Introduction to Musculoskeletal Radiographic Interpretation Flashcards
What are 6 functions of bone?
- protective covering of body cavities
- supports extremities and muscles
- levers for locomotion
- fat storage
- mineral storage for homeostasis
- source of hematopoiesis
How is bone health maintained?
hormonal regulation of calcium (99%) and phosphorus (85%) metabolism
What 5 organs take part in calcium metabolism?
- GIT - absorbs vitamin D from the diet
- LIVER - metabolizes vitamin D into 25OHD and produces albumin for circulating calcium
- KIDNEYS - converts 25OHD into 1,25(OH)2D and mobilizes calcium and phosphorus from bone and GIT
- PARATHYROID - produces PTH, which stimulates production of 1,25(OH2)D, osteoclasts, and calcium retention in the kidneys
- THYROID - produces calcitonin, which reduces osteoclast activity, increases calcium and phosphorus excretion, and reduces blood calcium levels
What paradigm is used for assessing the musculoskeletal system?
- Alignment: Are the components of the bone or joint in the proper plane?
- Bone: periosteum, cortex, endosteum, trabeculae, medulla
- Cartilage: effusion, incongruity, articular cartilage at joints, physis of young animals
- Soft tissues: juxta-articular, peri-articular, appendicular, intra or extra-capsular swelling
What paradigm is used for assessing bone healing and fractures?
- Alignment: Have segments maintained anatomic alignment?
- Apposition: Are fracture margins in contact with one another for proper healing?
- Activity: Is there evidence of healing?
- Apparatus: What device is being used for stabilization and is there any signs of loosening?
What is proper alignment? How is it evaluated?
expected appearance of how bones should line up at a joint and the bone itself
on orthogonal radiographs (90 degrees from original view) —> oblique projections (single views) can be misinterpreted
How is bone interpreted on radiographs?
cortex to cortex, epiphysis to epiphysis
- periosteum: should see no reactions
- cortex: more mineralized with higher opacity especially at the mid diaphysis
- endosteum
- medulla
What aspect of the musculoskeletal system are not observed on radiographs?
cartilage —> should be translucent and can see joint space
What 3 things are typically assessed to make observations about joints?
- joint space size
- subchondral bone opacity
- subchondral bone margins
What 3 aspects of soft tissue can be assess on radiographs?
- musculature
- fascial planes
- lymph nodes
What is seen in this radiograph?
- subluxation of the femur —> acetabulum and femoral head are deviated
- physeal line is observable, indicating the patient is young
- muscle volume on the right thigh is decreased, indicating chronic lameness and disuse atrophy
What is bone modeling? What is indicative of this occurring? In what patients is this most commonly seen?
shaping and reshaping of bone from existing bone tissue where osteoblasts and osteoclasts act independently at different sites
major adjustments in the size and shape of bone —> immature skeletons of infants and adolescents
What is bone remodeling? What is indicative of this occurring?
bone is resorbed and formed at the same site from growth to death as a form of maintenance and repair
less obvious —> replacement of structurally inferior woven bone-fibered bone with stronger, more organized, lamellar bone
What are 3 characteristics of juvenile bones?
- cut back zone of bone modeling
- irregular margins at the level of the physes and metaphyses
- bones model to the diameter of the diaphysis
What is Wolff’s Law?
bone remodels in response to the mechanical stresses it experiences so as to produce an anatomical structure best able to resist the applied stress
- cortex and width of articular surface thickens in response to strain or stress
What are the 2 general responses of bone to injury?
- LYSIS - destruction of bone that was already present
- PRODUCTION - periosteal reactions, osteophyte production at osteochondral junctions, enthesophyte production at attachments of ligaments and tendons
What is cortical bone? Cancellous bone?
CORTICAL = outer portion of a bone surrounded by periosteum on the outside and endosteum on the inside (aka compact)
CANCELLOUS = contains trabeculae and collagen, mostly in the metaphyses and diaphyses and short/irregular bones (aka spongy, trabecular)
What are the diaphysis, epiphysis, physis, and metaphysis?
DIAPHYSIS = central portion of a long bone that contains marrow elements (thinnest)
EPIPHYSIS = ends of the bone at a (synovial) joint that ends in a thickened subchondral bone covered in hyaline cartilage
PHYSIS = growth plate of long bones found between the epiphysis and metaphysis
METAPHYSIS = located between physis and diaphysis on both ends of long bones
When is the physis open? What is it called when it closes?
open and cartilaginous (radiolucent) when the animal is growing until they reach maturity
physeal scar —> thin, mineral opaque line commonly seen in animals from 1-5 years of age and is ultimately remodeled and disappears after
What happens to the metaphysis of skeletally immature animals?
undergoes active endochondral ossification, converting the physeal cartilage into mature bone
What is the cut back zone?
area of active remodeling of the metaphyseal cortex adjacent to the physis
What is the apophysis? What are 3 examples?
separate centers of ossification of the insertion points of major muscle groups
- tuber olecranon (triceps brachii insertion)
- tibial tuberosity (quadriceps insertion)
- tuber calcaneus (common calcaneal tendon insertion)
What is a synovial joint?
movable joints where there is hyaline cartilage covering the articular surface of the bones and a synovial membrane that contains lubricating synovial fluid that provides nutritional support
What is osteopenia? How is it seen radiographically?
decreased bone density per unit volume of bone tissue
thinning of cortices and a reduction in the number of trabeculae
(thin cortices in the right radius compared to the normal left antebrachium)
What is sclerosis? What are causes of focal and generalized sclerosis?
increased mineral opacity of bone
- FOCAL = degenerative joint disease, panosteitis
- GENERALIZED = chronic retroviral infection (FeLV)
How does hyperparathyroidism affect bones? What are 2 causes?
generalized reduction in bone mineral density and cortical thinning (osteopenia)
- PRIMARY = parathyroid tumor
- SECONDARY = nutritional or renal
What 2 things should be checked if osteopenia is suspected?
- dietary habits (raw diet)
- renal disease with calciuria
In what 2 ways does osteopenia manifest? What should be considered when it is present throughout the skeleton?
- reduction in cortical thickness of bone
- coarse trabeculation patterns
metabolic disturbances that result in the diffuse mobilization of calcium from storage in the bone —> hyperparathyroidism
Osteopenia:
LEFT = normal radial diaphyseal cortex and trabeculae (fine webbing)
RIGHT = thin radial cortex and a reduction in trabeculae due to resorbed calcium
