Achilles tendon tear

Typically, in a young 'normal' individual, the Achilles tendon ruptures in the 'critical zone', a region of relative watershed hypovascularity 2-6cm proximal to insertion. Due to sports related trauma, especially squash and basketball, males ore well over represented (M:F 5:1 - 6:1). Predisposing condidions include: diabetes mellitus; systemic inflamatory illnesses (e.g. RA, SLE); repeated microtrauma; gout; use of fluoroquinolone antibiotics.

Plain film shows soft tissue swelling and obliteration of pre-Achilles fat pad (Kager's triangle).

MRI appearances vary:

• partial thickness tear shows high signal on long TR, and tendon swelling to >7mm AP
• full-thickness tear 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)

Classification

• Type 1 Partial ruptures <= 50%
• Type 2 Complete rupture with tendinous gap <= 3 cm
• Type 3 Complete rupture with tendinous gap 3 to 6 cm
• Type 4 Complete rupture with defect of > 6 cm (neglected ruptures)

see also:

• Haglund's syndrome
• calcaneal tuberosity avulsion fracture is a separate entity.