Appendicular Skeleton
The appendicular skeleton is formed by:
- Pectoral girdles
- Upper limbs
- Pelvic girdle
- Lower limbs
Axial Skeleton
The axial skeleton is formed by:
- Vertebral column
- Rib cage (12 pairs of ribs and the sternum)
- Skull
Tympanic bullae
Circular structure behind zygomatic arch
Chronic external ear infections extend into middle ear here
Most important imaging reason for skull x-rays
If only interested in one bulla, turn head 45 degrees oblique (take two views from both sides)
Lateral Projection of Skull
Medial-Lateral
Need foam/rubber wedges
Canines, ramus of mandible line up - no obliquety
Lateral View of Skull
Centers/Measures:
- TMJ: Joint/Zygoma
- Bullae: Over/Zygoma
- Nares: Rostral to canthi
Keep nose from falling/skull from twisting; use foamy wedge, if needed!
DV Skull
**Centers/Measures:
TMJ: Rostral to ears
Bullae: Base of ears
Nares: Rostral to ears
Teeth & Nares more rostral
**To imagine/pre-visualize:
Imagine that hard palate is parallel to table top
(for VD projection skull will be extended until hard palate is parallel with table top)
Note: Both projections yield superimposition of the mandibular rami over some anatomy (but not the calvarium)
Rostro-caudal closed mouth
Skyline to profile the frontal sinuses (looking for fluid)
Measure: midpoint at level of eyes
Center: between eyes
Zero degree oblique
Technician’s trick for frontal 90* rostro-caudal closed mouth
Use the calipers as an alignment tool to visualize skull as parallel to table top
Ventral-Caudal Dorsal Closed Mouth 10* oblique
“Bullae shot”
This view is to profile the air-filled tympanic bullae
This view is preferred for cats and brachycephalic dogs
Rostrocaudal Open Mouth 10* Oblique
This view is for tympanic bullae in dogs with normal shaped skulls
Watch for airway security when ET tube is removed!
Secure tongue to mandible!
Rostrocaudal 30* Oblique Closed Mouth
This view is to profile the size & shape of the foramen magnum for a congenital defect.
These pets are usually small poodles and may be neurologically impaired.
How many cervical vertebrae in all mammalian spp?
7 (from giraffe to mouse)
Lateral Cervical Spine
Centering: C3-C4 intervertebral space
Landmark: Wings of atlas
**Positioning:
In lateral recumbency
Ensure collar removed
Use foam/sponges to ensure entire cervical spine is lateral
Extend forelimb caudally (ensuring this doesn’t rotate the thorax)
Neck in a neutral position
Center over 3-4th cervical vertebrae
Collimate to include the base of the skull and T2
Ensure L/R marker in primary beam.
**What to look for:
Ensure transverse processes overly each other (left and right)
**Top tips:
Padding under the dogs chin can often help prevent the skull rotating.
Lateral Projection of T-L Spine
Use palpation to find last rib and center at T-L
**Positioning
In lateral recumbency
Ensure spine parallel to cassette/table top
Use sponges under sternum to prevent rotation
Centre over T6-T7
Collimate to include entire thoracic spine, including spinous processes
Ensure L/R marker in primary beam.
**What to look for
Ensure no rotation of the spine - look to see if transverse processes are superimposed.
**Top tips
Avoid extending limbs too far cranially/caudally as can cause spine to distort
A pad between the hindlimbs can reduce the risk of rotation.
Ventral Dorsal of T-L Spine
**Positioning
Dorsal recumbency
Use cradle under thorax, sandbags under hips
Extend thoracic limbs cranially, pelvic limbs caudally
Centre over L3-midway between lower costal margin and iliac crests, in the midline
Collimate to include entire lumbar spine, and sacroiliac joints
Ensure L/R marker in primary beam.
**What to look for
Ensure not rotated - transverse processes should be the same size
Avoid having cradle under area of interest due to risk of artifact.
**Top tips
If limbs extended too far this can cause the spine to arch, making the joint spaces narrower.
Quality of spinal positioning?
Lateral View
- Rib heads are superimposed
- Intervertebral foramina are the same size
- Transverse processes are superimposed at the origin from vertebral bodies
- Coxofemoral joints are superimposed
Ventrodorsal View
- Spinous processes are aligned in the center of the vertebral bodies
- Rib and abdominal symmetry
- Wings of the ilium are symmetrical
- Obturator foramina are symmetrical
Lumbosacral Junction & Sacroiliac Joint
VD or DV views
Might nn to administer enema first
Lumbosacral joint is where pelvis meets spine
There are a lot of motor nerves in the sacrum
**Positioning
Position in dorsal recumbency
Use a cradle under thoracic spine
Hind limbs in a neutral position
Centre over L-S Junction- just below the iliac crests, in the midline
Collimate to include the lumbosacral spine
Ensure L/R marker in primary beam.
**What to look for
Ensure pelvis not rotated.
**Top tips
Foam pads under the pelvis can help prevent rotation.
Coxofemoral (Hips)
Canine Hip Dysplasia
Starts w/puppyhood
Polygenic = many genes influence final outcome
Doesn’t seem to affect greyhounds
**Presentation:
- Tight hips
- Painful
- Crying
- Bunny hopping
- Good & bad days
- Chronic
- Sits funny
What does OFA stand for?
Orthopedic Foundation for Animals
A panel of specialists evaluate hip radiographs and give a grading (mainly used by breeders and show people)
VD Pelvis/Coxofemoral Joints
No enema needed
Parallel everything equally (straight up and down)
All of upper pelvis, all of patellas
Foramina equal?
**Positioning
Dorsal recumbency
Dog ideally in a trough
Fully extend the hind legs and adduct, so the femurs lie parallel to each other and parallel to the film/cassette
The legs should be rotated inwards, patellae central - over the trochlear grooves
Align the tail straight between the thighs
Center in the midline, over the level of the cranial edge of the pubis, directly between the femoral heads
Use ties and tape to retain this position
Ensure left or right marker is visible.
**What to look for
Both patellae should be central to the trochlear grooves, and the iliac crests and hips should appear symmetrical.
**Top tips
If the pelvis appears to be rotated this can be corrected by lifting the hip on the side which appears to have a smaller obturator foramen.
OFA Extended Hip Positioning
Adducting the hip joints
Penn Hip Certification
PennHIP stands for University of Pennsylvania Hip Improvement Program
“Penn” is a system developed at University of Pennsylvania with an objective to assess hip joint laxity
Hip laxity is compared to a breed specific data base
Conclusion is how much laxity does this individual demonstrate versus the statistical mean of the breed
10 hours of instruction to radiographers
PennHip Distraction Projection Laxity Index
A ratio between the physical position of the resting position CF joint vs the distracted joint
“Frog leg view”
Animal in dorsal recumbency
Drive hips as much as possible into acetabulum
Drive hips as little as possible away from acetabulum
Hip certification is based on calculation of the distraction index (dividing one number into another)
How to position a dog with PennHip distractor
What does PennHip distractor do to hip position?
PennHip Distractor Assembly
