 |
CLINICAL INDICATIONS Primary:
Secondary:
|
|||||||||||||||||
|
BI-DIRECTIONAL DISTRACTOR In that most hypoplasia of the lower jaw predominantly affects the ascending ramus, elongation at this site can result only through the optimal positioning of the Uni-Directional distractor, i.e., vertically or obliquely as indicated. When the congenital mandibular deficiency is such that both the ramus and body of the mandible are affected, a multiplaner distraction is required. The Bi-Directional distractor allows, in addition to a divided elongation in two directions, a variable adjustment in the angle between the two arms of the appliance. Following a single or double osteotomy, one can distract both vertically and horizontally. In very difficult cases of mandibular hypoplasia, a double osteotomy may be undertaken in order to obtain two callus sites. This allows a more rapid distraction as well as the development of a mandibular angle.
|
||||||||||||||||||
| MULTI-DIRECTIONAL DISTRACTOR | ||||||||||||||||||
|
Before Osteodistraction  
After |
Pronounced mandibular micrognathia, either unilateral or bilateral, are either congenitally present as characteristic symptoms of various syndromes, or arise as a result of early childhood temporomandibular joint trauma. The latter, untreated, leads to ankylosis and developmental disturbances of the mandible on the affected side. Because the midface adapts to the mandible in the early growth phases, a disturbance in mandibular development results in decreased midface development as well. Concepts of treatment, to date, employ either orthodontic preparation to bridge the time from diagnosis to the age at which the patient is able to undergo bimaxillary repositioning osteotomies, or placement of costochondral grafts at the disturbed mandibular sites in childhood, after which orthodontic treatment is employed to effect correct development of the midface. Alternately, the Multi-Directional Distractor may be used at an earlier age, avoiding secondary growth disturbances in the maxilla. The Multi-Directional Distractor provides the additional benefit of allowing transverse movements. Both arms can be changed in all planes. Independent of one another in their relationship to the middle section of the appliance, because their fixation to the middle section is effected by a ratchet and ball-joint combination. The selection of the appropriate distractor depends upon the individual deformity, as well as the condition at the point of placement. As a general rule, the Multi-Directional Distractor is used in older children, and the Bi-Directional in younger individuals. |
|
The degree of hypoplasia and the age of the patient determine the number (1 or 2) and location of the osteotomies, as well as the approach to the operative area. Two ipsilateral osteotomies allow the reconstruction of a mandibular angle. In cases of severe disturbance, as well those of very small or limited anatomy, an extraoral approach is preferable, in which the incision on is made below the lower border of the mandible in the angle region, care being taken to note the position of the marginal branch of the facial nerve. Very small or severely hypoplastic mandibles often allow only single osteotomies. Because the tooth buds must be protected, the first osteotomy is made, in any case, proximal to the posterior-most tooth bud. Via the intraoral approach, a mucoperiosteal incision is made along the external oblique ridge. Following reflection of the mucoperiosteum and exposure of the mandibular angle region, a buccal corticotomy is made with the oscillating saw and copious irrigation using the guidance offered by the 3-D CT images and conventional radiographs, which demonstrate the location of the tooth buds. Through the incision, the external oblique line and lower cortical plate are grasped. The pairs of retention pins are now placed in bicortical fashion at extended distances anterior and posterior to the corticotomy or corticotomies, either intraorally with the use of the double-bur attachment or through the extraoral approach. Care must be taken in this maneuver to ensure the generally parallel placement of all the pins groups. The loosened distractor, either Bi-Directional or Multi-Directional, is then provisionally set on the pins and all screws tightened. Depending on the conditions at the placement sites, the scored rods can be adjusted either toward or away from the joint, with their advancement screws. Before the lingual corticotomy is made, the definitively adjusted distractor is removed by loosening only the head fixation screws. The ultimate division of the bone in osteotomy fashion is effected with a chisel inserted into the corticotomy itself and twisted along its long axis. After complete mobilization of the fragments, the previously adjusted distractor is again laced onto the fixation pins, and firmly tightened. Following the closure of the incisions, an extraoral dressing is applied. This dressing should be changed daily for three to four days. On the fourth or fifth postoperative day, distraction at a rate of 1 mm/day is undertaken along each geared rod. |
|
|
|
|
|
|
The riders can be moved incrementally in either direction.
The screws numbered with an 11 above and marked with an "F"
on the device are the fixation screws. The screws numbered with
a 5 above and marked with an "M" on the device are
the advancement screws.
To move a Rider: Using the screwdriver, turn the advancement screw ("M") to move the rider in the desired direction. The distance the rider is moved is indicated by the scale (marked in 1mm increments) etched on the geared rod. Once the desired position of the rider is reached, the rider must be stabilized by tightening the fixation screw ("F"). This is done by turning the screw clockwise. Because the distraction process will be carried out primarily by home-caregivers (relatives or friends of the patient), the fixation and advancement screws are clearly marked with the letters "F" and "M", respectively. |
 |
Procedure for Placement of the Distractor Make an incision along the external oblique ridge similar to that of a sagittal split osteotomy. Raise a full-thickness flap, separating the muscle from the overlying periosteum. Identify the area of bone deficiency. Identify and mark the area of preplanned mandibular osteotomy. Using a percutaneous approach, drill 1.5mm bicortical holes 6mm to either side of the planned osteotomy site. Make a second pin site 4mm to either side of the first pin site. Consequently, you need a minimum of 20mm of bone stock for pin placement. |
|
Prepare the osteotomy by making full thickness drill holes along the osteotomy site via an intraoral approach. Then connect the holes with a reciprocating saw. Complete and verify the osteotomy with an osteotome. Next introduce the 2.0mm pins (35-60mm length) into the previously made pin hole sites. Apply the distraction device. Then stabilize on a trial basis. Remove and complete the osteotomy on the lingual cortex and reapply distraction device. Irrigate the wound and close it with 4-0 cat gut suture. Beginning on the fifth to seventh post-operative day activate the distraction device (1mm per day). Expand the mandible until the pogonion is past midline and a posterior open bite is created. After expansion, leave the distractor in place for six to eight weeks, until radiographic evidence of mineralization is seen. Then remove the distractor as an in-office procedure. Taken from Selected Readings in Oral and Maxillofacial Surgery, Osteodistraction, Suzanne U. McCormick, MS, DDS, Volume 4, Number 7 |
|
| Distractor Models
|
|
 |
|
|
|
|
|
|
|
Bi-Directional |
|
|
|
|
Blocking disc for modification to Uni-Directional device |
 54-080-00 |
|
|
|
Multi-Directional Distractor |
54-025-00 Applied in the same manner as the Bi-Directional but
allows for transverse |
Copyright © 2001 KLS Martin, L.P. All
rights reserved
