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Achilles tendon tear

Achilles tendon tear is the most common of ankle tendon injuries, and is most commonly seen secondary to a sports related injury, especially squash and basketball.

Epidemiology

There is strong male over-representation presumably as a result of the predominantly sport related aetiology. Patients are typically aged 30-50 years and have no antecedent history of calf or heel pain.There are however numerous recognised predisposing factors including:

Clinical presentation

Typically patients present with sudden onset of pain and swelling in the achilles region, often accompanied by a audible snap during forceful dorsiflexion of the foot. A classic example is that of an unfit 'weekend warrior' playing squash.  

If complete a defect may be felt and the patient will have only minimal plantar flexion against resistance. 

Pathology

The spectrum of tears ranges from microtears to interstitial tears (parallel to the long axis of the Achilles), to partial tears, and eventually to complete tears

Tears can be acute or chronic, with repeated minor trauma. At the mildest end of the spectrum all that may be present is peritendonitis.

Location

Typically, in a young 'normal' individual, the Achilles tendon ruptures in the 'critical zone', which is a region of relative watershed hypovascularity 2-6cm's proximal to insertion. 

Classification 

This is primarily based on degree of retration. See - Achilles tendon tear classification

Radiographic features

Plain film

Plain radiographs may show soft tissue swelling and obliteration of pre-Achilles fat pad (Kager triangle).

Ultrasound
For partial thickness tears
  • there is often enlargement of the tendon ( >1cm) with abnormally hypoechoic or anechoic areas within which correspond to the tear and associated adjacent tendinosis
For full thickness tears
  • often shows separation of the torn ends with a contour change of the tendon
  • there is acoustic shadowing at the margins of the tear from sound beam refraction,and adjacent hypoechoic tendinosis
MRI 

Appearances can vary :

  • T2 : partial thickness or interstitial tears may show high signal on long TR, and tendon swelling to > 7 mm AP
  • a full-thickness tear often shows a tendinous gap filled with oedema or blood
  • complete rupture shows retraction of tendon ends

When a plantaris muscle is present then its tendon is usually spared due to its more anterior insertion on the calcaneum (see Case 1)

Treatment and prognosis

Treatement depends on the extent of the tear. Partial thickness tears can initially be treated conservatively, with surgery reserved for failure of conservative management, on in some cases for high performace athletes. Full-thickness tears are normally surgically repair. If the patient is not deemed suitable for surgical repair (frail, ill etc..) casting of the ankle in the talipes equinus position may be an alteranative.

Etymology

A true rupture of the Achilles tendon was first described by Ambroise Pare in 1575 and first reported in the medical literature in 1633 3.

See also

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