Posterior ankle impingement - os trigonum syndrome

Case contributed by Bruno Di Muzio
Diagnosis almost certain


Posterior ankle pain.

Patient Data

Age: 55 years
Gender: Female

A fused os trigonum is noted with mild bony irregularity and moderate degenerative change in the medial aspect of the os trigonum/calcaneal articulation. 

There is also a small plantar calcaneal spur as well as a punctate focus of calcification in the posterior plantar fascia. 

No significant bony degenerative change is present in the midfoot. The talar dome is unremarkable. 

No evidence of tarsal coalition. 

Bone Scan 99mTc MDP

Nuclear medicine

A triple-phase bone scan was performed. Dynamic flow and blood pool images show focal intense tracer uptake at the posterior aspect of the right ankle joint. Delayed static images and SPECT-CT images show intense uptake corresponding to the location of the os trigonum at the posterior aspect of the right talus. Mild degenerative changes are seen in the right midfoot, knees, sternoclavicular joints, acromioclavicular joints and hands. No other significant abnormalities are seen.

The findings are consistent with right ankle posterior impingement/os trigonum syndrome with intense uptake seen at the location of the known os trigonum.

Case Discussion

This case illustrates a partially fused os trigonum causing posterior ankle impingement

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