Hemifacial Microsomia is a birth deformity affecting the bony skeleton and soft tissues of the craniofacial region. It is typically characterized by pronounced asymmetry of the face due to deficient growth of the lower jaw (mandible) on one side, deficient soft tissues of the face and underdeveloped ear (microtia).
Bony and soft tissue structures on one side of the face grow lesser than the other side. The affected side of the face appears disproportionately smaller than the other. Commonly affected are the lower jaw, eye, ear, facial nerve and cheek. The most significant of these deformities is that of the jaws, which when corrected, minimizes the entire deformity and makes the face look more symmetric.
In hemifacial microsomia, the shape and size of the lower jaw is deformed on one side causing an asymmetric face. The chin appears deviated to the affected side. Facial asymmetry progresses as the patient grows. As a result, teeth bite (occlusion) is slanted.
Based on various parameters like severity of the defect and age of the patient, there are different treatment options. Cheek and eye socket bone defects if present, can be corrected with specialized craniofacial surgeries. Ear and soft tissue defects can be rehabilitated with reconstructive surgeries.
The goal of treatment in hemifacial microsomia is to elongate the deficient jaw bone to restore facial symmetry and correct the slanting bite (occlusion). To achieve this, an advanced and effective treatment technique is distraction osteogenesis. This is a new technique for regenerating new bone by slow, progressive stretching of the bone, without requiring a bone graft.
The jaw bone on the deficient side is cut. A sophisticated device called distractor is placed such that the two arms of the device are fixed to the two segments of jaw bone. After a few days, a screw attached to the distractor is turned gradually, ideally at a rate of 1 mm per day. When this is done, the two cut segments move apart and new bone is formed in the resultant gap. After the new bone is stabilized, the distractor device is removed.