Tendoachilles tear-MRI

57 year old male,  with history of slipping on the staircase, shows on MRI an apparent tendoachilles discontinuity and disruption of approximately 3 cms in the critical zone of vascularity from the calcaneum (4 cms) with paratendon edema with no retraction of the ends, suggestive of partial tear.  Case by Dr MGK Murthy, Mr Gupta and Mr Venkat

Teaching points :

1. Lateral head of the gastrocnemius from the lateral femoral condyle joints the medial head fibres (from medial femoral condyle) at the junction of proximal and mid calf with soleus fibres joining them 3 to 4 cms down to form tendoachilles.  Plantaris muscle from the lateral meniscus and lateral femoral epicodyle travels between gastrocnemius and soleus and inserts 1 cm anterior and medial to the tendoachilles on calcaneum.
2. Tendoachilles tears are more in males (left  more than right for unknown reasons) with a peak age of presentation 36 with usually no antecedent history of diseases. However steroids / diabetes / collagen disorders / gout / hyperparathyroidism / drugs like fluoroquinolones / repeatitive  microtrauma could predispose an individual.
3. Critical zone (2 to 6 cms from the calcaneal insertion) is the commonest location in view of muscular branches proximally and periosteal branches distally giving extravascular supply to the paratendon supply.
4. MR criteria of partial thickness tear includes heterogeneity linear streaks of altered signals of fibromatous / lipoid degeneration with AP dimension more than 7 mms.  Full thickness tears suggest complete gap with paratendon fluid and retracted ends of the tendon. Retrocalcaneal bursa should measure less than 6 x 3 x 2 mms approximate normally.