Journal of Cranio-Maxillofacial Surgery (1997) 25, 116-123 © 1997 European Association for Cranio-Maxillofacial Surgery

Submerged intraoral device for mandibular lengthening

P. A. Diner, E. Kollar, H. Martinez, M. P. Vazquez

Maxillofacial & Plastic Department (Chief" M. P. Vazquez), Children's Hospital A. Trousseau, Paris, France

SUMMARY. The authors report a new technique for mandibular distraction. Lengthening of the mandible by gradual intraoral distraction was obtained in nine young patients. An intraoral device was used in order to avoid external scars. Seven patients had hemifacial microsomia, one patient had a ramus hypoplasia after TMJ ankylosis and one patient had the Treacher-Collins syndrome. The amount of mandibular lengthening ranged from 12 to 28 mm depending on the duration of expansion. Retention after expansion, to allow ossification to take place, lasted for 3 weeks on average. The follow-up period ranged from a minimum of 5 months to a maximum of 44 months.

I N T R O D U C T I O N

Lengthening of underdeveloped bones, including the mandible, has been obtained by application of distrac- tion osteogenesis (Ilizarov, 1971; Synder et al., 1973; Ilizarov, 1988; Cruerrero, 1990; Aytemiz and Sengezer, 1992; Karp et al., 1992; Constantino et al., 1993; Perrot et al., 1993; Sengezer, 1993; Havlik and Bartlett, 1994; McCormick, 1996).

Mandibular lengthening is now becoming an accepted method of treating severe underdevelopment which cannot be corrected by orthodontic means (Michielis and Miotti, 1977; Ortiz-Monasterio, 1982; Melsen et al., 1986; McCarthy et al., 1992; McCarthy, 1994; Klein and Howald, 1995; Losken et al., 1995). The bone lengthening is also associated with soft tissue changes (Molina and Ortiz-Monasterio, 1995).

The devices are usually inserted extraorally, but scarring and formation of granulation tissue can occur. They can be avoided to a certain degree by proper planning and positioning of the transcu- taneous pins, but, in addition, there always remains an increased risk of t rauma and it is often necessary to construct rather cumbersome external protection.

The external nature of the device impairs professional or scholastic activities during the entire period of distraction and retention.

This led to the development of intraoral distractors as reported by Cruerrero (1992), McCarthy et al. (1995), Chin and Toth (1996) and Diner et al. (1996).

In this paper, the results of the treatment of nine children are reported, all of whom had a severe growth impairment of the mandible. They were treated with the updated version of the device that we described in 1996. The first prototype was used in December 1993 in our department and, since 1995 (with the assistance of Leibinger Co.) we have modi- fied the device to its present standardized model (How Medica Leibinger G m b H , Freiburg).

MATERIALS AND M E T H O D S

Patients

There were nine children in whom the method was applied. Seven of them had unilateral hemifacial microsomia (one of these also suffering f rom hemi-

Table 1 - Clinical series results

Sex Years Diagn. Study Start distr. ° Active distr. ° Retention Total (month) (days) (days) (days) (days)

A.B. F 7,5 HFM R 26 9 34 21 55 O.P. F 6 HFM R 13 5 21 15 36 M.M. F 10 HFM R 5 3 21 28 49 C.S. F 6,5 HFM R 5 3 17 28 45 V.B. M 5 HFM R 13 5 21 15 36 Y.G. M 7,5 HFM L 18 5 42 35 77 F.B. M 8,5 HFM L 14 3 28 15 43 L.H. F 8,5 TM ankylosis L 9 5 16 34 50 I.L. M 10 Treacher-Collins 10 5 20 15 35 Mean 7,7 12,5 4 24 22 39,8

F: female, M: male, HFM: Hemi-Facial-Microsomia, R: right, L: left.

116

Submerged intraoral device for mandibular lengthening 117

Fig. 1 - An osteotomy situation high on the ascending ramus. The distractor is fixed along the lateral cortex of the ramus.

Fig. 2 - Simulation of distraction. Distraction by turning the rod (a 360 ° rotation = 0.45 ram).

arhinia and anorbitism), and one had ramus- hypoplasia after TMJ Ankylosis. Other patients with the Treacher-Collins Franceschetti syndrome under- went simultaneous and symmetric bilateral mandibu- lar elongation.

The patients were classified in accordance with the severity of the mandibular hypoplasia as described by Figueroa and Pruzanski (1982), Lauritzen et al. (1985) and Vento et al. (1991). According to the Pruzanski classification, three patients had a IIa deformity, five patients were classified IIb and one

Fig. 3 - The osteotomy on the lateral cortex is made with a saw or cutting drill and is bounded by bicortical notching in the region of the anterior and posterior margins (arrows).

had a grade III deformity. Further particulars are presented in Tables 1 and 2.

Distraction device

The first generation device has been previously described by us (Diner and al., 1996). However, the marketed, standardized device consists of a distractor frame with two double pinholders and a distraction rod at one end, which allows distraction of the pins. The rod has one or two joints to preserve the covering mucosa. The working length is 18 mm or 28 mm, depending on the type of distractor used. The rod is located inside the mouth, under the mucosa except for the labial tip which emerges at the angle of the mouth. The rod allows activation with a key, representing a distraction of 0.45 mm per turn (Figs. 1 & 2).

Surgery

Under general anaesthesia, a horizontal incision is made in the vestibulum. There is subperiosteal expo- sure of the ascending ramus and/or mandibular body including the posterior and anterior and/or upper and lower borders, respectively. Wide exposure is necessary in order to allow the distractor to be placed in the desired position in the subperiosteal pockets.

T a b l e 2 - Clinical series

Sex Years Diagn. O.M.E.N.S. Pruzanski Distractor Follow-up

A.B. F 7,5 H F M R 02,M2A,E0,N0,S2 IIa 18 mm UP 44 months O.P. F 6 H F M R 00,M2B,E0,N0,S0 IIb 18 mm - - D O W N 13 months M.M. F 10 H F M R 00,M2A,E3,N2,S2 IIb 28 mm - - UP 5 months C.S. F 6,5 HFM R 03,M2B,E3,N0,S3 IIb 18 mm - - UP 5 months V.B. M 5 HFM R 00,M2,E2,N0,S3 IIa 18 mm - - UP 13 months Y.G. M 7,5 HFM L 00,M2B,E3,N0,S2 IIb 18 mm UP 18 months F.B. M 8,5 H F M L 02,M1,E3,N2,S2 IIa 18 mm - - UP 14 months L.H. F 8,5 TM ankylosis L 00,M2B,E0,N0,S1 IIb 18 mm - - UP 9 months I.L. M 10 Treacher-Collins 02,M3,E2,N2,S3 III 28 mm UP 10 months Mean 7,7 12.5 months

F: female, M: male, HFM: Hemi-Facial-Microsomia, R: right, L: left.

118 Journal of Cranio-Maxillofacial Surgery

It is essential to insert the pins on both sides of the intended bone cut. The distractor should be opened a little to avoid damaging tooth buds. Placement of the distractors has to be in accordance with the preoperat- ively chosen direction of the distraction. The oste- otomy, also in accordance with the preoperative plan, is performed with a drill or saw. A partial cut is made on the lateral aspect of the mandible, but on the upper and lower (anterior and posterior) borders the cut is made through both cortical plates in order to weaken these strong trajectories, thus facilitating the sub- sequent 'greenstick fracture' (Fig. 3).

As for the bicorticals pins, they are chosen to match the thickness of the mandible as determined radiologically before surgery. They are inserted through a transbuccal trocar using a hand drill. It should be noted that the upper (posterior) pins are inserted after the partial osteotomy, at which point the carrier is tightened. After the greenstick fracture has been established with an osteotome or chisel, the pins located below the fracture line are inserted and the carrier is tightened (Fig. 4).

Distraction

Elongation is started on the 4th postoperative day at a rate of 1 mm per day in a single step, first by the medical team, then by the parents. Towards the end of the elongation some pain may be noticed, probably due to the stretching of the masseter and/or tem- poralis muscles. Some medication may therefore be required. No significant limitation of mouth opening is to be expected. A soft diet is required during the active phase of distraction and during retention,

RESULTS

The average amount of distraction as measured on the device was 18 mm with a range of 12-28 ram.

The retention period lasted, on average, 22 days, with a range of 15-35 days.

Except for the device itself, no other means of fixation were used. Removal of the distractor required only an intraoral approach. There were no cases of infection or other disturbance of wound healing. No pseudarthrosis occurred, nor was premature removal of the device necessary. However, two partial modifi- cations of the first prototype of the device required a second operation.

The inferior dental nerve was never compromised except in the case of 28 mm distraction, where a reversible dysaesthesia was observed, in accordance with Block et al. (1993). The clinical follow-up covered a period which ranged from 5 to 44 months. The parameters used for evaluation were analysed with respect to the changes obtained in mandibular dimensions, dental occlusion and facial aesthetics.

In cases of hemifacial microsomia, the slanting of the oral commissure was largely corrected by the procedure (Fig. 5). Whenever the hypoplasia of the soft tissues was mild, the aesthetic results were excel- lent (Figs 6-8). The scars from the transbuccal approach were minimal in all cases (Fig. 9), In two cases with pronounced hypoplasia of the soft tissues associated with facial nerve impairment (inferior branch), the facial contour did show a restricted bulging of the cheek compared with the contralateral side. In seven cases of hemifacial microsomia, the chin could be moved into the midline and its lower border came into a horizontal position. Over- correction was not affected except in one case, which had previously had a bone grafting procedure into the body of the mandible and which presented a contralateral deviation of the chin postoperatively.

In the Treacher-Collins case, the distraction achieved a good projection of the chin, in spite of the fact that an anterior open bite ensued because of the maxillary deformity in combination with the vector of distraction. However, the increase in mouth opening facilitated feeding.

Fig. 4 - The distractor is placed along the lateral surface of the mandible and the rod emerged at the angle of the mouth. The rod allows activation.

DISCUSSION

The introduction of an intraoral device gave rise to new problems, which have now been resolved. Miniaturization was essential and the apparatus now weighs 10 grams, is 5mm in thickness and 18 or 28 mm in length. The length of the device chosen in a particular case depends on the required distraction distance, its construction being such that the length of the distractor very closely matches the length of the distraction itself.

The biomechanical properties are as follows: all parts of the apparatus including the pins are made from stainless steel 18/8 and thus have identical inherent mechanical properties. The maximum torque

Submerged intraoral device for mandibular lengthening 119

Fig. 5 - Correction of unilateral microsomia ( A ) ~ i g h t - s i d e d microsomia, level of occlusion prior of distraction. (B)--Altered level of occlusion after distraction.

Fig. 6 - Comparative pictures showing preoperative (A) and postoperative appearance (B) which documents the situation 3 months after removal of the intraoral distractor.

120 Journal of Cranio-Maxillofacial Surgery

Fig. 7 - Comparative pictures showing preoperative (A) and postoperative appearance (B) document the situation 10 months after removal of the intraoral distractor.

Fig. 8 - Underdevelopment of left-sided costochondral graft (A) used for treating a TMJ Ankylosis 4 years before. The correction was achieved using an intraoral distractor. (B) Postoperative appearance 6 months after distraction.

Submerged intraoral device for mandibular lengthening 121

Fig. 9 - (A)--This photograph shows the minimal scar from the insertion of the trocar (see Figs 6 & 7) (B)--This photograph shows the minimal scar from the trocar (see Fig. 8).

Fig. 10 - Comparative x-rays showing the beginning of the distraction (A) and the new bone formation after intraoral distraction (B).

of the device attains 300 Nmm resulting in a distracting force of 900 N (approximately 90 kg). The design's aim has to be such that a rigid rod pressing into the lip commissure is avoided. This is realized by the use

of one or two universal joints. The joint rod is stabilized and gives a total angulation of 75°-80 ° in the case of two double joint rods or 40 ° for the single joint rod. Is the height of the vertical ramus a limiting

122 Journal of Cranio-Maxillofacial Surgery

Fig. 11 - Comparative x-rays showing the new bone formation after mandibular distraction. (A)--Miniplate previously inserted for fixation of a cranial bone graft. (B)--The newly formed bone can be visualized by the distance between the two segments of the divided miniplate.

factor for the use of an Intraoral Distractor? The use of the device was restricted by the degree of anatomical deformity/deficiency. In our series, the average height of the ramus was 57 ram, the minimum being 32 ram, in which case an 18 m m distractor was used. Our youngest patient was 5 years old.

Another feature to be analysed is the influence of the location of the osteotomy site: angle, body or ramus and, in the latter case, somewhere in the middle or rather high. The movement of the mobile carrier of the distractor should not be restricted by anatom- ical obstructions, e.g. the zygomatic arch, whenever the osteotomy is very high in the ascending ramus. It is better in such a case to perform the distraction with the mobile carrier at the upper end of the

distractor combined with a downward movement without any limitation of movement. In cases where the osteotomy is located lower in the ramus, the soft tissues might become a limiting factor, in which case it is better to use the mobile carrier at the lower end of the distractor combined with upward movement, and use its maximum length.

Unerupted teeth are a problem in both intra and extra-oral distractions. However, upon opening the distractor and using a pin extender, one is able to insert the pins at the optimal location. The subperios- teal placing of the device did not pose any problems, although in cases of hemifacial microsomia, hypotro- phy of the soft tissues was encountered. No retard- ation in bony consolidation was observed; on the

Submerged intraoral device for mandibular lengthening 123

contrary, bone thickness as well as soft tissue volume seemed to increase markedly by this procedure. An extra increase in cheek volume could be observed after up to 4 months in the follow-up period.

At present, the intraoral distractor operates only in a unidimensional way, but in our series (as well as those reported by other authors), a mere vertical elongation produces an anterior movement of the mandible as well, in the sense of a 'pendulum move- ment'. This is in spite of the fact that the axis of the ramus does not run in a purely 'vertical' direction, but is tilted in a lateral direction.

We have noticed a permanent remodelling bone formation, as if the functional matrix (Moss 1969) had been freed, in accordance with Molina and Ortiz- Monasterio (1995) (See Figs 10 & 11). In fact, in our opinion, a unidirectional distractor can treat all cases of hypoplastic deficiency of the mandible whether they be located in the ascending ramus ('vertical' elongation) or in the mandibular body ('horizontal' elongation).

In the case of bilateral underdevelopment of both ramus and body, a bidirectional distractor would ensure more adaptability in treatment. We think that evolution of the intraoral distractor should parallel the development of the extraoral one, which first was unidirectional but later became multidirectional (Glat et al., 1994). Finally, some of our patients had postoperative orthodontic treatment since all of them had a mixed dentition. The intention is to continue the stimulation of bone formation. In addition, stab- ility was provided by the bone formation process. We must also note the importance of the presence of the first molar. In our x-ray analysis, the elongation of the mandible could also be observed on the contralat- eral side in unilateral cases.

CONCLUSION

Insertion of the intraoral distraction apparatus in juvenile cases of mandibular hypoplasia yielded excel- lent results. No complications occurred; and the method can thus be recommended.

References

Aytemiz, C, M. Sengezer: Gradual distraction technique in correction of mandibular deformities. Proceeding of the Xth Congress of the International Confederation for Plastic Surgery, Madrid, Spain, 28 June-3 July 1992, Amsterdam Excerpta Medica, 1992, 29%298

Block, M. S., J. Daire, J. Stouer, M. Matthews: Changes in the inferior-alveolar nerve following mandibular lengthening in the dog, using distraction osteogenesis. J. Oral Maxillofac. Surg. 51 (1993) 652-660

Costantino, P. D., C D. Friedman, M. L. Shindo, G. Houston, G. A. Sisson: Experimental mandibular regrowth by distraction osteogen- esis. Long term results. Arch. Otolaryngol. Head Neck Surg. 119 (1993) 511-516

Chin, M., B. Toth: Proceeding of the 17th Annual conference of the

American College of Oral and Maxillofacial Surgeons, Philaddphia, 9-12 May 1996

Diner, JR A., E. M. Kollar, I-L Martinez, M. P. Vazquez: Intraoral distraction for mandibular lengthening: a technical innovation. J. Cranio-Maxfac. Surg. 24 (1996) 92-95

Figueroa, A. A., S. Pruzanski." The external ear, mandible and other components of bemifacial microsomia. J. Cranio-Maxfac. Surg. 10 (1982) 20(>211

Glat, P. M., D. A. Staffenberg, N. S. Karp, R. A. Holliday, G. Steiner, 31. G. McCarthy. Multidirectional distraction osteogenesis: the canine zygoma. Plast. Reconstr. Surg. 94 (1994) 753-758

Guerrero, C A.: Rapid mandibular expansion. Rev. Venez. Orthod. 1 (2) (1990) 48

Guerrero, C A.: lntraoral mandibular distraction osteogenesis. J. Oral Maxillofac. Surg. 115 (199) (1992)

Havlik, R. J., S. P. Bartlett: Mandibular distraction lengthening in the severely hypoplastic mandible: a problematic case with tongue aplasia. J. Cranio-Maxfac. Surg. 5 (1994) 30~312

Ilizarov, G. A.: Basic principles of transosseous compression and dis- traction osteosynthesis. Ortop. Traumatol. Protez. 32 (11) (1971) 7

Ilizarov, G. A.: The principles of the Illzarov method. Bull. Hosp. Joint Dis. Orthop. Inst. 48 (1988) 1-11

Karp, N. S., ,L. G. MacCarthy, J. S. Schreiber, H. A. Sissons, Ch. M. Thorne: Membranous bone lengthening: a serial histological study. Ann. Plast. Surg. 29 (1) (1992) 27

Klein, C, H. JR Howald. Lengthening of the hypoplastic mandible by gradual distraction in childhood: a preliminary report. J. Cranio- Maxfac. Surg. 23 (1995) 68 74

Lauritzen, C, L K Munro, K B. Ross: Classification and treatment of hemifacial microsomia. Scand. J. Plast. Surg. 19 (1985) 33-39

Losken, H. W., G. T. Patterson, S. A. Lazarou, T. Whitney: Planning mandibular distraction: preliminary report. Cleft Pal.-Craniofac. J. 32 (1) (1995) 71-76

McCarthy, J. G., J. Schreiber, N. Karp, Ch. M. Thorne, B. H. Grayson: Lengthening the human mandible by gradual distraction. Plast. Reconstr. Surg., 89 (1) (1992) 1-8

McCarthy, J. G.: The role of distraction osteogenesis in the reconstruc- tion of the mandible in unilateral craniofacial microsomia. Clin. Plast. Surg. 21 (1994) 625-361

McCarthy, J. G., D. A. Staffenberg, K ~ Wood, C 13. Cutting, B. H. Grayson, C H. Thorne: Introduction of an intraoral lengthening device. Plast Reconstr. Surg. 96 (1995) 978-981

McCormick, S. U.: Osteodistraction selected readings in oral and maxillofacial surgery. University of Texas Southwestern Medical Center, 1996, Vol 4

Melsen, B., Y.. Bjerrejaard, M. Bundgaard: The effect of treatment with functional appliance on pathologic growth pattern of the condyle. Ann. Orthod. 90 (1986) 503

Michielis, S., B. Miott# Lengthening of mandibular body by gradual surgical and orthodontic distraction. J. Oral Surg. 35 (1977) 187- 192

Molina, F., F. Ortiz-Monasterio: Mandibular elongation and remodeling by distraction: a farewell to major osteotomies. Plast. Reconstr. Surg. 96 (1995) 825-840

Moss, M. L.: The primary role of functional matrices in facial growth. Am. J. Orthod. 55 (1969) 566-577

Ortiz-Monasterio, F.: Early mandibular and maxillary osteotomies for the correction of hemifallcal microsomia. Clin. Plast. Surg. 9 (1982) 509

Perrot, D. H., JR. Berger, K. Vagervik, L. B. Kaban: Use of a skeletal distraction device to widen the mandible: a case report. J. Oral Maxillofac. Surg. 51 (1993)435-439

Sengezer, M.: Mandibular lengthening by gradual distraction. Plast Reconstr. Surg. 92 (1993) 372

Snyder, C C, G. A. Levine, H. M. Swanson, E. Z. Browne: Mandibular lengthening by gradual distraction. Preliminary report. Plast. Reconstr. Surg. 51 (1973) 506-508

Vento, A. K , ,L. B. Mulliken, K A. Labrie: The O.M.E.N.S. classifi- cation of the hemifacial microsomia. Cleft Palate J. 28 ( 1991) 68-77

Dr P. A. Diner 29 rue de la Sant6 75013 Paris France

Paper received 7 October 1996 Accepted 10 April 1997