A 28-year-old male presents to the emergency department following a motorcycle accident with severe traction injury to the left upper limb. Clinical examination reveals complete loss of sensation in the lateral aspect of the forearm and thumb, weakness of elbow flexion and shoulder abduction, and loss of the biceps reflex. MRI shows avulsion of nerve roots from the spinal cord at C5–C6 levels. What is the most appropriate immediate next step in management?