BSAVA MSK Flashcards
What are the 3 inherent characteristics of tissue which influence Xray absorption?
1) Density (e.g. gas has low density so poor Xray absorber)
2) Physical thickness
3) Atomic number
If there is clinical concern for a fistula/sinus contacting the epidural or subarachnoid space what type of contrast media should be used?
Non-ionic
What are 3 mechanisms of muscle atrophy?
1) Disuse
2) Neurogenic
3) Long term sequel to myositis
Describe the location and appearance of calcinosis circumscripta? What age and breed(s) are predisposed?
- Young (< 2 yo) large breed dogs [especially GSDs]
- Usually solitary, well-marginated lesions
- Stippled calcified areas
- Typical locations = distal limbs, especially over prominencies; neck and tongue
- Boston Terriers & Boxers are predisposed to cheek & pinna lesions
Calcinosis cutis occurs secondary to what underlying disease conditions?
- Cushing’s
- Primary or secondary hyperparathyroidism
Metastatic mineralization occurs secondary to what underlying disease conditions?
Pathophysiology - systemic disturbance of calcium or phosphorus levels
- CKD
- Hypervitaminosis A
- Hypervitaminosis D
What is another term for pseudogout and where does it occur?
Chondrocalcinosis or calcium pyrophosphate deposition disease (CPDD)
- mineral deposits in or around joints
What is myositis ossificans?
- Benign bone formation WITHIN striated muscle & tendon
- Can occur after major surgery, secondary to chronic disease, or idiopathic
What condition appears similar to myositis ossificans and what are the differentiating features?
- Fibrodysplasia ossificans
- Occurs in cats
- Multiple symmetrical formations of bone within the soft tissues
- DISPLACES muscle but does not actually involve it
Bone is covered by periosteum everywhere except what locations?
Wherever there is articular cartilage
Most bones in the body develop by what route? And explain the process?
Endochondral ossification
- cartilage precursor converted to bone
How do flat bones of the skull form?
Intramembranous ossification directly from connective tissue
What is the preferred location for hematogenous osteomyelitis in immature animals and why?
- Metaphysis
- rich blood supply from nutrient foramen vessels
(physis is essentially avascular b/c metaphysis and epiphysis are supplied separately)
{Epiphyseal blood mainly via joint capsule}
In mature bones where does periosteal blood supply come from?
Vestigial supply via nutrient artery as well as metaphyseal arteries
What direction is medullary blood supply to the cortex?
-Centrifugal :: cortical venous drainage via periosteum & medullary drainage via nutrient foramen
What is the characteristic location for Panosteitis?
Diaphyseal in the Medulla of long bones, often starting in region of nutrient foramen
What are the two most common locations for marked growth abnormalities to occur? (
Distal radius & ulna (greatest contributors to overall bone length)
New medullary bone matrix production may be composed of what 3 things?
1) Osteoid (e.g osteosarcoma production; ivory like opacity with osteomas)
2) Fibrous tissue (results in woven bone production with ground glass appearance)
3) Cartilaginous tissue (stippled appearance which when replaced by endochondral bone develops circular/semicircular opacities—typical of Chondrosarcoma)
What disease processes can cause bone infarction? Which locations does it occur at?
-primary malignant neoplasia such as Osteosarcoma
-Feline leukemia
- affects all or most bones distal to mid femur
What are the 6 types of periosteal reaction from least to most aggressive?
1) Solid
-opacity indicative of duration
- indicate benign slow growing processes (e.g. callus, chronic osteomyelitis, Panosteitis)
2) Lamellar (parallel)
- periosteum lifted by subperiosteal exudate, hematoma, rarely Neoplastic cells
-usually indicate benign processes
3) Lamellated (onion like)
-indicates a fairly slow process but more aggressive than the above two
-caused by repeated sequential insults (e.g. fungal osteomyelitis, malignant neoplasia)
4) Brush-like
-osteoblastic activity along vertically oriented Sharpey fibers
- if thicker/palisading reaction is less aggressive/slower growing
-thinner rxn with acute hematogenous osteomyelitis, neoplasia, hypertrophic osteopathy
5) Sunburst
-indicates highly aggressive process (e.g. OSA)
-osteoblastic Sharpey fiber activity
6) Amorphous
-NOT periosteal reaction but Neoplastic new bone formation
-periosteum destroyed
-cotton wool or candy floss appearance
Where do Codman’s triangles tend to appear/what is their orientation?
-Usually present on diaphyseal side of metaphyseal lesion
-acts as buttress for partially/totally destroyed cortex adjacent to it
Radiographically when does osteoclast activity become evident (percent of bone loss & # of days)?
-After 30-50% of bone loss
- usually 7-10 days (May only see soft tissue changes)
What is the least aggressive form of bone lysis? Describe some of its characteristics.
- Geographic bone loss
-usually slower growing lesions - common in cancellous bone at extremities
-usually a sclerotic rim (No rim —> think more aggressive e.g. multiple myeloma/metastatic bone disease) - narrow lytic area & transitional zone
Describe some characteristics of moth eaten lysis.
-multiple separate lytic foci (~2-3mm)
- typically in cortex & usually endosteal in origin
- intermediate aggressiveness
-usually involve cortical destruction
-wide transitional zone
Describe the characteristics of permeative lysis.
- most aggressive form
- 1 to 2mm poorly defined lytic areas
-cortical destruction - wide indistinct transition zone
- often see cortical scalloping/defects
What is the difference between endosteal and subperiosteal scalloping? Name a disease process associated with each.
- Endosteal scalloping results from intramedullary neoplasia (destroys more cortex near center of neoplasm)
- Subperiosteal scalloping usually associated with hematogenous osteomyelitis where exudate oozes from medulla through Volkmann’s canals to subperiosteum
What are the two main hormones involved in bone production/resorption and what are their respective MOAs?
1) PTH (parathyroid hormone) - moves calcium from skeletal reserves to ECF via increased osteoclastic activity & osteocyte-osteoblast pump
2) Calcitonin - inhibits bone resorption stimulated by PTH
What are the 3 mechanisms by which glucocorticoids affect serum calcium levels?
1) Increased renal excretion of Ca2+
2) Decreased intestinal absorption
3) Catabolic protein effect -> abnormal bone matrix
What is the basic pathophys of chondrodysplasias? What are the key radiographic features?
-Abnormal cartilage development
= slowed growth of ling bones (shorter & thicker)
=widened physes
= +- retained cartilage cores
= Epiphyseal stippling/distortion
= irregular ossification of vertebral end plates
What two dog breeds can have ocular changes associated with skeletal chondrodysplasia?
- Labrador Retrievers & Samoyeds
Describe the lesions associated with epiphyseal dysplasia? What 2 dog & 2 cat breeds are predisposed?
- Beagles & Mini Poodles
- Scottish & Highland fold cats (affects distal limbs & tails)
= delayed appearance of epiphyseal ossification centers
= ossification centers have punctuate mineralizations & stippled appearance when formed
-deformed epiphyses-> OA
Describe the characteristics of physeal chondrodysplasia? Breed predisposition?
- Endochondrodystrophy in Pointers —> disproportionate dwarfism (females > males)
= most dramatic changes in distal ulna, radial & tibial physes
-> patchy erosion of articular cartilage —> OA
-> shortened & bowed long bones - similar condition in Alaskan Malamutes but without cartilage erosion & OA (anemia present)
What dog breeds are predisposed to metaphyseal chondrodysplasia? Any key features?
- Pyrenean Mountain dogs (metaphyses of long bones & vertebrae)
-Deerhounds - Oculoskeletal dysplasia in Labradors (radius, ulna, tibia) & Samoyeds
- Hypochondroplastic dwarfism in Irish Setters (few X-ray changes - epiphyses/metaphyses/physes normal but long bones shortened & some Bowing
What are the radiographic features of osteopetrosis?
- Inc cortical bone thickness (May obliterate medullary cavity)
- Inc opacity of subchondral bone
- pathologic fx May occurs
DDX = acquired medullary sclerosis with FeLV, bone infarcts, Basenjis w/ anemia due to erythrocyte PK deficiency
What portion of the bone does hematogenous osteomyelitis tend to affect?
Metaphysis (May spread to diaphysis)
What condition in Irish Setter puppies has been described with multiple metaphyseal sites of osteomyelitis?
Leukocyte adhesion deficiency
Describe some features of osteochondromas.
-hereditary Developmental lesions (usually cease when skeletal maturity reached)
-Often benign (but can undergo malignant transformation)
- if multiple, known as multiple cartilaginous exostoses
- typical locations = metaphyses of long bones, flat bones of ribs/pelvis/vertebrae
- no evidence of bone destruction or periosteal proliferation
What are some key differences in feline osteochondromas?
- thought to viral etiology
- can be diaphyseal or metaphyseal of long bones & in flat bones
- less organized in appearance
-often develop AFTER skeletal maturity & continue to grow
What 3 bones are often show more dramatic changes in immature dogs with metabolic disorders?
-Distal radius
-ulna
-tibia
Describe radiographic appearance of metabolic disorders.
- Decreased overall bone opacity
- Reduction in cortical thickness -> double cortical line (due to intracortical resorption)
-Pathologic fractures (often folding or compression) - loss of normal zone of provisional calcification on metaphyseal side of physis
- abnormal metaphyseal flaring/ trabecular changes
Radiographic features of nutritional secondary hyperparathyroidism.
- Dec bone opacity
- cortical thinking of long bones
- Double cortical line (intracortical bone resorption)
- pelvic/spine changes
- multiple folding/compression fx
- NORMAL PHYSES
What is a key distinguishing feature in renal secondary hyperparathyroidism?
Striking skull abnormalities
- can give rise to osteopetrosis instead of osteopenia (vitamin D deficiency b/c kidneys cannot metabolize/activate vitamin D)
What are the radiographic features of Rickets?
-vitamin D deficiency (e.g. congenital renal or hepatic enzyme deficiency)
- marked physeal widening
- flared metaphyses with beaked margins
- No zone of provisional calcification
- reduced skeletal mineralization & thin cortices (Dec intestinal calcium absorption)
What dog breed in predisposed to congenital hypothyroidism?
Boxers
What are the radiographic features of congenital hypothyroidism?
- delayed & irregular epiphyseal ossification
- delayed physeal closure
- thickened radial/ulnar cortices
-radial bowing
Describe the MOA of pituitary dwarfism, radiographic features, & breed predisposition.
- GSDs
- inadequate GH production +- concurrent hypothyroidism
- CHARACTERISTIC proportionate dwarfism (helps to differentiate it from other inherited or metabolic forms of dwarfism)
- delayed epiphyseal ossification center appearance
- incomplete epiphyseal ossification
- delayed physeal closure
What are the radiographic features of hypervitaminosis A?
- most often seen in adult cats
-shortened long bones
-premature physeal closure - metaphyseal perisoteal proliferation
-periarticular osteophytes
-pathologic fx
What dogs are most commonly affected with bone cysts?
Young male large breed, especially Dobermans & GSDs
-most common in long bones
Aneurysmal bone cysts are seen in what demographic of dog & what are they usually associated with?
Older animals
- usually regional vascular anomaly
-typical “soap bubble” appearance (blood filled compartments)
-can undergo malignant transformation
What is another rare tumor that may mimic a bone cyst?
Osteoclastoma
-generally older animals than with bone cysts
- primarily metaphyseal but tend to extend into epiphysis (bone cysts restricted to metaphysis/diaphysis)
-Giant cell tumor
- distal ulna
- multiloculated septate appearance
What 2 dog breeds may be predisposed to metaphyseal osteopathy?
Great Danes & Weimaraners
Where do osseous lesions of histoplasmosis tend to occur?
Metaphyseal regions adjacent to carpi & tarsi
Describe the key osseous features of Leishmania.
-mixed lytic & proliferative
- occasionally polyostotic
- in long bones, most common pattern is diaphyseal periosteal & intramedullary proliferation (related to nutrient foramen)
What dog breeds are predisposed to Craniomandibular osteopathy?
-West Highland White Terriers
- Scottish Terriers
-Cairn terriers
(Lesions regress once skeletal maturity reached)
What dog breed is predisposed to Chondrosarcoma?
Golden Retrievers
Describe the key osseous features of blastomycosis?
-majority of lesions are solitary
- most occur distal to stifle & elbow
- bone involvement in ~30% of cases
Where do chondrosarcomas tend to occur?
Flat bones ( pelvis, scapula, skull, ribs)
- Only 14% of cases go to long bones
Which monostotic osseous neoplasia is more likely to invade an adjacent joint space?
Fibrosarcoma
Metastatic osseous neoplasias tend to occur in what region of bones?
Diaphyseal (spread via nutrient foramen)
What is the difference between osteomalacia and osteoporosis?
Osteomalacia = decreased skeletal mineralization WITH MATRIX present (e.g. lack of vitamin D)
Osteoporosis = decreased skeletal mineralization AND DECREASED bone matrix (e.g. secondary hyperparathyroidism & hypervitaminosis A)
For high contrast
, a ___ kVp technique is preferred?
Low kVp
For high contrast
, a ___ kVp technique is preferred?
Low kVp
Periarticular blood vessels that supply & drain epiphyses also provide vascularity to where?
Synovium & joint capsule
Irregularity of subchondral bone margins is a feature of normal endochondral ossification for several months after birth. This is seen particularly in which two bones?
- Greater tubercle of humerus
- Distal femoral condyle
What is the key initiating factor of osteochondrosis?
local ischemia (—> failure of joint cartilage mineralization —> thickened & weak articular cartilage —> exposes subchondral bone to synovial fluid)
What are 4 broad diseases/categories that can result in osteochondral fragmentation or destruction?
- OCD
- Sepsis
- Avascular necrosis
- Immune mediated joint disease
What disease is characterized by ankylosing arthropathy of the carpi & tarsi that progresses to metacarpi/metatarsi/phalanges? Which animal breed in predisposed?
Osteochondrodysplasia of Scottish fold cats
-caudal vertebral elements often malformed too
-tail shorter & wider than normal
How does the feline form of rheumatoid arthritis differ from dogs?
Feline form predominated by periosteal proliferation & mineralization (exclusive in young male cats)
Erosion predominates in dogs
Which mucopolysaccaridosis occurs in Siamese cats?
MPS VI
What percentage of synovial cell sarcomas eventually metastasize?
50% (~20% of cases have distant metastasis to lymph nodes/spleen/lungs at time of diagnosis)
What are the 4 chronological changes in order from first to last in the development of osteoarthrosis?
1) Increased subchondral opacity
2) Bony remodeling of normal joint contours
3) Osteophyte/enthesophyte formation
4) intra & periarticular calcifications
What dogs are typically affected by rheumatoid/immune mediated polyarthropathies? Which location of bones?
Distal joints of the extremities of small/toy breeds
What radiographic features are seen with synovial cell sarcomas?
- Cortical erosion
- Multiple lucent cyst like changes in cancellous bone
What is the first stage of lesions in secondary osteomyelitis?
Subchondral bone erosion
What is the pathophysiology of hypervitaminosis A? What osseous lesions result?
- Reduces proliferation & differentiation of cartilage cells —> ankylosing polyarthropathy, periarticular enthesopathy, & spondylopathy
- changes most pronounced in cervical vertebral column, shoulder & elbow joints
What are the 3 types of fracture healing?
1) Classical
2) Primary
3) Bridging osteosynthesis
What are the two main reasons fracture ends are absorbed during classical fracture healing during the period of early response?
1) Fragment ends deprived of blood supply so therefore “die back”
2) Increasing the fracture gap reduces the stress in the interposed tissues (caused by fragment movement) thus preventing stresses exceeding physiological limits of invading cells
Callus formation is the result of differentiation of what cell line?
Mesenchymal cells (externally from periosteum & internally from endosteum)
The production of _______tissue within a fracture gap creates a barrier to healing rather than contributing to bone union.
Fibrous
Bridging callus formation usually how soon after injury?
Within 2 weeks
________ cells differentiate into _______ producing hyaline cartilage that becomes mineralized and converted to bone by the process of ____________ ___________.
Mesenchymal
Chondroblasts
Endochondral ossification
During classical fracture healing when tissue is under tension, mesenchymal cells differentiate into what?
Fibroblasts—> production of fibrous tissue
What occurs once a fracture gap is bridged by woven bone?
Callus undergoes compaction & remodelling —> woven bone converted to compact bone by osteoblasts
Which has a more abundant blood supply and greater inherent cellular activity, cortical or cancellous bone?
Cancellous
Fractures in which region of ling bones heal more quickly and why?
Epiphyseal & metaphyseal > diaphyseal
B/c cancellous bone has greater blood supply and greater cellular activity than cortical bone
Primary bone healing (e.g. secondary plate fixation) is slower or faster than classical healing via IM pinning/external coaptation/external fixation
Slower
What oblique view can be taken for better assessment of the intertubercular groove?
Cranioproximal - craniodistal oblique
Describe the unique anatomical difference of the shoulder in cats?
Prominent coracoid process of the supraglenoid tubercle.
- extends from medial side
What are the 3 main ossification centers of the shoulder joint?
1) Supraglenoid tubercle
2) Humeral head
3) Greater tubercle of the humerus
Where is the so called “accessory ossification center” of the shoulder in dogs?
- Caudal rim of the glenoid
- DO NOT confuse with OCD lesion that occurs on caudal aspect of humeral head
What type of contrast media & what volume should be used for positive contrast arthrography of the shoulder joint in dogs/cats?
Non-ionic, low osmolar
- diluted to 100mgI /mL (otherwise too opaque & can mask lesions)
Which bursa in the shoulder joint is only occasionally seen on arthrography? Which 2 are always seen?
- Infraspinatous bursa : occasionally seen
- subscapular recess & bicipital tendon sheath always visible
Where does the supraspinatous tendon insert at?
Greater tubercle of the humerus.
Shoulder luxations in toy breeds occur in what direction and are usually of what etiology? In
Usually congenital and most often medial location
(Lateral traumatic luxation more common in large breed dogs)
What is a pathognomonic lesion on U/S for the presence of a shoulder OCD flap?
A second hyperechoic line at the bottom of the subchondral defect
What is the most sensitive radiographic indicator of bicipital tenosynovitis?
Sclerosis along the bicipital groove
What is the cell origin of synovial sarcoma?
Mesenchymal
What dog breed is predisposed to mineralization of the supraspinatous muscle?
Rottweilers
What radiographic projection can be used to optimize interpretation of the cranial border of the medial coronoid process?
Extended supinated mediolateral aka Cd75MCrLO
What radiographic projection optimizes the visibility of the medial coronoid process and the medial humeral condyle (to check for OC lesions)?
Craniolateral-Caudomedial oblique aka Cr15LCdMO
Which projection optimized the lateral humeral condyle? By supinating the leg 15 degrees, what disease process of the humerus can best be identified?
Craniomedial-caudolateral oblique aka Cr45MCdLO
-Incomplete ossification of the humeral condyle
What are the characteristic U/S features of a subcutaneous lipoma?
- Well marginated
- Avascular hypoechoic mass
- Echogenic streaks parallel to skin surface
What is the ideal exposure setting for MSK imaging?
Moderate-low kVp
moderate-high mAs
The characteristic curve of screen-film systems have a sigmoid shape with a toe and shoulder regions; these two regions correspond to what?
Toe region = too bright
Shoulder region = too dark
Intrinsic sharpness of screen film systems is dependent on what 2 factors?
1) Thickness of the screen layer
2) Size of grains in film emulsion
Lead grid lines are used to measure the _______ ________ of radiography systems.
Resolving power
DQE generally increases or decreases with increasing spatial frequency.
Decreases
What is the origin of Uberschwinger artifact?
Processing error (edge-enhancing algorithms were applied)
What is another name for aliasing artifact?
Moire pattern
What is the origin of Moire pattern and how does one eliminate this artifact?
Origin = error of signal recording (signal registration interacts with low frequency antiscatter grid lines)
Elimination = retake image using higher frequency antiscatter grid
What is the only type of contrast media suitable for myelography?
Non-ionic
What are 3 sonographic features that have been associated with metastatic lymph nodes?
- Long axis ratio > 0.5
- Peripheral rather than hilar vascularity
- Pulsatility index > 1.49
Are foreign bodies within an abscess more likely to show acoustic shadowing on transverse or longitudinal images?
Transverse
What 2 tendons are commonly affected by calcifying tendinopathy?
Supraspinatous & abductor pollicis longus.
With respect to CT, window width and window level correspond to what basic principles?
window width = scales of contrast
Window level = brightness
Soft tissues are viewed using a narrower or wider window than osseous structures on CT?
Narrower
On CT, the number on the Hounsfield scale set to middle grey is referred to as what?
The window level
What does window width refer to on CT?
The range of greyscale mapped on the Hounsfield scale
All CT numbers BELOW the window width are displayed as ____ & thr CT number above the window width are ____.
Black; white
What is the definition of Tesla?
The SI derived unit of magnetic flux density
If one axis of the image in MRI is frequency encoded, the other must be spatially encoded by what?
Creating shifts in precessional phase of the signal (portions of the patient exhibiting stronger gradient will cause faster spin precession)
T1 and T2 magnetization occur in what image planes respectively?
T1 relaxation = regrowth of longitudinal magnetization
T2 decay = transverse loss (spins dephase)
Spin-spin relaxation & spin-lattice relaxation after called what respectively?
T2 and T1 relaxation
T1 relaxation occurs ______in fat and _____in water?
Rapidly; slowly
T1 relaxation time is the duration it takes for ____% of ________magnetization to recover.
63; longitudinal
Fill in the following chart::
Imagewt:TR:TE:CSF/H2O
T2W
T1W
PD
FLAIR
T2W:: long TR:: long TE:: high signal
T1W:: short TR:: short TE:: low signal
PD:: long TR::short TE:: mid signal
FLAIR:: long TR:: long TE:: low signal
Vasogenic edema occurs as a result of ________and mainly affects what portion of the brain?
-increased vascular permeability
- white matter
(Secondary to many brain pathologies such as inflammation/tumor/trauma)
Which form of brain edema tends to cause a significant mass effect and is usually poorly marginated/diffuse?
Vasogenic edema
(Cytotoxic edema usually sharply marginated and has minimal to no mass effect)
What are the three forms of brain edema?
1) Cytotoxic
2) Vasogenic
3) Hydrocephalic
What commonly causes cytotoxic edema and what areas of the brain does it commonly affect?
Ischemia/infarct/post-ictal changes (results in increased intracellular water)
-preferentially occurs in high-metabolic areas such as grey matter
What are the 5 main ddx for an area of marked increased radiopharmaceutical update?
1) Neoplasia
2) Fracture
3) Infection
4) Enthesopathy
5) Subchondral erosion
Neoplasms that are primarily or exclusively lytic or proliferative are NOT readily identified using bone scintigraphy? And why is this?
Lytic; because they lack osteoblastic activity
Multiple poorly defined focal areas of T2W hyperintensity may be present in what muscles affected by masticatory muscle myositis?
Temporalis
Lateral pterygoids
Masseter
What is the main function of cancellous bone?
Support subchondral bone & transmit mechanical forces to the diaphyseal cortex
In which direction does bone growth from the physis occur?
Towards the diaphysis
The growth plate has distinct zones characterized by alterations in chondrodysplasia morphology, what are they in order from epiphysis to diaphysis?
Resting zone
Proliferation zone
Maturation zone
Hypertrophy zone
Calcification zone
What is unique about the blood supply to the physis of an immature long bone?
Essentially avascular
The neural arch is what type of bone?
Flat bone
Bone infarction has been associated with what conditions in dogs and cats, respectively?
Dog - osteosarcoma
Cat - feline leukemia
Is interrupted periosteal reaction more suggestive of a benign or aggressive process?
Aggressive
Cortical expansion results from what?
Endosteal resorption -secondary to pressure from impinging growth or hyperemia
What are the functions of calcitriol?
Increase absorption of dietary calcium
Renal tubular calcium absorption
Increases renal excretion of phosphorus
Negative feedback loop with PTH (which is secreted when there is LOW serum calcium)
What are the two main functions of PTH?
- Intestinal calcium absorption
- Mobilizes calcium & phosphorus from bone
What are the functions of calcitonin?
-inhibits osteoclastic activity
- stimulates endochondral ossification
The distal ulnar physis contributes what percentage of bone growth?
85%
Are immature dogs or cats more susceptible to premature distal ulnar physeal closure and why?
Dogs due to the conical shape of the distal physis .
-Any lateral shearing force applied translates into compressive forces
The distal radial physis contributes what percentage of bone growth?
70%
ALD is more likely to occur secondary to premature of which physis in the thoracic limb?
Distal ulna
Asymmetric closure of the distal radial physis usually involves closure of which margin?
Lateral
What is the weakest layer of the physis?
Hypertrophic chondrocytes (this is where slipped capital femoral physeal fx occur)
What is a differential diagnosis for osteogenesis imperfecta?
Nutritional secondary hyperparathyroidism
What bones are affected by osteochondromas?
-Vertebrae
-Ribs
- Long bones
- Digits
-Pelvis (particularly cats)
What is characteristic of osteochondroma lesions?
Cartilage-capped bony protuberances
What is the difference in growth between osteochondromas in cats versus dogs?
Cats - continue to grow throughout adult life
Dogs - cease to grow once patient reaches skeletal maturity
What is the characteristic lesion of Rickets?
Failure of mineralization i the area of provisional calcification of the physes
What dog breed is more predisposed to Type 1 vitamin-D dependent rickets?
Saint Bernards
What dog breed is predisposed to canine leucocyte adhesion deficiency (CLAD)? And what are the radiographic findings?
-Irish Setters & Irish setter cross breeds
-Thickened distal radial/ulnar metaphyses & mandible
-skeletal changes range be, craniomandibular osteopathy (WHWT & Scottish terriers) & osteomyelitis
The humeral trochlea is composed of what two pieces? At what age do these ossify?
The medial trochlea & lateral capitulum
- Closed by 3 months old
Caudal surface of the humerus forms what seen on the ML view ?
Lateral supracondylar crest
On the craniocaudal view in cats, the anconeal process engages what?
Supratrochlear fossa
- NO Supratrochlear foramen in cats
The extensor fossa may be seen on the cranioproximal aspect of what?
Lateral femoral condyle
What is the most common form of hematogeneous osteomyelitis in adult dogs?
Discospondylitis
Hematogeneous osteomyelitis in adult dogs may result in pathological diaphyseal fractures through what mechanism?
Spread via nutrient artery
A seuquestrum is an isolated bone fragment separated from healthy bone which lies within a __what radiopacity_______ cavity (called the _______) and is surrounded by a sclerotic rim of proliferative bone called the _________. The sequestrum is usually what opacity in relation to the surrounding bone?
Radiolucent
Cloaca
Involucrum
- Sequestrum More radiopaque
Parosteal osteosarcoma arises from where?
Periosteal connective tissue on the bone surface
Bone lesions of histiocytic sarcoma are most common in which locations?
-Predilection site for proximal humerus & periarticular sites
- Vertebrae
- ribs
In cats, ossifying fibromas & osteomas are more likely to occur where?
In the skull
Flexor tendon enthesopathy occurs at which distal humeral epicondyle?
Medial epicondyle
Where does the abductor pollicis long is insert at?
Proximal aspect of 1st metacarpal
What are the radiographic changes associated with tenosynovitis of the abductor pollicis longus?
- Deep radiolucent medial radial sulcus
- Bony proliferations medial & slightly cranial to the distal radius
Stress fractures/stress remodelling (regular periosteal reaction) are most commonly seen in Greyhounds in which bones?
-Metacarpal/metatarsal bones
- Lateral humeral epicondylar crest
Briefly describe the steps of classical fracture healing.
1) Hematoma formation at fracture site & inflammatory chemical mediators stimulate mitosis/differentiation of mesenchymal cells & angiogenesis
-bone ends tend to resorb at this stage
2) mesenchymal cells differentiate into chondroblasts, fibroblasts, or osteoblasts depending on local environment —> production of hyaline cartilage, fibrous tissue, or woven bone respectively
-for example, results in bridging callus formation peripherally but hyaline cartilage at level of fx (occurs by 2 wks after injury)
3) Compaction & remodeling of mineralized callus
If fracture healing occurs WITHOUT external callus formation it is termed what?
Direct or contact healing
What are 4 radiographic features of a delayed union fracture?
1) persistent fx line with evidence of healing
2) Open medullary cavity
3) Uneven fx surfaces
4) No sclerosis of fx ends
What are 5 radiographic features of a non-union fracture?
1) Gap between fx ends
2) Closed medullary cavity (unless pinned)
3) Smooth fx surfaces
4) Sclerosis of fx ends
5) +- Hypertrophy or atrophy of bone ends
Non-union fractures are further subdivided into what 2 broad categories? And what subcategories are within each of these?
Biologically active or viable non-unions & biologically inactive or non-viable non-unions.
3 subcategories of viable non-unions = 1) Hypertrophic non-union (elephant foot callus)
2) Slightly hypertrophic non-union (horse foot callus) 3) Oligotrophic non-union (no or limited callus formation)
4 subcategories of non-viable non-union = 1) Dystrophic non-union (intermediate fragment united with one of the main fragments but not other —> devitalized portion) 2) Necrotic non-union 3) Defect non-union (significant bone loss or overzealous removal of fx) 4) Atrophic non-union (usually RU fx of small breed dogs)
Describe the location of the coracoid process in cats? What attaches to it?
Medial side of the supraglenoid tubercle
-coracobrachialis muscle
Positive contrast arthrography helps to assess whether a non-mineralized cartilage flap is present in a shoulder with OC what percentage of the time?
80%
What is the pathophysiology of synovial osteochondromatosis?
Nodular cartilaginous metaplasia of the synovial membrane of the shoulder joint or bicipital tendon sheath
-cartilage can be replaced by cancellous bone
What may be a radiographic finding associated with infraspinatous muscle contracture?
Narrowing of the lateral scapulohumeral joint space (CdCr view)
What are the 7 anatomical locations where calcinosis circumscripta develop?
-Lateral metatarsus & digits
- Elbow
- Shoulder
- Spine
-Hip
-Tongue
-Footpads
Which fracture of humerus is the most common and why?
Lateral condylar fx.
- bears the most weight (via radial head) & has weak attachment to the humeral diaphysis
What is a Monteggia fx?
Non-articular or articular fx of the proximal ulna accompanied by cranial luxation of the proximal radius & distal ulnar fragment
What muscle group attaches to the olecranon?
Triceps
What dog breed is predisposed to an ununited medial humeral epicondyle?
Labrador Retrievers
What is the more common direction for elbow luxations to occur in?
Radius and/or ulna usually locate laterally (due to sloped medial condylar ridge)
In cases of traumatic premature closure of the distal radial and distal ulnar physes, what are the respective changes to the trochlear notch & humeroradial/humeroulnar joint spaces?
Distal ulnar physeal closure —> DISTAL subluxation of trochlear notch & widened humeroulnar joint space
Distal radial physeal closure —> PROXIMAL subluxation of trochlear notch & widened humeroradial joint space
At what age does the physis of the anconeal process close?
5 months
What humeral condyle is more affected by OCD?
Medial
The physis of the medial humeral epicondyle fuses how long AFTER normal anconeal process fusion?
1-2 months
What is the pathophys mechanism behind lameness in cats with hypervitaminosis A? Where are two common lesion locations?
Lameness due to proliferative new bone formation at tendon/ligament insertions or origins.
- common locations = triceps insertion on olecranon & cervical changes
Describe the location of the acetabular bone & when does it ossify?
Between the ilium & ischium, forming the floor of the acetabulum.
Ossification 6-8 wks after birth
Describe a hip broomstick conformation and what breed is it commonly seen in?
-Slender femoral neck merges WITHOUT clear demarcation with the smaller femoral head
-GSDs
What breed is commonly affected by avascular necrosis of the femoral head?
WHWT
What percentage of avascular femoral head necrosis disease is unilateral?
~90%
What is the 1st radiographic sign of avascular femoral head necrosis?
Widening of the coxofemoral joint space (due to thickened cartilage)
True or false, a subtle Morgan’s line is never visible in normal joints.
False, in large or heavy dogs it IS often visible
What are the 6 common radiographic findings associated with mucopolysaccharidosis 6?
1) Vertebral deformities
2) Pectus excavatum
3) Epiphyseal dysplasia
4) Cervical vertebral fusion
5) Hip laxity
6) Hip luxation
(The latter 2 are due to dysplastic acetabula)
What are the two most frequently affected cat breeds with mucopolysaccharidosis 6?
Siamese & European Shorthair
Discuss the pathophysiology of genu varum?
Secondary to disturbance of the proximal tibial or distal femoral physis —> allows medial side of physis to grow more rapidly —> medial bowing of distal femur & lateral deviation of distal limb
+- lateral patellar luxation
OC/OCD is common or uncommon in the stifle? Additionally where is the usual location in the stifle?
Uncommon
-medial aspect of the lateral condyle
Following the elbow and spine, where is a predilection site for hypervitaminosis A?
Stifle
True or false, mineralized bodies associated with synovial osteochondromatosis are both intra- and periarticular?
True
How many ossification centers fuse to form the radial carpal bone?
3
What are three differential diagnoses for delayed appearance of ossification centers?
1) Disorders of endochondral ossification
2) Hypothyroidism
3) Hypopituitarism
What are the radiographic changes associated with stenosing tenosynovitis of the abductor pollicis longus?
- Deeper, more lucent medial radial sulcus (due to bone proliferation on craniomedial aspect of distal radius)
- Soft tissue swelling
Where does the Achilles tendon insert proximally?
Calcaneal tuberosity
OCD of the tarsocrural joint occurs where and which site is more common?
Medial trochlear ridge of the talus > lateral trochlear ridge of the talus
What are the differences in the radiographic appearance of OCD of the medial & lateral trochlear ridges of the talus respectively?
Medial trochlear ridge = crescent shaped subchondral bone fragment with increased width of the medial tarsocrural joint space
Lateral trochlear ridge = oblique osteochondral fx through lateral condyle —> large osseous joint mouse within lateral tarsocrural joint space
At what location in the long bones do osteochondromas tend to develop?
Towards the distal metaphyseal end
Osteochondrodysplasia is commonly seen in which cat breed and what are the predominant radiographic abnormalities?
Scottish Fold cats
- Bilaterally symmetric carpal & tarsal ankylosis
Metacarpophalangeal sesamoid fragmentation is regarded as a potential cause of lameness, particularly in what dog breed?
Rottweilers
Explain the radiographic appearance of lesions associated with hypovitaminosis D (Rickets)
Normal production of physeal cartilage but concurrent failure of metaphyseal ossification (No endochondral ossification)
- results in physis growing WIDER than normal & adjacent metaphyseal bone is present as an opaque margin wider than normal & may be saucer shaped
-most dramatic changes in distal RU
What are the 3 parts of the temporal bone?
Squamous, petrosal, & tympanic
What is unique about the tympanic bulla in cats?
Separated into two unequal parts, dorsolateral & ventromedial compartments, separated by a thin bony shelf
Asymmetry of the ventricles is a common finding. Which one is usually larger?
Left lateral ventricle
What are the 3 most common malignant neoplasms of the cranium??
1) Osteosarcoma
2) Chondrosarcoma
Multilobular osteochondrosarcoma
What is the characteristic radiographic appearance of an MLO?
Well-defined mass with a dense pattern of coarse stippled ossification and little to no osteolysis
What is a radiographic pathognomic finding of feline intracranial meningioma?
Calvarial hyperostosis
What is the cause of feline acromegaly (hypersomatotropism)? And what other disease can it be associated with?
Functional adenoma of the pars distal is of the pituitary gland.
-Insulin resistant diabetes
Is metastasis to the lungs from primary nasal neoplasia common or rare?
Rare
What are 5 radiographic features of mucopolysaccharidosis 6?
-Abnormal nasal turbinate pattern
-Pectus excavatum
- Spinal epiphyseal dysplasia (looks similar to Hypervitaminosis A changes)
- Hip dysplasia
- Hyoid hypoplasia
What dog breed is predisposed to idiopathic Calvarial hyperostosis?
Young bullmastiffs
What is the characteristic appearance of orbital myxosarcoma on MRI?
-Large complex fluid-filled cavities extending caudally to TMJ along fascial planes
- TMJ osteolysis is possible
What is the main DDx for orbital myxosarcoma?
Zygomatic sialocele
Renal secondary hyperparathyroidism predominantly causes bony changes in what location?
The skull, aka “rubber jaw”
What are ddx for cystic or pseudocystic lesions of the maxilla?
- Nasolacrimal duct cysts
- Epidermoid cysts
- Epithelial cysts
- Cholesterol granuloma
- Giant cell granuloma
What direction does the Mandibular condyle usually go in cases of TMJ luxation?
Condyle luxated rostrodorsally (—> joint space widens)
What 2 dog breeds are predisposed to TMJ dysplasia?
Irish Setters
Bassett Hounds
CKCS (usually sub clinical)
What is a ddx for a nasopharyngeal polyp lesion that is less likely to cause bony bulla changes?
Lymphoma
What salivary glands are most commonly inflamed, leading to sialoadenitis?
Zygomatic
What salivary gland and duct are the most likely to suffer from sialoliths?
Parotid gland and duct
Most sialoceles arise as an abnormality from where?
The rostral part of the sublingual gland
-submandibular salivary glands are less common
Where is the vomer bone located?
Long narrow bone that lies between the maxillae
-superimposes the cartilaginous nasal septum
The nasal cavity is divided into what 3 zones & which is contained in each?
1) Rostral : fine slightly wavy parallel lines represent the nasal conchae
2) Mid zone : nasal turbinates rounded & more widely spaced producing “bubbly” appearance
- maxillary recess is medial to PM4
3) Caudal : series of paired line represent ethmoturbinates (originate from cribriform)
What is dacryops?
A congenital cyst of the lacrimal gland
What is the mechanism behind asymmetrical nasal mucosal thickness that is observed normally in CT/MRI of dog nasal cavities?
Reflects the nasal cycle - a physiologic process of regular periodic congestion & decongestion of venous sinusoids lining the mucosa
What are the 5 concurrent abnormalities associated with brachycephalic obstructed airway syndrome?
1) Elongated & thickened soft palate
2) Everted laryngeal saccules
3) Stenotic nares
4) Tracheal hypoplasia
5) Everted tonsils
What combination of findings is known as Kartagener’s syndrome?
1) Immotile cilia (ciliary dyskinesia)
2) Bronchiectasis
3) Situs inversus
What are the six classifications of rhinitis & sinusitis?
1) FB associated
2) Lymphocytic plasmacytic
3) Allergic
4) Hyperplastic
5) Infectious
6) Secondary to dental dz
What are the 3 most common nasal/sinus neoplasms in cats?
Lymphoma
SCC
Adenocarcinoma
What dog breed have been described to suffer from congenital nasopharyngeal stenosis?
Dachshunds
What is the normal adult dental formulas in cats & dogs?
Cat = 30 total
2 x [ I 3/3, C 1/1, PM 3/2, M 1/1]
Dog = 42 total
2 x [I 3/3, C 1/1, PM 4/4, M 2/3]
What are the four categories of odontogenic tumors?
1) Cystic (ameloblastomas)
2) Lytic (acanthomatous epulis)
3) Associated with new bone formation (peripheral odontogenic fibromas)
4) Sequelae to malformed tooth/teeth (odontomas)
In cervical myelography, if a lesion is seen on lateral views in the upper & lower cervical regions, what orthogonal projections should be taken respectively to optimize the amount of contrast medium around the lesion?
Upper cervical lesion - VD
Lower cervical lesion = DV
What causes widening of the lumbar spinal cord near the region of L4?
Lumbar intumescence
Which type of vertebral canal lesion causes a “ golf tee” sign?
Intradural extramedullary cord compression (b/c it splits the contrast medium column)
Where does the vertebral body nutrient foramen appear on spinal CT?
Originates dorsally as a central cleft (do not mistake for a fx)
With MRI, cystic fluid is typically ________ on T1W & _______ on T2W images.
Hypointense
hyperintense
What are 3 ddx for hyperintense intraparenchymal cord lesions on T2W images?
1) Gliosis
2) Edema
3) Dilated central canal
The dens of the axis arises embryologically from where?
The body of the atlas
What are the two most common locations for arachnoid cysts to develop?
Dorsal region of cranial cervical & thoracolumbar spine
What 2 dog breeds are predisposed to arachnoid cysts?
Dobermanns
Rottweilers
Arachnoid cysts are most commonly oriented in which direction?
Cranially to caudally (thinner cranially —> mild progressive widening caudally)
Where are synovial cysts positioned with respect to the spinal cord?
dorsolaterally
-can extend into the foramen
What differs between the locations of Spondylosis and spondylitis?
Spondylosis : arises from the region of the vertebral endplate
Spondylitis: typically only involves the central part of the vertebral body (causes loss of ventral mid body concavity)
What disease processes can result from infection with the nematode gurltia paralysans? And what animals are infected?
Invades leptomeningeal vasculature —> diffuse meningomyelitis & thrombophlebitis, mainly thoracolumbarly in domestic cats
Multiple cartilaginous exostoses that occur within the vertebrae are typically associated with which part?
Spinous processes
A focal isolated cartilaginous non-osseous form of osteochondromatosis is occasionally seen in what size dogs and at what location in the vertebral column?
Large breed dogs
Dorsal aspects of C1-C2
Calcinosis circumscripta has been associated with what two other systemic/physical disease processes?
Chronic renal failure & footpad mineralization
What MRI change or lack thereof can help to differentiate FCE from spinal cord contusions resulting from non-compressive disc herniation?
An absence of contrast enhancement
Vacuum phenomenon is more frequent in chondrodystrophic or non-chondrodystrophic dogs?
Non-chondrodystrophic
In those cases with bilateral filling defects in thecal contrast, disc material is more likely to be in the shorter or longer filling defect?
Shorter (83%)
Contrast enhancement of disc material is present in about what percentage of cases?
50%
Contrast enhancement of herniated disc material is more common with protrusion or extrusion?
Extrusion
True or false, the degree of spinal cord compression is a prognostic indicator?
False
What is a negative prognostic indicator on spinal cord MRI?
Presence of T2W hyperintensity in the spinal cord
-length of T2W change in comparison to length of L2
What is the most common site for disc herniation in cats?
L4 to L5
What is the most common cause of cervical spondylomyelopathy in dogs? What breed is predisposed?
Disc-associated wobbler syndrome
-Dobermann
What are the most commonly affected discs with disc-associated Wobbler syndrome?
Caudal cervical C5 - C7
Vertebral canal stenosis due to bony malformation causing Wobbler’s in common in what size dogs and breed in particular?
-Adolescent & young adult large or giant breed dogs
-Great Danes
Vertebral osteochondrosis is most often observed where?
Dorsal aspect of the Cranial endplate of S1
-occasionally at dorsal aspect of caudal endplate of L7
