Clinical signs and diagnosis
The clinical signs associated with hind limb PSL desmopathy can vary from extremely mild to moderate lameness. Horses may
show classic, unilateral low-grade lameness and be unable to perform certain specific athletic movements (i.e., uneven or poorly performed canter pirouettes in the dressage ring, uneven stops or resistance and twisting when backing
up in western events, uneven jumping and landing over fences and so on) or may exhibit very subtle performance problems that
are only "felt" by upper-level riders as a resistance or hesitancy in specific movements. Even more subtle signs, such as
altered head carriage, bolting or other behavioral changes, have been caused by PSL desmopathy.
Diagnosis of this particular injury can be difficult because of the number of structures present in the area of the PSL. Clinicians
must try to rule out the distal limb and the hock joint and capsule as sources for the hind limb pain and lameness. Thermography
can often confirm increased heat in the area of the PSL but cannot differentiate between ligamentous inflammation and neuritis
at that location.
Proximal suspensory desmopathy cases often show no swelling or palpable tenderness. Regional anesthesia can be helpful in
this diagnostic process, but closely associated structures in this area other than the PSL may also be affected so nerve blocks
are not considered completely diagnostic. Ultrasound evaluation is the field diagnostic modality of choice, and abnormalities
of an affected PSL include changes in size (bigger), shape (uneven), echogenicity (small- to large-core lesions) and fiber
pattern (disrupted fiber development). But even ultrasound leaves something to be desired and can underrepresent the amount
of damage to the PSL.
Robert Cole, DVM, DACVR, an assistant professor of radiology at Auburn University's College of Veterinary Medicine, cautions
that a complete workup of a case of suspected PSL desmopathy should also include radiography. Primary bone pathology, distal
intertarsal joint issues, avulsions and numerous other bony causes of lameness can mimic PSL desmopathy and should be properly
Cole also adds that magnetic resonance imaging (MRI) is rapidly becoming the gold-standard diagnostic tool for cases of PSL
desmopathy, as it allows surgeons to know if the ligament is the primary issue or if nerve compression is the major cause
of lameness. "Neurectomy is not a procedure done casually, and MRI really lets the surgeon be sure that it's the correct procedure
for the condition," says Cole.
Treatment and outcomes
Initial cases of proximal suspensory desmopathy are treated routinely utilizing cold therapy, compression and rest. These
injuries are monitored over the following eight weeks before any attempts at surgery are made.
"Case selection is extremely important for success when using a fasciotomy–neurectomy treatment approach for PSL desmopathy,"
explains Reid Hansen, DVM, DACVS, DACVECC, professor of equine surgery and lameness at Auburn University's College of Veterinary
Some surgeons, such as John Peroni, DVM, MS, DACVS, an associate professor of large animal surgery at the University of Georgia's
College of Veterinary Medicine, believe there are no contraindications for a fasciotomy at almost any point in the suspensory
ligament injury timeline. "Relieving pressure can only help the underlying ligament heal, so performing this procedure—even
in acute desmitis cases—is quite acceptable," states Peroni.
The neurectomy part of the procedure, however, is saved for a time much later in the disease process. Horses are given four
to eight weeks of rest and then reevaluated. If significant healing is occurring, as evidenced by ultrasonographic changes
in the thickness and character of the suspensory ligament, then the horse is given additional healing time along with appropriate
Nathaniel White, DVM, MS, DACVS, a professor emeritus of equine surgery at the Marion DuPont Scott Equine Medical Center at
Virginia-Maryland Regional College of Veterinary Medicine at Virginia Technical Institute, teaches that rest is the most common
and often most effective treatment for proximal suspensory desmopathy.
"The greatest success with no relapses," says White, "includes absolute stall rest for four weeks prior to initiating controlled
and gradual increase in walking concurrent with stall rest." Horses that do not respond to this initial healing phase are
then candidates for fasciotomy and ligament splitting.
Excellent results are being reported for this approach to these performance injuries. White summarizes, "To date, 95 percent
of horses with rear limb proximal suspensory desmitis, which did not heal with rest or rest and shock wave therapy, healed
and returned to normal work after suspensory desmoplasty."
Horses that respond to time and treatment and eventually have well-healed suspensory ligaments, as shown with sequential ultrasound
evaluations or preferably MRI, but that are still painful and lame are candidates for neurectomy. These athletes have strong
enough ligaments to handle a return to work, and neurectomy can be beneficial in eliminating neuritis of the lateral plantar
nerve and the associated lameness.
Horses that do not respond after longer periods of rest are labeled as chronic, and their thickened, fibrotic, hypoechoic
suspensory ligaments are not likely to change. These horses are poorer candidates for a fasciotomy-neurectomy procedure. Once
these horses undergo a neurectomy they are more likely to load the suspensory ligament, and there is no remaining pain response
to keep them from excessive activity. A number of horses that have had neurectomies without well-healed ligaments have suffered
catastrophic breakdowns of the hind limb suspensory apparatus following a return to exercise.
Fasciotomy and neurectomy of the proximal suspensory ligament and associated nerve is a procedure that offers hope to affected
horses, but the selection of candidates must be done carefully. MRI should be utilized if at all possible to identify those
horses best suited to these surgeries, and strict postoperative care and rehabilitation are required to achieve a positive
Dr. Kenneth Marcella is an equine practitioner in Canton, Ga.
1. Toth F, Schumacher J, Schramme M, et al. Compressive damage to the deep branch of the lateral plantar nerve associated with
lameness caused by proximal suspensory desmitis. Vet Surg 2008;37:328-335.