Over the past decades, distraction osteogenesis has been popular for lengthening procedures in long bones and bone-segment transfer. Today, it is of increasing importance in the CMF field. During distraction woven bone forms in the distraction gap. The distraction's progress must be fast enough to prevent bony bridging and slow enough to permit the bone's differentiation. Distraction of 1 mm per day, in one to four steps, has been found to be adequate. An advantage of distraction osteogenesis is that it allows for reconstruction of skeletal deformities in a controlled fashion with the native bone [1].

Transverse maxillary hypoplasia [2] is a clinical entity characterized by diminished growth of the maxilla in the transverse dimension, leading to anterior and posterior crowding of the maxillary dentition. This constriction of the maxillary arch occurs spontaneously or in association with congenital cleft lip and palate deformities. Clinical manifestations include unilateral or bilateral palatal crossbite, dental rotation or tilting, and malocclusion. An adequate transverse maxillary dimension [3] is an important factor of stable occlusion, and it positively affects facial aesthetics. A narrow and V-shaped dental arch, dental crowding, a posterior crossbite, unaesthetic black buccal corridors upon smiling and maxillary transverse deficiency are generally interrelated. The underlying structural abnormalities may secondarily lead to gingivaperiosteal and periodontal disease, speech pathology, nasal airway obstruction, andwhen a cleft palate is presentalveolar ridge collapse and oronasal fistula. The corrective goal of expanding the transverse dimensions of the palate allows for normal position and function of the dentition, improvement in occlusion, airway and speech, and optimization of aesthetic appearance. Maxillary transverse deficiency and malocclusions can be corrected with slow orthodontic expansion, rapid palatal expansion, surgically assisted rapid palatal expansion, or two-segmented Le Fort I type osteotomy with expansion at different growth status [4].

Surgically assisted rapid palatal expansion takes advantage of bone formation at the maxillary edges of the midline while they are separated by an external force.

The amount of desired expansion is an important factor for selecting maxillary expansion in adults. In general, an orthodontist can camouflage transverse maxillary deficiency of less than 5 mm with orthopaedic or orthodontic forces alone. When the maxillary transverse deficiency is greater than 5 mm, surgical assistance is required.

The transpalatal distractor system consists of a central body, plus left and right threaded pins that join with the respective footplate (Fig 3). They are fixed to the bone via four spikes on the bottom of the footplate (Fig 2).

Each rotation of the central body from one number to the next expands the transpalatal distractor by 0.33 mm. Therefore, a full rotation (360) would achieve an expansion of 1 mm.

Further rotation of the central body is prevented by inserting a blocking screw completely through one of the three threaded holes on the footplate's left side (Fig 3).

Recommendations

Ensure before the procedure that the safety wires are in the operating room. The preferred surgeon position relative to the patient's body while implanting the distractor is the top of the patient head position, since it facilitates facial symmetry observation. The bigger diameter screws are also preferred.

References

1 Prein J (1997) Manual of Internal Fixation in the Cranio-Facial Skeleton: Techniques Recommended by the AO/Asif Maxillofacial Group. Berlin Heidelberg New York: Springer-Verlag.

2 Vyas RM, Jarrahy R, Sisodia M, et al (2009) Bone-borne palatal distraction to correct the constricted cleft maxilla. J Craniofac Surg; 20(3):733736.

3 Gnbay T, Akay MC, Gnbay S, et al (2008) Transpalatal distraction using bone-borne distractor: clinical observations and dental and skeletal changes. J Oral Maxillofac Surg; 66(12):25032514.

4 Mommaerts MY (1999) Transpalatal distraction as a method of maxillary expansion. Br J Oral Maxillofac Surg; 37(4):268272.

A 17-year-old girl with a long face and vertical maxillary excess. Class II malocclusion, narrow maxilla, hypoplastic cheekbones, and nasal deformity. The steps shown in Fig 1Fig 6 show a normal implantation procedure of the transpalatal distractor following surgical planning and standard osteotomy.

Case provided by Maurice Mommaerts, Bruges, Belgium

Postoperative distraction is achieved using an activation instrument that joins with the distractor central body. A rotation from one number to the next etched on the central body, expands the distractor 0.33 mm. Activation is recommended 0.33 mm once per day. After distraction is complete, the distractor is blocked again with the blocking screw during the consolidation period