Tarsal sinus syndrome In 1957, O’Connor first introduced tarsal sinus syndrome, which typically presents with chronic pain in the lateral ankle and tarsal sinus, mostly with a history of trauma. Anatomy】The tarsal sinus is a conical cavity located between the neck of the talus and the anterosuperior aspect of the heel bone, which runs from posterior to anterior. It is lined by the funnel-shaped tarsal sinus canal, and the posterior part of the tarsal sinus canal is immediately adjacent to the talar process. The tarsal sinus is the division between the posterior heel talar joint and the anterior and middle joints, and the main structures in it include the fat pad, small blood vessels, joint capsule, nerve endings, bursa, and ligaments (the medial, middle, and lateral roots of the heel talar interosseous ligament, the cervical ligament, and the subextensor support band). Etiology】 1. Trauma About 70% of patients have a history of ankle joint trauma (entropion injury). The ligamentous structure in the tarsal sinus has the effect of limiting excessive inversion of the subtalar joint. In the case of posterior foot rotation injury, the heel-fibular ligament ruptures first, followed by the cervical ligament and the intercalary ligament of the heel talus. Ligament rupture is the main cause of tarsal sinus syndrome. 2.Other About 30% of patients have no history of trauma, but are related to foot deformity, gouty arthritis or rheumatoid arthritis, etc. [Injury pathology] Tarsal sinus syndrome in the tarsal sinus may be caused by thickening of the synovial membrane in it, tendon sheath cysts, etc. In cases caused by trauma there is usually a partial tear of the intertarsal ligament and cervical ligament of the heel talus, etc., which is also responsible for proprioceptive disorders. In patients with rheumatoid arthritis, gout, and hyperpigmented villous nodular synovitis, fat pads are commonly associated with synovial inflammation. Diagnosis and differential diagnosis】 1. Symptoms Pain in the tarsal sinus region, aggravated by posterior rotation or internal rotation of the foot. Localized pain when walking, especially on uneven surfaces. Most patients have symptoms of tenderness, but no mechanical instability. 2. Signs (1) Pressure pain There is sharp pressure pain in the tarsal sinus area. (2) Ankle passive inversion pain: pain in the tarsal sinus area when doing passive inversion or rotation of the ankle joint. (3) Drawer test and inversion test: no ankle instability. 3. Auxiliary examinations include ankle X-ray, subtalar arthrography and MRI. (1) X-ray: including anteroposterior and lateral ankle joint, generally no abnormal findings. (2) Subtalar arthrography: The normal image of the lateral view is a slightly convex capsule at the anterior part of the subtalar joint with a small serration at the front (normal crypt). If the normal fossa is absent, it suggests tarsal sinus syndrome. (3) MRI: It can show partial rupture of the tarsal sinus ligament and soft tissue edema. It can also exclude osteochondral injury of the ankle and talocrural joint, and old injury of the lateral collateral ligament of the ankle joint. (4) Diagnostic closure: local injection of 2% lidocaine 2ml into the tarsal sinus, if the pain disappears, the diagnosis can be confirmed. 4. Differential diagnosis (1) Old injury of the lateral collateral ligament of the ankle joint: the symptoms are mainly instability, the pressure point is at the anterior talofibular ligament or heel-fibular ligament, the drawer test and inversion test reveal poor stability of the ankle joint, and MRI can show old injury of the ligament. (2) Injury of the subtalar joint: X-ray or MRI shows signs of osteochondral injury of the subtalar joint. Treatment】 1. Conservative treatment includes ultrasonic physiotherapy, hydrotherapy, oral non-steroidal anti-inflammatory drugs and local closure. Injecting a mixture of 2% lidocaine 2ml and prednisone 1ml into the tarsal sinus is usually effective. 50-70% of patients with conservative treatment are effective. 2.Surgical treatment When conservative treatment is not effective, surgical treatment can be performed. (1) Incisional surgery Ollier incision of the lateral ankle, pay attention to protect the lateral dorsal cutaneous nerve of the foot and remove the fat pad of the tarsal sinus. If there is damage to the intertarsal ligament of the heel talus and it causes inflammation, the inflammatory tissue should be removed. (2) Arthroscopic surgery Arthroscopic technique can be applied to remove the inflammatory tissue in the tarsal sinus, and at the same time, it can determine whether there is any damage to the ligament of the tarsal sinus, which is less invasive and has good clinical results.