Simultaneous flexion and extension checkrein deformity following tibial and fibular fractures: a rare case treated with concomitant surgical intervention.

Checkrein deformity of the hallux is commonly characterized by rigid flexion of the interphalangeal joint in ankle dorsiflexion but with flexibility in ankle plantarflexion which can be named as flexion checkrein deformity and as rare condition, extension checkrein deformity, characterized by rigid extension of the first metatarsophalangeal joint in ankle plantarflexion and flexibility in ankle dorsiflexion, has been reported. However, there has not reported coexistence of flexion and extension checkrein deformity. The patient, a 27-year-old male, was referred to our department 3 years after tibial and fibular fractures which was treated by open reduction and internal fixation at a previous hospital. His chief complaint was pain and impaired plantarflexion of the affected great toe. The diagnosis was double checkrein deformity characterized by simultaneous rigidity in both flexion and extension of the hallux due to the adhesion of the flexor hallucis longus (FHL) muscle and the extensor hallucis longus (EHL) tendon after a fracture. Surgical intervention was performed, which involved the transection of the FHL tendon using hindfoot endoscopy and transfer of the EHL to the extensor digitorum longus, resulting in a successful outcome with no postoperative complications. The patient demonstrated a favorable prognosis 2 years after the procedure. This report represents the first documented case of double checkrein deformity and underscores the importance of considering this condition and the potential advantages of surgical intervention.