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MRI NEWSLETTER Sinus Tarsi Syndrome

Sinus tarsi syndrome is an inflammatory condition causing lateral hindfoot pain and instability. The most common cause for the syndrome is ankle trauma (about 70%) in particular an inversion injury, which can be treated with steroid injection into the sinus tarsi. A more serious cause of sinus tarsi syndrome is posterior tibial tendon dysfunction and spring ligament tears which frequently lead to the syndrome.

Sinus Tarsi Syndrome – Arthroscopic Path Findings:
– Tear of Interosseous ligament 88%
– Tear of Cervical ligament 33%
– Synovitis 55%
– Arthrofibrosis 24%
– Soft Tissue Impingement 21%
– Obliteration of fat that reaches the critical angle of gissane

The sinus tarsi contain the cervical ligament and the intraosseous ligament, and the 3 roots of the inferior extensor retinaculum (medial, intermediate and lateral). The cervical ligament is the thickest and anterior-lateral to the intraosseous ligament (ITO). In between the cervical ligament and the intraosseous ligament are the 3 roots of the inferior extensor retinaculum which make up most of the ligamentous structures within the sinus tarsus. The roots act as a sling to hold the extensor digitorum longus and peroneus tertius tendons against the talus and calcaneus.

On MRI, findings suggestive of sinus tarsi syndrome include:
– Obliteration of the fat by intermediate to low T1 and variable T2 signal intensity tissue
– Tears of the interosseous and cervical┬áligaments
– Cystic change along the roof and posterior subtalar joint osteoarthritis

MR shows inflammatory and fibrotic changes well. MRI is good for diagnosing sinus tarsi fat alterations and synovial thickening. MR is okay for accurate for diagnosing cervical ligament tear (sensitivity of 73% and specificity of 89%) but less so for interosseous ligament tear (sensitivity of 44% and specificity of 60%).

Non-surgical management includes control of pain and inflammation with analgesics, an inflammatory medication and steroid injections into the sinus tarsi with about 90% improved with this treatment.

The surgical treatment of sinus tarsi syndrome is arthroscopic debridement of the posterior subtalar joint and sinus tarsi. 94% were improved at 1-8 years follow-up although half had some residual symptoms.

In addition, surgical treatment may be indicated for concomitant ankle synovitis, subtalar instability or posterior tibial tendon dysfunction and spring ligament tears.

Read the full article here Sinus Tarsi Sydrome

By Dr. William Renner

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