Isolated complete dislocation of hamate bone with an ulnar nerve injury: a case report and literature review

BACKGROUND: Isolated complete dislocation of the hamate bone is a rare wrist injury. Only 22 cases have been reported in the literature. Four of them were associated with nerve injury, but it is a pity that the causes of ulnar nerve injury had never been deeply analyzed. In the case report, it was stated that the ulnar nerve injury was caused by both displacement of uncinate bone and change of position of transverse carpal ligament. The complete dislocation of the hamate bone is mostly caused by direct force, often accompanied by tears of the surrounding ligaments. CASE DESCRIPTION: A 30-year-old woman was treated because her left hand was crushed by a machine roller. Plain film X-ray showed isolated dislocation of the volar hamate and rotation of the hamate bone to the volar side. Clinical manifestations and computed tomography (CT) signs suggest ulnar nerve injury. The patient was quickly transported to the operating room for open reduction and internal fixation of the hamate bone and repair of the dorsal carpal ligament. The patient fully recovered after 12 months. CONCLUSIONS: Isolated complete dislocation of the hamate bone is a rare injury. The most common cause is direct compression force to the wrist. Diagnosis can be made through review of the patient’s medical history, physical examination and X-ray, however, CT can accurately evaluate the displacement and rotation of the hamate bone, hamate bone fracture and other concomitant wrist fractures, suggesting compression changes of the median nerve and ulnar nerve to provide a reliable basis for the formulation of a clinical care plan. The case report added the evidence-based practice, and discussed the anatomical mechanism and imaging manifestation of ulnar nerve injury associated with complete dislocation of hamate bone.