Clean Run magazine/Dr Canapp

[Guest guest]

I picked up the April issue of Clean Run magazine to look over at lunch today and what did I find but an article by Dr Sherman Canapp on "Jump Down Syndrome". Although I've never seen reference to this syndrome in the veterinary literature (yet), I found an explanation for some of the perplexing problems I sometimes see in canine athletes.

Thanks for the terrific article. I look forward to learning more.

Regards,

Carol Helfer, DVM

Portland, OR

[Guest guest]

So tell us more. I compete in agility and never heard of this.

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[Guest guest]

Carol,

Thank you very much for your kind words regarding the " Jump Down

Syndrome " article. I wish I could take full credit for this

interesting condition, however it was first described by the co-

author of the paper Don Hulse, DVM, DACVS….we just happen to see this

condition commonly at VOSM and I decided to include it in our Clean

Run sports medicine series. Unfortunately, according to Clean Run

they will not allow dissemination of the article until 120 days after

the date of publication; however you can find it at:

http://www.cleanrun.com/index.cfm?

fuseaction=product.display & Product_ID=1533 & ParentCat=372

Just a brief skinny on the condition:

" Jump down syndrome " or traumatic fragmented medial coronoid process

is a condition in the elbow joint of dogs which appears to occur

commonly in performance dogs. Unlike the classic condition of

fragmented medial coronoid process (FMCP) affecting the elbow joints

of skeletally immature large to giant breed dogs, jump down syndrome

(JDS) appears to have no age or size limitations.

The cause and pathogenesis of JDS are poorly understood. It is

possible that abnormal repetitive loading such as landing from a

jump, hitting contacts, a fly ball box, etc. may lead to subchondral

bone fracture. Additionally, increase repetitive loading can arise

from contraction of the biceps/brachialis muscle complex. When the

biceps/brachialis contracts, a froce is generated which rotates the

medial coronoid into the radius. This action leads to internal

stresses which may lead to microcracks within the coronoid bone

structure. Repeated loading from mechanical overload (jumping etc.)

or muscle contraction of bone leads to formation of microcracks

within the mineralized tissue. These microcracks disturb the

mechanical properties of bone, and if not repaired properly through

normal body mechanisms, fatigue fractures develop. Additionally, loss

of osteocytes, indicated by decreased osteocyte densities, has been

strongly associated with the presence of microdamage after fatigue

loading. These studies imply that excess load may lead to fatigue

microdamage of the subchondral trabecular bone and eventual fracture,

which may play an important role in the pathogenesis of JDS. Dogs

may be further predisposed to this condition if they have elbow

dysplasia. Dogs with elbow dysplasia had asymmetric growth of the

radius and ulna during development resulting in elbow joint

incongruity. Elbow incongruity such as radioulnar step defects,

humero-ulnar incongruence/conflict and varus deformity of the humerus

causes abnormal contact patterns in the elbow, specifically at the

coronoid trochlear articulation which is theorized to increase the

load on the medial coronoid process. A second theory is that there

is an imbalance between skeletal and muscular mechanics and the

fragment arises from internal shear stress (within the cancellous

bone of the coronoid) secondary to the load produced by the polar

moment resulting from biceps contraction. These theories are

currently being investigated through biomechanical studies.

We are currently in the process of submitting a paper on this

condition to Vet Surg. One of our coauthors, Acciani, PT is

helping with the post-op rehabilitation therapy section. Please let

me know if you have additional questions regarding this condition.

Best Regards,

Sherman

Sherman O. Canapp Jr., DVM, MS

Diplomate ACVS

Veterinary Orthopedic &

Sports Medicine Group

10270 Baltimore National Pike

Ellicott City, MD 21042

Phone:

Fax:

http://www.vosm.org

>

>

> I picked up the April issue of Clean Run magazine to look over at

lunch today and what did I find but an article by Dr Sherman Canapp

on " Jump Down Syndrome " . Although I've never seen reference to this

syndrome in the veterinary literature (yet), I found an explanation

for some of the perplexing problems I sometimes see in canine

athletes.

>

> Thanks for the terrific article. I look forward to learning more.

>

> Regards,

> Carol Helfer, DVM

> Portland, OR

>