Conditions of the Arm Quiz

See Supracondylar fracture of distal humerus. Option C is correct. A supracondylar fracture is a break through the thin part of the humerus just above the elbow, and it is the most common elbow fracture in children. In the typical extension-type pattern, a fall onto an outstretched hand pushes the lower fragment backwards. The upper fragment then points forwards, towards the structures at the front of the elbow, including the brachial artery and the median nerve. The anterior interosseous nerve is a branch of the median nerve that supplies the deep forearm muscles, including those that bend the end joints of the thumb and index finger. A child with this injury cannot make a round OK sign, because the thumb and index finger end joints do not flex. The branch has no skin supply, so there is no numbness, and the injury can be missed unless the doctor asks the child to move the fingers as well as testing sensation. These nerve injuries are usually neurapraxias, meaning the nerve has been bruised or stretched rather than cut.

• Mechanism: in the extension-type fracture the upper fragment points forwards, towards the brachial artery and the median nerve.
• Nerve: the anterior interosseous nerve is a branch of the median nerve that supplies the deep forearm muscles.
• Sign: the child cannot make an OK sign, because the thumb and index finger end joints do not flex.
• Sensation: the branch has no skin supply, so there is no numbness.

Think of the direction the fragment points: forwards in the typical fracture, so the front of the elbow suffers.