Transantral maxillary distraction

14.1 Indications

Key words: Binder syndrome; clefts of lip, alveolus, and palate; maxillary retrognathia, midface deficit, midface trauma

The indication for transantral distraction of the maxilla is severe midface deficits with maxillary retrognathia or hypoplasia in syndromes (eg, Binder syndrome) or preoperated malformations such as clefts of lip, alveolus, and palate. Indications are also midface deficits as consequences of severe trauma with destruction of the bony midface structures. Transantral distraction of the maxilla should always be preferred if the alternative Le Fort I osteotomy and advancement of the maxilla with stable fixation by miniosteosynthesis plates and, if necessary, additional bone grafting cannot achieve a permanently stable occlusion result because scar traction and unstable bone structures lead to recurrence. Transantral distraction of the maxilla is also indicated if the patient is unable to wear an external distraction device fixed to the cranial dome for several months for psychosocial reasons.

14.2 Methodology

Key words: attachment of activation pins, complete intraoral mucosal coverage of distractors, downfracture, fixation of mobile maxilla to distractor, individual size adjustment of distractor, intraoperative vector adjustment, Le Fort I osteotomy, local anesthesia, parallel distractor fixation to midface, planning of distraction vector, preparation of large palatal vascular nerve bundles, preservation of posterior wall of maxillary sinus, trial distraction, unlimited retention time

The schematic procedure is shown in Fig 14-1, and see Figs 14-3 and 14-4 for example cases.

Figs 14-1a to 14-1d Technical details of the transantral maxillary distraction and schematic procedure.

Figs 14-1a to 14-1d (a and b) Transantral distractor pair (Medicon) for bilateral unidirectional distraction of the maxilla anteriorly: the threaded rod between the two osteosynthesis plates shows the extent of activation of 25 mm. The laterally offset pointed posterior distractor tip is used for device fixation in the posterior wall of the maxillary sinus. The jointed extension rods, which fit the threaded rods on the angled osteosynthesis plates per Imbuss (arrows), enables intraoral activation in the maxillary vestibule. The locking ring can be seen on the extension rod in the middle of the picture. (c) The double-ended screwdriver with its hexagonal socket (left) is used for intraoperative trial activation of the distractor and for postoperative stepwise distraction using an extension rod (360-degree rotation = 0.4 mm distraction). The square socket at the other end of the screwdriver (right) is used to activate the posterior distractor tip. (d) The posterior distractor tip can be turned out by means of a square foot and thus adapted to the individual sagittal expansion of the antrum. The distractor length can thus also be individually adjusted to size-differentiated maxillary sinuses. (Reproduced from Wangerin et al,1 by permission of Thieme Verlag).

Figs 14-1e to 14-1i Technical details of the transantral maxillary distraction and schematic procedure.

Figs 14-1e to 14-1h After downfracture of the maxilla, the distractor is pressed with its pointed posterior end into the center of the stably preserved (!) bony posterior wall of the maxillary sinus. The wing-like lateral displacement of the pointed distractor end allows the large palatal vascular nerve bundle to be safely protected. Adjusting the distractor length with the thin square foot (arrows), the distractor is lifted anteriorly and the straight miniplate is fixed to the lateral nasal entrance with three miniscrews (right). Care is taken to position both distractors parallel to each other in their course through the maxillary sinus, which establishes the distraction vector. The mobile maxilla is then lifted anteriorly and screwed to the angled osteosynthesis plates with three miniscrews. (Reproduced from Wangerin et al,1 by permission of Thieme Verlag)

Figs 14-1i and 14-1j (i) The jointed extension rods are clamped onto the anterior end of the distraction screw to position them tension-free vertically in the vestibule. Unhindered activation of the distractor is possible. (j) Postoperative swellings at the nostrils often occur during activation time, which disappear after removal of the extension rods.

The methodology is as follows: Injection of local anesthetic and vasoconstrictor (eg, Xylonest 1% with adrenaline 1:200,000) in the maxillary vestibule of region 16 to 26, followed by incision (or high-frequency surgery) above the mucogingival border through the mucous maxillary vestibule of region 16 to 26, free preparation of the canine fossa bilaterally from the piriform aperture up to and including the buccal tuberosity region, loosening of the mucosa of the lower nasal passages, loosening of the cartilaginous septum including the nasal spine and separation of the septum from the maxillary bony base, followed by osteotomy of the lateral nasal walls bilaterally and then Le Fort I osteotomy with the longitudinal oscillating saw and/or piezoelectrically from the piriform aperture up to retromolar to the maxillary tuberosity.

In severe malformation cases, an individual staged Le Fort I osteotomy may also be necessary (see Figs 14-3a and 14-3b). Note that insertion of the curved Obwegeser chisel parallel to the occlusal plane is performed before bony pterygomaxillary retraction, then bilateral chisel osteotomy without fracturing the posterior wall of the maxillary sinus! (The use of the chisel in the classic Le Fort I osteotomy is in the same direction, but is located 5 mm more posteriorly in the pterygomaxillary retraction and usually fractures the posterior wall of the maxillary sinus, which is included in the preparation area, for example, in cranial or posterior displacements of the maxilla.) Then follows downfracture of the entire maxilla, complete mobilization of the entire maxilla, and careful exposure of the major palatal vascular nerve bundles, with mobilization and relocation if necessary. The posterior wall of the maxillary sinus is used for posterior fixation of the transantral distractors, which are available for both the left and right sides of the maxilla. After setting the size of the distractors (see Fig 14-1d), the laterally offset posterior distractor tips are pressed as far caudally as possible into the center of the two posterior walls of the maxillary sinus while protecting the vascular nerve bundles. This is not always feasible in severe malformation cases with reduced bone availability. This is followed by aligning both distraction axes as parallel and median as possible and then fixing both straight three-hole miniplates to the two lateral nasal entrance margins with monocortical miniscrews (see Fig 14-3c). The mobile caudally folded-down maxilla is moved back to its initial position (see Fig 14-3d

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Jan 19, 2024 | Posted by in Orthodontics | Comments Off on Transantral maxillary distraction

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