Articles and Information
Degenerative Suspensory Ligament Desmitis
by Janice Young, DVM
Degenerative Suspensory Ligament Desmitis (DSLD) is a chronic, degenerative condition that affects bilateral suspensory ligaments in many breeds of horses. This condition was first recognized by a study done at UC Davis in 1981 and was described by Drs. Wheat, Pool and Pryor. It was termed Passive Suspensory Ligament Failure. To date very little has been published to describe this syndrome.
Horses will present with a history of an obscure lameness problem. Cases may be mildly affected and have only a painful response to palpation of the suspensory ligaments, especially in the branches just proximal to the proximal sesamoid bones.
There is always a bilateral distribution of this problem, either both hind legs, both front legs or all four legs. Not the usual suspensory injury of the jumper or racer. An exaggerated dropping of the fetlock will occur with motion, during gait or perhaps only evident with the weight of the rider. Lameness may be hard to detect in a gaited horse. The horse may default to trotting or pacing. Some horses may become difficult to shoe. The weight bearing of the off leg causes the pain and the fighting during the shoeing procedure. These horses may exhibit a painful withdrawal reflex and stand with the leg held close to the belly, if forced to stand on an affected limb for long periods of time or secondary to palpation of the suspensory branches. As the suspensory ligaments become more involved, the fetlocks drop. The horse becomes more painful, more upright through the hind conformation, and becomes very straight in the hock and stifle area. Some horses may dig holes and stand in them and refuse to move out of these holes, even for feed or water. Owners will fill in the holes and the horse will be found digging them out again to stand there. Eventually the horses become end stage with the fetlocks on the ground and very painful and spend most of the time down. Some of these cases have been confused with chronic colicers. Acute rupture of the suspensory ligaments may occur and Dr. Pool has seen a few cases involving the distal sesmoidean ligaments.
The diagnosis of DSLD would involve palpation, blocking, radiographs, ultrasound and nuclear scintigraphy.
Palpation of bilaterial suspensory branches could indicate a case of DSLD. These cases will block to a high volar and even a hock block may make these horses look sound.
Ultrasound imaging will conform the diagnosis. There will be a poor fiber pattern and enlarged circumference with microtearing at the level of insertion to the proximal sesamoid bone. Enlargement greater than 1.2 cm in circumference affecting both hind legs, both front legs, or all four legs would be diagnostic.
Radiographs will reveal a gradual lowering of the proximal sesamoid bones over time (years). Mineralization of the tissue in the area of the suspensory branches is common and subluxation of the pastern joint wth eventual development of high ringbone can be seen in various stages of DSLD. All changes are usually bilateral.
Nuclear scintigraphy clearly demonstrates a unique signature in both the soft tissue phase and the bone phase. During the soft tissue phase the suspensory branches will light up. On the bone phase the proximal sesamoid bones and the pastern joint will also be hot. These changes are also bilateral or affect all four legs. Dr. Hood has told me that the proximal sesamoid bones had lesions in the DSLD horses shipped from Phoenix to Texas AM after the DSLD siminar in Phoenix, 1998.
The clinical pathology of will reveal the extent of the degeneration that has been sustained by the suspensory ligament. The ligament will be enlarged grossly and has a hard, fibrous feel. There may be adhesions of the suspensory ligament to the cannon bone, splint bones and the DDFT. The bifurcation between the suspensory branches may be totally filled with fibrocartliage. Histopathology on more than 30 cases done by Dr. Pool in 1992 showed a consistent pathological process. Speculation is that, at some point in the life of a predisposed horse, a previously normal suspensory ligament begins to undergo a strain the causes microtears. A "normal" horse would repair this ligament damage with Type III collagen. The new collagen fibers would orient themselves in line with the stress on the tissue as the healing progressed. In predisposed horses, cartilage is laid down instead of collagen. It is how the DSLD horse "heal" that is the problem. Fibroblasts defect and become chondryocytes and lay down cartilage that is not supportive enough to bear the strain on the suspensory tissue. These ligaments continue to break down with time. This tendency to be predisposed to this problem seems to follow direct family lines.
Treatment involves confinement and analgesics as needed. Supportive leg wraps may help initially. Therapeutic shoes that will elevate and give caudal support to the foot will give immediate relief. Patton shoes are helpful behind and wedged eggbar support is used on the front legs. Although this shoeing is not what the book says, it gives immediate relief to these horses and the ligaments "heal" over time as monitored by ultrasound. MSM seems to help as well as Promotion EQ.
The prognosis is poor for any athletic performance and the best to be hoped for is a comfortable pasture pet.
Horses will present with a history of an obscure lameness problem. Cases may be mildly affected and have only a painful response to palpation of the suspensory ligaments, especially in the branches just proximal to the proximal sesamoid bones.
There is always a bilateral distribution of this problem, either both hind legs, both front legs or all four legs. Not the usual suspensory injury of the jumper or racer. An exaggerated dropping of the fetlock will occur with motion, during gait or perhaps only evident with the weight of the rider. Lameness may be hard to detect in a gaited horse. The horse may default to trotting or pacing. Some horses may become difficult to shoe. The weight bearing of the off leg causes the pain and the fighting during the shoeing procedure. These horses may exhibit a painful withdrawal reflex and stand with the leg held close to the belly, if forced to stand on an affected limb for long periods of time or secondary to palpation of the suspensory branches. As the suspensory ligaments become more involved, the fetlocks drop. The horse becomes more painful, more upright through the hind conformation, and becomes very straight in the hock and stifle area. Some horses may dig holes and stand in them and refuse to move out of these holes, even for feed or water. Owners will fill in the holes and the horse will be found digging them out again to stand there. Eventually the horses become end stage with the fetlocks on the ground and very painful and spend most of the time down. Some of these cases have been confused with chronic colicers. Acute rupture of the suspensory ligaments may occur and Dr. Pool has seen a few cases involving the distal sesmoidean ligaments.
The diagnosis of DSLD would involve palpation, blocking, radiographs, ultrasound and nuclear scintigraphy.
Palpation of bilaterial suspensory branches could indicate a case of DSLD. These cases will block to a high volar and even a hock block may make these horses look sound.
Ultrasound imaging will conform the diagnosis. There will be a poor fiber pattern and enlarged circumference with microtearing at the level of insertion to the proximal sesamoid bone. Enlargement greater than 1.2 cm in circumference affecting both hind legs, both front legs, or all four legs would be diagnostic.
Radiographs will reveal a gradual lowering of the proximal sesamoid bones over time (years). Mineralization of the tissue in the area of the suspensory branches is common and subluxation of the pastern joint wth eventual development of high ringbone can be seen in various stages of DSLD. All changes are usually bilateral.
Nuclear scintigraphy clearly demonstrates a unique signature in both the soft tissue phase and the bone phase. During the soft tissue phase the suspensory branches will light up. On the bone phase the proximal sesamoid bones and the pastern joint will also be hot. These changes are also bilateral or affect all four legs. Dr. Hood has told me that the proximal sesamoid bones had lesions in the DSLD horses shipped from Phoenix to Texas AM after the DSLD siminar in Phoenix, 1998.
The clinical pathology of will reveal the extent of the degeneration that has been sustained by the suspensory ligament. The ligament will be enlarged grossly and has a hard, fibrous feel. There may be adhesions of the suspensory ligament to the cannon bone, splint bones and the DDFT. The bifurcation between the suspensory branches may be totally filled with fibrocartliage. Histopathology on more than 30 cases done by Dr. Pool in 1992 showed a consistent pathological process. Speculation is that, at some point in the life of a predisposed horse, a previously normal suspensory ligament begins to undergo a strain the causes microtears. A "normal" horse would repair this ligament damage with Type III collagen. The new collagen fibers would orient themselves in line with the stress on the tissue as the healing progressed. In predisposed horses, cartilage is laid down instead of collagen. It is how the DSLD horse "heal" that is the problem. Fibroblasts defect and become chondryocytes and lay down cartilage that is not supportive enough to bear the strain on the suspensory tissue. These ligaments continue to break down with time. This tendency to be predisposed to this problem seems to follow direct family lines.
Treatment involves confinement and analgesics as needed. Supportive leg wraps may help initially. Therapeutic shoes that will elevate and give caudal support to the foot will give immediate relief. Patton shoes are helpful behind and wedged eggbar support is used on the front legs. Although this shoeing is not what the book says, it gives immediate relief to these horses and the ligaments "heal" over time as monitored by ultrasound. MSM seems to help as well as Promotion EQ.
The prognosis is poor for any athletic performance and the best to be hoped for is a comfortable pasture pet.
It should be noted here that from the time of the writing of this article there has been strides in the recognizing and treatment of this disease but it is still all too often misdiagnosed.
There are now several good articles out there about this disease.
I find this one by Dr Deb Bennett, PhD to be one of the best.
"Are Post-legged horses DSLD carriers?"
Links
The following are links to sites that we feel you may find helpful.
We are in no way responsible for the content on these sites.
The Emergency Euthanasia of Horses
http://www.vetmed.ucdavis.edu/vetext/inf-an/inf-an_emergeuth-horses.html
UC Davis link explaining how euthanize a horse in the event of an emergency.
A must have print out for anyone that hauls horses or does trail riding
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The American Farriers Association
http://americanfarriers.org/
A site where you can find a good Farrier in your area and see examples of good shoeing.
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