A 66 y.o. woman was hit in the back of the leg by a heavy hedge trimmer which fell from nine feet

What do you notice on her xray?

Hint: it has something to do with a triangle.

Our patient had inflammation in Kager’s triangle which occurs with injuries to the Achilles, flexor hallucis longus and calcaneus.  Opacification of  Kager’s triangle was described as a finding of Achilles tendon injury in 1939. Kager was a German orthopedic surgeon. 

Kager’s triangle

the anatomy of Kager’s triangle.

If there is suspicion of an Achilles tendon injury , the Thompson test can be performed.  With the foot hanging off the end of the table or with a patient kneeling in a chair, the calf muscle is squeezed and plantar flexion of the foot should occur.  If it does not, the Achilles is ruptured. The gastrocnemius and the soleus combine to form the Achilles tendon.  In contrast, the plantaris tendon  inserts separately into the  medial calcaneus. If it ruptures it causes no significant loss of function.

Achilles was the strongest warrior in the Greek army during the Trojan War. He had one vulnerability; his heel. His mother’s hand had covered his heel when she dipped him in the River Styx to make him invulnerable.

The os trigonum is an extra accessory bone that develops behind the talus in about 7% of people.  It is not a fracture. It can occur in one foot or both feet so a comparison view will not necessarily help in determining if there is a fracture.  

the os trigonum is NOT a fracture.

Our patient had a distal fibula avulsion fracture which required surgery for stabilization. She did not have an Achilles tendon rupture. She had passive plantarflexion with calf squeeze that was equal bilaterally.

So,  which fibular fractures require surgery?

Injuries to the distal fibular are divided into three Weber classes.  Injuries to the distal fibula below the talar dome are class A and  usually stable.  Weber B fractures occur at the level of the tibiofibular ligaments  usually with external rotation injuries. They require a stress view to see if the joint is stable.  Weber C fractures are above the ankle joint and are associated with a syndesmotic injury.  They always require surgery.  

Theobald P, Bydder G, Dent C, et al. The functional anatomy of Kager’s fat pad in relation to retrocalcaneal problems and other hindfoot disorder. J Anat 2006 Jan; 208(1):91-97.i

Thompson T, Doherty J. Spontaneous rupture of the tendon of Achilles:a new clinical diagnostic test. J Trauma. 1962 Mar;2:126-9.

Yap R, Babel A, Phoon K, Ward A.  functional outcomes following operative and nonoperative management of Weber C ankle fractures: a systematic review. J Foot Ankle Surg 2020  Jan-Feb;59(1:105-111.