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
