three planes: _____, _____, and _______. A deformity is described in terms of the relationship of the _____ portion of the bone or joint to the more proximal portion of the same structure.
deformities can occur in one of three planes: frontal, sagittal, and transverse. A deformity is described in terms of the relationship of the distal portion of the bone or joint to the more proximal portion of the same structure.
frontal plane (cranial to caudal radiographs) evaluate ____ and _____ deformities
varus and valgus
sagittal plane (lateral to medial radiographs) evaluate _____ and ______ deformities
procurvatum (cranial bowing) and recurvatum (caudal bowing).
Transverse plane (CTimaging) is used to evaluate _____ deformities
torsional
anatomic axis
a line that passes through the center or mid-diaphysis of the bone in the frontal or sagittal plane. If the bone is straight, only one line will be centered (canine radius in frontal plane) when the bone is curved, multiple straight lines are created (canine radius in sagittal plane).
mechanical axis
a straight line that connects the center points of the joints proximal and distal to the bone in the frontal or sagittal plane. Used for bones with curvature. AKA weight bearing axis of the bone (canine tibia in frontal plane)
joint orientation line
represents the orientation of a joint in a particular plane. The line is determined by selecting two specific bone-specific anatomic landmarks on each joint surface that are repeatable from bone to bone in a specific plane.
joint orientation angle nomenclature:
aLDFA
mMPTA
anatomic axis, lateral, distal, femoral angle
mechanical axis, medial, proximal, tibial angle
Humerus
mechanical axis -
joint orientation line -
mLDHA -
best fit oval is centered over the humeral head and the center of the oval is determined. Then a line is drawn between this point and a point at the center of the humeral condyle.
- drawn from the distolateral most aspect of the distomedial most aspect of the humeral condyle
= 87.3 +/-2.9 degrees (large breed dogs)
Radiographs (elbow straight) for planning should be aligned with no appearance of the ____or _____surfaces of the ____process and the distance from the medial epicondyle to the medial cortex of the olecranon equivalent to ____% of the transcondylar distance.
Radiographs for planning should be aligned with no appearance of the medial or lateral surfaces of the anconeal process and the distance from the medial epicondyle to the medial cortex of the olecranon equivalent to 45% of the transcondylar distance.
radius - predominant weight bearing bone of the antebrachium and provides the largest articular surface for both the elbow joint and carpal joint.
Frontal plane: anatomic axis - proximal joint orientation line - distal joint orientation line - aMPRA aLDRA
Sagittal plane: anatomic axis - proximal joint orientation line - distal joint orientation line - aCdPRA aCdDRA Procurvatum
Frontal plane:
anatomic axis - drawn by connecting three points with a best-fit line that bisects the radius at levels witin the metaphyses and mid-diaphysis.
proximal joint orientation line - proximolateral edge of the radial head and the medial portion of the coronoid process
distal joint orientation line - lateral most aspect of the articular surface and the medial aspect of the articular surface.
aMPRA = 83 (81.7 - 83.3)
aLDRA = 86 (85.1 - 86.9)
Sagittal plane: radius has procurvatum. radiographs should be performed to have concentric circles of the medial and lateral condyle overlapping.
anatomic axis - two independent lines (proximal and distal). The intersection (θ) is within the cortical confines of the bone and is quantifiable.
proximal joint orientation line - proximal extent of the cranial and caudal aspects of the radial head.
distal joint orientation line - cranial and caudal aspects of the radial articular surface
aCdPRA = 85 (84.1 - 86.1)
aCdDRA = 77 (75.9-78.0)
Procurvatum = 27 (21.3 - 31.8)
procurvatum measurement for the radius
(90 degrees - aCdPRA) + (90 degrees - aCdDRA) + θ
Femur Frontal plane: anatomic axis - mechanical axis - proximal joint orientation line - distal joint orientation line - aLDFA aLPFA mLDFA mLPFA
Frontal plane:
anatomic axis - determine by a line that connects points selected 33% and 50% below the proximal aspect of the femoral neck in the middle of the femur.
mechanical axis - determined by a line that runs from the center of the femoral head to the center of the distal femoral joint orientation line.
proximal joint orientation line - runs from the center of the femoral head to the dorsal-most aspect of the greater trochanter of the femur.
distal joint orientation line - line that just touches the distal-most aspect of the lateral and medial femoral condyles.
aLDFA 94-98 (breed dependent)
aLPFA 96-103
mLDFA 97-100
mLPFA 93-100
Inclination angle of the femoral head and neck -
measured from the frontal plane radiographs and is the angle formed by the proximal femoral anatomic axis and a line that bisects the femoral neck. 132-137 (breed dependent)
coxa vara
decreased angle of inclination
coxa valga
increased angle of inclination
anteversion angle -
the angle between the neck and frontal plane as described by the caudal aspect of the femoral condyles. A line is drawn from the center of the femoral head to a point that bisects the femoral neck. Then a second line is drawn so that it just touches the caudal aspect of the femoral condyles. The intersection of these two points is the anteversion angle.
16-30.8 (breed dependent)
Tibia Frontal plane: mechanical axis - proximal joint orientation line - distal joint orientation line - mMPTA mMDTA
Sagittal plane: mechanical axis - proximal joint orientation line - distal joint orientation line - mCdPTA mCrDTA
Frontal plane:
mechanical axis - (used because of the sigmoid shape of the tibia in the frontal plane). Defined by a point in the center of the proximal-most aspect of the intercondylar fossa of the femur and the most distal point of the subchondral bone of the distal intermediate tibial ridge.
proximal joint orientation line - distal points of the subchondral bone concavities of the medial and lateral tibial condyles
distal joint orientation line - most proximal points of the subchondral bone of the two arciform grooves of the cochlear tibiae
mMPTA 93
mMDTA 96
Sagittal plane:
mechanical axis - midpoint between the apices of the two tibial intercondylar eminences and the center of the circle created by the talus.
proximal joint orientation line - cranial and caudal aspect of the medial tibial condyle
distal joint orientation line - distal aspect of the distal intermediate ridge of the tibia cranially and the caudodistal aspect of the cochlea tibia caudally.
mCdPTA 64
mCrDTA 82
Tibial slope (proximal tibial angle) tibial plateau angle
the reciprocal angle to the mCdPTA 24-26 degrees
principle of imaging for CORA deformity correction planning
i. _____of the limb is key to obtaining usable radiographic views.
ii. _____ in excess of 15 degrees results in a greater than 5 degree miscalculation of frontal plane deformities if planning is based on standard orthogonal radiographic views.
iii. CT examination and _____ (3-D printing) is useful in correctly planning and executing surgical corrections
i. Positioning of the limb is key to obtaining usable radiographic views.
ii. Torsion in excess of 15 degrees results in a greater than 5 degree miscalculation of frontal plane deformities if planning is based on standard orthogonal radiographic views.
iii. CT examination and stereolithography (3-D printing) is useful in correctly planning and executing surgical corrections
Steps to define CORA
- Step 1: the joint orientation lines, axes, and intersecting joint orientation angles are measured and recorded for normal bone in the frontal and sagittal planes, as previously described
- Step 2: the joint orientation lines are determined for affected bone in both frontal and sagittal planes
- Step 3: Using the joint orientation lines as a starting point on the affected bone, the axes are determined based on joint orientation angles in the frontal and sagittal planes, as obtained from the normal side or from the library of reference values
- Step 4: determine where the axes intersect within the cortical confines of the bone in the two planes. This demarcates the location of the CORA. Measure the angular magnitude and location of this CORA. The magnitude of the CORA equates to the degree of correction required to eliminate the deformity.
- Step 5: If angulation is apparent in both orthogonal planes, then an oblique plane deformity is present. It is necessary to determine the plane of the deformity. This can be done by using a graphical interpretation of oblique plane analysis, as discussed in the next section
The plane of the CORA is always in the direction _________of how the bone is deviated.
opposite
- Frontal plane deformity that has resulted in valgus (lateral deviation of the distal aspect of the bone), the plane of deformity is medial.
- If excessive procurvatum and valgus then the plane of deformity will be oriented between cranial and medial. “The distal aspect of the limb is angled caudal and therefore the CORA is cranial”