Ch 46 ALD Flashcards
What are the two types of bone axis which can be used when calculating ALD
Anatomical and mechanical
frontal plane
examined from a cranial-to-caudal radiographic image and is used to evaluate for valgus or varus deformity (lateral or medial deviation, respectively).
sagittal plane
assessed from a lateral-to-medial radiographic image and is used to evaluate for procurvatum (cranial bowing) and recurvatum (caudal bowing).
transverse plane
studied from an image obtained with the beam directed axially along the bone and is used to evaluate for torsional deformity
The summation of the aLDFA and the aMDFA will always equal 180 degrees. Thus, the measurement of one angle will allow the immediate calculation of the other by simply subtracting it from 180. When joint orientation angles are reported for human extremities, it is common to use the acute value. This method has not been followed as closely in the reporting of canine values, and whereas the aMPRA (acute) is a more frequently cited value for the radius, when examining the femur, the aLDFA (obtuse) is more popularly discussed.
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?
77-86
procurvTUM: 27
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?
94-101
What is the mean femoral inclincation angle in Labs, Goldens, GSDs and Rottweilers?
134-137
What is the range of reported anteversion angles?
~30
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
what is CORA?
The CORA of an angular limb deformity is essentially the apex of the deformity. A bone is not limited to a single CORA and may possess multiple CORAs. Each CORA has a location, plane, and magnitude
The Transverse Bisecting Line
The CORA has been defined as the point of intersection of the axes of two segments of bone that are angled relative to one another. However, this point is more accurately referred to as a neutral CORA
mediolateral pair is bisected with a straight line that runs through the CORA, called the transverse bisecting line, which, similar to any line in geometry, is composed of an infinite number of points. Each point is actually a CORA. The points along this line on the convex side of the neutral CORA are referred to as opening CORAs, and those on the concave side are defined as closing CORA
What is meant by a biapical, partially compensated deformity?
The effected bone has 2 CORAs in opposite planes
Classification System of Angular Limb Deformities
direction of angulation in each of the planes (varus and valgus for the frontal plane, procurvatum and recurvatum for the sagittal plane, and internal and external torsion for the transverse plane)
single CORA is called a uniapical deformity, an affected bone with two CORAs is referred to as a biapical deformity, and if more than two CORAs exist, the deformity is considered to be multiapical.
CORAs with planes that are in opposite directions, which is called partially compensated because the joints are somewhat parallel despite the fact that the bone possesses a large translation .
When the planes of the two deformities are in the same direction, resulting in a magnification of angulation the deformity is designated as noncompensated.
biapical, partially compensated radial deformity with a proximal varus and distal valgus and concurrent procurvatum and external torsion
How many antebrachial deformities are biapical in chondrodystrophic dogs as apposed to non-chondrodystrophic dogs?
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
Deformity Types Based on Plane
translational deformity
Combination of frontal and sagittal plane angulation
Oblique plane deformities. It is interesting to note that an oblique plane deformity can be assessed radiographically by capturing a view of the affected bone perpendicular to the plane of the deformity,
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 of osteotomies?
example of the second rule is the tibial plateau leveling osteotomy,
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)
angulation correction axis
hinge point on which rotation of two segments of bone can be made; it is under the control of the surgeon.
is an axis and thus is represented by a line around which the angular correction will be completed.
axis always possesses a perpendicular relationship to the plane of the deformity
Straight-Cut or Linear Osteotomies
open wedge
Opening wedge osteotomy
- opening CORA (on the convex surface of the bone) is used as hinge point
- when the bone segments are reangulated, the osteotomy opens
- advantages include their versatility and ease of completion
- some bone lengthening will occur
- less stable configuration
- consider locking plate, bridging required
closing wedge
Closing wedge osteotomy
- basing the ACA on a closing CORA on the concave surface
- requiring the removal of a wedge-shaped piece of bone
- Bone shortening occurs
- bone plates and screws because load sharing can be achieved.
Radial (cylindrical) osteotomies
Radial (cylindrical) osteotomies
- only rules 2 and 3 truly apply to their execution.
- involve basing the ACA-CORA at the center of the proposed cylindrical cut, and the actual osteotomy will be offset from the angulation correction axis-CORA by the radius of the arced saw blade
- bone will be realigned via the second rule of osteotomies
- versatility without the need for additional cuts to be made
- maintenance of bone length,
- apposition
- excellent resistance to shearing loads.
- disadvantage: completed only in a single plane.
Dome osteotomies
Dome osteotomies
- cut a true spherical dome
- correct deformities in three planes. Thus, torsion angulation deformities can potentially be corrected with the completion of a single cut.
- Limitations as blade must be size-matched with the bone in the widest dimension, which results in size mismatching in the sagittal plane
Methods of fixation - bone plate
Bone Plates and Screws
- reserved for skeletally mature animals in order to provide an acute, definitive correction
- Good to excellent results with minimal complications have been reported
- sufficient bone must be present proximal and distal for adequate number of screws.
- closing wedge ostectomy is performed to maximize reduction of the bone segments
- return to function faster.
- Plate fixation requires less intensive postoperative care
- locking screw and plate technology makes exact contouring less critical.
- multiapical deformities may possess severe degrees of soft tissue contracture that cannot be stretched acutely and thus may be more amenable to gradual correction
- gain more area for screw placement, Paley’s second rule of osteotomies may be employed,
Methods of fixation - ESF
- placed farther from the neutral axis of the bone, and thus are at a mechanical disadvantage compared with internal fixation
- opening wedge osteotomies can minimize surgical invasiveness, allow correctional versatility, and provide the opportunity for bone lengthening.
- circular external skeletal fixators concluded that long-term function and cosmesis were good to excellent despite frequent complications.
- small fixation wires, circular external skeletal fixators can be used when only small segments of bone are available proximal or distal to the osteotomy, as seen with juxta-articular deformities
- angulation correction axis can be established with the hinge axis of the designed frame.
- allow gradual correction with the use of an angular motor, positioned on the side opposite the hinge axis, along the CORA plane
- soft tissues are able to stretch, and the regenerative response of the bone occurs via properties of distraction osteogenesis
- study: frame construction was completed preoperatively utilizing polymer replicas from CT reconstructions
- an be designed to accomplish axial elongation
- Substantial wound and apparatus care is required postoperatively
Pes varus correction in dachshunds with mini hybrid external skeletal
fixators
L Chau 2022
cute
medial opening wedge osteotomy, IMEX mini HESF
All osteotomies healed
and fixators were removed between 6 and 12 weeks.
Lameness resolved in 18 dachshunds (90%)
Lateral patella luxation (LPL) 39.2% , all of which resolved
following correction.
Accuracy of virtual surgical planning
and custom three-dimensionally printed osteotomy
and reduction guides for acute uni- and biapical
correction of antebrachial deformities in dogs
De Armond 2022
11 dogs
Guides were abandoned in 2 deformities due to soft tissue tension
over 90% of parameters were within the acceptable range of ≤ 5° angulation and rotation or ≤ 5 mm of translation from the VSP. Lameness scores were improved in 7/8 deformities
Complications included reduced range of carpal motion (n = 2), implant sensitivity (n = 2), fracture (n = 1), and tendon laceration (n = 1).
facilitated accurate antebrachial limb deformity correction in the majority of deformities in this case series.
A systematic review found that AM implants resulted in reduced surgery time, increased accuracy, and improved outcomes in humans
Hemiepiphysiodesis for the Correction of Distal
Femoral Valgus in Growing Dogs
Luca Vezzoni 2022
published reference range 94 degrees
its effect on
the anatomical lateral distal femoral angle (aLDFA).
total of 11 dogs
The mean difference between the preoperative and final aLDFA was 11 degrees, which was
significant.
Undercorrection occurred in 2/17 cases, whereas overcorrection was not
recorded.
The implants were removed in 12/17 cases, and rebound growth occurred in 3 of these.
Monitoring for possible overcorrection using
serial radiography is important. Implant removal when the desired aLDFA has been
achieved is recommended because the incidence of rebound growth is uncommon
The age of the animal at the time of hemiepiphysiodesis
influences the success of the procedure. Residual growth is
one of themost important factors to consider when performing
hemiepiphysiodesis and can result in undercorrection,
overcorrection or rebound growth. Rebound growth is the
recurrence of the deformity after implant removal necessitating
further surgery and is not well described in veterinary
medicine
The average age of the dogs at the time of surgery in the present study was 5.3 months. Closure of the distal femoral physis occurs between 8 and 11 months of age
dogs older than 6monthswith severe valgusmay not benefit from hemiepiphysiodesis because residual growth is not sufficient
vs
suggested that undercorrection was not
related to insufficient residual growth but rather to suboptimal
implant positioning across the growth plate
Staples were shown to act as an immediate brake by inhibiting
much of the peripheral growth, whereas plates were
determined to have a latency period before acting as a
fulcrum, depending on the intrinsic elasticity of the
system
Distal femoral corrective osteotomy has been
reported in growing dogs as an effective method of restoring
bone alignment, but is considered invasive and demanding.
28,32 The advantages of hemiepiphysiodesis in growing
dogs include the less invasive nature of the surgery, low
morbidity, less-demanding postoperative care and early
return to normal limb function
Three-Dimensional-Printed Patient-Specific
Osteotomy Guides, Repositioning Guides and
Titanium Plates for Acute Correction of
Antebrachial Limb Deformities in Dogs
Carwardine 2021
Retrospective, in four dogs
All limbs were corrected to within 3.5 degrees ) and 7.5 degrees of the pre-planned deformity correction in
the frontal and sagittal planes, respectively. No complications were encountered.
The decision to add a
standard medial plate (Synthes, United States) in two of the
described caseswasmade at the time of surgery based on the
surgeons perceived construct stiffness.
facilitated accurate acute correction of antebrachial deformities in this case
series. The methodology described simplifies intraoperative surgical decision-making
on limb position with good clinical outcomes seen in a small number of clinical cases
Guidelines for the Execution of True Spherical
Osteotomies Using a Modified Dome Blade Design
Christos Nikolaou 2020
The trigonometric principles for the execution of neutral,
closing and opening spherical osteotomies were explored in silico.
Computer-Assisted Surgery Using 3D Printed
Saw Guides for Acute Correction of Antebrachial
Angular Limb Deformities in Dogs
Worth 2019
Five limbs healed without complications. One limb was re-operated due to a
poorly resolved rotational component of the deformity. One limb required additional
stabilisation with external fixation due to screw loosening
Despite the encouraging results, accurate correction of
rotational deformity was problematic and this aspect requires further development.
2/5 dogs at follow-up, most likely due to preexisting
joint deterioration.
In using computer-assisted surgery for angular limb
deformity in dogs, we hoped to achieve the benefits reported
in the human medical field. In human surgery, creation of a
cutting guide template fromamodel and surgical simulation
overcomes inaccuracy translating the rehearsal surgery to
the patient
The authors recommend
printing limb models and spare saw guides with which to
physically rehearse the surgery.
Effects of short- and long-term administration of nonsteroidal
anti-inflammatory drugs on osteotomy healing in dogs
Gallaher 2019
To determine the influence of short-term administration of carprofen on
bone healing in dogs.
Study design: Randomized controlled experimental study.
Animals: Eighteen purpose-bred sexually mature hound dogs.
Bone healing was evaluated radiographically at 4 and 8 weeks postoperatively.
Postmortem, fracture healing was assessed via biomechanical testing (threepoint
bending), histological cartilage:callus ratio, and bone mineral density (BMD)
with quantitative computed tomography
In conclusion, short-term administration of carprofen
(2 weeks) after fracture repair in dogs did not delay radiographic
healing; however, long-term administration (8 weeks)
affected biomechanical strength and radiographic healing of
the tibial osteotomy. Histological evaluation of cartilage
within the fracture callus and BMD of the fracture callus provided
inadequate assessments of bone healing 8 weeks postosteotomy
in our model
Radiographic healing scores did not differ between dogs that
did not receive carprofen and those that received 2 weeks of
carprofen, both of which were superior to the scores received
by dogs treated with 8 weeks of carprofen
The RUST was created by physicians42 to
improve the reliability of traumatologists’ fracture healing
assessment and has shown substantial ICC of 0.86 (95%
confidence interval [CI], 0.79–0.91) and high intraobserver
reliability (ICC, 0.88; 95% CI, 0.80–0.96). A
Early elevation
in PGE is consistent with a role in bone healing. In the same
study,27 PGE2 levels rebounded higher compared with those
in control rats 14 days after initial fracture when a nonspecific
or COX-2 specific NSAID was administered for
7 days, further validating a role of PGE2 during the early
phases of bone healing.
Automated computation of femoral angles in dogs from
three-dimensional computed tomography reconstructions:
Comparison with manual techniques
F. Longoa 2018
22 femurs obtained from 16 cadavers
three manual radiography,
manual CT reconstructions and the aCAD method for the measurement of three femoral angles were
evaluated: (1) anatomical lateral distal femoral angle (aLDFA); (2) femoral neck angle (FNA); and (3)
femoral torsion angle (FTA).
Repeatability (intra-ob) and reproducibility (inter-ob) of measurements using the aCAD method were excellent for all three angles assessed, provided the highest repeatability and reproducibility among the tested methodologies.
