Medial Malleolar Screw Fixation Causing Flexor Hallucis Longus Impingement: A Rare Case of Checkrein Deformity.

INTRODUCTION: Checkrein deformity is a rare complication that manifests as dynamic flexion of the great toe during ankle dorsiflexion. Although most cases arise from adhesions or scarring of the flexor hallucis longus (FHL) tendon, mechanical impingement due to hardware placement has seldom been described. CASE REPORT: We present a 42-year-old male who developed checkrein deformity following open reduction and internal fixation of a trimalleolar ankle fracture. Dynamic ultrasonography revealed FHL tendon impingement beneath the medial malleolar screws. Hardware removal led to immediate resolution of the deformity, confirming the diagnosis. Post-operative rehabilitation restored full motion and function. CONCLUSION: This case highlights the importance of considering tendon mechanics during medial malleolar fixation and of using dynamic imaging to differentiate between tendon adhesions and mechanical impingement.