-start 10.31.96 clinical correlation----

anatomy is extremely important and may be the most important thing we 
learn...

when making a surgical approach, you need to know the landmarks and what 
you need to avoid.

in the hock, making a dorsal approach, you need to avoid the dorsal pedal 
artery which is located in the front of the tarsus lateral to the 
midline.

you also need to avoid the saphenous vein, peroneus tertius, long digital 
extensor.

slide: two foals ADR. not moving right. weanling thoroughbreds, about 8 
mos. one of these foals is standing on its toes in the R forelimb. the 
other one is on the toe of the R hind, but that's just because he's 
resting, but he also has the L forelimb involved in this "toe stepping" 
thing.

as it turned out, the horse COULD push the heel toward the ground when 
bearing wt, but at rest it was off the ground.

on radiographs we see that the coffin bone is not positioned correctly. 
anatomically, the distal phalanx is flexed such that the distal portion 
is reflected in a palmar direction from the normal anatomical position. 
This is a flexural deformity of the distal interphalangeal joint, and is 
pretty common in horses of this age. it's also called "contracted 
tendons" - what tendons are involved? the DEEP digital flexor, because 
it's the one that inserts on the distal phalanx.

aside: there's a laryngeal muscle called the cricoerytenoideus dorsalis 
muscle. paralysis of this causes roaring. this is a good anatomical name, 
because you can tell where it originates and inserts...

deep digital flexor tendon name doesn't help. the DDF originates at the 
proximal radius and ulna and distal humerus. the deep flexor then becomes 
tendinous and passes through the carpal canal - down the back of the 
metacarpus, over the palmar aspect of the sesamoids, and over the 
pastern, over the navicular bone(caudal to navicular bursa) and it 
inserts broadly on Piii.

it's important to have a broad insertion. "street nail" can occur when a 
horse steps on something sharp and cuts through the frog and into the 
insertion of the deep flexor tendon and into either the navicular bursa 
or the coffin bone.

to fix you have to cut a window in the bottom of the foot to drain it.

because the insertion is broad, you don't lose all function with this 
pathology.

superficial flexor inserts on Pi and Pii. clinical injury to superficial 
flexor often occurs at the point where it splits to form its two branches 
of insertion.

treatment....corrective trimming, lower the heel, lengthen tthe toe, this 
can stretch the tendon. now, if the dz is advanced, and the heel is 
already off the ground, this won't help. also, clinically, this isn't 
always going to work, because sometimes this problem is seen in foals who 
are already foot sore, and it just makes it worse.

other treatment options (nonsurgical) include backing off nutritionally 
or a shoe with a toe extender, also will have the effect of stretching 
the ddf tendon.

surgically you COULD cut the ddf, but that would have problems.you could 
cut the check ligament of the DDF. if you do cut the inferior check 
ligament, where do you cut it? well, you have to do it above the 
midmetacarpal region, because distally it is blended entirely with the 
ddf tendon. and you don't want to do it just distal to the carpus, 
because there are too many other things in the way.

incise about 1/3 of the way down the metacarpus on the medial side. it's 
easier going laterally, but it's done medially because it will look 
nicer....the scar, if any, will be on the medial side. So, at the 
palmar/proximal/medial part of the metacarpus, you'll cut skin and light 
filmy CT and then you get to some very dense fascia. you cut through that 
and just under that you'll see the neurovascular bundle, so you have to 
be extremely careful. so you separate the neurovascular bundle away from 
the ligaments and tendons. pull out the inferior check ligament and cut 
it...it has a kind of crescent shape in cross section.

it is VERY important not to cut the wrong things.

once the check lig is cut you can extend the foot, and the cut edges will 
separate.

aftercare: NSAIDs, pressure bandage, stall rest, corrective shoeing - toe 
extender. toe extender will stretch the ddf as you recall..

in VERY severe cases you do have to cut the tendon of the DDF. You cut 
close to the distal phalanx in the midpastern region.

cause of flexural deformity as presented today is not completely clear. 
it may be related to bad running surface or other cause of soreness. may 
be excessive growth/bones outgrowing tendons, likely not however.



in the HIND limb, the inferior check ligament is MUCH much smaller, and 
cutting it isn't as helpful.

slide: 3 yo thoroughbred filly, went lame in race, had to be removed via 
ambulance. when FORCED to bear wt on L foreleg, it was seen that the 
caudal metacarpal region was severely swollen, and the 
metacarpophalangeal joint was severely hyperextended. 

well, if you cut the DDFT, the TOE will flip up, and the horse will stand 
on the heel. if you cut the SDFT, the fetlock will drop, but not fall to 
the ground, because the suspensory is still in place.

radiographs of this limb show proximal displacement of the proximal 
sesamoid. in this horse, the straight, oblique, and cruciate sesamoidean 
ligaments were ruptured, so the sesamoids get pulled up the leg because 
nothing is there to hold them down.

in another case, the sesamoids are too low, and therefore there had to 
have been an injury with the interosseus body or branches.

SUSPENSORY APPARATUS: origin is the palmar proximal aspect of the 
metacarpus, where you the suspensory ligament starts. distally the 
suspensory bifurcates into lateral and medial branches which attach to 
the proximal sesamoid bones (small branches go on as extensor branches 
but that isn't important).

to treat a failure of the supsensory apparatus you may end up fusing the 
joints. you put a plate on dorsally.



---end cc----