Last updated: 02/17/2009

Developmental anatomy

Important structures of the embryo's mouth form at four to seven weeks of gestation. Development during this period entails migration and fusion of mesenchymal cells with facial structures. If this migration and...

fusion is interrupted (usually by a combination of genetic and environmental factors), a cleft can develop along the lip. The type of clefting varies with the embryonic stage when its development occurred.

There are several types of cleft lip, ranging from a small groove on the border of the upper lip to a larger deformity that extends into the floor of the nostril and part of the maxilla (upper jawbone).

Unilateral cleft lip results from failure of the maxillary prominence on the affected side to fuse with medial nasal prominences. The result is called a persistant labial groove. The cells of the lip become stretched and the tissues in the persistent groove break down, resulting in a lip that is divided into medial (middle) and lateral (side) portions. In some cases, a bridge of tissue (simart band) joins together the two incomplete lip portions.

Bilateral cleft lip occurs in a fashion similar to the unilateral cleft. Patients with bilateral cleft lip may have varying degrees of deformity on each side of the defect. An anatomical structure (intermaxillary segment) projects to the front and hangs unattached. Defects associated with bilateral cleft lip are particularly problematic due to discontinuity of the muscle fibers of the orbicularis oris (primary muscle of the lip.) This deformity can result in closure of the mouth and pursing of the lip.

Classification

In addition to classification as unilateral or bilateral, cleft lips are further classified as complete or incomplete. A complete cleft involves the entire lip, and typically the alveolar arch. An incomplete cleft involves only part of the lip. The Iowa system (which also classifies cleft palate) classifies cleft lip in five groups:

• Group I—clefts of the lip only
• Group II—clefts of palate only
• Group III—clefts of lip, alveolus, and palate
• Group IV—clefts of lip and alveolus
• Group V—miscellaneous

Another widely accepted cleft lip classification is based on recommendations of the American Cleft Palate Association. This classification divides cleft lip into unilateral or bilateral (right, left or extent) in thirds—(i.e., one-third, two-thirds, three-thirds), or median cleft lip, the extent of which is also measured in thirds.

Surgical procedure

Cleft lip repair can be initiated at any age, but optimal results occur when the first operation is performed between two and six months of age. Surgery is usually scheduled during the third month of life.

While the patient is under general anesthesia, the anatomical landmarks and incisions are carefully demarcated with methylene blue ink. An endotracheal tube prevents aspiration of blood. The surgical field is injected with a local anesthestic to provide further numbing and blood vessel constriction (to limit bleeding). Myringotomy (incisions in one or both eardrums) is performed, and myringotomy tubes are inserted to permit fluid drainage.

There are several operative techniques for cleft lip reconstruction. The Millard rotation advancement (R-A) technique is the most widely accepted form of repair. This method involves rotation of the entire philtral dimple (groove in the upper lip) and Cupid's bow (double curve of the upper lip). The scar falls along the new philtral column (central section of the upper lip), and is adjusted as required since the procedure allows for flexibility.

The Millard procedure begins with an incision on the edge of the cleft side of the philtrum, and the cutting continues upward, medially, and to the side. A second incision extends to the buccal sulcus (top part of the upper jaw). The length of this incision depends on the size of the gap to be closed. In this second incision, the surgeon frees soft tissue, which allows him or her to completely lift the lip from the underlying bone. This dissection should be tested to ensure free advancement toward the middle (inadequate dissection is the root cause of poor results). Nasal deformity can be dealt with by a procedure known as the McComb nasal tip plasty, which elevates the depressed nasal dome and rim. Cartilage from the cleft side is freed from the opposite side, and is positioned and reshaped using nylon sutures.

Advantages of the Millard rotation advancement technique (include:

• It is the most common procedure (i.e., surgeons more familiar with it).
• The technique is adaptable and flexible.
• It permits construction of a normal-looking Cupid's bow.
• A minimal amount of tissue is discarded.
• The suture line is camouflaged.

The disadvantage of the Millard rotation advancement technique is the possible development of a vermilion notch (shortening of the entire lip in the vertical direction), resulting from contracture of the vertical scar.

Cupid's bow is a critical part of the repair, making it very important to accurately determine the high point of Cupid's bow on the lateral lip.