Hemifacial Microsomia

Hemifacial microsomia is a congenital disorder that affects the development of the lower half of the face, most commonly the ears, mouth and the lower jaw. If can affect one side of the face or both. 

If severe, it can lead to difficulties in breathing. It is the second most common facial birth defect after cleft lip and palate, with an incidence in the range of one in 3,500 to 4,500.

What surgery is available, and what techniques are involved?

A relatively new surgical technique called bone distraction is often used in the treatment of hemifacial microsomia. Developed from limb lengthening operations first described in Russia, this technique is based on the principle of pushing small pins into bone, and moving these pins apart by a connecting bar which incorporates a screw thread. As the pins are gradually stretched apart, the bone and surrounding soft tissue is stretched also.

What should I expect as a patient/parent of a patient?

In bone distraction procedures, two operations are usually required. In the first operation, a cut is made in the bone which is to be stretched. This is known as a corticotomy. Pins are passed through the skin and into the bone on either side of the cut. These pins are then connected together by the distractor. In most cases, the distractor is opened by approximately one to two millimetres each day through the turning of a small screw. An average distraction length is likely to be in the region of two to two and half centimetres, which will probably take about three weeks to achieve.

At the end of the period of distraction, the distractor is left in position for six to eight weeks while new bone fills the gaps which have been created. A second small operation is then required to remove the distractor.
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