TECHNICAL STRATEGY
Application of a Novel Intraorally Customized Transport Distraction Device in the Reconstruction of Segmental Mandibular Defect Ming Cai, DDS, MD, Xiaofeng Lu, DDS, MD, Danling Yang, DDS, Huijuan Cheng, DDS, and Guofang Shen, DDS, MD Purpose: The purpose of this study was to evaluate the clinical result of segmental mandible reconstruction by using a novel intraorally customized trifocal curvilinear distractor. Methods: A customized curvilinear distractor with self-locking system and bidirection transport assembly was designed on the basis of the mandibular contour of a patient diagnosed with ameloblastoma. Two transport disks, each containing the first molar, were designed for trifocal distraction osteogenesis after partial mandibulectomy intraorally. The latency period is 7 days and distraction rhythm is 1 mm/d. After 6 months of consolidation, the second operation was performed to remove the device. Results: A new bone bridged the mandibular defects through transport distraction successfully. Partial bony nonunion between the transport disks was noted when removing the distractor; rigid internal fixation using a titanium plate and bone graft was carried out to ensure the continuity. Bilateral sagittal split ramus osteotomy was performed to advance the mandible when anterior-posterior jaw bone discrepancy occurred before final denture restoration. Conclusions: Customized trifocal curvilinear transport distraction osteogenesis can successfully reconstruct segmental mandible defect intraorally, but special consideration should be paid on the dock site bone healing and overcorrection of curvilinear reconstruction in the future. Key Words: Transport distraction osteogenesis, customized distraction, mandibular reconstruction, curvilinear distraction (J Craniofac Surg 2014;25: 1015–1018)
L
arge mandibular defects resulting from ablative oncologic surgery have significant aesthetic and functional sequelae. Although microvascular free tissue transfer remains the treatment of choice to obtain a predictable primary reconstruction for the extensive composite mandibular defects commonly encountered in ablative surgery, alternative less-invasive methods of reconstruction should be considered.
From the Department of Oral and Craniomaxillofacial Surgery, Shanghai Ninth People’s Hospital, Shanghai, China. Received December 12, 2013. Accepted for publication January 6, 2014. Address correspondence and reprint requests to Xiaofeng Lu, DDS, MD, Shanghai Ninth People’s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; E-mail: [email protected] Supported by the National Nature and Science Foundation of China grant 81100793. The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000725
Distraction osteogenesis is an established technique for the lengthening of bone and the surrounding soft tissue. The ability of new bone regeneration through transport distraction osteogenesis makes it an attractive concept in selected patients with mandibular defects.1,2 Animal experiments and early clinical experience have confirmed that transport distraction osteogenesis can be used for the reconstruction of segmental bony defects.3,4 However, most related publications reported an extraoral approach that resulted in obvious facial scars.5,6 Only few reports used a customized design and custom-made distraction device to reconstruct the original geometric outline of the mandible.7 In this study, we report the restoration of large mandibular continuity defects through a novel intraoral customized transport distraction device and discuss the advantages and technical limitations of this technique.
MATERIAL AND METHODS A 46-year-old woman diagnosed with mandibular ameloblastoma was included in this preliminary study. A panoramic radiography and three-dimensional computed tomography were performed before surgery. An intraoral partial mandibulectomy and transport distraction osteogenesis were selected for treatment goal.
Distractor Design The trifocal transport distractor consists of stabilization assembly, transport assembly, and threaded rod (Ningbo Cibei Medical Treatment Appliance Co, Ltd, Ningbo, China) (Fig. 1). The curvature of the rod conformed to the patient's mandibular contour, which was based on the presurgical rapid prototype skeletal model. Two transport disks were designed distal to the osteotomy region and each contained lower first molar. Each transport assembly could be activated either medially or distally, which allows the patient to use the activation screwdriver from both directions intraorally when the transport disk moves across the midline. In case of an incorrect use of the screwdriver, there is a self-lock spring on the transport assembly that can prevent an unexpected reverse movement of the transport disk (Fig. 2).
Surgical Procedure Before the operation, a model surgery was performed on the skeletal model. A premature contact had occurred at the midline between the 2 transport disks when using a same distraction rhythm. To achieve a well bony contact of the transport disks, the final distraction protocol was an 18-mm length of the right side and 36-mm length of the left side (Fig. 3). The surgery was performed under general anesthesia. According to the surgical plan, the location of the distractor was marked intraorally by drilling holes on the buccal side of the lower second molar region through the consolidation assembly before osteotomy. Partial
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1015
Cai et al
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
FIGURE 1. A and B, Design of the customized trifocal curvilinear transport distraction device based on the patient's mandibular contour and defect.
FIGURE 3. A, Premature contact can occur if 2 transport disks move by the same rhythm during model surgery. B, Move the left transport disk across the midline to meet the contralateral transport disk.
mandibulectomy was carried out from the left first molar to the right first molar. Vertical osteotomy was performed between the first and second molars, and 2 segments were mobilized with particular care to protect the lingual periosteum. When finishing the resection of tumor and preparing the transport disks, the distractor was repositioned and fixed using 8-mm– long titanium screws (2.0; Ningbo Cibei Medical Treatment Appliance Co, Ltd, China). After testing the activation of both transport assembly, a strict closure of wound was carried out to avoid postsurgical intraoral infection (Fig. 4).
Distraction Protocol Postoperatively, the patient was treated with intravenous antibiotics for 3 days and a routine mouth cleaning 3 times a day. The distraction began 7 days after the surgery and the amount of lengthening was 1 mm/d. Panoramic radiography was taken once a week. After reaching the end point and confirmation of transport disks contact through x-rays, the device was retained for 6 months for consolidation (Fig. 5). This study was approved by the local institutional review board and the ethics committee of Shanghai Ninth People’s Hospital, Shanghai Jiaotong University.
RESULTS The operation and distraction period was uneventful. The distal root of the right lower first molar was cut during osteotomy, but no complication was noticed. There was a little inconvenience when eating with the intraoral device, but the whole procedure was acceptable. The removal of the distractor was performed after the retention period. The distraction gap was filled with new bone and the
FIGURE 2. A and B, Transport assembly could be activated either medially or distally. C, A self-locking spring could prevent an unexpected reverse activation of transport disk.
1016
FIGURE 4. A and B, Distractor was positioned before mandibulectomy. C and D, The transport disk containing the first molar was prepared and the distractor was fixed.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
FIGURE 5. A and B, x-Ray films show the distraction device during the latency period and at the end of the consolidation phase.
2 first molars had contact at paramedian. A well lingual bony contact between the 2 transport disks and superficial nonunion still existed. Therefore, an autologous bone graft from the mandibular angle and rigid internal fixation was carried out at the time of the second surgery (Fig. 6). When the patient went to a prosthodontist for teeth restoration 6 months after the second operation, an anterior-posterior discrepancy of jaw bone was noticed. After discussing with the prosthodontist, moving the mandible forward to establish a correct maxillary-mandible relationship was necessary for teeth restoration. Thus, the bilateral sagittal split of the mandible was performed to move the mandible 8 mm anteriorly. Bone resorption at the gap of 2 disks was discovered during the surgery. Hence, the cancellous bone graft to form ileum was carried out and a new reconstructive plate was fixed simultaneously. Root canal therapy for the molars and overlay denture restoration was accomplished 3 months after the third surgery (Figs. 7, 8).
DISCUSSION The bone transport distraction is an effective method for partial mandibular reconstruction. Compared with conventional treatment
FIGURE 6. A, A new bone bridged the mandibular defects when removing the distractor. B and C, Partial nonunion was noted between the 2 transport disks; bone graft and rigid internal fixation was performed at the second operation.
Customized Transport Distraction Device
FIGURE 7. A and B, Anterior posterior discrepancy occurred after the distraction. C and D, Sagittal split ramus osteotomy for mandibular advancement and bone graft with reconstructive plate fixation to ensure the mandibular continuity.
by free bone graft, distraction osteogenesis is a relatively simple operation that can regenerate new bone and surrounding soft tissue with less complications and without donor-site morbidities. Bifocal transport distraction has been widely used in segmental mandibular reconstruction. Using a regular commercial distraction device makes this procedure suitable to many clinical requirements. However, almost all available transport distractor use a straight line vector that does not fit a curved mandibular configuration. In addition, those devices require a reconstruction plate for stabilization of the mandibular segments, which might increase the surgical difficulty.4,8 Moreover, additional operations may be added if the length of distractor is insufficient to restore the defects.5 The advantage of trifocal transport distraction is the reduction of distraction period with 2 transport disks moving simultaneously. To the knowledge of the authors, there is no specific production of trifocal transport distraction device so far. A customized distractor emerged for an alternative mandibular reconstruction. Some special designs of trifocal transport devices were based on the principle of traditional external distractor.9 Despite the acceptable clinical results, using the transcutaneous pins to connect the device onto mandibular segments may cause several facial scars.3,6 Whether using internal or external devices, an extraoral approach was performed for most transport distraction procedures according to the literature. Considering to avoid facial scar, an internal
FIGURE 8. A, B, and C, The patient’s frontal view, occlusal relationship, and x-ray film before the treatment. D, E, and F, The patient’s frontal view, reconstructive dentition, and x-ray film 2 years after the third operation.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1017
Cai et al
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
device under intraoral approach was suggested for a better clinical outcome. A modified novel internal device was designed on the basis of the former customized curvilinear trifocal distractor.7 The transport assembly can be activated from either medial or distal side, which allows the activation operable when the transport disk moves across the symphysis. A self-locker system was added to prevent unwanted reversal movement. The stabilization assembly is strong enough to connect residual mandibular segments in 1 piece, which replace the traditional reconstruction plate. All those modification ensured the whole intraoral distraction process smoothly. Regarding the reconstruction of symphysis using 2 transport disks, a presurgical model surgery is helpful to foresee the clinical result. In this study, an unexpected lingual side premature contact was noted when the disks moved at the same rhythm. Therefore, the distraction protocol was changed to moving 1 disk across the midline to avoid the bony interference. Considering the transport disk preparation, a molar was kept in each disk to maintain the width and height of the bony disks. Although 1 distal root was cut during the first surgery, no complications occurred during and after the distraction procedure. The molars can be used as abutments for dental restoration because the patient refused dental implants. The most challenging aspect of this procedure is the achievement of union at docking site. Partial bone nonunion was detected between the 2 transport disks when removing the distraction device. Therefore, autologous bone graft and rigid internal fixation was carried out to ensure the mandibular continuity. The key point for the success of docking site union is to maintain an adequate blood supply of the transport disk. Also, the transport assembly must remain stable and attached to the stabilization assembly firmly. In addition, a possible bony spike and/or interposition of soft tissue between the advancing edge of transport disks might prevent the contact of 2 transport disks.3,10 A well-designed bone transport distractor and careful operation on transport disks might increase docking site healing. Despite the fact that the trajectory of this customized distractor was designed on the basis of the curvature of patient’s preexisting mandible, the anterior-posterior discrepancy was noticed. The discrepancy of the contour of the regenerated bone in the distraction gap and the curvilinear pathway of the transport disks may be caused by the conflict of distraction vector and strain vector during consolidation. The distraction vector varies in curvilinear transport distraction osteogenesis, whereas strain vector during the consolidation phase is fixed
1018
linear.11 Thus, an overcorrection of curvilinear distraction osteogenesis could be considered in future treatments to avoid the additional surgery for the correction of maxillomandibular discrepancy. This novel distraction device proved to be stable, easy to use, and well tolerated. The result of this study indicated that intraoral trifocal curvilinear transport distraction osteogenesis can reconstruct a segmental mandibular defect without leaving a facial scar. Overcorrection of curvilinear distraction for a better mandibular contour will be modified in future distraction devices.
REFERENCES 1. Annino DJ Jr, Goguen LA, Karmody CS. Distraction osteogenesis for reconstruction of mandibular symphyseal defects. Arch Otolaryngol Head Neck Surg 1994;120:911 2. Andrade N, Reshamwala SM, Subburaj K. Mandibular reconstruction through transport distraction using intraoral appliance. J Oral Maxillofac Surg 2011;69:2260 3. Nagashia LK, Rondon-Newby M, Zakhaary IE, et al. Bone regeneration and docking site healing after bone transport distraction osteogenesis in the canine mandible. J Oral Maxillofac Surg 2012;70:429 4. Agarwal R, Agarwal S, Chandra R. Mandibular reconstruction using extraoal trifocal bone transport: report of a case using a new device. J Oral Maxillofac Surg 2012;70:1739 5. Wang JJ, Chen J, Ping FY, et al. Double-step transport distraction osteogenesis in the reconstruction of unilateral large mandibular defects after tumor resection using internal distraction devices. Int J Oral Maxillofac Surg 2012;41:587 6. Zwetyenga N, Siberchicot F, Emparanza A. Reconstruction of large mandibular and surrounding soft-tissue defects using distraction with bone transport. Int J Oral Maxillofac Surg 2012;41:1215 7. Cai M, Lu XF, Shen GF. A clinical study of customized bifocal and trifocal transport distraction osteogenesis device for extensive mandibular reconstruction. J Craniofac Surg 2011;22:562 8. Liu Y, Chen J, Yan F, et al. Mandible reconstruction with transport-disc distraction osteogenesis in children of deciduous dentition. Int J Oral Maxillofac Surg 2012;41:1223 9. Kurlakose MA, Shnayder Y, Delacure MD. Reconstruction of segmental mandibular defects by distraction osteogenesis for mandibular reconstruction. Head Neck 2003;25:816 10. Giotakis N, Narayan B, Nayagam S. Distraction osteogenesis and nonunion of the docking site: is there an ideal treatment option? Injury 2007;38:S100 11. Zhou LB, Shang HT, Feng ZH, et al. Segmental curvilinear distraction osteogenesis. Med Hypotheses 2012;79:427
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
Application of a Novel Intraorally Customized Transport Distraction Device in the Reconstruction of Segmental Mandibular Defect Ming Cai, DDS, MD, Xiaofeng Lu, DDS, MD, Danling Yang, DDS, Huijuan Cheng, DDS, and Guofang Shen, DDS, MD Purpose: The purpose of this study was to evaluate the clinical result of segmental mandible reconstruction by using a novel intraorally customized trifocal curvilinear distractor. Methods: A customized curvilinear distractor with self-locking system and bidirection transport assembly was designed on the basis of the mandibular contour of a patient diagnosed with ameloblastoma. Two transport disks, each containing the first molar, were designed for trifocal distraction osteogenesis after partial mandibulectomy intraorally. The latency period is 7 days and distraction rhythm is 1 mm/d. After 6 months of consolidation, the second operation was performed to remove the device. Results: A new bone bridged the mandibular defects through transport distraction successfully. Partial bony nonunion between the transport disks was noted when removing the distractor; rigid internal fixation using a titanium plate and bone graft was carried out to ensure the continuity. Bilateral sagittal split ramus osteotomy was performed to advance the mandible when anterior-posterior jaw bone discrepancy occurred before final denture restoration. Conclusions: Customized trifocal curvilinear transport distraction osteogenesis can successfully reconstruct segmental mandible defect intraorally, but special consideration should be paid on the dock site bone healing and overcorrection of curvilinear reconstruction in the future. Key Words: Transport distraction osteogenesis, customized distraction, mandibular reconstruction, curvilinear distraction (J Craniofac Surg 2014;25: 1015–1018)
L
arge mandibular defects resulting from ablative oncologic surgery have significant aesthetic and functional sequelae. Although microvascular free tissue transfer remains the treatment of choice to obtain a predictable primary reconstruction for the extensive composite mandibular defects commonly encountered in ablative surgery, alternative less-invasive methods of reconstruction should be considered.
From the Department of Oral and Craniomaxillofacial Surgery, Shanghai Ninth People’s Hospital, Shanghai, China. Received December 12, 2013. Accepted for publication January 6, 2014. Address correspondence and reprint requests to Xiaofeng Lu, DDS, MD, Shanghai Ninth People’s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; E-mail: [email protected] Supported by the National Nature and Science Foundation of China grant 81100793. The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000725
Distraction osteogenesis is an established technique for the lengthening of bone and the surrounding soft tissue. The ability of new bone regeneration through transport distraction osteogenesis makes it an attractive concept in selected patients with mandibular defects.1,2 Animal experiments and early clinical experience have confirmed that transport distraction osteogenesis can be used for the reconstruction of segmental bony defects.3,4 However, most related publications reported an extraoral approach that resulted in obvious facial scars.5,6 Only few reports used a customized design and custom-made distraction device to reconstruct the original geometric outline of the mandible.7 In this study, we report the restoration of large mandibular continuity defects through a novel intraoral customized transport distraction device and discuss the advantages and technical limitations of this technique.
MATERIAL AND METHODS A 46-year-old woman diagnosed with mandibular ameloblastoma was included in this preliminary study. A panoramic radiography and three-dimensional computed tomography were performed before surgery. An intraoral partial mandibulectomy and transport distraction osteogenesis were selected for treatment goal.
Distractor Design The trifocal transport distractor consists of stabilization assembly, transport assembly, and threaded rod (Ningbo Cibei Medical Treatment Appliance Co, Ltd, Ningbo, China) (Fig. 1). The curvature of the rod conformed to the patient's mandibular contour, which was based on the presurgical rapid prototype skeletal model. Two transport disks were designed distal to the osteotomy region and each contained lower first molar. Each transport assembly could be activated either medially or distally, which allows the patient to use the activation screwdriver from both directions intraorally when the transport disk moves across the midline. In case of an incorrect use of the screwdriver, there is a self-lock spring on the transport assembly that can prevent an unexpected reverse movement of the transport disk (Fig. 2).
Surgical Procedure Before the operation, a model surgery was performed on the skeletal model. A premature contact had occurred at the midline between the 2 transport disks when using a same distraction rhythm. To achieve a well bony contact of the transport disks, the final distraction protocol was an 18-mm length of the right side and 36-mm length of the left side (Fig. 3). The surgery was performed under general anesthesia. According to the surgical plan, the location of the distractor was marked intraorally by drilling holes on the buccal side of the lower second molar region through the consolidation assembly before osteotomy. Partial
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1015
Cai et al
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
FIGURE 1. A and B, Design of the customized trifocal curvilinear transport distraction device based on the patient's mandibular contour and defect.
FIGURE 3. A, Premature contact can occur if 2 transport disks move by the same rhythm during model surgery. B, Move the left transport disk across the midline to meet the contralateral transport disk.
mandibulectomy was carried out from the left first molar to the right first molar. Vertical osteotomy was performed between the first and second molars, and 2 segments were mobilized with particular care to protect the lingual periosteum. When finishing the resection of tumor and preparing the transport disks, the distractor was repositioned and fixed using 8-mm– long titanium screws (2.0; Ningbo Cibei Medical Treatment Appliance Co, Ltd, China). After testing the activation of both transport assembly, a strict closure of wound was carried out to avoid postsurgical intraoral infection (Fig. 4).
Distraction Protocol Postoperatively, the patient was treated with intravenous antibiotics for 3 days and a routine mouth cleaning 3 times a day. The distraction began 7 days after the surgery and the amount of lengthening was 1 mm/d. Panoramic radiography was taken once a week. After reaching the end point and confirmation of transport disks contact through x-rays, the device was retained for 6 months for consolidation (Fig. 5). This study was approved by the local institutional review board and the ethics committee of Shanghai Ninth People’s Hospital, Shanghai Jiaotong University.
RESULTS The operation and distraction period was uneventful. The distal root of the right lower first molar was cut during osteotomy, but no complication was noticed. There was a little inconvenience when eating with the intraoral device, but the whole procedure was acceptable. The removal of the distractor was performed after the retention period. The distraction gap was filled with new bone and the
FIGURE 2. A and B, Transport assembly could be activated either medially or distally. C, A self-locking spring could prevent an unexpected reverse activation of transport disk.
1016
FIGURE 4. A and B, Distractor was positioned before mandibulectomy. C and D, The transport disk containing the first molar was prepared and the distractor was fixed.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
FIGURE 5. A and B, x-Ray films show the distraction device during the latency period and at the end of the consolidation phase.
2 first molars had contact at paramedian. A well lingual bony contact between the 2 transport disks and superficial nonunion still existed. Therefore, an autologous bone graft from the mandibular angle and rigid internal fixation was carried out at the time of the second surgery (Fig. 6). When the patient went to a prosthodontist for teeth restoration 6 months after the second operation, an anterior-posterior discrepancy of jaw bone was noticed. After discussing with the prosthodontist, moving the mandible forward to establish a correct maxillary-mandible relationship was necessary for teeth restoration. Thus, the bilateral sagittal split of the mandible was performed to move the mandible 8 mm anteriorly. Bone resorption at the gap of 2 disks was discovered during the surgery. Hence, the cancellous bone graft to form ileum was carried out and a new reconstructive plate was fixed simultaneously. Root canal therapy for the molars and overlay denture restoration was accomplished 3 months after the third surgery (Figs. 7, 8).
DISCUSSION The bone transport distraction is an effective method for partial mandibular reconstruction. Compared with conventional treatment
FIGURE 6. A, A new bone bridged the mandibular defects when removing the distractor. B and C, Partial nonunion was noted between the 2 transport disks; bone graft and rigid internal fixation was performed at the second operation.
Customized Transport Distraction Device
FIGURE 7. A and B, Anterior posterior discrepancy occurred after the distraction. C and D, Sagittal split ramus osteotomy for mandibular advancement and bone graft with reconstructive plate fixation to ensure the mandibular continuity.
by free bone graft, distraction osteogenesis is a relatively simple operation that can regenerate new bone and surrounding soft tissue with less complications and without donor-site morbidities. Bifocal transport distraction has been widely used in segmental mandibular reconstruction. Using a regular commercial distraction device makes this procedure suitable to many clinical requirements. However, almost all available transport distractor use a straight line vector that does not fit a curved mandibular configuration. In addition, those devices require a reconstruction plate for stabilization of the mandibular segments, which might increase the surgical difficulty.4,8 Moreover, additional operations may be added if the length of distractor is insufficient to restore the defects.5 The advantage of trifocal transport distraction is the reduction of distraction period with 2 transport disks moving simultaneously. To the knowledge of the authors, there is no specific production of trifocal transport distraction device so far. A customized distractor emerged for an alternative mandibular reconstruction. Some special designs of trifocal transport devices were based on the principle of traditional external distractor.9 Despite the acceptable clinical results, using the transcutaneous pins to connect the device onto mandibular segments may cause several facial scars.3,6 Whether using internal or external devices, an extraoral approach was performed for most transport distraction procedures according to the literature. Considering to avoid facial scar, an internal
FIGURE 8. A, B, and C, The patient’s frontal view, occlusal relationship, and x-ray film before the treatment. D, E, and F, The patient’s frontal view, reconstructive dentition, and x-ray film 2 years after the third operation.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1017
Cai et al
The Journal of Craniofacial Surgery • Volume 25, Number 3, May 2014
device under intraoral approach was suggested for a better clinical outcome. A modified novel internal device was designed on the basis of the former customized curvilinear trifocal distractor.7 The transport assembly can be activated from either medial or distal side, which allows the activation operable when the transport disk moves across the symphysis. A self-locker system was added to prevent unwanted reversal movement. The stabilization assembly is strong enough to connect residual mandibular segments in 1 piece, which replace the traditional reconstruction plate. All those modification ensured the whole intraoral distraction process smoothly. Regarding the reconstruction of symphysis using 2 transport disks, a presurgical model surgery is helpful to foresee the clinical result. In this study, an unexpected lingual side premature contact was noted when the disks moved at the same rhythm. Therefore, the distraction protocol was changed to moving 1 disk across the midline to avoid the bony interference. Considering the transport disk preparation, a molar was kept in each disk to maintain the width and height of the bony disks. Although 1 distal root was cut during the first surgery, no complications occurred during and after the distraction procedure. The molars can be used as abutments for dental restoration because the patient refused dental implants. The most challenging aspect of this procedure is the achievement of union at docking site. Partial bone nonunion was detected between the 2 transport disks when removing the distraction device. Therefore, autologous bone graft and rigid internal fixation was carried out to ensure the mandibular continuity. The key point for the success of docking site union is to maintain an adequate blood supply of the transport disk. Also, the transport assembly must remain stable and attached to the stabilization assembly firmly. In addition, a possible bony spike and/or interposition of soft tissue between the advancing edge of transport disks might prevent the contact of 2 transport disks.3,10 A well-designed bone transport distractor and careful operation on transport disks might increase docking site healing. Despite the fact that the trajectory of this customized distractor was designed on the basis of the curvature of patient’s preexisting mandible, the anterior-posterior discrepancy was noticed. The discrepancy of the contour of the regenerated bone in the distraction gap and the curvilinear pathway of the transport disks may be caused by the conflict of distraction vector and strain vector during consolidation. The distraction vector varies in curvilinear transport distraction osteogenesis, whereas strain vector during the consolidation phase is fixed
1018
linear.11 Thus, an overcorrection of curvilinear distraction osteogenesis could be considered in future treatments to avoid the additional surgery for the correction of maxillomandibular discrepancy. This novel distraction device proved to be stable, easy to use, and well tolerated. The result of this study indicated that intraoral trifocal curvilinear transport distraction osteogenesis can reconstruct a segmental mandibular defect without leaving a facial scar. Overcorrection of curvilinear distraction for a better mandibular contour will be modified in future distraction devices.
REFERENCES 1. Annino DJ Jr, Goguen LA, Karmody CS. Distraction osteogenesis for reconstruction of mandibular symphyseal defects. Arch Otolaryngol Head Neck Surg 1994;120:911 2. Andrade N, Reshamwala SM, Subburaj K. Mandibular reconstruction through transport distraction using intraoral appliance. J Oral Maxillofac Surg 2011;69:2260 3. Nagashia LK, Rondon-Newby M, Zakhaary IE, et al. Bone regeneration and docking site healing after bone transport distraction osteogenesis in the canine mandible. J Oral Maxillofac Surg 2012;70:429 4. Agarwal R, Agarwal S, Chandra R. Mandibular reconstruction using extraoal trifocal bone transport: report of a case using a new device. J Oral Maxillofac Surg 2012;70:1739 5. Wang JJ, Chen J, Ping FY, et al. Double-step transport distraction osteogenesis in the reconstruction of unilateral large mandibular defects after tumor resection using internal distraction devices. Int J Oral Maxillofac Surg 2012;41:587 6. Zwetyenga N, Siberchicot F, Emparanza A. Reconstruction of large mandibular and surrounding soft-tissue defects using distraction with bone transport. Int J Oral Maxillofac Surg 2012;41:1215 7. Cai M, Lu XF, Shen GF. A clinical study of customized bifocal and trifocal transport distraction osteogenesis device for extensive mandibular reconstruction. J Craniofac Surg 2011;22:562 8. Liu Y, Chen J, Yan F, et al. Mandible reconstruction with transport-disc distraction osteogenesis in children of deciduous dentition. Int J Oral Maxillofac Surg 2012;41:1223 9. Kurlakose MA, Shnayder Y, Delacure MD. Reconstruction of segmental mandibular defects by distraction osteogenesis for mandibular reconstruction. Head Neck 2003;25:816 10. Giotakis N, Narayan B, Nayagam S. Distraction osteogenesis and nonunion of the docking site: is there an ideal treatment option? Injury 2007;38:S100 11. Zhou LB, Shang HT, Feng ZH, et al. Segmental curvilinear distraction osteogenesis. Med Hypotheses 2012;79:427
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
