Suspensory Ligament Damage

Proximal Suspensory Ligament Desmitis (PSD)

  • Caused by repetitive strain or single overloading injury
  • Generally acute onset lameness in the forelimb but usually a chronic progressive problem in the hindlimb
  • Diagnosis is based on nerve blocks and ultrasound scan
  • Treatment options include: box rest, anti-inflammatories, controlled exercise for minimum 3 months, injections into the suspensory ligament or surgery
  • Potentially much more serious in the hindlimb than the forelimb; guarded prognosis for forelimb and hindlimb acute injury, but poor for chronic hindlimb PSD.

What is the suspensory ligament?

The suspensory ligament is attached to the back of the upper cannon bone and knee (in the front legs) or hock (in the hind legs), runs downwards close to the back of the cannon and divides into two branches, each of which attaches to a sesamoid bone at the back of the fetlock, before ending attached to the upper pastern. The suspensory ligament supports the fetlock and protects it from dropping at exercise.

Presenting signs

In the forelimbs acute onset lameness – often resolves with rest but returns with premature work, lameness may become chronic and persistent. In the hindlimbs there is occasionally a sudden onset lameness but is usually insidious, mild to severe lameness – this may persist as a serious chronic lameness despite box rest, with the hindlimbs being more commonly affected in both legs than in forelimbs.

Diagnosis

Presenting problems may include any of the following: Hindlimb lameness, forelimb lameness, lameness after strenuous exercise, loss of action and impulsion (especially in hindlimb cases), poor performance during jumping or specific dressage movements.

Forelimb

  • Acute lameness – mild to moderate; may be apparent only at high speeds
  • Chronic cases consistently mild to moderate lameness
  • More common to have lameness in one leg only
  • In acute cases, mild localised heat and possible swelling with pain at the back of the knee
  • In chronic cases may be palpable thickening and rounding of the ligament
  • Lameness often transiently accentuated following distal limb flexion
  • Lameness worse with affected limb on the outside of the circle and on a soft surface
  • Often more obvious when ridden
  • If both legs affected, may lead to loss of action and shortened stride rather than overt lameness

Hindlimb

  • Rarely sudden onset, mild to severe lameness in one leg
  • Usually insidious lameness, or just poor performance with both legs affected (often affecting the whole horse’s movement and impulsion)
  • Lameness may persist and remain despite box rest
  • Localized heat, pain, swelling, although more often no localizing clinical signs
  • If both hindlimbs affected, results in poor hindlimb action – reduced impulsion, stiffness, difficulty in turning, reduced jumping power
  • Lameness often more obvious on a circle and also when ridden, and especially on a soft surface
  • Lower and upper flexion tests may be positive

Nerve blocks

Nerve blocks may be performed to localise pain to specific areas. None of these techniques are specific for PSD and false-negatives may result from inadvertent injection into other structures.

Ultrasound scan

High quality imaging is essential because changes can be subtle and artefacts readily created. Transverse and longitudinal views will need to be taken and oblique images for edge lesions. Ultrasound is often compared to the opposite limb. There may also be some evidence of bony changes on ultrasound, however to confirm these, X-rays may need to be taken.

Scintigraphy (‘Bone scan’)

‘Bone scan’ may be only means of diagnosis for cases where there is predominantly bone injury with minimal changes on X-ray or ultrasound scan. However, it is not a sensitive means of detection of PSD in the hindlimbs and negative scintigraphic images do not exclude the presence of PSD.

Treatment

Phase 1 – Acute (inflammatory) phase lasting 7-10 days

Aggressive anti-inflammatory treatment (bute) – aim to decrease local inflammation and limit mechanical strain by placing horse on strict box rest. Cold water or ice (15 min 3-6 times daily) helps to decrease inflammation, as well as topical NSAIDs (e.g. compagel).

Phase 2 – Subacute or repair phase lasting 2-4 months

Local signs of inflammation receded, therefore can start controlled exercise and in-hand walking, this will be a graduated program over 6-8 weeks, often enabling ridden work (at walk) after 4 weeks post-injury if not ruptured. Controlled exercise is superior to box or field rest.  Physiotherapy techniques may be used at this stage such as laser therapy or shockwave therapy.

Phase 3 – Remodelling phase lasting 4-12 months

Rest should be continued until ultrasound scan shows adequate, stable repair. Uniform fibre pattern is never restored – a stable appearance on ultrasound is the desired outcome. Preferably light exercise (ridden or horse walker), or turn out. Gradual return to full exercise (not before 3-6 months) under ultrasound monitoring.

Other treatments

  • Corrective foot-trimming is essential to restore mediolateral balance, shorten elongated toes and increase hoof angle
  • Corrective shoeing to reduce fetlock drop: eggbar shoes in hindlimb
  • Injections into the suspensory ligament – mainly used for chronic, refractory cases
  • Shockwave at 10-14 day intervals (for both forelimb and hindlimb suspensory desmitis).

Surgical treatments

Percutaneous fasciotomy +/- longitudinal splitting. In the chronic hindlimb cases, deep lateral plantar neurectomy and fasciotomy has become a common procedure to manage cases which have not responded to other conservative treatments. This surgery involves removing a section of the nerve that innervates the suspensory ligament, thereby removing the sensation of pain and discomfort. Varying levels of success have been described but in general success rates for return to previous performance have ranged from 60-80%. It should be noted that under FEI rules and the Jockey Club rules of racing, this surgery is not permitted.

Monitoring

Ultrasound scan is essential to monitor progress – lesions may persist and/or progress in the hindlimb despite box rest, especially in those with abnormal conformation.

Prognosis

Depends on severity of lesion(s) – Fair for forelimb injuries and acute hindlimb injuries if managed aggressively from the outset, but poor for chronic hindlimb injuries, despite treatment and prolonged box rest.

Midbody Suspensory Ligament Desmitis

  • Caused by athletic injury (especially over fences)
  • Clinical signs are often pain, swelling, local heat and acute lameness
  • Diagnosis is via ultrasound scan
  • Must be treated aggressively from the outset – rest minimum of 3 months, anti-inflammatories
  • Prognosis: good in forelimb, guarded in hindlimb unless treated aggressively from the outset

What is the suspensory ligament?

The suspensory ligament is attached to the back of the upper cannon bone and knee (in the front legs) or hock (in the hind legs), runs downwards close to the back of the cannon and divides into two branches, each of which attaches to a sesamoid bone at the back of the fetlock, before ending attached to the upper pastern. The suspensory ligament supports the fetlock and protects it from dropping too low at exercise.

Diagnosis

Presenting problems are often forelimb or hindlimb lameness, although there may be more obvious signs such as localized heat and swelling over the suspensory ligament and pain on direct palpation or passive flexion. In very severe cases there may be fetlock drop due to the loss of support from the suspensory apparatus.

Nerve blocks

Nerve blocks rarely necessary unless recurrence of the chronic condition.

Ultrasound scan

Ultrasound shows loss of definition of the suspensory ligament, enlargement of the cross sectional area and disruption of the fiber pattern. Both limbs are often examined because bilateral injury can occur, variations in normal appearance, especially at bifurcation.

Treatment options

Phase 1 – Acute (inflammatory) phase lasting 7-10 days

Aggressive anti-inflammatory treatment (bute) – aim to decrease local inflammation and limit mechanical strain by placing horse on strict box rest (box rest is not always indicated in chronic cases). Cold water or ice (15 min 3-6 times daily) helps to decrease inflammation, as well as topical NSAIDs (e.g. compagel).

Phase 2 – Subacute or repair phase lasting 2-4 months

Local signs of inflammation receded, therefore can start controlled exercise and in-hand walking, this will be a graduated program over 6-8 weeks, often enabling ridden work (at walk) after 4 weeks post-injury if not ruptured. Controlled exercise is superior to box or field rest.  Physiotherapy techniques may be used at this stage such as laser therapy or shockwave therapy.

Phase 3 – Remodeling phase (4-12 months)

By this stage, ultrasound examination should reveal a decrease in inflammation, allowing a gradual return to light exercise (ridden or horse walker) or turn out. Ultrasound scan monitoring is essential to ensure work rate is not increased at too great a rate.

Other treatments

Injections into the suspensory ligament with a variety of substances:

  • Polysulfated glycosaminoglycans.
  • Hyaluronate acid Sodium hyaluronate or growth factors.
  • Beta-aminoproprionytrile fumate (BAPTn).
  • Platelet rich plasma (PRP).
  • Autologous pluripotential stem cells (Bone marrow or fat derived)

Surgical treatments:

  • Percutaneous longitudinal tenotomy (‘splitting’) – rarely advocated unless associated with splint bone fractures
  • Fetlock fusion may be required in extreme or chronic cases as a salvage procedure.

Monitoring

Ultrasound monitoring is aiming to see an improvement in fibre pattern, decrease in cross-sectional surface area and improvement of fiber alignment. Many lesions persist long-term which hinders objective assessment for readiness to return to work, resulting in a high incidence of recurrence.

Follow-up ultrasound scan examination at 8 weeks, then every 8 weeks or prior to changes in exercise level.

Prognosis

Depends on severity of lesion(s), generally good in the forelimb; guarded in the hindlimb unless managed aggressively from the outset. If there is no ultrasound scan improvement the prognosis is guarded; can persist despite improvement in lameness, with recurrence being very common in the same or contralateral limb.

Branch Suspensory Ligament Desmitis

  • A relatively common Sport horse injury
  • Branches in one or more legs may be affected (common in both hindlimbs and forelimbs)
  • Cause: degenerative conditions, foot imbalance, regular loading of limbs at speed
  • Signs: lameness in one or more legs
  • Diagnosis: clinical signs, palpation, ultrasound, x-rays
  • Treatment: rest, anti-inflammatories, foot trimming and shoeing, physiotherapy, controlled exercise program (often prolonged up to 9 months)
  • Prognosis: guarded to poor

What is the suspensory ligament?

The suspensory ligament is attached to the back of the upper cannon bone and knee (in the front legs) or hock (in the hind legs), runs downwards close to the back of the cannon and divides into two branches, each of which attaches to a sesamoid bone at the back of the fetlock, before ending attached to the upper pastern. The suspensory ligament supports the fetlock and protects it from dropping too low at exercise.

Presenting signs

Often the presenting signs will be a lameness in one or more leg, however the signs may be as subtle as an unwillingness to go forward. Acute presentation can cause severe, persistent lameness in one or more legs.

Cause of branch suspensory ligament desmitis

Some injuries, especially in the hindlimbs, may be degenerative conditions, however there are a few pre disposing factors that may increase the risk of your horse developing suspensory ligament problems, these include factors such as: Foot imbalance, specific regular loading of the limb at high speed or excessively straight hind leg conformation.

Diagnosis

Presenting problems are often forelimb or hindlimb lameness, although there may be more obvious signs such as localized heat and swelling over the suspensory ligament and pain on direct palpation or passive flexion. In very severe cases there may be fetlock drop due to the loss of support from the suspensory apparatus.

Ultrasound

Examine entire suspensory ligament both transverse and longitudinally, this will enable assessment of enlargement and change in shape of branch, loss of definition of edges as well as central or peripheral areas of loss of fibre pattern.

X-rays

The splint bone and sesamoid bone of fetlock may be examined for signs of fracture and/or distortion and/or remodelling. Such conditions will affect treatment and prognosis.

Nerve blocks

Nerve blocks to block the suspensory ligament may aid in diagnosis.

Treatment

Initial symptomatic treatment involves box rest, reduction of inflammation (cold hosing and bute) and support bandages. Treatment will then progress on to include controlled exercise programme over 6-9months. Additional treatment options may include remedial foot trimming and intralesional injections (Stem cell therapy, platelet rich plasma). The treatment however does depend on the breed of horse, use of horse, severity of clinical signs and ultrasound scan findings.

Monitoring

Regular ultrasound examinations are essential until there is no change in the appearance of the SL for 3 months. It is advised that the suspensory ligament is scanned prior to any increase in work load.

Prognosis

Guarded for mild lameness with subtle ultrasound scan changes with conservative treatment (rest followed by up to 9 months of controlled exercise), horse may recover fully or may progress to more serious lesions. The prognosis is also guarded where level of work is high: condition will inevitably progresses to more serious lesions.

The main reason for treatment failure is return to exercise too soon or increasing work load without assessing the level of repair via ultrasound scan.