A 23-year-old man was riding his motor bike on a wet country road. Negotiating a sharp curve the bike slipped and he landed on his outstretched left hand while the bike toppled over him, trapping the left leg underneath. On examination there was an obvious deformity of his left leg with swelling and bruising over the left shoulder along with some friction burns. Radiographs revealed a closed, displaced fracture of the tibia and fibula (figure 1). Anteroposterior, lateral and transthoracic views of the shoulder joint were read as normal in the casualty department (figure 2). A diagnosis of soft tissue injury to the shoulder was made. The patient was given a broad arm sling and was admitted for an intramedullary nailing of the tibia. On orthopaedic review in the morning the patient complained of progressive swelling and pain in his left shoulder. The limb was held close to the body with the elbow flexed. Attempts to move the shoulder generated severe pain and no active or passive external rotation was possible. The patient was taken to theatre for intramedullary nailing prior to which, under general anaesthesia, an axillary view of his left shoulder was obtained using the image intensifier (figure3). Figure 1 Radiograph of the fractured tibia and fibula Figure 2 Anteroposterior radiograph of the left shoulder Figure 3 Axillary view of the shoulder under image intensifier 1 : What is the diagnosis and what are the pathomechanics of the injury? 2 : How would you treat the problem? ### QUESTION 1 This is a posterior fracture dislocation of the anatomical head of the humerus. Electrical or neurological seizures, fall on an outstretched limb, or a blow to the anterior shoulder …