Musculoskeletal

Question 1

Osteopenia

Answer 1

Decreased bone density

Question 2

Two forms of osteopenia

Answer 2

• Osteomalacia - loss of bone density due to a decrease in bone matrix mineralization. The amount of matrix present is normal or increased but the mineral content is low and much of the osteoid is uncalcified. The lesions are the product of decreased mineralization of new matrix, not the removal of mineral from existing matrix.
• Osteoporosis - loss of bone density due to a decrease in the amount of mineral and matrix present. The bone which is present is normal in composition. Caused by an increase in osteoclastic activity in relation to osteoblastic activity

Question 3

Three main categories of causes for osteomalacia:

Answer 3

1. Vitamin D deficiency
2. Hpophosphatemia with normal vitamin D intake
3. Defective nutrition with abnormal Ca, P, or Vit. D

Question 4

Causes for osteoporosis

Answer 4

1. Congenital defects in collagen matrix formation
2. Acquired generalized response to aging
3. Endocrine disorders
4. Vitamin C, protein, and Ca deficiency
5. Malnutrition
6. Disuse, infalmmatory
7. Neoplasia and ischemia

Question 5

Osteosclerosis

Answer 5

• Increased bone density due to an increased osteoblastic activity relative to osteoclastic activity

Question 6

Real sclerosis vs Apparent sclerosis

Answer 6

• Real sclerosis - increase in density without an increase in size of the bone. Represents endosteal or medullary new bown growth
• Apparent sclerosis is an increase in the density of the bone shadow caused by periosteal new bone growth, this enlarges the diameter of the bone with compact bone

Question 7

Enthesophytes vs Osteophytes

Answer 7

• Enthesophytes are abnormal bony projections at the attachment of a tendon or ligament
• Osteophytes are abnormal bony projections in joint spaces

Question 8

Pathogenesis of degenerative joint disease

Answer 8

1. Instability of the joint
2. Increased or uneven wear on the joint cartilage
3. Increased stress on joint margins and joint capsule, synovium and ligaments
4. Calcification of the articular cartilage margins and formation of enthesiophytes at joint ligament and capsule insertions on bone
5. Progressive fracturing of cartilage margins due to increased brittleness of calcified cartilage
6. Bone inflammation due to synovial contact
7. Synovitis
8. Progressive dissolution joint cartilage
9. bone to bone contact
10. Increased spur formation and fibrosis as a response to increased pain, instability and inflammation
11. Reduced joint motion
12. Progressive inflammation of bone proliferation of subchondral and periarticular bone
13. Fusion of joint. Once complete fusion is achieved pain and inflammation subside.

Question 9

Autoimmune Erosive Arthritis (Rheumatoid type)

Answer 9

• Changes are principally lytic or erosive
• Very little sclerosis is present until LATE in the disease
• Radiographic lesions:
  
  • Severe erosion of the joint surface subchondral bone
  • Often develop multiple subchondral bone cysts (type Ia punctate)
  • Periarticular bony erosions
  • As disease advances, the subchondral bone cyst formation may become confluent leading eventually to collapse of the subchondral bone and joint surface
  • Soft tissue swelling is usually present and may be extensive in advanced cases

Question 10

Nonerosive Autoimmune Arthritis

Answer 10

• Lupus type - group of infalmmatory arthritides of which systemic lupus erythematosus (SLE) is the most common representative
• Joint swelling and typical alterations in synovial fluid composition
• Radiographic lesions in this type of arthritis are minimal! - mainly soft tissue swelling and osteoporosis (loss of bone density) in the periarticular bone
• Multiple joint involvement without destruction

Question 11

Canine Hip Dysplasia

Answer 11

• Most common and economically important skeletal developmental disorder
• End result - severe degenerative osteoarthritis of the hips secondary to the instability of the hip joints

Question 12

The animal must be how old before “hip dysplasia free” registration?

Answer 12

2 years old

Question 13

Criteria for a normal hip joint

Answer 13

• Coxofemoral joint is not subluxated
• Acetabulum should approximate a hemisphere
• 50% of the capital physeal scar shoudl lie within the acetabulum

Question 14

Congenital Patellar Luxation

Answer 14

• Caused by abnormal structural alignment of the distal femur and proximal tibia (lateral or medial dispalcement of the tibial tuberosity)
• Most commonly medial displacement in small breeds; lateral displacement in large dogs
• Secondary bowing of the distal femur and proximal tibia is usually present if the luxation was present while the dog was growing

Question 15

Elbow Dysplasia - Ununited Anconeal Process

Answer 15

• Anconeal process is often a separate ossification center in large breed dogs (german shepherds)
• Separate growth center usually fuses with the proximal ulna by 20 weeks of age
• Instability results in severe degenerative arthritis at young age
• Radiographic findings - radiolucent line across the base of the anconeal process seen on an extreme flexed lateral projection of the elbow

Question 16

Elbow dysplasia - Fragmented Medial Coronoid Process

Answer 16

• Probably as a result of synchronous growth of the radius and ulna
• Radiographic findings:
  
  • lipping of the medial coronoid process on the cranial-caudal view
  • inability to visualize the medial coronoid process on the lateral view
  • sclerosis of the semilunar notch and periosteal new bone growth along the dorsal part of the aconeal process on the lateral view

Question 17

Elbow Dysplasia - Congenital elbow luxation

Answer 17

• RARE, seen in large breeds of dogs
• Radiographic lesions:
  
  • Radial head does not articulate with the humerus
  • The semilunar notch is missing or distorted
  • ANimals are clinically crippled at early age

Question 18

Legg-Perthes Disease

Answer 18

• Avascular necrosis of the femoral head and neck
• Disease seen in immature dogs of small breeds - females
• Radiographic appearance:
  
  • Earliest changes consist of moth eaten or lucent changes present in the femoral head and neck
  • Loss of normal apperance of the subchondral bone is noted
  • Femoral neck becomes thinned, collapse of the femoral neck and fragmentation of femoral head may occur

Question 19

Osteochondritis Dissicans (osteochondrosis)

Answer 19

• Lesion of the subchondral bone - usually in fast growing giant breeds
• Shoulder is most commonly affected in the dog
• Stifle, hocks and shoulder commonly affected in horses
• Rare in cats
• Lesions related to ischemic or traumatic injury to the joint cartilage during hte rapid growth phase of development
• Radiographic appearance:
  
  • Radiographic lucency - flattening or caivty formation in subchondral bone
  • Lucent area surrounded by sclerotic zone
  • Degenerative osteoarthritis will be present in long standing cases

Question 20

Achondroplastic Dwarfism

Answer 20

• Characterized by a short legged animal with short, thick, curved long bones.
• Spine and skull are unaffected
• *bassets and dachshunds are naturally achondrodystrophoid dwarfs

Question 21

Retained cartilage cores

Answer 21

• Ossification defect sometimes seen in the distal ulna of large and giant breed dogs
• Recognized radiographically as a triangular radiolucency extending from the distal physis proximally into the metaphysis and ditsal diaphysis

Question 22

Nutritional Secondary Hyperparathyroidism

Answer 22

• usually seen in young animals on all meat diets with little or no calcium and vitamine D supplementation - severe Ca/P imbalance - parathyroid glands are stimulated resulting in mobilization of calcium from bone
• Radiographic apperance:
  
  • Osteomalacia
  • Cortices become very thin and “shell-like”
  • May be thickening of bone’s overall dimension due to an excessive amount of matrix formation which represents body’s attempt to strengthen the bones (bone increases in diameter)
  • Pathologic fractures are usually of the folding or greenstick type and result in skeletal deformities

Question 23

Renal Secondary Hyperparathyroidism

Answer 23

• Signs similar to nutritional secondary hyperparathryoidsim but typically associated with the skull
• “rubber jaw”
• flexibility of hte mandible
• Seen in chronic renal failur

Question 24

Hypertrophic Osteodystrophy (HOD)

Answer 24

• Disease of young rapidly growing dogs of large and giant breed dogs - dogs are often being “pushed” nutritionally
• The earliest described sign is the presence of an irregular radiolucent band in the metaphyseal region of the long bones
• Next sign seen is development of a distinct laminar cuff of bone around the metaphyseal region of the bone. The cuff is distinctly separated from the cortex by thin radiolucent zone (laminar periosteal reaction) - in severe cases there may be more than one cuff

Question 25

Hypertrophic Osteopathy (HPO)

Answer 25

• Associated with the presence of a mass in the thorax or more rarely in the abdomen
• Radiographically there is a palisading periosteal reaction present. The reaction begins first on the phalanges, metacarpals, and metatarsals, and subsequently appears on the more proximal long bones.
• The periosteal reaciton is centered on diaphysis.
• Soft tissue swelling over the lesion
• Original cortex is slowly incorporated into the reaction

Question 26

Craniomandibular Osteoapthy

Answer 26

• Unkown etiology, seen almost excusively in Highland type terriers.
• Juvenile animals
• Radiographic apperance consists of the presence of extensive new bone formation on the petrous temple bone and some ont he angle of the mandibles.
• Proliferation is bilaterally symmetrical with an irregular border

Question 27

Panosteitis

Answer 27

• Usually Disease of young dogs usually of large breeds (german shepherd)
• Patients usually have eosinophilia
• Earliest radiographic sign is an overall mild to marked increase in the medullary density of an affected bone. With time, this may proceed to a mottled medullary appearance with marked sclerosis of patchy areas of the medullary cavity of the diaphysis
• Lesions best appreciated in the femur, humerus, ulna and radius
• Lesions typically most severe near the nutrient foramens
• Disease is self-limiting

Question 28

Hypervitaminosis A of cats

Answer 28

• Excessive dietary intake of vitamin A, often associated with diets high in liver meat
• Periarticular bony proliferation to the point of ankylosis of the joint
• Lesions appear first in the cervical spine and proceed to appear in the remainder of the spine and then to the rest of the skeleton.
• Do not mistake with spondylosis which is much less severe and extensive