Final Exam - Joint Disease of the Thoracic Limb

Question 1

what is the pathogenesis of osteochondrosis?

Answer 1

altered PTHrP-IHH-TGFB axis & abnormal cartilage canals

abnormal endochondral ossification that occurs during the transformation of the epiphyseal growth plate from cartilage or bone

necrosis of the abnormal area of the physis occurs next which spares the overlying articular cartilage & underlying subchondral bone

focal necrosis results in fissure formation at the physis which spreads through the articular cartilage causing a flap or loose body

Question 2

what is osteochondrosis dissicans?

Answer 2

diseased cartilage separates from the bone - flap of cartilage is formed, once generated, subchondral bone & other wound signals enter the joint resulting in synovitis & subsequent osteoarthritis

Question 3

what animals are typically affected by OCD?

Answer 3

large & giant breeds, males more so than females, at 4-10 months of age

Question 4

what are the common clinical signs seen with osteochondrosis dissicans of the shoulder?

Answer 4

chronic thoracic limb lameness (2-4/5) that worsens with exercise - pain presents during shoulder flexion & extension

shortened stride of affected limb with predictable head bob

Question 5

where is OCD commonly seen in the shoulder?

Answer 5

caudocentral humerus

Question 6

how is osteochondrosis diagnosed?

Answer 6

shoulder radiography with focus on the lateral view

shoulder CT

arthroscopy

Question 7

what is the treatment for osteochondrosis?

Answer 7

surgery to remove the OCD flap or loose bodies & currettage & microfracture of subchondral bone is the treatment of choice with a good to excellent prognosis

medical treatment of OA as needed

Question 8

depending on anatomical location, what is the prognosis of OCD in the shoulder, elbow, tarsus, & stifle?

Answer 8

shoulder - most forgiving

elbow & tarsus - less forgiving

stifle - least forgiving

Question 9

T/F: some level of OA will develop in every joint with OCD

Answer 9

true

Question 10

what is an example of another treatment of OCD?

Answer 10

osteochondral transplant - healthy cartilage/bone is harvested from a healthy donor site & OCD site is removed during coring

Question 11

what are the anatomic points of interest of the elbow?

Answer 11

olecranon, trochlear notch, medial/lateral coronoid process, radial notch, articular fovea

Question 12

what is the normal local transmission through the elbow joint?

Answer 12

traditionally, the radial head thought to transmit 80% of the load, but new studies suggest a near 50:50 load distribution

Question 13

what diseases fall under elbow dysplasia?

Answer 13

OCD, medial coronoid disease, UAP, & elbow incongruence

Question 14

what is the common signalment of animals affected by elbow dysplasia?

Answer 14

large/giant breeds (also small dogs & cats)

immature - 5-12 months, males more affected than females

Question 15

T/F: a mature population of older dogs commonly presenting with medial coronoid disease late in life (6-10 years)

Answer 15

true

Question 16

what are the 4 common developmental conditions referred to as elbow dysplasia?

Answer 16

ununited anconeal process, fragmented coronoid process, osteochondrosis dissicans, & OA

Question 17

what breeds are commonly affected by elbow dysplasia?

Answer 17

labradors & bernese mountain dogs

Question 18

what clinical signs are associated with elbow dysplasia?

Answer 18

progressive osteoarthritis, exercise-induced lameness, pain after exercise, loss of endurance, & reduced quality of life

clinical signs & pathology develop early

Question 19

what is the suggested pathogenesis of elbow dysplasia?

Answer 19

incompletely understood - genetic, disturbance in coordinated growth of radius/ulna, abnormal endochondral ossification, incongruence, altered limb alignment, chronic mechanical overload

Question 20

what signs are seen in gait evaluation in animals with elbow dysplasia?

Answer 20

observable lameness, effusion, fibrosis/thickening, decreased range of motion, pain on extension, deep medial palpation

some dogs may be normal on physical exam

Question 21

how is elbow dysplasia diagnosed?

Answer 21

well positioned, high quality, 3 radiographs - least sensitive, low cost, sedation necessary

CT better than rads

arthroscopy - limited availability but ability to concurrently initiate treatment

Question 22

T/F: you can use radiographs to rule out elbow dysplasia

Answer 22

false - can have normal rads but clinical signs suggesting otherwise, 1/3 of dogs will have normal rads

Question 23

what does CT provide when assessing an elbow for elbow dysplasia?

Answer 23

details about trabecular bone around coronoid (decrease in bone opacity)

allows thorough assessment for all components of dysplasia

Question 24

other than MRI, arthroscopy is the only other method to evaluate what?

Answer 24

cartilage

Question 25

what is the prognosis for a young dog with little OA with medial coronoid disease?

Answer 25

fair to good with arthroscopic debridement

Question 26

what is the prognosis for a dog with coronoid disease with OCD or incongruity?

Answer 26

fair to guarded prognosis

Question 27

what is the prognosis for coronoid disease with severe OA?

Answer 27

guarded to grave prognosis

long-term medical management, limb realignment, salvage procedures (total elbow)

Question 28

what is the signalment & history of animals with ununited anconeal process?

Answer 28

young, large, & giant breed dogs with history/clinical signs similar to other conditions associated with elbow dysplasia, muscle atrophy

intermittent progressive lameness & more obvious pain during elbow extension

Question 29

what breeds are commonly affected by ununited anconeal process?

Answer 29

shepherds & ridgebacks

Question 30

what is the pathogenesis of ununited anconeal process?

Answer 30

1. disturbance in endochondral ossification
2. disruption in microcirculation required during normal ossification
3. joint incongruity (radioulnar) causes the elevation of the radial head above the articular portion of the ulna
4. joint incongruity (reduced size of trochlear notch)

Question 31

what is the most common cause of thoracic limb lameness?

Answer 31

elbow dysplasia

Question 32

what is the definition of UAP?

Answer 32

failure of union between the anconeus & the remainder of the ulna beyond 20 weeks of age

Question 33

why is medical management typically not recommended for treating UAP?

Answer 33

the UAP will persist & result in progressive lameness & profound OA

Question 34

what 3 surgical options are provided for treatment UAP?

Answer 34

1. proximal ulnar ostectomy
2. surgical excision
3. surgical reattachment with or without ulnar ostectomy

Question 35

when is proximal ulnar ostectomy indicated for treating UAP?

Answer 35

option if a dog is less than 6 months of age & the UAP is firmly attached to the parent ulna during arthroscopic exam - goal is to eliminate stress on the anconeal process allowing it to fuse on its own

Question 36

when is surgical excision indicated for treating UAP?

Answer 36

if the dog is 9-12 months or older & the clients have a low tolerance for risk - excision definitively removes the ununited anconeal process but results in long-term instability of the joint which will cause some degree of progressive OA

Question 37

when is surgical reattachment with or without ulnar ostectomy indicated for treating UAP?

Answer 37

dog is older than 6 months, the UAP is non-adherent during arthroscopy, & the clients wants to salvage the UAP with the goal of having superior long term function with reduced incidence of OA using lag screw fixation of the UAP to the parent ulna

Question 38

of the clinical conditions associated with elbow dysplasia, which is the most common?

Answer 38

medial coronoid disease

Question 39

what is medial coronoid disease?

Answer 39

primary lesion is fissuring or fragmentation of the craniolateral aspect of the medial portion of the coronoid process - can involve cartilage alone, subchondral bone alone, or both

Question 40

what are the 4 theories of pathogenesis of medial coronoid disease?

Answer 40

1. delayed ossification of this region of the joint
2. atypical OC/OCD
3. joint incongruity - radioulnar incongruency
4. excessive mechanical overloading by the biceps tendon insertion

Question 41

what are the 2 distinct populations of animals presenting with MCD?

Answer 41

1. young dogs with an identical signalment to OCD
2. older dogs (labs) that have been completely normal throughout their life prior presenting with chondromalacia or osteomalacia of the medial coronoid process & not a distinct fragment

Question 42

what are the orthopedic findings on a dog with MCD?

Answer 42

thoracic limb muscle atrophy, elbow joint effusion, thickened fibrotic elbow, decreased ROM, pain, & +/- crepitus during manipulation

or could be normal

Question 43

what diagnostics are used to diagnose MCD?

Answer 43

3 view rads of both elbow joints & a craniolateral-caudomedial oblique view provides the highest sensitivity for identifying MCD

Question 44

what radiographic findings support a diagnosis of MCD?

Answer 44

lack of visualization of the medial coronoid process, trochlear notch sclerosis, peri-articular osteophytosis, & elbow incongruity

Question 45

what should you do if you have a dog with suspect MCD but has normal radiographs?

Answer 45

CT!!!!!! most sensitive & specific

Question 46

what is the treatment of choice for MCD?

Answer 46

arthroscopic debridement of the MCD - fair to good prognosis

Question 47

why must client expectations be managed prior to surgical correction?

Answer 47

a surgical cure is unlikely in the majority of cases - goal of surgery is to remove the diseased bone/cartilage, expose the healthy bone for fibrocartilage ingrowth which will slow the progression of OA