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When Kirschner wires are used in fixation of a dislocated sternoclavicular joint, disappearance of a wire beneath the skin demands urgent attention.
A motorcyclist aged 36 was involved in a road traffic accident and sustained a grade III anterior dislocation of the right clavicle at the sternoclavicular joint. He underwent open reduction and internal fixation with two straight Kirschner wires (K-wires). For three weeks after fixation, serial chest radiographs confirmed satisfactory reduction with the K-wires in a good position. In the fourth week, he sought advice from the accident and emergency department because he could see only one of the K-wires over his clavicle. He was symptom-free but chest X-rays and CT scans indicated that one of the K-wires had migrated to the anterior mediastinum (Figures (Figures11 and and2).2). A median sternotomy was performed and the K-wire was easily removed. It had passed anterior to the brachiocephalic vein and headed inferiorly, with its tip coming to lie adjacent to and abutting the aortic arch. There was no active bleeding, but a small tear in the adventia of the aorta was repaired with 4/0 prolene. The patient recovered without incident.
Metallic orthopaedic fixation devices (pins and wires) have been used since the 1930s, but the incidence of migration is unknown. Reviewing all reported cases from 1943 to 1981 Lyons and Rockwood1 found 47 instances of wire migration, with the wire migrating to a major vascular structure in 17. It is noteworthy that, in 21 of the 47, the wire had been used for internal fixation of a dislocated sternoclavicular joint.
Why should K-wires, used in this way, migrate into the thorax? Theories include muscle action, the great freedom of movement of the shoulder, negative intrathoracic pressures associated with respiration, regional resorption of bone, gravitational force and even capillary action1,2. Migration of K-wires has been reported as early as the day after fixation and as late as 21 years. Usually the process causes no symptoms, as here. Intrathoracic migration of wires or pins to heart3, lung4, aorta1 and almost every other intrathoracic blood vessel has been reported. They can also migrate elsewhere—for example, to the spleen (which a K-wire reached from the right shoulder within 12 hours)5 and the spinal canal6. The type of wire, smooth, threaded or bent, seems not to be a factor in incidence.
The most important step in preventing this potentially lethal complication is to bend the exposed part of the wire/pin after fixation. However, this does not guarantee safety since wires sometimes migrate after breakage2. Close clinical follow-up with frequent postoperative radiographs has been recommended, but in the case here routine radiographs showed no sign of migration in the three weeks after fixation—i.e. it can happen quickly. In this case the exposed part of the wire had not been bent.
Once intrathoracic migration of a K-wire is recognized, urgent removal is mandatory. Fatalities from wire migration have all been related to catastrophic cardiovascular events, and one patient died while awaiting elective thoracotomy. A CT scan of the chest will help determine the surgical approach. Sternotomy is preferable to thoracotomy in patients with suspected cardiac or intrapericardial vascular injury3. Video-assisted thoracoscopy may also have a role, though experience has been mixed and an open procedure has often proved necessary7.
Since there is an increasing trend towards internal fixation of dislocated sternoclavicular joints, surgeons and others need to be aware of this potentially lethal complication.