Complications after mandibular distraction osteogenesis: a retrospective study of 131 patients

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1 Complications after mandibular distraction osteogenesis: a retrospective study of 131 patients Sven Erik Nørholt, DDS, PhD, a John Jensen, DDS, PhD, b Søren Schou, DDS, PhD, DrOdont, c and Thomas Klit Pedersen, DDS, PhD, d Aarhus, Denmark AARHUS UNIVERSITY HOSPITAL AND AARHUS UNIVERSITY Objectives. The objectives of this study were to evaluate the occurrence and severity of complications after mandibular distraction osteogenesis (DO) with internal devices. Study design. The study was a retrospective analysis of 131 patients (mean age: 16.2 years) consecutively treated by mandibular DO from 1998 to Ninety-two patients had unilateral and 39 had bilateral distraction, yielding a total of 170 procedures. The mean follow-up period was 21 months. Severity of complications was ranked in terms of need of intervention and risk of a compromised outcome. Results. Minor, moderate, and severe complications occurred in 58%, 8%, and 3% of the patients, respectively. Most minor complications were related to device activation or temporary hypesthesia. Moderate complications often related to hardware, whereas severe complications occurred in 4 patients with sensory deficit or temporomandibular joint problems. Conclusions. Although minor complications were frequent, they did not compromise treatment outcome, so mandibular DO is considered a safe method for correction of mandibular deformities. Moreover, some of the complications could be prevented by proper precautions. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011; 111: ) a Consultant Surgeon, Associate Professor, Departments of Oral and Maxillofacial Surgery, Aarhus University Hospital and Aarhus University, Aarhus, Denmark. b Head of Department, Associate Professor, Departments of Oral and Maxillofacial Surgery, Aarhus University Hospital and Aarhus University, Aarhus, Denmark. c Professor and Chairman, Department of Oral & Maxillofacial Surgery and Oral Pathology, School of Dentistry, Aarhus University, Aarhus, Denmark. d Chief Orthodontist, Associate Professor, Department of Orthodontics, Aarhus University and Aarhus University Hospital, Aarhus, Denmark. Received for publication Apr 12, 2010; returned for revision May 19, 2010; accepted for publication May 21, /$ - see front matter 2011 Mosby, Inc. All rights reserved. doi: /j.tripleo Distraction osteogenesis (DO) is widely used for improving the morphology of the facial skeleton in patients with congenital or acquired deformities. The treatment principles for correction of facial deformities rest mainly on traditional combined orthodontic and surgical methods, which include osteotomy and various bone-grafting techniques. In patients in whom extensive facial modification and soft tissue improvements are required, DO may be an attractive alternative because bone grafting can be avoided. Moreover a more predictable treatment outcome may be obtained. 1 DO has been addressed in several reports. The technique has mainly been used for corrections of congenital mandibular malformations (e.g., Pierre Robin syndrome, hemifacial microsomia, Goldenhar syndrome, and idiopathic micrognathia), syndromes involving the facial skeleton (Aperts, Crouzon, and Pfeiffer syndrome), and maxillary hypoplasia in patients with cleft lip and palate. 2-9 Advances in surgical technique, as well as the technical equipment, have allowed the indications for DO to be widened. The method is now also being used for nonsyndromic deformities like mandibular retrognathism and asymmetry, whether these deformities are congenital or acquired growth impairment because of fractures or juvenile idiopathic arthritis of the temporomandibular joint. 10,11 Recent years have seen a rapid rise in the number and types of distraction devices, and small, submerged devices have been introduced to maximize patient comfort and psychological and physical acceptability. In spite of these advances, the surgical procedure can be challenging and the treatment carries an inherent risk of complications. 12,13 The aim of this retrospective study was to describe and quantify the complications after internal mandibular distraction osteogenesis by a thorough analysis of a series of consecutively treated patients. Furthermore, it was the purpose of the study to categorize the observed complications by severity. MATERIAL AND METHODS Patients During a 12-year period ( ), a total of 131 patients (79 females [60%] and 52 males [40%]) were 420

2 Volume 111, Number 4 Nørholt et al. 421 Table I. Diagnosis related to the mandibular deformity Diagnosis No. of patients Juvenile idiopathic arthritis 39 Trauma sequelae 31 Idiopathic mandibular hypoplasia 22 Hemifacial microsomia 17 Infection sequelae 5 Ankylosis 1 Cleft deformity 3 Treacher Collins syndrome 2 Arthrosis sequelae 9 Smith-Opits-Lendl syndrome 1 Torticollis 1 Total 131 Table II. Treatment variables No. of patients Mean Range Standard deviation Age at surgery, y Latency period, d Rate, mm/d Total distraction, right side, mm Total distraction, left side, mm Consolidation period, d treated with internal mandibular distraction osteogenesis at the Department of Oral and Maxillofacial Surgery, Aarhus University Hospital, Aarhus, Denmark. All patients undergoing mandibular distraction procedures were included. The details of the diagnoses are summarized in Table I. The age distribution is outlined in Fig. 1. A unilateral distraction was performed in 92 patients (70%) and a bilateral distraction was performed in 39 patients (30%). Thus, a total of 170 distraction procedures were performed. The mean latency phase after insertion of the distraction device was 4.1 days (range: 2-7); the activation was set to 0.8 to 1.2 mm per day. The mean period of active distraction was 19 days (range: 9-35) followed by an average consolidation period of 66 days (range: ). Further details are given in Table II. At the time of the removal of the distraction device, concomitant surgical procedures were performed in 59 patients (41 patients: Le Fort I osteotomy; 7 patients: Le Fort I osteotomy and genioplasty; and 11 patients: genioplasty). Another 39 patients later underwent orthognathic surgery (20 patients: Le Fort I osteotomy; 9 patients: Le Fort I osteotomy and genioplasty; 6 patients: genioplasty; and 4 patients: Le Fort I osteotomy and mandibular osteotomy); no further surgery was performed in the remaining 30 patients. Fig. 1. Age distribution of patients at time of surgery. Treatment planning All patients were treated according to a standardized protocol using an internal monodirectional distraction device. A Medicon vertical mandibular distraction device (Medicon eg, Tuttlingen, Germany), a Martin paediatric mandibular distractor (KLS Martin GmbH, Tuttlingen, Germany), and a Synthes mandibular single vector distractor (Synthes AG, Chur, Switzerland) were used in 113, 10, and 4 patients, respectively. The remaining 4 patients were treated by devices from various companies. Fixed orthodontic appliances were placed in all patients before surgery. The age of the patients varied and, accordingly, the treatment protocols differed substantially. Roughly, the treatment sequences could be divided into 3 age groups: (1) Before puberty. In most of the younger patients, the appliances remained inserted only during the period of DO because the final orthodontic treatment was scheduled to be performed at a later time or because the occlusion could be normalized using removable orthopedic appliances. (2) Early puberty. Distraction osteogenesis was planned to correct the mandibular deformity and after the distraction procedure was completed, orthopedic and orthodontic treatment were performed with the aim of completing the treatment with no further surgical procedures. (3) Late puberty or adulthood. In most patients with an affection of the maxillary growth that could not be treated without surgery, distraction osteogenesis was postponed so as to be able to perform Le Fort I osteotomy at the time of removal of the distraction device.

3 422 Nørholt et al. April 2011 Fig. 2. Splint and rod for transfer of distraction vector. During surgery the distraction device is initially fixated with 1 screw; thereafter, it can be rotated until the rod and the splint are parallel, ensuring the desired vector. Further details of the treatment protocol for the various age groups will be presented in a later publication. In our early studies of distraction osteogenesis, we routinely used stereolithographic models; in the present study, however, such models were used only in severe cases. The reason for abandoning the use of stereolithographic models was a development in the method of transferring the distraction vector; in most of the straightforward cases this could be done by use of an individual splint as described in the following section. In all patients, the primary treatment aim was to increase the height of the mandibular ramus, and device insertion was planned to accomplish this aim. The distraction vector was determined by lateral cephalometric analysis, and described in terms of its angle to the mandibular occlusal plane. To insert the device according to the planned distraction vector, a splint with a rod perpendicular to the vector was manufactured for each side and used during the surgical procedure (Fig. 2). Surgery The surgical procedure was performed under general anesthesia after intravenous administration of 2 MIU penicillin. Through an intraoral incision with elevation of the buccal, posterior, and anterior periosteum of the ramus, the internal distraction device was fixated with 1 screw approximately in the desired position. The specially designed rod was fixed perpendicularly to the distraction device and the device was rotated until the rod was parallel to the rod in the splint to ensure correct angulation of the distraction device (Fig. 2). A second screw was then inserted and both screws were tightened. The remaining screw holes were marked and the distraction device was removed to complete the osteotomy. The osteotomy was performed as a horizontal cut of the ascending ramus at a level below the mandibular foramen. At this level the mandibular bone usually has sufficient thickness and central cancellous bone allowing a good osseous healing capacity. The cortical bone of the ramus was cut in the posterior, lateral, and anterior parts leaving the central cancellous bone and medial cortex to be fractured. Osteotomy was performed with a Lindeman bur until After 2005, all procedures have been performed with a piezoelectric device (PiezoSurgery, Mectron, Carasco, Italy). Depending on the type of device, the activation arm penetrated either intraorally (e.g., Medicon) or extraorally (e.g., KLS Martin or Synthes). The incision was closed using resorbable sutures. Most patients were discharged the day after surgery and were given oral penicillin (50 mg/kg/d) for 5 days and acetaminophen and ibuprofen for pain control at doses corresponding to weight. Additional tramadol (200 mg/d) was given on indication to patients older than 12 years. At a follow-up visit 4 to 5 days after surgery, the patients or their relatives were instructed to activate the distraction device. The patients were seen on a regular weekly basis until the desired length of distraction was obtained. During the entire treatment period, the patients wore a permanent occlusal splint on the lower dental arch. The splint was gradually adjusted to support the occlusion bilaterally to relieve the temporomandibular joint (TMJ) and the distraction area. The distraction device was removed after the retention period under general anesthesia, and orthodontic treatment was continued as previously described. The amount of distraction was determined by measuring the length of the distraction device on radiographs, which was done by calibrating the panoramic radiograph by use of the known dimension of the distraction devices. In most of the cases, the full 20-mm capacity of the distraction device was used. Data extraction for evaluation of complications All patients were treated according to a defined protocol, which involved regular follow-up after distraction (mean: 21 months, range: 2-135). The surgical and orthodontic records were reviewed to extract relevant data. This included panoramic radiographs and lateral cephalograms. Complications occurring during the treatment period were registered and classified by severity according to the stratification system presented by Shetye et al. 13 In their study, the term incident was used to describe adverse events. The term complication will be used for all adverse events in the present study. The classification of complications is presented in Table III. A minor incident/complication was one that resolved sat-

4 Volume 111, Number 4 Nørholt et al. 423 Table III. Frequency of patients with complications (modified from Shetye et al. 13 ) Frequency, % No. of patients No complications Minor complications Hardware related 1. Difficulty in device activation Device rotating backwards Improper vector Inadequate device length Hard and soft tissue related 1. Pain at bony generate site Hypertrophic scar Cyst caused by pins Psychological problem Neuropraxia Infection Trismus during treatment or device removal 8. Parotid gland injury 0 0 Moderate complications 8 11 Hardware related 1. Inadequate device length Improper vector Device rotating backwards Unstable device Unstable device following trauma Device deformation or breakage Hard and soft tissue related 1. Premature ossification Scar revision required Major complications 3 4 Hardware related 1. Unstable device Device breakage 0 0 Hard and soft tissue related 1. Tooth follicle damage Premature consolidation Fibrous union TMJ ankylosis and degenerative changes 5. Fracture Nerve injury (e.g., neurotmesis) Medical 1. Systemic infection/sepsis Embolism Cardiac event Anoxia/airway problem Death 0 0 TMJ, temporomandibular joint. isfactorily with minimal or no invasive intervention. A moderate incident/complication was one that resolved satisfactorily with moderate clinical intervention. A major incident/complication was one that did not resolve or could not be resolved with surgical or other interventions, and which compromised the final treatment outcome. To quantify the subjective assessment of the neurosensory function of the inferior alveolar nerve (IAN), the patients described their sensibility in the lower lip as follows: (1) Normal: No difference from preoperative situation or no difference between the operated and nonoperated side. (2) Slightly reduced without any discomfort: The sensibility of their lower lip had changed slightly but that this did not disturb their daily comfort. (3) Reduced noticeable: Decreased sensibility in the lower lip that was noticed on a daily basis. (3) Anesthetic: No sensibility in the lower lip. Evaluation of the neurosensory function was performed postoperatively (within 5 days after surgery) and at the last follow-up visit (range months). Ideally, objective measures of neurosensory function could have been added but this was not applicable in this retrospective study. Statistical analyses Data were handled and analyzed using Statistical Package of Social Sciences (SPSS, Chicago, IL) version Chi-square tests with a significance level of.05 were used to detect any significant correlations between complications and age or diagnosis. RESULTS The observed complications are outlined in Table III. In most patients, minor incidents were observed and these incidents were related to (1) practical difficulties in device activation (19.8%); (2) pain on activation (30.5%); (3) neuropraxia (40.0%); (4) infection in relation to the distraction device (12.2%); and (5) trismus during distraction (9.9%). Moderate complications occurred in a limited number of patients and were mainly related to the hardware: (1) unstable device (2.3%); and (2) deformation of device (3.1%). Finally, severe incidents comprised permanent IAN lesion (1.5%) and TMJ degeneration (1.5%). The patients subjective evaluations of neurosensory function related to age (younger or older than 18 years) and diagnosis (juvenile idiopathic arthritis [JIA] and idiopathic hypoplasia [IH] versus other diagnoses) are presented in Tables IV and V. The neurosensory function was not statistically significantly influenced by age (P.9). It was chosen to compare patients younger and older than 18 years old because this age is usually the limit for performing conventional orthognathic surgery, and thus it could be investigated whether DO caused more or fewer sensory problems. The neurosensory function for patients with JIA or IH compared with patients with other diagnoses was

5 424 Nørholt et al. April 2011 Table IV. Neurosensory function, subjectively, related to age Neurosensory function 1-10 days after surgery* Final follow-up* All patients n 148 n 118 n 30 All patients n 153 n 118 n 35 Normal 73 (49%) 57 (48%) 16 (53%) 134 (88%) 104 (88%) 30 (86%) Slightly reduced, no discomfort 60 (41%) 49 (42%) 11 (37%) 17 (11%) 12 (10%) 5 (14%) Reduced, noticeable 15 (10%) 12 (10%) 3 (10%) 2 (1%) 2 (2%) 0 (0%) Anesthesia, numbness *P.9, chi-square test for difference between age groups. All figures relate to number of surgical sites. Table V. Neurosensory function, subjectively, related to diagnosis Neurosensory function Postoperative 1-10 days* All patients n 148 JIA or IH n 77 Others n 71 All patients n 153 Follow-up JIA or IH n 81 Others n 72 Normal 73 (49%) 45 (58%) 28 (40%) 134 (88%) 71 (88%) 63 (88%) Slightly reduced, no discomfort 60 (41%) 20 (26%) 40 (56%) 17 (11%) 8 (10%) 9 (12%) Reduced, noticeable 15 (10%) 12 (16%) 3 (4%) 2 (1%) 2 (2%) 0 (%) Anesthesia, numbness JIA, juvenile idiopathic arthritis; IH, idiopathic hypoplasia. *P.05, chi-square test for difference between diagnoses. P.25, chi-square test for difference between diagnoses. All figures relate to number of surgical sites. Table VI. Pain and activation problems related to age Total n 131 n 102 n 29 Pain at activation* 40 (31%) 27 (27%) 13 (44%) No pain at activation 91 (69%) 75 (73%) 16 (56%) Difficulties with 26 (20%) 21 (21%) 5 (17%) activation No difficulties with activation 105 (80%) 81 (79%) 24 (83%) *P.06, chi-square test for difference between age groups. P.6, chi-square test for difference between age groups. statistically significantly impaired in the postoperative period (P.05). However, this difference was not present at the last follow-up visit (P.25). The rationale for comparing these diagnoses was the anatomy of the ramus, which was usually found to be less abnormal in the patients with JIA or IH. Neither pain nor difficulties with activation were statistically significantly related to the age (P.06 and P.6, respectively) (Table VI). DISCUSSION This retrospective study focused on complications after intraoral mandibular DO. It was revealed that minor complications occurred in 58% of the patients. Moderate complications with a potential adverse effect on treatment outcome were observed in 8% of the patients. Finally, severe complications were seen in 3% of the treated patients. The stratification of complications was performed according to the method described by Shetye et al. 13 In their study, the occurrence of incidents in 141 patients undergoing 226 mandibular DO procedures were registered and divided according to severity. The complications were divided into minor, moderate, and major reflecting the consequences for the final treatment outcome. Minor (27%), moderate (20%), and major complications (5%) were observed. The percentage of minor complications was higher in the present study, whereas the numbers of moderate and severe complications were lower. The most important aspects are discussed within the section. Neurosensory dysfunction Mild neurosensory dysfunction (NSD) was observed in 40% of the patients just after surgery and the occurrence was significantly related to the diagnosis of the patient. This dysfunction subsequently either resolved completely or was reduced to a slightly altered sensory function causing the patient no particular discomfort

6 Volume 111, Number 4 Nørholt et al. 425 over time. In contrast, neuropraxia was seen in only 1 of 226 distraction sites in the previously mentioned study. 13 The background of this difference may be related to differences in included patients, surgical techniques, and evaluation criteria. The risk of injury to the IAN has been evaluated in several studies comparing bilateral sagittal split osteotomy (BSSO) and DO. In a study by Wijbenga et al., 14 the postoperative percentage of NSD reported after DO for mandibular advancement was 57%. At the follow-up at least 1 year after DO, Wijbenga et al. 14 found that 23% of the surgical sites had NSD (35% of patients). Moreover, 13% of the sites with NSD were bothering the patients. In our study, the corresponding figures were 12% and 1%, respectively (Table IV). In the study of Shetye and coworkers, 13 no permanent NSD was reported. Injury to the IAN is a major concern when osteotomies of the mandible are performed, and several studies have compared the risk after DO and BSSO. Wijbenga et al. 14 found no statistically significant difference in the function of the IAN after DO and BSSO, whereas Ow and Cheung 15 in a recently published review concluded that the risk of persistent neurosensory disturbance was higher following BSSO than DO. The risk of NSD was not influenced by either age or diagnosis in the present study. Piezoelectric surgery has been used routinely since It has been shown that the use of piezoelectric surgery for the BSSO reduces the blood loss and the risk of injury to the IAN. 16 Therefore, piezoelectric surgery may also decrease the risk of IAN injury after DO. In the present study, we could not detect a statistically significant decrease in neurosensory disturbances, pain, or infections as a result of using piezoelectric surgery. However, further studies are needed before final conclusions can be made. Most of the patients in the present study underwent treatment with DO as an alternative to conventional orthognathic surgery. In patients with moderate mandibular asymmetries, the deformity could be corrected by a surgical procedure involving the affected side only. This approach limited the risk of damage to the IAN to one side. If both sides had been involved as in BSSO, the risk would evidently have been applied to both sides. In 4 patients only, a supplementary mandibular osteotomy was needed after DO, indicating that the mandibular deformity can be successfully corrected by DO in most cases. Pain Most of the reported complications were minor and many were related to the activation of the device. The activation rod is situated intraorally, it can be difficult to access, and can cause pain or discomfort to the surrounding soft tissues. However, it is of significant importance for the patients and their relatives that no hardware is visible. Therefore, they are strongly motivated to accept the discomfort from the intraoral position of the distraction device. Pain and functional problems are a common finding in relation to DO. 12 In spite of the apparently high number of patients who encountered problems in activating the device, nobody failed to complete the distraction procedure in their own homes. Our findings indicate that measures should be taken to ease access to the distraction device (for example, by fixing the activation arm in a proper position, by choosing a proper length of the distraction arm, and by ensuring thorough instruction of the patient). Moreover, administration of sufficient doses of analgesics throughout the active distraction phase seems mandatory. The standard regimen for pain control has involved acetaminophen and nonsteroidal antiinflammatory drugs (NSAIDs) in relevant doses. Moreover, it can be necessary to add a mild opiate like tramadol. Simplified treatment At our institution, mandibular DO was introduced to replace the complex conventional orthognathic surgical procedure with a predictable, sequenced correction of mandibular deficiency in the nonsyndromic patient. In addition, the elongation of the mandibular ramus creates a posterior open bite, which allows the vertical growth of the dentoalveolar complex to be controlled by guided eruption of teeth and can therefore be used with advantage in younger individuals. When more severe malformations are present, the rationale is to reduce and simplify the need for later bone graft or alloplastic reconstruction. Breuning et al. 17 showed that the total treatment time was significantly shorter in patients with mandibular retrognathism treated with DO compared with conventional orthognathic surgery. Depending on the patient s age, the treatment after DO may involve fixed or removable orthodontic appliances. Moreover, a surgical correction of the maxilla is often required. However, it is our clinical experience that the subsequent surgery is usually predictable and stable in contrast to the 1-stage correction of severe deformities. Distraction devices An internal distraction device with a high rigidity and strength was used in all patients and we therefore encountered minor deformations of the hardware in 4 patients only. However, this complication did not affect the final treatment outcome, as the distraction process could be completed to the planned end point.

7 426 Nørholt et al. April 2011 In external distraction, force is applied at a distance from the distraction site, and therefore the pins may deform or migrate through the bone. 18 Internal devices are able to transfer the force to the bone with a minimum of distortion. 19 This is an advantage in terms of stability and predictability of the vector of distraction. Infection In 12% of the distractions sites it was necessary to treat a local infection around the distraction device by means of supplementary antibiotic therapy. In all cases the infection was controlled without any consequences to the final treatment outcome and no devices were removed before the planned consolidation period. The intraoral penetration of the activation arm implies a communication between the oral cavity and the distraction site. To prevent late infections it is very important to maintain optimal hygiene around the distraction device throughout the entire consolidation period. The risk of late infections can be reduced if the activation arm can be disconnected after the active distraction phase. This is, however, not possible with all systems. The problem with infection around intraoral distraction devices has been reported in other studies; in an evaluation of midline distraction in 23 patients, Mommaerts et al. 20 reported 7 (30%) of 30 patients with infection at some point of time during the treatment. Incomplete osteotomy To avoid later complications, the osteotomy must be completely mobilized to ensure that there is no obstruction to the distraction process. Three patients experienced pain when trying to activate the device because of insufficient mobility of the osteotomy. For 2 of the patients, the segments could be mobilized by activating the device 3 to 4 mm under local anaesthesia. The osteotomy had to be completed under general anesthesia in 1 patient. Piezoelectric surgery provides the possibility of an osteotomy line with minimal bone loss, which makes it easier to complete a total corticotomy with minimal risk of injury to soft tissues. 16 Temporomandibular joint Most complications involving the TMJ were related to decreased mobility during the distraction process. In 10% of the patients, trismus was observed mainly owing to the extension of the activated distraction device under the zygomatic arch. After removal of the distraction device, the TMJ function was gradually normalized in all but 2 patients. One of the patients had degenerative changes of the mandibular condyles owing to an earlier involvement by juvenile arthritis; the other patient had a fibrous ankylosis owing to a condylar fracture at a young age. To relieve both the TMJ and the distraction site, all patients wore a full-time occlusal splint, which was adjusted once a week to maintain occlusal support. This is probably an important factor to avoid TMJ dysfunction as a consequence of the distraction process. Our patients with previous involvement of their TMJ by juvenile idiopathic arthritis could be at particular risk of recurrence of joint symptoms. As distraction osteogenesis has become widely used within a limited period of time and as the potential for complications is significant, it is important to gain increased knowledge about complications. Many problems can be avoided if attention is paid to these factors in due time and others can be resolved with adequate intervention. A systematic monitoring of the patients during the treatment procedures is essential, thereby reducing the risk of the most severe complications. Therefore, a consideration of cost-benefit should be a central part of the treatment planning. CONCLUSIONS The present retrospective study focused on complications after intraoral mandibular distraction osteogenesis. It was revealed that minor complications occurred in 58% of the patients. Moderate complications with the potential of affecting the final treatment outcome were observed in 8% of the patients. Finally, severe complications were seen in 3% of the treated patients. Therefore, mandibular distraction osteogenesis by internal devices may give rise to a number of complications during and after the distraction phase. Most complications have no consequence to the final treatment outcome, but all measures should be taken to prevent as many complications as possible. REFERENCES 1. Molina F. Mandibular distraction osteogenesis: a clinical experience of the last 17 years. J Craniofac Surg 2009;20(Suppl 2): Figueroa AA, Polley JW. Management of the severe cleft and syndromic midface hypoplasia. Orthod Craniofac Res 2007;10(3): Jacobsen HC, Sieg P, Hakim SG. 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8 Volume 111, Number 4 Nørholt et al. 427 niosynostosis: device selection, problems, indications, and a proposal for use of a parallel bar for device-setting. J Craniofac Surg 2006;17(6): Shetye PR, Giannoutsos E, Grayson BH, McCarthy JG. Le Fort III distraction: Part I. Controlling position and vectors of the midface segment. Plast Reconstr Surg 2009;124(3): Van Sickels JE. Distraction osteogenesis: advancements in the last 10 years. Oral Maxillofac Surg Clin North Am 2007;19(4): , vii. 10. Kofod T, Norholt SE, Pedersen TK, Jensen J. Unilateral mandibular ramus elongation by intraoral distraction osteogenesis. J Craniofac Surg 2005;16(2): Mackool RL, Shetye P, Grayson B, McCarthy JG. Distraction osteogenesis in a patient with juvenile arthritis. J Craniofac Surg 2006;17(2): Hurmerinta K, Peltomaki T, Hukki J. Unexpected events during mandibular distraction osteogenesis. Scand J Plast Reconstr Surg Hand Surg 2004;38(4): Shetye PR, Warren SM, Brown D, Garfinkle JS, Grayson BH, McCarthy JG. Documentation of the incidents associated with mandibular distraction: introduction of a new stratification system. Plast Reconstr Surg 2009;123(2): Wijbenga JG, Verlinden CR, Jansma J, Becking AG, Stegenga B. Long-lasting neurosensory disturbance following advancement of the retrognathic mandible: distraction osteogenesis versus bilateral sagittal split osteotomy. Int J Oral Maxillofac Surg 2009;38(7): Ow A, Cheung LK. Skeletal stability and complications of bilateral sagittal split osteotomies and mandibular distraction osteogenesis: an evidence-based review. J Oral Maxillofac Surg 2009;67(11): Landes CA, Stubinger S, Rieger J, Williger B, Ha TK, Sader R. Critical evaluation of piezoelectric osteotomy in orthognathic surgery: operative technique, blood loss, time requirement, nerve and vessel integrity. J Oral Maxillofac Surg 2008;66(4): Breuning KH, van Strijen PJ, Prahl-Andersen B, Tuinzing DB. Duration of orthodontic treatment and mandibular lengthening by means of distraction or bilateral sagittal split osteotomy in patients with Angle Class II malocclusions. Am J Orthod Dentofacial Orthop 2005;127(1): Hollier LH Jr, Higuera S, Stal S, Taylor TD. Distraction rate and latency: factors in the outcome of pediatric mandibular distraction. Plast Reconstr Surg 2006;117(7): Robinson RC, O Neal PJ, Robinson GH. Mandibular distraction force: laboratory data and clinical correlation. J Oral Maxillofac Surg 2001;59(5): Mommaerts MY, Spaey YJ, Soares Correia PE, Swennen GR. Morbidity related to transmandibular distraction osteogenesis for patients with developmental deformities. J Craniomaxillofac Surg 2008;36(4): Reprint requests: Sven Erik Nørholt, DDS, PhD Department of Oral and Maxillofacial Surgery Aarhus University Hospital Norrebrogade 44 DK-8000 Aarhus C, Denmark svenoe@rm.dk