Osteoblastic activity and neoangiogenesis in distracted bone of irradiated rabbit mandible with or without hyperbaric oxygen treatment

The effects of irradiation and hyperbaric oxygenation (HBO) on osteoblastic activity and angiogenesis in rabbit mandibular distraction (DO) were evaluated. Three groups were studied. The mandible of two groups received a 22.4Gy dose of irradiation. One of the irradiated groups was also given HBO, 18 times at 2.5ATA for 90min per day preoperatively. The third group was given neither radiotherapy nor HBO. Mandibular lengthening was performed unilaterally. Osteoblastic activity was assessed ex vivo by [18F]fluoride digital autoradiography. Neovascularization of distracted bone was evaluated histomorphometrically. Osteoblastic activity was higher in non-irradiated than irradiated animals. In non-irradiated rabbits, the activity was evenly distributed over the distraction area. In the irradiated groups, the activity was greater in the central third of the lengthened bone than the peripheral thirds. HBO changed the osteogenic pattern towards that of non-irradiated bone. In the non-irradiated group the number of blood vessels was 1.7-fold as compared to irradiated rabbits without HBO (P=0.0012), and the fewest number of vessels was found in irradiated rabbits without HBO. Blood vessels were more numerous in the central region than in peripheral regions in non-irradiated animals and irradiated animals with HBO, but not in irradiated rabbits without HBO therapy. It is concluded that radiotherapy disturbs distraction bone formation and neovascularization related to DO. HBO increases osteoblastic activity, but not to the level of non-irradiated bone. Angiogenic response is markedly increased by HBO.     

Effect of mandibular distraction osteogenesis on temporomandibular joint after previous irradiation and hyperbaric oxygenation

The purpose was to evaluate the effect of mandibular distraction osteogenesis (DO) on condylar cartilage after radiotherapy and hyperbaric oxygenation (HBO). Unilateral DO was performed on low- and high-dose irradiated rabbits with or without accompanying HBO, and non-irradiated animals. High-dose irradiated animals were given irradiation in the temporomandibular joint (TMJ) equivalent to 50 Gy in 25 fractions. Low-dose irradiated rabbits received scattered irradiation of 10% of that of high-dose irradiated animals. After radiotherapy, some of the animals were given HBO 18 times at 2.5 ATA for 90 min/day. One month after completion of radiotherapy, distraction osteotomy with distractor placement was performed. After a latency period, distraction was started at the rate of 1 mm/day, continued for 2 weeks, and the regenerate was allowed to consolidate for 1 month. Condyles of non-operated rabbits served as controls. Histological changes were more evident on the distracted than on the non-distracted side. In distracted, non-irradiated animals, condylar cartilage changes were minor and probably clinically insignificant. In irradiated rabbits, condylar cartilage changes on the lengthened side were severe, and often cartilage was either totally or partially sealed off by bone. Condylar heads were morphologically deformed. Even low doses of irradiation resulted in notable changes on the operated side, and HBO did not prevent disadvantageous effects.     

The effects of irradiation and hyperbaric oxygen on bone formation during rabbit mandibular distraction

[18F-]fluoride positron-emission tomography (PET) was used to assess bone formation during mandibular distraction osteogenesis. There were three study groups: irradiation, irradiation+hyperbaric oxygen and control. The two experimental groups received a tumoricidal dose of irradiation to the mandible, and one group was also given hyperbaric oxygen (2.5 ATA (atmospheres absolute) for 90 min) 18 times preoperatively. Control animals received neither irradiation nor oxygen. A unilateral osteotomy was made and, after a period of latency, bone distraction was started, continued for 2 weeks, and the distraction generated was then allowed to consolidate for 4 weeks. The first PET study was performed at the end of distraction and the second at the end of consolidation. At the end of distraction, the metabolic activity of bone in the distracted area was significantly higher in the controls than in either experimental group; differences between the experimental groups were not statistically significant. By the end of consolidation, activity in the control group had diminished to the same as in the two experimental groups, in which no significant change had occurred. Radioactivity was still significantly higher at second imaging on the distracted than non-distracted side in the control and irradiation+hyperbaric oxygen groups, but not in the group that was only irradiated. The results indicate that previous irradiation disturbs bone formation during mandibular distraction osteogenesis. Hyperbaric oxygen was not able to prevent the suppression of osteogenesis caused by radiotherapy but it might improve bone formation by prolonging high osteogenic activity.     

The effect of irradiation and hyperbaric oxygenation (HBO) on extracellular matrix of the condylar cartilage after mandibular distraction osteogenesis in the rabbit

The effects of irradiation and hyperbaric oxygenation (HBO) on the extracellular matrix of condylar cartilage after mandibular distraction were evaluated. Unilateral distraction was performed on 19 rabbits. Five study groups were included: control, low- and high-dose irradiation, and low- and high-dose irradiation groups with HBO. Additionally, four temporomandibular joints (TMJ) were used as control material. The high-dose irradiated animals were given in the TMJ 22.4 Gy/4 fractions irradiation (equivalent to 50 Gy/25 fractions). Low-dose irradiation group received a 2.2 Gy dosage. Two groups were also given preoperatively HBO 18 x 2.5ATA x 90 min. After a two-week distraction period (14 mm lengthening) and four-week consolidation period the TMJs were removed. Proteoglycan (PG) distribution of the extracellular matrix was evaluated using safranin O staining and collagen I and II using immunohistochemistry. The organization of fibrillar network was studied by polarized light microscopy. On the operated side of the control group and on the unoperated side in all, except for high-dose irradiated group, PG distribution and fibrillar network were normal appearing. In the irradiated groups, with or without HBO, the cartilaginous layer was partially or totally devoid of PG and the network structure was severely damaged. In conclusion, irradiation in conjunction with the pressure applied by distraction causes severe damage to extracellular matrix of condylar cartilage.     

犬下颌骨单侧不全截骨牵张时牵张侧位移状况有限元分析

目的 运用犬下颌单侧不全截骨牵张成骨有限元模型,计算下颌骨在牵张过程中牵张侧各部分位移状况。方法 有限元模型模拟犬下颌单侧不全截骨牵张,观察当滑动骨块未被牵开和被牵开时牵张侧关节、下颌角、喙突及牙齿等6个标志点的位移状况。结果 下颌滑动骨块未被牵开时牵张侧第五臼齿、髁状突前斜面前缘中点所受最大主应力为压应力,髁状突后斜面后缘中点为拉应力,各标志点在空间X、Y、Z三轴位移不明显;当下颌骨滑动骨块被牵开1 mm时,上述各点位移明显增加。结论 从牵张侧观察,牵张侧下颌骨在矢状平面上和冠状平面上都有以髁突顶点(横嵴中点)为中心的逆时针旋转趋势。     

Osteodistraction of a previously irradiated mandible with or without adjunctive hyperbaric oxygenation: an experimental study in rabbits

The purpose of this study was to analyse the effects of irradiation and hyperbaric oxygenation (HBO) on mandibular osteodistraction (OD). Eighteen rabbits were divided into three groups: 1. Irradiation (R), 2. Irradiation+HBO (R-HO), and 3. Control group (C). Animals of groups R and R-HO received in the mandible irradiation 22.4 Gy in four 5.6 Gy fractions (equivalent to 50 Gy/25 fractions). In addition, group R-HO was given HBO at 2.5 ATA for 90 min per day 18 times preoperatively. Unilateral osteotomy was made 1 month after completion of radiotherapy. After a 1 week latency period bone distraction was started at rate of 1 mm per day, continued for 2 weeks, and left to consolidate for 4 weeks. Amount of new bone was measured histomorphometrically from midsagittal sections. Area of new bone was equal in all groups. Bone was more mature and bone spicules better organized in group C than in groups R and R-HO. Cartilaginous cells were found in distracted bone in all groups but larger chondroid islands were evident only in group R. It seems that despite delayed bone formation, OD can be performed after radiotherapy. HBO had a beneficial effect on bone quality of a previously irradiated mandible.     

不同牵张速率对山羊下颌骨牵张成骨中新骨形成的影响

目的:探讨山羊下颌骨牵张成骨中不同牵张速率对术后新骨形成的影响。方法:12只山羊随机分为3组,每组各4只,在对动物右下颌骨行骨皮质切开术后进行牵张,第1组动物以0.8mm/d的牵张速率进行牵张,第2组动物以1.6mm/d的牵张速率进行牵张,第3组动物以2.0mm/d的牵张速率进行牵张,随机选取实验组4只动物未手术侧正常下颌骨作为对照组。将各组新骨组织和对照组下颌骨组织分别进行骨密度检测和三点弯曲测试,对采用不同速率进行骨牵张后动物下颌骨新骨的生物力学强度和骨密度进行了对比观察。结果:0.8mm/d牵张组新骨骨密度值显著高于其余各牵张组,0.8mm/d牵张组新生骨三点弯曲实验指标均大于另2牵张组。结论:采用0.8mm/d的牵张速率进行牵张能最快促进新骨形成,提高成骨质量。     

Effect of recombinant human bone morphogenetic protein-2 on mandibular distraction osteogenesis

The purpose of this investigation was to study the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone formation of mandibular distraction osteogenesis. Six skeletally mature sheep underwent 10 mm of bilateral mandibular distraction osteogenesis via a custom-made distractor. Three micrograms of rhBMP-2 with a collagen carrier was implanted in the osteotomy site of one side of the mandible during the osteotomy phase. The contralateral side was used as the control group, and no material was implanted into the distracted area. At 10 days after the end of distraction, all animals were killed, and the distracted calluses were harvested for radiologic and histologic analysis. New bone was generated in the distracted zone in all groups. Histologic and radiologic examination showed that the new bone formation was greater in the rhBMP-2 group than in the control group. Quantitative computed tomography evaluation, however, did not demonstrate a significantly different mean bone density of the regenerates between the 2 groups. The results indicate that application of a rhBMP-2/collagen implant during the osteotomy phase of distraction osteogenesis increased bone formation but did not have a significant effect on bone density of the regenerates.     

羊颧骨缝三维牵张成骨的组织学观察

目的探索不截骨的骨缝牵张成骨组织学变化。方法采用10～13个月龄普通山羊为实验对象，每只动物左颧骨行三维牵张成骨，固定1、3、5、8周后取材，和对侧空白对照标本比较，观察缝区组织变化、新骨形成情况。结果骨缝被牵开后1周，成纤维细胞、成骨细胞、毛细血管增生，大量纤维软组织排列有序并连接骨缝两侧，骨缝两侧组织面不整齐，牵张侧成骨活跃，大量类骨质形成；3周时形成较成熟的骨小梁；5周时编织骨形成；8周时结构成熟完整。结论不截骨的骨缝三维牵张成骨，骨缝牵张侧新骨快速形成；     

HIF—1α在犬下颌骨持续牵张成骨中的表达及与局部血管形成的关系

目的初步探讨缺氧诱导因子-1α（HIF-1α）在犬下颌骨镍钛记忆合金持续牵张成骨中的表达．及HIF--1α在持续牵张成骨中的作用及与局部血管生成的关系。方法成年Beagle犬12只．实验组10只．双侧下颌骨制造1．5cm×1．0cm矩形缺损并在其近中形成相同大小的骨传松盘（采用保留骨松质的骨皮质切开术）．行镍钛记忆合金牵张器持续牵张术，于术后第1、4、7、10、15天取材．每组2只：对照组2只，下颌骨相同部位行相同大小的骨皮质切开术后未行骨牵张术，术后10d取材。RT-PCR法检测HIF-1α mRNA的表达．免疫组化SP法检测HIF—1α、VEGF的蛋白表达，CD34标记内皮细胞检测新生微血管密度（MVD），采用SPSS11．5统计软件分析。结果RT—PCR及免疫组化显示实验组HIF—1α mRNA和HIF-1α蛋白在术后第4、7、10、15天呈阳性表达，两者主要在牵张区的成骨细胞内表达．皆在第7d达最大值。免疫组化显示VEGF在术后第4、7、10、15天呈阳性表达．VEGF在牵张区内皮细胞和成骨细胞内表达，从术后第4天至第10天不断增加，术后第10天达最大值．新生微血管密度在牵张期逐渐升高、术后第7天达峰值（P〈0．05）。对照组HIF—1α mRNA及蛋白和VEGF皆未见明显表达。结论HIF—1α在犬下颌骨持续牵张成骨中高效表达，牵张末期是其发挥作用的关键时期．可能通过上调VEGF的表达，促进牵张成骨局部的血管生成过程。     

Effect of calcium sulfate pellets on early bone mineralization in distraction osteogenesis for craniofacial microsomia in adults

The purpose of this project was to study the effect of calcium sulfate pellets on early bony consolidation in distraction osteogenesis. A total of 13 patients (control group: five patients; calcium sulfate group: eight patients) were operated on between April 2001 and December 2004. The age of the patients ranged from 18 to 25 years. In the calcium sulfate group, after completing a mandibular osteotomy, a total of 4 mm was distracted initially. Nine to 10 calcium sulfate (Osteoset) pellets were implanted into the 4-mm distracted gap of mandible. In the control group, a mandibular osteotomy alone was created without the initial 4-mm distraction gap and the implantation of calcium sulfate. Five days after the operation, the distraction of the mandible was performed at a rate of 1 mm per day. The distracted length of the mandible was between 7 and 23 mm. The follow-up period ranged between 10 and 22 months. In the calcium sulfate group, the percentage of bone mineral density in the distracted area, compared with the normal mandible, was much higher than in the control group with a statistical significance of P < 0.05. The external distraction devices of the calcium sulfate group were removed 5 to 7 weeks after distraction. The devices of the control group were removed by 11 or 12 weeks. In conclusion, results of the present study suggested that calcium sulfate is a very active, economic, and biocompatible osteoconductive material, which has a good effect on early consolidation in distraction osteogenesis.     

Evaluation of the effects of guided bone regeneration and periosteum on newly formed bone in a distraction gap

We determined the causes of bone resorption within a distraction gap and determined whether it could be prevented via guided bone regeneration during distraction. Another goal was to determine the effect of periosteum in bone healing in a distraction gap.Twelve sheep mandibles were bilaterally distracted. One side of the 6 sheep mandibles formed the control group; the other side was the study group, from which the periosteum was excised and distraction was performed. In the other 6 sheep, on the study side, guided bone regeneration was applied with distraction; on the other study side, guided bone regeneration was applied, and the periosteum was excised at the distraction. At the end of a 1-week latent period, all subjects were distracted 10 mm (1 mm/d), and we waited 3 months for consolidation. At the end of this period, all animals were killed, and radiologic evaluations of the newly formed bone within the distraction gap were conducted.The surface area of the regenerating bone in the membrane groups was significantly higher than in the groups without a membrane. However, no additional effect of the periosteum on the bone surface area was observed. No significant difference between the groups in densitometric values was observed.Concomitant use of guided bone regeneration with distraction osteogenesis may be the optimal way to generate a flat bone surface within a distraction gap.     

rhBMP-2对兔下颌骨牵引成骨区骨保护素表达的影响

目的：通过动物实验,研究应用外源性rhBMP-2对兔下颌骨牵引成骨区骨保护素（osteoprotegerin,OPG）的影响。方法：在48只成年大耳白兔的一侧下颌骨前部行骨切开术,分别将空白胶原、rhBMP-2 1.5mg胶原复合物植入下颌骨切开处,用牵引器延长一侧下颌骨4mm,稳定期第1、3、7、14天,分别处死各组动物,取牵引区新生骨痂行组织学及OPG免疫组化染色。结果：下颌牵引延长后牵引间隙均有新骨形成,应用rhBMP-2 1.5mg效果好。免疫组化染色OPG主要定位于成骨细胞的胞浆中。在同一时间内,应用rhBMP-2组较对照组有显著性差异（P〈0.05）。结论：动物实验表明,rhBMP-2能促进兔下颌骨牵引成骨区新骨的生成。     

Effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone consolidation on distraction osteogenesis: a preliminary study in rabbit mandibles.

AIM: To examine the effectiveness of administering recombinant human bone morphogenetic protein-2 (rhBMP-2) in distraction osteogenesis. MATERIAL AND METHODS: Twenty-one mature male Japanese white rabbits underwent unilateral mandibular osteotomy. After 5 days, the osteotomized mandibles were distracted 1mm/day for 10 days. On the first day (groups A-1 [n=4] and A-2 [n=4]) or on the last day (group B [n=5]) of distraction, rhBMP-2 mixed with collagen gel was injected into the distraction zone. In control groups (groups C-1 [n=4] and C-2 [n=4]), the mandibles were distracted without rhBMP-2 injection. At the end of the distraction period (groups A-1 and C-1) and after 2 weeks of consolidation (groups A-2, B, and C-2), the distracted mandibles were harvested and examined with soft radiographs, peripheral quantitative computed tomography (pQCT), and microscopy. RESULTS: Radioopacity was more marked in the distraction zone of the groups with rhBMP-2 than in control groups. The mineral density of the cortical bone (BMD) was higher in groups B and A-2 than in group C-2. Histologically, bone formation was more advanced in groups A-2 and B than in group C-2. The cortical BMD was higher in group A-1 than in group C-1. Histologically, bone formation was more advanced in groups A-2 and B than in group C-2. CONCLUSION: These results suggest that rhBMP-2 promotes bone formation in distraction osteogenesis.     

Effect of calcium sulphate on the rate of osteogenesis in distracted bone.

The effect of applying resorbable calcium sulphate material to newly distracted bone to hasten osteogenesis and consolidation was investigated using 24 New Zealand rabbits. The animals were divided into four groups each containing six rabbits. Groups 1 and 2 were test groups and Groups 3 and 4 were controls. A custom-made submerged distractor was used to distract the rabbit mandibles. The distractor was first used on the third postoperative day at a rate of 1 mm/day for a total of 10 mm. After the completion of distraction, a medical grade resorbable calcium sulphate mixture was applied on the distracted bones in the test groups, whereas the distracted bones in the control groups were exposed postdistraction and closed without intervention. Groups 1 and 3 were sacrificed 11 days postdistraction and Groups 2 and 4 were sacrificed 21 days postdistraction. Undecalcified sections of the distracted bone were examined. Half of the distracted mandibles in each group were stained with Goldner's trichome stain to identify the amount and maturity of the new bone in the distraction zone. The other half of each group was stained with von Kossa stain to identify the amount of calcification and calcium deposition in the distracted bone. Osteogenesis was seen as early as 11 days postdistraction in test animals. Rich lamellar bone deposition was noted in Group 2 (21 days postdistraction +CaSO4). Calcification of the newly formed bone was predominant in the distraction zone in the test groups, especially Group 2, compared to the control groups, which showed incomplete bone deposition and calcification. In conclusion, the application of calcium sulphate to newly distracted bone increased the rate of osteogenesis and calcification.     

Quantitative study of new bone formation in distraction osteogenesis of craniofacial bones by bone scintigraphy

Although distraction osteogenesis is widely accepted as a technique to augment the craniofacial skeleton, timing to start distraction after an osteotomy or to remove distractors is basically based on studies on long bones. Because bone scintigraphy is well known to be the gold standard for quantitative measurement of bone formation, we conducted this pilot study to evaluate its feasibility as a tool for assessing new bone formation by distraction osteogenesis. Five patients with midface hypoplasia and four with mandibular hypoplasia were studied. Each patient had five bone scans: before surgery, 3 and 30 days after stopping distraction, and 3 days before and 3 months after distractor removal. Radiotracer uptake values at distraction sites were measured at 1 and 3 hours. Each uptake value was compared with preoperative study as uptake ratio. A typical pattern of radiotracer uptake ratio was observed in all cases with successful distraction. Uptake rose to the maximum during the consolidation period and remained at or above the preoperative level until the study end point. In one patient who had mandibular distraction and nonunion of the right ramus, there was no uptake peak during early consolidation as seen in the successfully distracted body and in the other cases. Bone scintigraphy was found to be a useful investigation in craniofacial distraction. It showed the dynamic of new bone formation by demonstrating the osteoblastic activity, which is important objective information for determining distraction rate and consolidation duration in each case. It may also be a tool that can predict the outcome of distraction osteogenesis.     

核素骨显像在局部应用rh-BMP/bFGF加速山羊下颌骨牵张成骨实验研究中的应用价值

目的:应用核素骨显像观察局部应用rh-BMP/bFGF加速山羊下颌骨牵张成骨的效果.方法:利用外置式牵张器进行山羊下颌骨牵张成骨.将10只实验用山羊随机分为5组,每组2只,在下颌第2和第3前磨牙之间行骨皮质切开,将含有rh-BMP15mg及bFGF 2000 UI的载体胶原膜置入左侧牵张骨折间隙,即刻牵开1 mm以利容纳置入的载体胶原膜.对照侧不加生长因子,牵引速度同实验侧.术后5 d开始牵引,3 mm/d,0.5 mm/次×6次/d,分别于牵张完成当日及第2、4、6、12周时将动物进行放射性核素骨扫描检查.结果:随着时间的延长,在不同周期,实验侧牵张间隙中央出现核素浓聚,强度明显较对照侧强.牵张完成12周:实验侧和对照侧核素浓聚变弱,基本上回复到周围正常骨组织密度水平,两者差异明显减少.结论:局部应用rh-BMP/bFGF后实验侧下颌牵张后新骨生成速度和数量优于对照侧,说明外源性生长因子能够加速下颌骨牵张延长区的骨愈合,核素骨扫描检查在观察牵张成骨的效果中具有较高的应用价值.     

Comparison of different distraction rates in the mandible: an experimental investigation.

This study evaluated bone distracted in rabbit mandibles at different intervals and with different daily rates of distraction histologically with the goal of attaining a universally accepted distraction protocol. Osteogenesis was investigated in mandibles distracted at different rates in 24 New Zealand rabbits using a custom-made submerged distractor. Distraction was started on the third postoperative day for a total of 10 mm. The animals were divided into four groups each containing six rabbits. Group 1 was distracted 0.5 mm twice a day; Group 2 was distracted 1.0 mm once a day; Group 3 was distracted 1.0 mm twice a day and Group 4 was distracted 2.0 mm once a day. All the animals were sacrificed 6 weeks after completion of distraction. Half of the distracted mandibles were decalcified for H&E staining and polarized light microscopy studies. Sections of the undecalcified half of the samples were stained with Goldner's stain. The results indicate that a distraction rate of 1.0 mm per day produced the best osteogenesis among the tested rates. There was no great difference in osteogenesis between 1.0 mm once a day and 0.5 mm twice a day. However, 0.5-mm distraction may result in immature bone healing. Distraction of 1.0 mm twice a day resulted in incomplete osteogenesis, while distraction of 2.0 mm once a day resulted in fibrous union. It is clear from these results that a shorter period of device fixation should be achieved by methods other than rapid distraction.     

The role of hyaluronic acid,chitosan, and calcium sulfate and their combined effect on early bony consolidation in distraction osteogenesis of a canine model

The purpose of this project was to study the effect of hyaluronic acid, calcium sulfate, and chitosan on early bony consolidation in distraction osteogenesis of a canine model. Sixteen dogs were used for this study. The lateral surface of the mandibular body was exposed in the subperiosteal plane, and the vertical osteotomy on the mandibular body was extended downward. An external distraction device was applied to the mandibular body, and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was then divided into a control group, chitosan group, hyaluronic acid group, calcium sulfate combined with hyaluronic acid group, and calcium sulfate combined with chitosan group, depending on the type of implantation material in the distracted area. After completing the distraction, implantation material was injected into the distracted area, although no material was implanted into the distracted area of the control group. After implanting the materials, the distraction device was left in place for 6 weeks to allow for bony consolidation. Four dogs were allocated to each group. Two dogs in each group (total of 8 dogs) were killed 3 weeks after implantation of the material, and the other 8 dogs were killed after 6 weeks. New bone was generated in the distracted zone of all groups. In the calcium sulfate combined with chitosan group and calcium sulfate combined with hyaluronic acid group, the formation of active woven bone was observed throughout the distracted zone. Moreover, the new bone seemed to be nearly normal cortical bone at 6 weeks after implantation. In the chitosan group and hyaluronic acid group, the development of new bone was observed in the distracted zone at 6 weeks. The amount was less than that in the calcium sulfate combined with hyaluronic acid group and calcium sulfate combined with chitosan group. These findings suggest that calcium sulfate and its combined materials seem to be quite effective in early bony consolidation in distraction osteogenesis.     

The effect of radiation in distraction osteogenesis for reconstruction of mandibular segmental defects

Distraction osteogenesis is useful in the reconstruction of mandibular segmental defects. The effects of radiotherapy on distracted bone after resection of squamous cell carcinoma of the oral cavity are still unknown. We report the outcome in six patients who had distraction osteogenesis after postoperative radiotherapy. Distraction was by a unidirectional semi-buried device and panoramic radiographs were taken monthly during the distraction and consolidation periods to monitor the progress of the distraction. Follow-up ranged from 15 to 45 months (mean 33). The dose of radiation ranged from 60 to 70Gy. In one patient the bone was completely exposed and all the screws were loosened. There was no calcification and the gap remained radiolucent in the panoramic radiographs. The other five patients had excellent or good quality of bone. We conclude that radiotherapy may not interfere substantially with distraction osteogenesis although larger series the necessary.