Diagnostic Imaging - Bone

Question 1

What must be evaluated on radiograph before interpreting a radiograph of limbs?

Answer 1

Exposure/processing.
POSITIONING.

Question 2

Points for evaluation of a limb radiograph.

Answer 2

Soft tissues.
Alignment.
Cortices.
Medulla.
Articular surfaces.
Immature animals.

Question 3

What to look for w/ regards to soft tissues when interpreting radiographs of limbs.

Answer 3

Swelling.
Joint effusion (cannot be differentiated from the ST structures around it - except stifle).
Muscle wastage.
Foreign material.
Gas.
Some tissues may mineralise as a result of chronicity.

Question 4

How can stifle effusion be identified on radiograph.

Answer 4

Positioning of the caudal fascial planes helps know of effusion present - get pushed back if effusion present.
Size of cranial fat pad helps know of effusion present - if fat pad smaller, effusion present, as compressed.

Question 5

Bone alignment.

Answer 5

Check alignment of bone w/ adjacent bones.
Look for any alteration of normal relationship.
Positioning can alter appearance.
Use orthogonal views.

Question 6

Normal stifle alignment.

Answer 6

Intercondylar eminences of the tibia should meet femoral condyles.

Question 7

Stifle alignment w/ cruciate rupture?

Answer 7

Tibia can move forwards and the midpoint of condyle does not make contact w/ the tibia.

Question 8

Evaluating cortices of bone on radiograph?

Answer 8

Outline - overall shape of bone.
Continuous cortex? - nutrient foramen and not fracture.
Thickness - even?.
Periosteal surface - abnormal prominence or irregularity e,g, sequestra and infection?
Endosteal surface (internal).
- changes less easy to see.

Question 9

Evaluating the medulla of the bone on radiography?

Answer 9

Assess integrity of trabecular pattern.
Changes in opacity:
- may be no visible medullary pattern in mid-diaphysis of long bones due to bone marrow being ST opacity, not mineralised.

Question 10

Panosteitis.

Answer 10

Self-limiting disease.
Usually <12m old.
- reported up to 7yrs.
Large breeds esp. GSD.
Affects long bones.
Typically shifting lameness.
May be mistaken for joint pain.
Area of increased opacity in medulla on radiograph.

Question 11

Assessing articular surfaces on radiography.

Answer 11

Contours of surfaces.
Subchondral bone.
- opacity – increase = arthritic.
– decrease = osteochondrosis?
- defects present – osteochondrosis (osteochondritis dissecans if flap)?
Congruity.
- expect surfaces to meet appropriately.

Question 12

Evaluation of immature animal bone on radiography.

Answer 12

Open physes.
Do not mistake for fractures.
BUT physeal fractures are common.
Look for alignment, physeal line width, comparison to normal, alter positioning for radiograph to gauge the level of possible displacement.

Question 13

What condition may be bilateral?

Answer 13

Osteochondrosis.

Question 14

Response of bone to injury / disease.

Answer 14

Bone loss.
Bone production.
Often combination.

Question 15

Bone loss on radiography.

Answer 15

Overall opacity reduces relative to STs.
Thinning of cortices.
Loss/thinning medullary trabeculae.
Need approx. 40% mineral loss before radiographically apparent.
- cannot identify subtle or early changes radiographically.

Question 16

Causes of bone loss.

Answer 16

Multi/focal.
- infection - e.g. cat bite.
- neoplasia - important to differentiate aggressive form benign.
– can look moth-eaten.
- trauma.
- infarction.
*infection and neoplasia are difficult to differentiate radiographically.
Diffuse:
- disuse.
- nutritional / metabolic
– can be caused by hyperparathyroidism.

Question 17

Causes of bone production.

Answer 17

Trauma - fracture healing.
Neoplasia.
Infection.
(Miscellaneous).

Question 18

Assessing bone production on radiograph.

Answer 18

Distribution / character may indicate cause.
- pattern.
– e.g. smooth (benign/chronic) vs spicular (active/aggressive).
- margination and transition to normal bone.
– long ‘zone of transition’ w/ aggressive lesions.
Bone vs ST tissue mineralisation?
- trabecular structure / location distinguishes bone from dystrophic calcification of STs.
- different projections and views can help.
Benign vs aggressive informs plan going forward.

Question 19

Craniomandibular osteopathy.

Answer 19

Terrier breeds.
Innature.
New bone on:
- mandible.
- tympanic bullae.
- calvarium.
Aetiology unknown.
Colloquially known as ‘Lion Jaw’.
Self-limiting – as reach skeletal maturity, will remodel.
Only likely to be clinical if involving bullae and spreads to impinge on the temporomandibular joint.
- rare.
- can cause some pain due to active nature of the bone.

Question 20

Hypertrophic osteopathy.

Answer 20

New bone production on limb in response to a space-occupying lesion in the thorax or abdomen.
Thought to be due to mediators released by primary lesion that affect blood supply to periosteum.
Patients often present with signs related to primary lesion but occasionally get presented because swollen limb.
Tends to affect surfaces of bone that face away from midline.
Tends to start distally and grow proximally.
Investigate thorax and abdomen.

Question 21

Calcinosis circumscripta.

Answer 21

ST mineralisation on ‘pressure points.
Often close to joints.
ST swelling and discomfort.

Question 22

Classifying fractures.

Answer 22

Orientation:
- e.g. transverse, oblique, spiral.
Number and position of fragments:
- simple vs comminuted.
- distracted, impacted, overriding.
?Involvement of growth plates:
- Salter-Harris classification.
?Involvement of articular surfaces:

Question 23

Assessing fractures on radiographs.

Answer 23

Check STs:
- open/closed.
- swelling.
Position:
- describe distal part relative to proximal part.
Consider age of fracture.
- what the owner reports vs what the radiograph indicates.

Question 24

Fracture aging.

Answer 24

Recent - end are well-defined.
7-10 days - rounder, less well-defined ends, cortices may be a little thinner.
10-14 days - periosteal new bone.
4-6wks - bony union (under optimal conditions). Generally time of post op fracture repair radiographs.
Remodelling thereafter.

Question 25

Luxations/subluxations.

Answer 25

Luxation = complete separation.
Subluxation = partial contact.
Can be traumatic or congenital.
Common in hips.

Question 26

Nutritional secondary hyperparathyroidism.

Answer 26

Low calcium or high phosphorus in diet.
Increased parathyroid hormone.
Mineral loss from bone.
Generalised decrease in bone opacity.
Thin cortices.
Pathological complete or folding fractures.
Normal growth plates.
Hormonal so affects all bones.

Question 27

Renal secondary hyperparathyroidism.

Answer 27

Due to chronic renal failure.
Similar radiographic appearance.
Skull most affected - rubber jaw.
– mandibles lose calcium and become soft.
Usually older animals.
- but animals born with dysplastic kidneys could be affected younger.
Radiographically, reduced opacity of the jaw.
Teeth described to be floating as not really well mineralised bone surrounding them.

Question 28

Rickets.

Answer 28

Rare now except exotics.
- husbandry-related.
Lack of vit D or Ca:P imbalance.
Radiological features:
- wide physes.
– esp. distal radius/ulna.
- flared metaphyses.
- overall mineralisation often normal.

Question 29

Hypervitaminosis A.

Answer 29

Excess vit A (liver diet).
Periosteal new bone.
- cervical spine.
- rest of spine.
- limb joints.
Can cause fusion.
Remodel but do not resolve when diet corrected.