Lateral ankle ligaments injury and accessory flexor digitorum longus muscle
Presentation
Pain and swelling on the lateral side of right ankle after an inversion injury few days prior to presentation.
Patient Data
There is no fracture or dislocation. There is mild soft tissue swelling on the lateral side of the ankle.
There is a discontinuity of mid part of the anterior talofibular ligament. The calcaneofibular ligament is thick and hypoechoic without loss of continuity.
There is an extra-structure on the medial side of the ankle showing muscle echopattern. It is posterior to the neurovascular bundle, superficial to flexure hallucis longus tendon and anterior to the medial edge of the Achilles tendon. It passes deep to the flexure retinaculum. The medial ankle tendons are normal. The nerve in the tarsal tunnel shows normal echopattern without hypoechogenesity.
Case Discussion
Ultrasound findings favor lateral ankle ligaments injury in a young male with inversion injury. There is a complete tear of the anterior talofibular ligament associated with the calcaneofibular ligament sprain.
There is an accessory muscle passing through the tarsal tunnel. It is the accessory flexor digitorum longus muscle. However, there is no hypoechoic nerve edema in the tarsal tunnel. The accessory muscle was also present in the opposite lower limb ( The image is not posted ).