Rapid maxillary distraction protocol utilizing the halo distraction system and rigid internal fixation.

OBJECTIVE: To shorten head frame wear time associated with external halo distraction (HD), we have adapted a protocol for maxillary distraction with the halo system that integrates plate fixation. PARTICIPANTS: All patients had a history of cleft lip and/or palate and maxillary retrusion > or = 8 mm. Five patients treated with this protocol and followed for at least 1 year were included in this study. INTERVENTIONS: The protocol included a 3-day latency period, variable maxillary distraction, and removal of the halo device with simultaneous rigid internal fixation. Two patients had a variable period of maxillomandibular fixation (MMF), which maintained the maxillary advancement and idealized intercuspal position while permitting further callus maturation. Cephalographs were obtained preoperatively, immediately following distractor removal, and 1 year after rigid internal fixation. RESULTS: The mean age at time of surgery was 18.7 years. The maxillary deficiency ranged from 8 to 15 mm (mean = 10.6 mm). All five patients demonstrated excellent occlusion. Cephalometric analysis 1-year post rigid internal fixation revealed minimal (<1 mm) skeletal relapse. CONCLUSIONS: Rapid maxillary distraction followed by MMF to maintain maxillary advancement may reduce halo device wear to 1 to 2 weeks. MMF optimizes occlusion by forcing the maxillary teeth into maximal intercuspal position. Rigid fixation is not only associated with less long-term relapse compared to nonrigid forms of fixation, but also minimizes the incidence of nonunion. This treatment protocol provides the advancement possible with distraction osteogenesis and the accuracy of orthognathic surgery, thereby minimizing external head frame wear.     

Mandibular lengthening with an implanted motor-driven device: preliminary study in sheep.

Distraction osteogenesis with external or intraoral devices is an established method for lengthening human mandibles. In this preliminary study in three sheep a newly designed, fully implantable electromechanical device for mandibular lengthening was used. After osteotomy, the device was screw fixed to the mandible, and the power and control unit was inserted subcutaneously in the neck region. After a healing period of five days, the device was activated magnetically, allowing calibrated distraction steps of 0.04 mm/h, resulting in a total of 1.0 mm/day. Over a period of 14 days, a maximum mandibular lengthening of 13.6 mm could be achieved without transmucosal activation. Depending on stability of the screw fixation, membranous and/or cartilaginous bone formation was observed in the callus by radiological and histological evaluation. Further experimental research is ongoing to prove the clinical usefulness of this device.     

Mandibular distraction osteogenesis using an intraoral device and bite plate for a case of hemifacial microsomia.

OBJECTIVE: To present orthodontic treatment combined with mandibular distraction osteogenesis using an intraoral device and a bite plate in a patient with hemifacial microsomia, severe facial asymmetry, and unilateral mandibular hypoplasia. PATIENT: An 8-year-old girl exhibited mandibular deviation resulting from hypoplasia of the mandibular condyle and ramus on the left side. The patient was treated with an intraoral device for mandibular distraction osteogenesis, bite plate, and hybrid-type functional appliance. Facial asymmetry was improved, and the mandibular ramus was elongated in an anterior and primarily posterior direction with slightly posterior and superior displacement of the proximal segment. Postdistraction treatment results have been stable for 1 year. At the 1-year follow-up, the volume of the lateral and medial pterygoid muscles on the left side had increased. The condyle and disc on the right temporomandibular joint moved well and in harmony at open mouth position, and a rotational movement of the left temporomandibular joint was observed.     

Transoral vertical ramus osteotomy fixed with Kirschner pins

Transoral vertical ramus osteotomy (VRO) has been condemned because the condyle has the potential to sag, and because it needs lengthy maxillomandibular fixation. We have therefore introduced a simple method of fixation, and examined its effectiveness and complications. After the osteotomy, the proximal and distal segments are trimmed to adapt to each other. Four Kirschner (K) pins 0.9 mm in diameter are inserted percutaneously from the proximal to the distal segment while the condyle is positioned in the glenoid fossa. This is followed by a brief period of maxillomandibular fixation. We have reviewed the records of 95 patients who had unilateral or bilateral vertical ramus osteotomy fixed with K pins, after which the mean (SD) period of fixation was 19 (11) days. Fixation failed in two patients because excursion of the jaw was either too heavy or too early. The fixations were redone. All other fixations remained stable, including the 20 dual-jaw procedures in which VRO preceded maxillary osteotomy. The mean (SD) maximal mouth opening at final follow-up was 44 (7) mm, and in only one patient was it less than 30 mm. Numbness of the lip or chin developed in seven patients, five of whom had other anterior mandibular procedures. Four patients had discomfort on palpation of the site of the pins, and one required removal. The new method was effective, and resulted in few complications within its limitations.     

牵张方向对下颌骨牵张成骨应力分布与位移影响的生物力学分析

目的 建立优化的下颌骨牵张成骨的三维有限元模型以研究下颌骨体部模拟牵张成骨时牵张方向对下颌骨体部牵张成骨的影响.方法 测量不同加载条件下,下颌骨的VonMises应力、位移.结果 可以看出当牵张器平行于下颌骨体放置时,模型中的最大应力是牵张器平行于矢状轴模型中最大应力的2倍.Von Mises应力集中主要发生在加载部位(牵张器与骨的结合点)和髁状突的颈部前下方区域,可能导致局部骨质吸收,从而造成螺钉松动,影响牵张器的稳固性.当模型的加载位移增加时,最大应力与加载位移值成线性关系.平行于下颌骨体组模型存在明显的侧方力,牵引装置牢固固定在下颌骨体部表面,牵引装置所产生的反作用力使它的后臂产生向外侧位移,这种装置-骨界面效应,可导致近中骨段颊侧移位,从而使牵张后的下颌骨形态发生变化,导致咬合关系错乱,面形改变,颞颌关节滑动轨迹的变化可能导致关节功能的紊乱.牵引装置平行于矢状轴放置时,这种反作用力可降至最低程度.结论 牵张器平行于矢状轴优于平行于下颌骨体,此项研究为牵张器在临床应用中的放置位置和牵引方向提供了理论依据.     

Maxillomandibular growth 2 years after mandibular advancement surgery with and without suprahyoid myotomy in juvenile Macaca mulatta

There is conflict in the literature on whether continued and harmonious growth occurs after mandibular advancement in growing persons. The studies available are difficult to interpret because of the differing age ranges and the questionable growth potential inherent within the mandibular deficient patient. This study was performed to isolate the major question of interest to clinicians: Does the mandibular advancement surgical procedure inhibit future growth in a normally growing person? Six juvenile male Macaca mulatta monkeys were divided equally into two experimental groups. Group MAA had mandibular advancement surgery of approximately 4 mm. Group MAD had a similar surgical procedure with detachment of the suprahyoid musculature. All underwent 4 to 5 weeks of maxillomandibular fixation. Serial computerized cephalograms with the aid of bone markers were used to analyze the changes during a 2-year follow-up period. The postsurgical changes of the two experimental groups were compared statistically with control growth data on a large sample of normal Macaca mulatta animals available in our laboratory. The results showed the following. (1) There were significant short-term differences in the stability of the mandibular advancement between experimental groups. Group MAA (suprahyoid musculature attached) experienced significant relapse during the period of maxillomandibular fixation. Group MAD (suprahyoid musculature detached) experienced no relapse. (2) During the 2-year follow-up period after fixation, the rate and amount of mandibular growth in both experimental groups were not significantly different from age-matched controls or from each other. (3) At the end of the 2-year experimental period, the advanced mandibles were longer than the mandibles in age-matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

A new way to anchor the external device in mandibular distraction: three case reports with a Pierre Robin sequence

Pierre Robin sequence is a pathology derived from alteration in the first and second branchial arch. Patients have breathing problems due to micrognathia and glossoptosis, causing severe upper airway obstruction. One surgical treatment is distraction osteogenesis. Three patients with Pierre Robin sequence (case 1, 3 months old; cases 2 and 3, 1 month old) with severe upper airway obstruction requiring mechanical ventilator assistance, underwent mandibular distraction osteogenesis prematurely with a new anchoring system, thus avoiding tracheostomy and its consequences. An intraoral approach was used to avoid scarring. A new anchoring device with transfixing Kirschner wire in the proximal (mandibular ramus) and distal segment (chin zone) was used. This diminishes the risk of distractor device displacement, guaranteeing optimal stability. A more anterior installation reduces the risk of damaging tooth buds in the mandibular body and the inferior alveolar nerve. The more anterior the fixation, the more horizontal the distraction vector becomes. The position and stability of the device are crucial. In these three patients the placement of two transfixing Kirschner wires using an intraoral approach showed good results and stability during the period of distraction and consolidation, with optimal results on the upper airway, avoiding tracheostomy.     

Condylar position following mandibular advancement: Its relationship to relapse

Forty-one patients who elected to receive a bilateral sagittal osteotomy to advance the mandible were examined clinically and radiographically to assess condylar position preoperatively and at three specific times post-operatively. Parameters designed to measure changes in condylar and distal fragment position were located on tracings and digitized for statistical analysis. Changes in distal fragment position included advancement and clockwise rotation during the surgical interval and significant posterior relapse with continued clockwide rotation during the period of maxillomandibular fixation. A small amount of counterclockwise rotation associated with interocclusal splint removal was seen following fixation release. No significant condylar movement was seen during the surgical interval. During the period of maxillomandibular fixation, both condyles exhibited a significant superior movement, and the left condyle also moved posteriorly. No changes in condylar position were noted following release of fixation. The clinical significance of these condylar movements is not clear. Despite minimal changes, 18 patients, six of whom had had no preoperative symptoms and one of whom had exhibited reciprocal clicking, complained of temporomandibular joint pain or noise postoperatively. This suggests that maintenance of condylar position during surgery may not prevent temporomandibular joint dysfunction. In addition, the observed 37% relapse in surgical advancement in the absence of significant condylar distraction implies the interaction of other factors in the relapse process.     

涉及下颌骨体部和升支部缺损的定向二次牵引成骨治疗

目的探讨分期牵引成骨技术在下颌骨体部和升支部同期缺损修复中的应用方法及临床意义。方法对2001～2006年就诊的因各种原因导致下颌骨体部和升支部同期缺损患者12例,应用计算机辅助设计制作三维头颅模型,在模型上进行牵引成骨设计,预制个性化内置式颌骨牵引器,先期完成下颌体部及角部牵引,Ⅱ期完成下颌升支牵引。结果①下颌体及角部牵引长度4.5 cm～6.0 cm,平均5.2 cm;下颌升支牵引长度4.0 cm～6.0 cm,平均5.4 cm。②创口I期愈合,下颌外形良好,无感染等情况发生,下颌体及升支部成骨良好,健侧咬颌关系无偏斜。③平均追踪37.8个月,面下1/3外形恢复良好,张口度正常,咬合关系正常,牵引器放置软组织区无红肿等炎症表现。结论三维头颅模型为下颌骨体部和升支部同期缺损分期牵引成骨修复提供了精细的设计和操作平台,分期牵引成骨修复下颌骨体部和升支部同期缺损疗效确切。     

Backward distraction osteogenesis of condylar segment in patient with mandibular ramus deficiency--report of a case

A backward distraction osteogenesis (BDO) of the condylar segment for treatment of mandibular ramus deficiency was developed. This report describes the clinical progress of a patient with mandibular ramus deficiency in whom satisfactory occlusion was achieved and maintained by gradual posterosuperior repositioning of the displaced condyles into the glenoid fossae during intermaxillary fixation. Findings of pre- and postoperative clinical and magnetic resonance imaging indicate that the effect of BDO on the temporomandibular joint was negligible.     

Longitudinal dento-skeletal changes in UCLP patients following maxillary distraction osteogenesis using RED system

Longitudinal dento-skeletal changes in unilateral cleft lip and palate (UCLP) patients following maxillary distraction osteogenesis using the rigid external distraction device (RED) were analyzed. Twelve Japanese non-syndromic UCLP patients who underwent maxillary distraction at the mean age of 16.4 years were used as subjects. Serial sets of lateral cephalograms, taken at 4 stages: 1) before osteotomy, 2) immediately after distraction, 3) 6 months and 4) 12 months post-osteotomy, were analyzed. Statistical analyses, including a paired t test, Pearson correlation analysis and stepwise linear regression analysis, were performed to distill characteristic dento-skeletal changes. In accordance with maxillary advancement, significant amounts of up-forward movement of the nasal bone, mandibular rotation and maxillary dental changes were observed. Maxillary dental changes were significantly related to the amount of mandibular rotation and force system of maxillary traction. Significant dento-skeletal relapse was found to occur during the 0-to-6-month follow-up period, but not in the 6-to-12-month follow-up period. Maxillary relapse was significantly related to the amount of maxillary advancement and severity of pre-surgical maxillary hypoplasia, while mandibular relapse was significantly related to maxillary dento-skeletal relapse. Successful clinical application of this procedure therefore requires consideration of both the surrounding dento-skeletal changes and the traction force system.     

内置自加载牵张器重建兔下颌支的实验研究

目的 :探索牵张成骨重建下颌支缺损的新方法。方法 :以成年新西兰兔为实验动物 ,手术切除下颌骨一侧部分升支及髁状突 ,造成 1.5cm的节段性骨缺损 ,骨断端”L”形截骨形成传送盘 ,安置可完全埋置于组织内的镍钛记忆合金牵张器 ,术后 2个月时处死实验动物 ,取下颌骨观察骨缺损修复情况。结果 :镍钛记忆合金牵张器能自动完成牵张成骨 ,初步重建了缺损的下颌支 ,组织学检查可见牵张区有良好的新骨再生。结论 :内置镍钛记忆合金牵张器可自动持续弹性加载牵张成骨 ,可望成为一种具有良好应用前景的简便实用技术。     

A comparison of synovial fluid pressure after immediate versus gradual mandibular advancement in the miniature pig.

PURPOSE: Mandibular advancement is a commonly performed surgical procedure for the treatment of mandibular hypoplasia. With the increased use of rigid fixation, there has been a decrease in the amount of relapse but an increase in the amount of force transmitted to the condyles. Gradual advancement of the mandible by distraction osteogenesis slowly overcomes the soft-tissue envelope and may decrease the amount of force exerted on the condyles. The purpose of this study was to develop an animal model to measure the magnitude of pressure associated with immediate versus gradual mandibular advancement. MATERIALS AND METHODS: A 2.0-mm pressure transducer was placed in the superior joint space in 2 miniature pigs. In the first animal, immediate advancement of the mandible with rigid fixation was performed. The synovial fluid hydrostatic pressures were measured prior to surgery and postoperatively. A second animal underwent gradual advancement with distraction osteogenesis. The synovial fluid hydrostatic pressures were measured prior to and after each activation of the distraction device. The condyles were examined radiographically and microscopically. RESULTS: The superior joint space fluid pressures increased and remained elevated over a 5-week period after immediate advancement. In the gradually advanced mandible, the pressures were elevated but returned to near baseline prior to the activation the following day. CONCLUSION: This animal model is useful to directly measure the pressure that is exerted on the condyle. This will allow further studies to compare methods for mandibular advancement. It is likely that gradual advancement of the mandible by distraction osteogenesis produces less force and causes less condylar resorption than large mandibular advancement stabilized with rigid fixation.     

Long-term skeletal effects of mandibular symphyseal distraction osteogenesis. An implant study

The purpose of this study was to investigate the long-term skeletal effects of mandibular symphyseal distraction osteogenesis (MSDO) with a tooth- and bone-borne distraction device, analysed using the metallic implant method. The study sample comprised 20 patients between 15.8 and 25 years of age, with a mean age of 20.01 +/- 2.25 years at the start of treatment. In 12 subjects, titanium implants were inserted in the mandible to analyse mandibular skeletal changes in the short and long term. A custom-made intraoral, tooth- and bone-borne distractor was designed and used. After a latency period of 7 days, the distractor was activated twice daily, by a total amount of 1 mm. Postero-anterior (PA) cephalograms were obtained at the start of distraction and at the end of consolidation (94.95 +/- 5.79 days after surgery) and follow-up periods (21.5 +/- 4.6 months after consolidation). The data were analysed statistically using paired t-tests. The mean amount of screw activation was 8.10 +/- 1.68 mm. The inter-symphyseal and inter-molar implant distances and the bimolar width significantly increased during the consolidation period (P < 0.001) and were maintained at the end of the follow-up. On the other hand, the bicondylar width was markedly decreased (P < 0.05), while no significant skeletal changes were observed in bigonion and biantigonion widths, inter-ramal implant distance, or inter-ramal and implant angles at the end of the consolidation period. The long-term findings of this study indicate that MSDO provides an efficient and stable non-extraction treatment alternative, mainly by increasing the anterior mandibular skeletal and dental arches.     

Horizontal rotation of the condyle after sagittal split osteotomy of the mandible

Displacement of the proximal segment of the condyle such that the condyle is no longer in its correct position has been cited as a major factor in postsurgical skeletal relapse after mandibular, sagittal split osteotomy. This study examined the effects of sagittal split osteotomy on the horizontal rotation of the condyle in 16 dissected mandibles for which clamp, screw, and wire fixations were used to advance the mandible or set it back. The results showed that, after sagittal split osteotomy, horizontal rotation usually occurred, regardless of the position of the distal segment or the type of fixation used. Our finding that 82% of the condylar angles increased after surgery indicates that the lateral pole of the condyle had rotated anteriorly, while the medial pole had rotated posteriorly. There were no consistent differences in horizontal rotation between the condyles on the side where the proximal segment had been fixed first and those on the side where it had been fixed second; nor did the sizes of the original intercondylar angles affect the magnitudes of change in the postoperative intercondylar angles. The only statistically significant difference (p = 0.005) between the angles after fixation by the three different methods was between screw and wire osteosyntheses when the distal segments were in the forward position. The reason for this difference is unclear.     

牵张成骨修复兔下颌骨缺损中血管生成素-1的表达及意义

目的探讨血管生成素(Ang)-1在牵张成骨修复兔下颌骨缺损中的时空表达及生物学意义。方法对24只大白兔行单侧下颌骨缺损牵张成骨术,分别在延迟期末、牵张中期、牵张期末、固定期第12、、35、、7周末各处死3只动物,取牵张区骨痂,采用组织学和免疫组化法观察微血管生成以及Ang-1的表达变化。结果下颌骨牵张区主要以膜内成骨方式成骨,在牵张区内有明显的血管生成及较明显的Ang-1的表达。在新生血管管周前成骨细胞和成骨细胞中可见Ang-1的表达。非应力区(缺损区)以软骨内成骨为主,在肥大的软骨细胞中存在Ang-1弱表达。结论牵张力所产生的机械刺激可以导致牵张区中微血管和骨组织的生成,而Ang-1可能在牵张区新生血管的形成及稳定和新骨形成中起重要作用。     

Proximal segment position after distraction with the MD-DOS device

We investigated cephalometrically the movement of the proximal segment in the sagittal plane in patients treated with distraction (MD-DOS device) for mandibular lengthening. The proximal segment was anteriorly rotated, whilst the distal segment was posteriorly rotated after the lengthening procedure. Thus the angle of the jaw was advanced half the distance of the advancement of the distal segment. One possible reason for the anterior rotation of 3.3 degrees on average is the repositioning of the proximal segment during application of the anterior fixation unit in the cases where mobilization was complete. Another more plausible reason is the anterior pull by the masticatory muscles and elastic bands being greater than the reactive distraction vector component in concert with a flexible telescopic distraction module and a single posterior screw anchorage. The positional movements of both distal and proximal segments were similar to those observed after mandibular advancement with bilateral sagittal split osteotomies.     

Distraction osteogenesis for reconstruction after mandibular segmental resection.

Distraction osteogenesis with the shortening and lengthening method is a well-established procedure for repairing extremities. We used this technique for reconstruction after mandibular segmental resection. A 74-year-old woman underwent distraction osteogenesis with an intraoral device, initially shortening the mandible after a 20-mm-long segmental resection, followed by lengthening at a rate of 0.8 mm per day for 21 days. Eight weeks after the distraction, the device was removed and a dental implant was placed at the site of distraction. Radiographic observation showed new bone formation, and the implant was completely osseointegrated. Although the follow-up period is relatively short, the clinical course was uneventful. Distraction osteogenesis with the shortening and lengthening method seems to be a feasible option for reconstruction after segmental resection of the mandible.     

Temporomandibular joint bony ankylosis: comparison of treatment with transport distraction osteogenesis or the matthews device arthroplasty

Temporomandibular joint (TMJ) bony ankylosis with micrognathia is a rare congenital condition that is difficult to treat and may result in recurrence. In a series of affected patients, we compared two new methods of treatment: transport distraction osteogenesis and Matthews Device arthroplasty. All patients had computed tomography scan documented bilateral TMJ bony ankylosis. Group I (transport distraction osteogenesis) underwent distraction advancement of the mandible (for micrognathia) followed by resection of the condyles, recontouring of the glenoid fossas with interposition temporoparietal-fascial flaps, and transport distraction osteogenesis of mandibular rami segments. Group II (Matthews Device arthroplasty) underwent all of the above procedures except for transport distraction osteogenesis. Instead, the Matthews Devices were anchored to the temporal bone and mandibular rami. Hinged arms allowed for motion at the reconstructed TMJ. In both groups, patients underwent extensive postoperative therapy. Preoperative, postoperative, and follow-up lateral cephalograms were obtained, and incisor opening distances were recorded. All patients but one had severe micrognathia (n = 9). For group I (transport distraction osteogenesis), mean age was 6.8 years. and mean advancement was 28.5 mm. For group II (Matthews Device arthroplasty) mean age was 8.2 years, and mean advancement was 23.5 mm. In group I (transport distraction osteogenesis), mean incisor opening was 1 mm preoperatively and 27.5 mm postoperatively; however, it relapsed to 14.3 mm by 12.5 months follow-up (48% relapse). Mean incisor opening in group II (Matthews Device arthroplasty) was 3.9 mm preoperatively and 33.4 mm postoperatively and remained at 30.6 mm after 11.1 months follow-up (8% relapse). One patient in group I (transport distraction osteogenesis) underwent surgical revision because of relapse. Our data showed that for congenital TMJ bony ankylosis both transport distraction osteogenesis and Matthews Device arthroplasty techniques were successful initially; however, the Matthews Device arthroplasty avoided long-term relapse.     

应用螺旋扩弓器牵引兔下颌中缝后新骨的OPG及RANKL的表达

目的:利用螺旋扩弓器进行下颌正中联合横向牵张成骨,扩展下颌间隙,并探讨在机械张力作用下新骨组织中骨保护素(Osteoprotegerin,OPG)、破骨细胞分化因子(Receptor or Activator of NF-KB Ligand,RANKL)表达规律.方法:建立兔下颌骨正中联合牵张成骨模型,用免疫组化方法检测牵张后1d、牵张后4d、固定后1w,固定后4w、固定后12w的牵张区新生骨组织中骨保护素(OPG)、破骨细胞分化因子(RANKL)不同时期的分布和表达.结果:下颌正中联合牵张成骨除一只外,其余实验动物均成功,牵张平均量为4mm,牵张成骨1d和牵张成骨4dOPG的阳性细胞数百分比逐渐增加,固定1w到12w组织中阳性细胞数百分比逐渐减少,RANKL阳性细胞数的百分比仅在牙缝关闭后与对照组有差异,其余各时间点均无明显差异.结论:下颌正中联合横向牵张成骨是扩展下颌间隙的一种行之有效的方法.机械牵张力能够促进OPG表达,OPG可能在牵张成骨的早期起一定的抑制破骨并促进调节新骨形成作用,RANKL则与骨改建有关,发挥一定的作用.