Muscuolskeletal

Question 1

What is the hallmark sign of a non-union?

Answer 1

“Elephant’s foot”

Question 2

What bones are predisposed to non-union?

Answer 2

Radius and ulna

Make up ~ 60% of non-unions in dogs

Question 3

What is DJD considered a non-inflammatory disease?

Answer 3

Because the articular cartilage has no direct vascular supply and is incapable of generating an inflammatory reposes like normal tissues. (The synovial membrane, however, is very much capable of generating inflammation).

Question 4

When is the aconeal process supposed to fuse with the ulna in a normal dog?

Answer 4

15-18 weeks of age

(~4.5 months)

Question 5

In a 2000 Vet Surgery article 15/110 dogs developed ___ after total hip replacement. What were the predisposing factors?

Answer 5

Femoral infarction (one dog developed OSA after 5 years)

Predisposing factors:

• Increase in distance between the greater trochanter and nutrient foramen
• Younger age at time of surgery

Question 6

What are some abnormalities in fracture healing?

Answer 6

1. Delayed union (> 3 months)
2. Malunion:
   
   1. Functional
   2. Non-functional
3. Non union:
   
   1. Hypertrophic
   2. Atrophic

Question 7

What is the pathophysiology under OCD?

Answer 7

Failure of subchondral bone ossification. The cells in the zone of hypertrophy are no longer organized into columns and the zone is thickened. There is failure of vascularization and mineralization of this area which may cause necrosis. The weakened cortical is susceptible to fracture or fissure.

Question 8

What is inside a subchondral bone cyst?

Answer 8

Cartilage

Question 9

What are predisposing factors of DJD?

Answer 9

• Abnormal loading and stress
• Cartilage fibrillation occurs with disruption of surface collagen.
• The collagen in the gliding layer becomes disorganized and loosely woven together, with a smaller proportion of large fibrils.
• More water is retains in the cartilage and is less able to diffuse to the joint cavity.
• Enzymes from damaged cells contribute to necrosis.
• Fibrocartilage may be formed instead of hyaline cartilage.
• Synovial hyperplasia and osteophytes forms.

Question 10

Common sites of OCD?

Answer 10

Elbow:

• Humeral trochlea

Tarsus:

• Medial trochlear ridge of talus
• Lateral trochlear ridge

Question 11

What is cervical spondylomyelopathy? “Wobblers syndrome”

Answer 11

Disease of the spinal cord that is most common in large breed dogs:

• Doberman Pinscher
• Rottweilers
• Great Danes
• Irish Woolfounds
• Basset Hounds

Various types of vertebral malformations have been reported which result in vertebral canal stenosis:

• Deformities of the articular processes
• Deformities of the vertebral laminae
• Deformities of the ventral bodies Cervical spinal cord compression may also result in:
  
  • Vertebral column instability
  • Hypertrophy of soft tissue components:
    
    • Interarcuate ligaments
    • Dorsal longitudinal ligament
    • Capsule of the articular process
  • Prolapse/protrusion of IVD

C.S:

• Neurologic deficitis
• Cervical pain
• “wobbly gate”

Question 12

What are the 3 main hormones involved in calcium regulation?

Answer 12

1. Parathyroid hormone
2. Calcitonin
3. Vitamin D

Question 13

What does parathyroid hormone do?

Answer 13

Parathyroid hormone:

• Produced by parathyroid gland
• Increased blood calcium

Works on:

• Kidney - increased Ca and decreased P resorption
• Intestine- increased Ca absorption
• Bone- stim resorption by stim osteosclasts to produce osteoprotegrin ligand

Question 14

How does calcitonin work?

Answer 14

Calcitonin: a thyroid peptide hormone

• Directly inhibits action of osteoclasts, prevents release of Ca from bone

Question 15

How does Vit D work?

Answer 15

Vitamin D: Produced by skin, travels to bone, intestine, kidney where it binds & causes protein synthesis

• 1,25-dihydroxycholecalciferol = bone remodeling metabolite (also used in differentiation)
  
  • Starts as cholesterol precursor in skin, liver is step 1, kidney causes hydroxylation
  • Renal dz, agenesis have osteomalacia (decreased osteoid mineralization)
  • or rickets (defective cartilage calcification)

Question 16

How is renal osteodystrophy?

Answer 16

Renal Osteodystrophy- secondary to chronic renal failure

• Hyperparathyroidsim due to hyperphosphatemia b/c kidneys can’t excrete P
• Rickets due to inability to synthesize 1,25 Dihyroxy D3 so vitamin D deficient and can’t absorb Ca
• Changes usualy seen 1st in the head- mandible and maxilla soft, also see long bone probs. Obviously primarly see signs of renal failure

Question 17

What are the 2 main chategories of immune-mediated arthritis?

Answer 17

1. Erosive = rheumatoid arthritis
   
   1. Rads see soft tissue swelling, irregular destruction of the bone surface, ‘punched out’ erosions (cyst-like lesions), more generalized loss of mineralization of the epiphysis, calcification of soft tissues, bone erosion at tendon and ligament insertion
2. Non-erosive
   
   1. Associated with SLE (lupus- immune complexes are depositied in joints as well as other places), polyarthritis/polymyositis syndrome, polyarthritis/meningitis syndrome, Sjogrens syndrome (also get KCS and dry mouth), familial shar-pei fever, polyarthritis of adolescent akita, polyarteritis nodosa (inflamm of small arteries incl joints), drug induced arthritis, vaccine reactions, idiopathic

Question 18

What are common findings of septic arthritis?

Answer 18

Rad findings of septic arthritis:

• distension of joint capsule
• thickened synovial membrane
• widened joint space
• joint destruction
• subchondral sclerosis
• fibrous or bony ankylosis

Question 19

Fracture healing phases in equine:

Answer 19

• Day 5-10: osteoclastic activty along the fracture lines results in apparent broadening of the fracture line.
  
  • Thus a fracture line not readily visible on the acute phase may be visible 5-10 days later.
  • In an acute phase, scintigraphy may be better method of detdecting presence of an incomplete fracture of fatigue fracture.
• Folloing initial mineral resobrption along the fracture line, and formation of a firbous callus, calcified periosteal and endosteal callus develops. The amount and quality of the callus that develops depens upn the degree of stability of the fracture.
• Some bones (e.g. the proximal and distal sesamoud bones and accessory carpal bones) tens to heal by fibrous union, resulting in persistent lucent line.

Question 20

Joint Swelling

Answer 20

Soft tissue swelling in or around may be classified as:

1. Intra-articular: the joint capsul becomes distended and in a non-weight bearing patient there may be widedend joint space. It may obscure the normal intraarticula fat pads.
   
   • Spetic vs. aseptic
   • If several joints are involved a neonatal animal, septic arthritis should be considered
   • If several joints are involed in an adult animal, immune-mediated disease should be considered, especially if the occurence is cyclical in nature.
2. Periarticular: swelling does not involve the joint space, but may involve the joint capsul as seen in sprains.
   
   1. May be caused by wire cuts, puncture wounds and external trauma
   2. Generalized periarticular swelling may result in the inability to differentiate between intra-articular and extra-articular fluid accumulation

Question 21

Joint Trauma

Answer 21

Joint trauma can be classified as:

• Sprain:
  
  • The wrenching of a joint with partial rupture or other injury of attachemnts, but not with luxation of bones. There is usually rapid swelling, heat and pain.
  • If ligament rupture or avulsion is suspected, stressed radiographs should be obtained to asses the integrity of the joint and the possibility of subluxation.
  • US may yielf additional information.
• Luxation:
  
  • Complete loss of contant between the articular surfaces of a joint.
• Subluxation:
  
  • Partial loss of contact between joint surfaces and may be intermittent.

NOTE: congenital luxation of the patella can occur in horses. But usually luxation is caused by trauma in horses.

Question 22

What causes subluxation of the proximal interphalangeal joint in horses?

Answer 22

It may develop without obvious cause, but may also occur secondary to injury of the oblique or straight sesamoidean ligament.

Luxation is usually easily identified with radiographs but multiple projections are needed to rule out concurrent fractures which may negatively impact the prognosis.

Question 23

Intraarticular fracture are also known as what?

Answer 23

“Chip fractures”

Differentiation between chip fractures, ectopic mineralization and separate centers of ossification may not be possible.

“Slab fractures”

Articular fractures extending from one joint surface to another. These fractures may be really difficul to identify in the acute phase. Oblique views, including skyline views, are invaluable in the carpus.

Question 24

Setpic arthritis

Answer 24

• Most common in young foals and commonly involve many joints
• May be seen in adults with truama, but may be iatrogenic

Radiographic features include:

• Periarticular soft tissue swelling
• Joint capsule distention, with or without apparent widening of the joint space
• Irregularity of outline of the subchondral bone
• Lucent zones in the subchondral bone, with or without areas of increased opacity
• Periarticular osteophyte formation, sude to secondary degenerative joint disease
• Partial collapse of subchondral bone