Final Exam - Joint Disease of the Thoracic Limb Flashcards
what is the pathogenesis of osteochondrosis?
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
what is osteochondrosis dissicans?
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
what animals are typically affected by OCD?
large & giant breeds, males more so than females, at 4-10 months of age
what are the common clinical signs seen with osteochondrosis dissicans of the shoulder?
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
where is OCD commonly seen in the shoulder?
caudocentral humerus
how is osteochondrosis diagnosed?
shoulder radiography with focus on the lateral view
shoulder CT
arthroscopy
what is the treatment for osteochondrosis?
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
depending on anatomical location, what is the prognosis of OCD in the shoulder, elbow, tarsus, & stifle?
shoulder - most forgiving
elbow & tarsus - less forgiving
stifle - least forgiving
T/F: some level of OA will develop in every joint with OCD
true
what is an example of another treatment of OCD?
osteochondral transplant - healthy cartilage/bone is harvested from a healthy donor site & OCD site is removed during coring
what are the anatomic points of interest of the elbow?
olecranon, trochlear notch, medial/lateral coronoid process, radial notch, articular fovea
what is the normal local transmission through the elbow joint?
traditionally, the radial head thought to transmit 80% of the load, but new studies suggest a near 50:50 load distribution
what diseases fall under elbow dysplasia?
OCD, medial coronoid disease, UAP, & elbow incongruence
what is the common signalment of animals affected by elbow dysplasia?
large/giant breeds (also small dogs & cats)
immature - 5-12 months, males more affected than females
T/F: a mature population of older dogs commonly presenting with medial coronoid disease late in life (6-10 years)
true
what are the 4 common developmental conditions referred to as elbow dysplasia?
ununited anconeal process, fragmented coronoid process, osteochondrosis dissicans, & OA
what breeds are commonly affected by elbow dysplasia?
labradors & bernese mountain dogs
what clinical signs are associated with elbow dysplasia?
progressive osteoarthritis, exercise-induced lameness, pain after exercise, loss of endurance, & reduced quality of life
clinical signs & pathology develop early
what is the suggested pathogenesis of elbow dysplasia?
incompletely understood - genetic, disturbance in coordinated growth of radius/ulna, abnormal endochondral ossification, incongruence, altered limb alignment, chronic mechanical overload
what signs are seen in gait evaluation in animals with elbow dysplasia?
observable lameness, effusion, fibrosis/thickening, decreased range of motion, pain on extension, deep medial palpation
some dogs may be normal on physical exam
how is elbow dysplasia diagnosed?
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
T/F: you can use radiographs to rule out elbow dysplasia
false - can have normal rads but clinical signs suggesting otherwise, 1/3 of dogs will have normal rads
what does CT provide when assessing an elbow for elbow dysplasia?
details about trabecular bone around coronoid (decrease in bone opacity)
allows thorough assessment for all components of dysplasia
other than MRI, arthroscopy is the only other method to evaluate what?
cartilage
what is the prognosis for a young dog with little OA with medial coronoid disease?
fair to good with arthroscopic debridement
what is the prognosis for a dog with coronoid disease with OCD or incongruity?
fair to guarded prognosis
what is the prognosis for coronoid disease with severe OA?
guarded to grave prognosis
long-term medical management, limb realignment, salvage procedures (total elbow)
what is the signalment & history of animals with ununited anconeal process?
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
what breeds are commonly affected by ununited anconeal process?
shepherds & ridgebacks
what is the pathogenesis of ununited anconeal process?
- disturbance in endochondral ossification
- disruption in microcirculation required during normal ossification
- joint incongruity (radioulnar) causes the elevation of the radial head above the articular portion of the ulna
- joint incongruity (reduced size of trochlear notch)
what is the most common cause of thoracic limb lameness?
elbow dysplasia
what is the definition of UAP?
failure of union between the anconeus & the remainder of the ulna beyond 20 weeks of age
why is medical management typically not recommended for treating UAP?
the UAP will persist & result in progressive lameness & profound OA
what 3 surgical options are provided for treatment UAP?
- proximal ulnar ostectomy
- surgical excision
- surgical reattachment with or without ulnar ostectomy
when is proximal ulnar ostectomy indicated for treating UAP?
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
when is surgical excision indicated for treating UAP?
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
when is surgical reattachment with or without ulnar ostectomy indicated for treating UAP?
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
of the clinical conditions associated with elbow dysplasia, which is the most common?
medial coronoid disease
what is medial coronoid disease?
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
what are the 4 theories of pathogenesis of medial coronoid disease?
- delayed ossification of this region of the joint
- atypical OC/OCD
- joint incongruity - radioulnar incongruency
- excessive mechanical overloading by the biceps tendon insertion
what are the 2 distinct populations of animals presenting with MCD?
- young dogs with an identical signalment to OCD
- 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
what are the orthopedic findings on a dog with MCD?
thoracic limb muscle atrophy, elbow joint effusion, thickened fibrotic elbow, decreased ROM, pain, & +/- crepitus during manipulation
or could be normal
what diagnostics are used to diagnose MCD?
3 view rads of both elbow joints & a craniolateral-caudomedial oblique view provides the highest sensitivity for identifying MCD
what radiographic findings support a diagnosis of MCD?
lack of visualization of the medial coronoid process, trochlear notch sclerosis, peri-articular osteophytosis, & elbow incongruity
what should you do if you have a dog with suspect MCD but has normal radiographs?
CT!!!!!! most sensitive & specific
what is the treatment of choice for MCD?
arthroscopic debridement of the MCD - fair to good prognosis
why must client expectations be managed prior to surgical correction?
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
