Plantaris rupture: why is it important?

Abstract

Plantaris muscle is accessory plantar flexor of calf, a vestigial muscle of triceps surae complex. Its importance lies in the fact that its rupture cans mimic deep vein thrombosis (DVT). Sometimes when there is rupture of Achilles tendon, intact plantaris can still cause plantar flexion at ankle presenting a confusing picture. We present one such case of plantaris rupture confused by radiology resident with DVT. A 51-year-old man had a feeling as if kicked in back of calf along with a snapping sound and severe pain while playing tennis. On seeing fluid between muscle plane and a hypoechoic structure radiology resident labelled it DVT. MRI suggested ruptured plantaris as fluid and muscle stump were seen between gastronemius and soleus. Patient was treated conservatively with rest, ice compression and elevated leg and showed significant reduction in pain and swelling.

Figure 1

(A and B) Short tau inversion recovery coronal images of B/L calves showing fluid in the plane between gastrosoleus and retracted proximal (red arrow) and distal (yellow arrow) stumps of ruptured plantaris muscle of right leg.

Figure 2

(A and B) T2-weighted axial images of calf showing fluid in the plane between gastrosoleus, hyperintensity in medial head of gastrocnemius suggesting strain and retracted stump of ruptured plantaris (arrow).