In suspense

UNDERSTANDING SUSPENSORY LIGAMENT INJURIES

The suspensory ligament is one of the most common soft tissue structures to be affected by injury in the horse. This ligament plays a significant supportive role in the horse's lower leg, so injury to this structure can prove devastating.

THE SUSPENSORY LIGAMENT

The horse's suspensory ligament runs from just below the hock or knee and extends down the back of the cannon bone before attaching to the sesamoid bones at the back of the fetlock. It runs as one single band of tissue until about two-thirds of the way down the cannon bone, at which point it splits into two branches. Ultimately, there are three separate portions of the suspensory: 1. The proximal suspensory ligament 2. The suspensory body 3. The suspensory branches

Each portion of the ligament has individual characteristics and sustains different injuries.

INJURIES

The proximal suspensory ligament most commonly develops proximal suspensory desmitis (PSD). This inflammation of the ligament occurs due to an accumulation of damage over time, normally caused by the repetitive overload of the ligament. Unfortunately, in an athletic horse, it can be hard to avoid this injury due to the type of work we tend to ask them to perform. Having said this, this injury is more likely to occur in some horses than others due to conformation, discipline, level of work, exercise surface and the intensity of work. This disease process is more common in horses that are asked to 'sit' on their hindlimbs and collect.

Another less common injury of the proximal suspensory ligament is an acute tear of the ligament. This is normally also the result of overstrain. It tends to cause more severe lameness than PSD.

The body and branches of the suspensory ligament often sustain sudden onset injuries due to overstrain or trauma. There may be a tear or a hole in the ligament when it is examined with an ultrasound. These injuries are less common than PSD, and they tend to occur in showjumpers performing at a higher level due to the increased strain on the ligaments. These injuries can be made worse by uneven exercise surfaces and poor foot balance.

SIGNS OF INJURY

Horses with PSD are often reported to have been performing poorly. They may have started refusing jumps, not wanting to go forwards when ridden or struggling to do their lateral work. In some cases, lameness will be the presenting symptom. Due to the location of the ligament, swelling is very rarely seen on clinical examination, but in some cases, placing pressure over the area can elicit a pain response.

In cases of suspensory body injuries, horses are often lame with a swelling of the affected limb at the point of the injury. In the early stages of the injury, there may also be more generalised limb swelling.

Correct foot balance is important for horses with all horses but particularly those with suspensory issues.

DID YOU KNOW?

Horses performing at a high level of work at a young age are often more likely to develop PSD than those given time to mature before being asked to perform the same movements. PROXIMAL

BODY

BRANCHES Proximal suspensory ligament

Suspensory body

Suspensory branches

Suspensory branch injuries may or may not be associated with lameness. More commonly, there is localised swelling associated with the injury that is easily palpable due to the superficial nature of the ligament.

DIAGNOSIS

All suspensory ligament injuries are diagnosed in a similar way. A clinical history will be taken, and a physical examination performed. The reported issues from the rider may give clues, as may the physical examination.

The next stage usually involves nerve blocks to confirm the site of pain. This is most applicable to cases with PSD because there are unlikely to be localising signs. This process involves incrementally blocking structures in the limb, generally starting at the bottom and working upwards until the lameness has resolved. In cases where the suspensory body or branches are injured, and there is obvious swelling or heat in the region, nerve blocks

WHAT ARE ORTHOBIOLOGIC TREATMENTS?

Orthobiologic treatments are products made from the horse's own blood, which is concentrated down to collect the growth factors and cells responsible for aiding healing in the body. These are then injected into the damaged area to promote betterquality healing. These agents do not, however, dramatically reduce the rehabilitation time.

may not be necessary, and ultrasound might be the most appropriate next step.

Ultrasound is the most helpful imaging tool for suspensory ligament injuries. Ultrasound will give information about the lesion's location, size, severity and age. The ultrasound results often also determine the treatment method for the horse. Often both hind or both front legs would be scanned to check for similar damage on the other leg.

In some cases, it may also be recommended to assess the injury with MRI, which gives further information about the injury. This is very difficult to arrange in South Africa, so it is likely that ultrasound will be the main diagnostic modality.

TREATMENT

For PSD, there are two main treatment options. The first is surgical and involves cutting the small nerve branch that supplies the top of the suspensory ligament and the connective tissue that sits next to it to reduce compression. The second is much more conservative and involves shockwave therapy and local treatment with steroids.

Suspensory branch and body injuries, on the other hand, are treated differently. Cold hosing or icing of the affected limb is beneficial in the early stages. Further treatment for mild cases includes rest and controlled walking exercise. More severe cases can be treated with injections into the damaged area with orthobiologic drugs like plateletrich plasma (PRP), which aims to improve the quality of the healing within the ligament. In addition, high-powered laser therapy (Class 4 high-powered multi-frequency laser therapy) can be used to stimulate cells in the targeted area to encourage healing. This is often used in combination with the injections. Shockwave can also be used in cases where the horse is lame.

PROGNOSIS

The prognosis of returning to previous athletic function following a suspensory injury varies hugely depending on the type and location, the severity, the duration of the injury and the level of athleticism ultimately expected of the horse. With PSD, it is said that 70% of horses treated surgically and 40% of horses treated medically return to their previous level of competition. The prognosis is more guarded in cases with straight hocks or more severe lameness or ultrasound findings.

Re-injury to the proximal suspensory ligament is less likely theoretically due to the nature of the injury. Rather

than re-injury, it is more common to have a reoccurrence of lameness or poor performance. The risk of this depends on the chosen treatment method – surgical management often offers a long-term solution, whereas conservative treatment tends to last between 6 and 12 months.

The prognosis for suspensory branch and body injuries is more dependent upon the severity and type of injury. These injuries usually require the horse to have more time off and careful rehabilitation as they are more prone to re-injury. Following injury, these areas are also more likely to develop scar tissue, which is less elastic than the surrounding tissue and can predispose to more injuries above or below the site of the previous injury.

PREVENTION

Several steps can be taken to reduce the risk of suspensory injuries, such as: • Good foot balance, achieved through correct and regular farrier work, will prevent undue strains on the ligament. • Avoiding riding on deep, rutted or uneven ground. • Careful training to avoid too much repetitive strain. • Ensuring an appropriate fitness level for the work performed, as well as ensuring that supporting musculature is in place through correct training.

FINAL THOUGHTS

Suspensory injuries, while slow to recover from, don't have to mean the end of a horse's career. By managing the horse holistically and carefully, you can substantially reduce the risk of injury in the first place, and by promptly contacting your vet if you have concerns, you can improve your horse's outcome. Finally, by working closely with your vet and managing rehabilitation sensitively, you can give your horse the best chance of returning to good athletic function.