SCIENTIFIC FOUNDATION
Mandibular Distraction Osteogenesis With Newly Designed Electromechanical Distractor Andac Aykan, MD,* Rifat Ugurlutan, MD,† Fatih Zor, MD,* and Serdar Ozturk, MD*
D
Background: The purposes of this study were to design a fully automatic electromechanical distractor for continuous mandibular distraction osteogenesis and to investigate the efficacy of this newly developed distractor on sheep mandible model. Methods: Five sheep underwent unilateral mandibular osteotomy, and the mechanical component of electromechanical distractor was fixed on both sides of the osteotomy site using pins. After a 5-day latency period, the electromechanical distractor was activated at a rate of 0.30 mm per 8 hours using an electronic control unit. The bone was lengthened for 20 days without any intervention to the electromechanical distractor. The animals were killed on the sixth week of the consolidation period, and 5 distracted mandibles were examined through macroscopic observation and computed tomography. Distracted bone length was measured through computed tomography on sagittal slices. Results: The device was tolerated by the distraction process without complications in all animals. New callus formation was observed on the distraction gap. Radiologic evaluation showed new callus formation in the distraction gap. New callus length was found to be, in average, 18.28 mm. Conclusions: In this preliminary study, a newly designed electromechanical distractor was successfully used for mandible distraction, which mainly provided a continuous lengthening during activation period spontaneously without any intervention. We think that the clinical application of this electromechanic distractor may provide patient comfort during distraction. Moreover, electromechanical distractor has the potential for high-resolution movement capacity when compared with annual distraction. The promising results from this prototype are encouraging to further investigations for human applications.
istraction osteogenesis (DO) was initially used in orthopedic surgery by Alessandro Codivilla in 1905 as well as examined and developed as a technique for limb lengthening by Ilizarov in 1989.1,2 More recently, McCarthy et al3 reported the first clinical case of mandibular DO in 1992. Since then, mandibular DO has been widely used in the treatment of craniomaxillofacial deformities in plastic surgery.4,5 Distraction osteogenesis offers many advantages in craniofacial surgical practice, such as the ability of correction of the deformity without the need for a bone graft.4 Moreover, a more predictable treatment outcome may be obtained.5 Because of the advances in surgical technique and technical equipment, the indications of the DO have widened.6 Recently, a rapid rise in the number and types of distraction devices to maximize patient comfort as well as psychological and physical acceptability has been observed.6–8 However, the distraction devices used today are not ideal for the procedure and distraction device–related problems are met frequently.6 During the activation period, the distraction device must be activated manually to create callus elongation and several patient visits are required. The human-dependent activation of the device has the potential risk for making mistakes, especially on repeated applications. At the same time, long-term hospital stay results in complications, such as cost, infection risk, and psychological stress.9 The patient is required to have numerous office visits after the discharge to ensure proper distractor activation. This causes a major problem; hence, noncompliances of the patient and device failure are the leading causes of treatment failure.10,11 Moreover, frequent radiographs may be required to evaluate the distraction process and vector of movement. This study was designed to overcome such problems of DO by using newly developed electromechanical distractor (EMD). The efficiency of EMD was investigated by using sheep mandible distraction model.
Key Words: Electromechanical distractor, distraction osteogenesis, continuous distraction, sheep mandible, spontaneous distraction, activation period
MATERIALS AND METHODS
(J Craniofac Surg 2014;25: 1519–1523)
The Electromechanical Distractor
From the *Department of Plastic and Reconstructive Surgery, Gulhane Military Medical Academy, Ankara; and †3rd Main Jet Base Medical Center, Konya, Turkey. Received August 27, 2013. Accepted for publication February 16, 2014. Address correspondence and reprint requests to Andac Aykan, MD, Department of Plastic, Aesthetic and Reconstructive Surgery, Gulhane Military Medical Academy, 06010 Etlik, Ankara, Turkey; E-mail: [email protected]; [email protected] Presented at the Plastic Surgery Special Joint Meeting (Co-sponsored by Mayo Clinic), May 20–21, 2011, Konya, Turkey. The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000922
Electromechanical distractor is mainly composed of 2 components; electronical and mechanical (Fig. 1). Rotational encoder, electronic control unit (ECU), and direct current motor are the components of the electronical part. The rotational encoder is used to detect the amount of rotation and to send these data to the microprocessor, which is located within the ECU. The information coming from the rotational encoder is evaluated by the microprocessor, and the run or stop decision is made by the DC motor (Fig. 2). Simulation and analysis of the electronic system were performed using software (Proteus Design Suite; Labcenter Electronics, North Yorkshire, England). The result of this analysis revealed that the circuits need an electrical current of 0.50 μA. The lithium cell battery (3.6 V) was selected as an energy supply unit. The ECU is the electronic component of the EMD. By using the display panel on the ECU, the amount of distraction (distraction distance, D) was
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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FIGURE 3. The mechanical parts of the EMD. By using different diameter gears, movement resolution and gain of force were improved.
FIGURE 1. Electronical and mechanical components of the EMD.
monitored. The ECU was designed to allow the clinician to adjust the rate and rhythm via the display panel at the beginning of the distraction process. The mechanical part is composed of gear wheels and shaft (Fig. 3). The motion which was provided by the DC motor was transferred to the shaft by gear wheels. All mechanical units were designed by a software (SolidWorks Dassault Systèmes, SolidWorks Corp), and mechanical evaluation of fracture and strength analyses were performed on computer before the application of the EMD.
Surgical Procedure Five adult female sheep (age, 2–3 y; mean weight, 55 kg) were used in this study. All animal experiments were performed in accordance with the approved protocol of the scientific research board and ethics board of animal experiments. Each sheep was operated on under general anesthesia after 14 hours of nutritional abstinence. Anesthesia was induced through intravenous application of midazolam (0.2 mg/kg; Dormicum; Roche, Basel, Switzerland) and propofol (3 mg/kg; 1% Propofol-Lipuro; Braun, Melsungen, Germany), and after endotracheal intubation inhalation, anesthesia with isofluran (Isofluran-Lilly; Lilly, Giessen, Germany) was performed. The submandibular and cheek hairs were shaved using an electrical shaver, and the surgical area was disinfected using 10% povidone-iodine solution. Ten minutes before incision, a regional subcutaneous infiltration with 10 mL of 1% lidocaine (Xylocain; Astra Chemicals, Hamburg, Germany) was applied. The skin flaps were raised to expose the mandibular bone after a 4-cm longitudinal incision in the right submandibular area. The mandibular cortex was cut across the mandible using an electrical saw just 2 cm anterior to the angulus mandible (Fig. 4). The 2 mandibular segments were separated completely at the corticotomy line using a small bone chisel. Four holes were opened at both sides of the osteotomy line using an electrical drill, and pins were inserted. Then, the mechanical part of EMD was placed and fixed using screws. Subcutaneous tissues and skin were reapproximated in layers.
FIGURE 2. Schematic diagram showing the working principle of EMD.
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Postoperative Care Postoperative analgesia was provided with intramuscular injection of 0.01-mg/kg buprenorphine (Temgesic; Reckitt and Colman, Hull, United Kingdom) and 0.8-mL/kg carprofen for 2 days. Antibiotic prophylaxis was administered daily with subcutaneous injections of baytril (5-mg/kg enrofloxacin; Bayer AG, Leverkusen, Germany) for 3 days postoperatively.
Distraction Protocol After 5 days of latency, the ECU was secured on the neck area of the sheep and connected to the mechanical part of EMD (Fig. 5). The ECU was programmed to a distraction rate of 0.30 mm per 8 hours; then, the EMD was activated. The bone was lengthened for 20 days before the device was turned off. During the activation period, the distraction process was observed on the ECU daily without any intervention to the EMD. The ECU was disconnected from the neck area at the beginning of the consolidation period (Fig. 5).
Assessment The animals were killed on the sixth week after the consolidation period, and 5 distracted mandibles were examined through macroscopic observation and radiology. After removing the distractor from the sheep, the distracted mandibles were isolated from soft tissue and periosteum. New callus formation in the distraction gap was evaluated through direct radiography and computed tomography (Toshiba Aquilion). The sagittal volumetric computed tomographic images were obtained with a slice thickness of 0.5 mm, and
FIGURE 4. Intraoperative views of the surgical stages. After the marking of the mandible, monocortical osteotomy was achieved using an electrical saw (upper left). The holes were opened using a drill (upper right). Osteotomy was accomplished using a bone chisel (lower left). Pins were inserted, and the EMD was placed (lower right).
© 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 4, July 2014
FIGURE 5. The ECU was secured to the neck area of the sheep (left). After the distraction period, the ECU was disconnected from the neck area (right).
new callus length was measured by using software (Vitrea 2 4.1.2.0 version imaging software). The mean distraction length was calculated.
RESULTS Surgical procedure and postoperative care were uneventful. The animals were checked daily by veterinarians, and there was no significant change in body weight. Active distraction was painless for the animals and easy to handle. The distraction procedure was completed without any electronical and mechanical problem. The bone movement of bone segments was easily achieved, and there was no failure of the distraction devices.
Macroscopic Evaluation New callus formation was observed on the mandibular distraction gaps after the isolation of soft tissue and periosteum (Fig. 6).
Radiology New callus formation was observed on computed tomographic images (Fig. 6). New callus length was found to be, in average, 18.28 ± 0.19 mm.
DISCUSSION Because of the device-related drawbacks of DO, novel distraction devices were developed by various researchers.12–20 Improved patient compliance and decreased postoperative visit frequency were aimed in all of these experimental studies with self-activating distractors. As mentioned before in the comprehensive review of the distraction devices by Goldwaser et al,21 new designs of automated, continuous distraction would eliminate the need for patient participation in this process. Therefore, we developed a fully automatic EMD for continuous mandibular DO. Various methods of power were chosen for providing the mechanical movement of the device for distraction.12–20 Basically, electrical motors, springs, or hydraulic systems are used for continuous distraction. Because of some of the disadvantages of the spring-driven devices, the motor-driven and hydraulic systems have more potential for future applications.21 The major drawback of spring-driven devices is the generation of force. The force generated by the spring-driven devices is at maximum level when the spring is fully compressed in early distraction but gradually decreases as the spring expands in the later period.21 Moreover, the distraction process is not reversal in the spring-mediated systems and cannot be adjusted once the distraction is activated. The developed hydraulic distractors had functioned successfully in providing continuous distraction.18–20,22 However, when the distraction device is located internally, it still needs a flexible hydraulic tube connection that exits the skin to an extracorporeal steering unit. Although it is an internal device, this hydraulic tube connection may increase the risk for infection. The critically sized bone defect that had been created in the sheep mandible was successfully
Newly Designed EMD
reconstructed with hydraulic distraction device automatically by Ayoub et al.22 Of the 8 sheep, 2 animals were excluded from the study because of postoperative complications. Despite the satisfactory treatment with antibiotics, 4 animals (66.6%) had developed infection between the second and third postoperative days at the site of the connection tube. Similarly, in the study of Wiltfang et al,19 1 animal had developed a local inflammation (16.6%) where the hydraulic tube emerged from the skin and treated with antibiotics. It seems that, although the device was located internally, the flexible hydraulic tube's access site on the skin provides an important foundation for the development of infection. Although the device was located externally, there were no animals that had infection in our study. The EMD was fixated to the bone segments using 4 steel pins, which passed through the skin. Compared with the internally applied hydraulic devices that have only 1 skin opening to the external environment, the EMD had 4 skin openings for stabilization of the device to the bone segments using pins. However, low infection rate in EMD application compared with the hydraulic devices shows that it may not be related only to the skin openings to the external environment. The size of the skin openings and the material composition that passed through the skin may be associated with high infection rates. A flexible tube whose structure is not fully specified in the literature was used for connection between the internal distractor and an external steering unit in hydraulic systems.22 Because of the flexible behavior of the connection tube, it is suggested that the tube is probably composed of plastic material in these designs. This could be facilitating the bacterial adhesion and transmission from external environment. The diameter of the flexible tube that carries the fluid was not indicated in studies. The hydraulic distractor used in the study of Wiltfang et al19 consisted of a cylinder and a piston. The cylinder had an external diameter of 9 mm, and the flexible tube was connected between the external steering unit and cylinder. Accordingly, the diameter of the connection tube that passed through the skin was nearly 1 cm. Similar to other articles, tubes of the same diameters were used as seen in device photographs.18,23 This may provide the substantial amount of skin openings that facilitate the development of infection. Three of the novel distraction devices were motor-driven and successfully generated sufficient force to move the bone fragments in the literature.12–14 However, none of the motorized device allowed the clinician to measure progress without taking radiographs.12–14 The amount of distraction (distraction distance, D) was monitored with our newly developed EMD on the display panel. Moreover, the EMD allowed the clinician to adjust the rate and rhythm via the display panel and the electrical control unit at the beginning of the distraction process. The ECU was designed to provide the distraction rate in millimeters, and distraction periods in days were observed using the digital display located on the ECU. When designing a new device, it is essential to choose a suitable experimental model for preliminary studies. Small-animal models were mostly selected in studies that were subjected to automated
FIGURE 6. New callus formation was observed on the distraction gap (left) and computed tomographic image (right).
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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Aykan et al
mandibular DO in the literature.14–17 Small experimental mandible models for distraction have some advantages in comparison with the larger animal models, including lower cost, easy handling, and simple housing.24 However, these criteria are not suitable for the application of automated distractors to humans. To provide a clinically relevant model, the newly designed automated mandibular distraction device should be tested on animals whose mandibles are more similar to the human mandible. The similarity of the sheep mandible to the human mandible consists of not only anatomic or macroscopic properties but also physiologic properties.25,26 The physiologic similarities of the sheep mandible to the human mandible, in terms of distraction, have been revealed by Knabe et al.25 Growth factor expression after clinical mandibular DO in humans and its comparison with existing animal studies were reported by Knabe et al,25 and the authors found that the expression pattern of growth factors secondary to human DO closely resembled those observed in the sheep model. This similarity was also mentioned in studies performed by Ploder et al13 and Ayoub et al.22 Because of all these similarities, the sheep mandible model was selected in our study. However, the edentulous area between the anterior and posterior teeth on the ramus of mandible was selected as localization for osteotomy by these researchers.13,22 Swennen et al11 presented a comprehensive review about craniofacial DO, and in this review, they reported that, in the clinical setting, mandibular distraction was performed most frequently at the angle of the mandible. Although the location of the ramus of the mandible of the sheep is convenient and an easy area for the procedure, we think that the angulus mandible should be the preferred area for experimental models to create a clinically relevant model. For that reason, contrary to other studies, the angulus mandible was selected in our study. Mandibular DO is performed with external or internal devices in clinical applications, and there are advantages and limitations of each. Placement of intraoral devices reduced facial scarring and dislodgment compared with that of external devices.27,28 Despite the advantages of the internal device in this respect, external devices are used more often today in mandibular DO.11 Similar to clinical practice, we designed this prototype as external device and did not observe any complication. However, it is necessary to reduce the device dimensions for future human application. The effect of high distraction frequency resulted in a more rapid course of osteogenesis, which was shown by Ilizarov in the late 1980s.29,30 In addition, these studies showed that increased frequency of distraction improved the quality of new bone. More recently, similar findings were supported by other studies.19,31 However, the devices available today for clinical applications in the field of DO do not allow continuous distraction. In routine usage, the distraction process is achieved through manual activation of the distractor. To provide the high frequency distraction rate with short distance steps, the device must be manipulated more often. This also increases the probability of physician-dependent error. These problems can be overcome by the development of distraction devices that provide continuous distraction. By using EMD, high distraction frequency with regular intervals was achieved in our study. Moreover, the physician-dependent activation of distraction device was eliminated. The ECU was programmed to a distraction rate of 0.30 mm per 8 hours in our experimental design. However, by using a more advanced engineering design of EMD, higher frequency rate of DO can be achieved in future studies. However, even in the current design, EMD has the potential for high-resolution movement capacity when compared with the human hand.
CONCLUSIONS In this preliminary study, we reported a newly designed EMD that allows the desired period (frequency) and the amount
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of distraction (rate) with high-resolution movement capacity when compared with manual distraction. In addition, humanindependent activation of the EMD was shown to provide great ease for DO. The clinical use of the device will be facilitated by advanced engineering studies that will result in reduced distractor size and weight. Moreover, by the inclusion of the remote data transmission system to the EMD, dependence between the patient and the physician may be completely eliminated during distraction period. ACKNOWLEDGMENTS The authors thank Nisa Cem Oren, MD, and Yalcin Bozkurt, MD, for the evaluation of the radiologic images.
REFERENCES 1. Codivilla A. The classic: on the means of lengthening, in the lower limbs, the muscles and tissues which are shortened through deformity. Clin Orthop Relat Res 2008;466:2903–2909 2. Ilizarov GA. The principles of the Ilizarov method. Bull Hosp Jt Dis Orthop Inst 1988;48:1–11 3. McCarthy JG, Schreiber J, Karp N, et al. Lengthening the human mandible by gradual distraction. Plast Reconstr Surg 1992;89:1–10 4. Mofid MM, Manson PN, Robertson BC, et al. Craniofacial distraction osteogenesis: a review of 3278 cases. Plast Reconstr Surg 2001;108:1103–1117 5. Molina F. Mandibular distraction osteogenesis: a clinical experience of the last 17 years. J Craniofac Surg 2009;20:1794–1800 6. Norholt SE, Jensen J, Schou S, et al. Complications after mandibular distraction osteogenesis: a retrospective study of 131 patients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:420–427 7. McCarthy JG, Staffenberg DA, Wood RJ, et al. Introduction of an intraoral bone-lengthening device. Plast Reconstr Surg 1995;96:978–981 8. Diner PA, Kollar EM, Martinez H, et al. Intraoral distraction for mandibular lengthening: a technical innovation. J Craniomaxillofac Surg 1996;24:92–95 9. Primrose AC, Broadfoot E, Diner PA, et al. Patients’ responses to distraction osteogenesis: a multi-centre study. Int J Oral Maxillofac Surg 2005;34:238–242 10. Van Strijen PJ, Breuning KH, Becking AG, et al. Complications in bilateral mandibular distraction osteogenesis using internal devices. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;96:392–397 11. Swennen G, Schliephake H, Dempf R, et al. Craniofacial distraction osteogenesis: a review of the literature: part 1: clinical studies. Int J Oral Maxillofac Surg 2001;30:89–103 12. Schmelzeisen R, Neumann G, von der Fecht R. Distraction osteogenesis in the mandible with a motor-driven plate: a preliminary animal study. Br J Oral Maxillofac Surg 1996;34:375–378 13. Ploder O, Mayr W, Schnetz G, et al. Mandibular lengthening with an implanted motor-driven device: preliminary study in sheep. Br J Oral Maxillofac Surg 1999;37:273–276 14. Zheng LW, Cheung LK, Ma L, et al. High-rhythm automatic driver for bone traction: an experimental study in rabbits. Int J Oral Maxillofac Surg 2008;37:736–740 15. Mofid MM, Inoue N, Tufaro AP, et al. Spring-mediated mandibular distraction osteogenesis. J Craniofac Surg 2003;14:756–762 16. Idelsohn S, Pena J, Lacroix D, et al. Continuous mandibular distraction osteogenesis using superelastic shape memory alloy (SMA). J Mater Sci Mater Med 2004;15:541–546 17. Zhou HZ, Hu M, Yao J, et al. Rapid lengthening of rabbit mandibular ramus by using nitinol spring: a preliminary study. J Craniofac Surg 2004;15:725–729 18. Kessler P, Wiltfang J, Neukam FW. A new distraction device to compare continuous and discontinuous bone distraction in mini-pigs: a preliminary report. J Craniomaxillofac Surg 2000;28:5–11 19. Wiltfang J, Kessler P, Merten HA, et al. Continuous and intermittent bone distraction using a microhydraulic cylinder: an experimental study in minipigs. Br J Oral Maxillofac Surg 2001;39:2–7
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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20. Ayoub AF, Richardson W. A new device for microincremental automatic distraction osteogenesis. Br J Oral Maxillofac Surg 2001;39:353–355 21. Goldwaser BR, Papadaki ME, Kaban LB, et al. Automated continuous mandibular distraction osteogenesis: review of the literature. J Oral Maxillofac Surg 2012;70:407–416 22. Ayoub AF, Richardson W, Koppel D, et al. Segmental mandibular reconstruction by microincremental automatic distraction osteogenesis: an animal study. Br J Oral Maxillofac Surg 2001;39:356–364 23. Ayoub AF, Richardson W, Barbenel JC. Mandibular elongation by automatic distraction osteogenesis: the first application in humans. Br J Oral Maxillofac Surg 2005;43:324–328 24. Egermann M, Goldhahn J, Schneider E. Animal models for fracture treatment in osteoporosis. Osteoporos Int 2005;16:129–138 25. Knabe C, Nicklin S, Yu Y, et al. Growth factor expression following clinical mandibular distraction osteogenesis in humans and its comparison with existing animal studies. J Craniomaxillofac Surg 2005;33:361–369
Newly Designed EMD
26. Aykan A, Ozturk S, Sahin I, et al. Biomechanical analysis of the effect of mesenchymal stem cells on mandibular distraction osteogenesis. J Craniofac Surg 2013;24:169–175 27. Shetye PR, Warren SM, Brown D, et al. Documentation of the incidents associated with mandibular distraction: introduction of a new stratification system. Plast Reconstr Surg 2009;123:627–634 28. Davidson EH, Brown D, Shetye PR, et al. The evolution of mandibular distraction: device selection. Plast Reconstr Surg 2010;126:2061–2070 29. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues: I. The influence of stability of fixation and soft-tissue preservation. Clin Orthop 1989;238:249–281 30. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues: II. The influence of the rate and frequency of distraction. Clin Orthop 1989;239:263–285 31. Kessler P, Neukam FW, Wiltfang J. Effects of distraction forces and frequency of distraction on bony regeneration. Br J Oral Maxillofac Surg 2005;43:392–398
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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Mandibular Distraction Osteogenesis With Newly Designed Electromechanical Distractor Andac Aykan, MD,* Rifat Ugurlutan, MD,† Fatih Zor, MD,* and Serdar Ozturk, MD*
D
Background: The purposes of this study were to design a fully automatic electromechanical distractor for continuous mandibular distraction osteogenesis and to investigate the efficacy of this newly developed distractor on sheep mandible model. Methods: Five sheep underwent unilateral mandibular osteotomy, and the mechanical component of electromechanical distractor was fixed on both sides of the osteotomy site using pins. After a 5-day latency period, the electromechanical distractor was activated at a rate of 0.30 mm per 8 hours using an electronic control unit. The bone was lengthened for 20 days without any intervention to the electromechanical distractor. The animals were killed on the sixth week of the consolidation period, and 5 distracted mandibles were examined through macroscopic observation and computed tomography. Distracted bone length was measured through computed tomography on sagittal slices. Results: The device was tolerated by the distraction process without complications in all animals. New callus formation was observed on the distraction gap. Radiologic evaluation showed new callus formation in the distraction gap. New callus length was found to be, in average, 18.28 mm. Conclusions: In this preliminary study, a newly designed electromechanical distractor was successfully used for mandible distraction, which mainly provided a continuous lengthening during activation period spontaneously without any intervention. We think that the clinical application of this electromechanic distractor may provide patient comfort during distraction. Moreover, electromechanical distractor has the potential for high-resolution movement capacity when compared with annual distraction. The promising results from this prototype are encouraging to further investigations for human applications.
istraction osteogenesis (DO) was initially used in orthopedic surgery by Alessandro Codivilla in 1905 as well as examined and developed as a technique for limb lengthening by Ilizarov in 1989.1,2 More recently, McCarthy et al3 reported the first clinical case of mandibular DO in 1992. Since then, mandibular DO has been widely used in the treatment of craniomaxillofacial deformities in plastic surgery.4,5 Distraction osteogenesis offers many advantages in craniofacial surgical practice, such as the ability of correction of the deformity without the need for a bone graft.4 Moreover, a more predictable treatment outcome may be obtained.5 Because of the advances in surgical technique and technical equipment, the indications of the DO have widened.6 Recently, a rapid rise in the number and types of distraction devices to maximize patient comfort as well as psychological and physical acceptability has been observed.6–8 However, the distraction devices used today are not ideal for the procedure and distraction device–related problems are met frequently.6 During the activation period, the distraction device must be activated manually to create callus elongation and several patient visits are required. The human-dependent activation of the device has the potential risk for making mistakes, especially on repeated applications. At the same time, long-term hospital stay results in complications, such as cost, infection risk, and psychological stress.9 The patient is required to have numerous office visits after the discharge to ensure proper distractor activation. This causes a major problem; hence, noncompliances of the patient and device failure are the leading causes of treatment failure.10,11 Moreover, frequent radiographs may be required to evaluate the distraction process and vector of movement. This study was designed to overcome such problems of DO by using newly developed electromechanical distractor (EMD). The efficiency of EMD was investigated by using sheep mandible distraction model.
Key Words: Electromechanical distractor, distraction osteogenesis, continuous distraction, sheep mandible, spontaneous distraction, activation period
MATERIALS AND METHODS
(J Craniofac Surg 2014;25: 1519–1523)
The Electromechanical Distractor
From the *Department of Plastic and Reconstructive Surgery, Gulhane Military Medical Academy, Ankara; and †3rd Main Jet Base Medical Center, Konya, Turkey. Received August 27, 2013. Accepted for publication February 16, 2014. Address correspondence and reprint requests to Andac Aykan, MD, Department of Plastic, Aesthetic and Reconstructive Surgery, Gulhane Military Medical Academy, 06010 Etlik, Ankara, Turkey; E-mail: [email protected]; [email protected] Presented at the Plastic Surgery Special Joint Meeting (Co-sponsored by Mayo Clinic), May 20–21, 2011, Konya, Turkey. The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000922
Electromechanical distractor is mainly composed of 2 components; electronical and mechanical (Fig. 1). Rotational encoder, electronic control unit (ECU), and direct current motor are the components of the electronical part. The rotational encoder is used to detect the amount of rotation and to send these data to the microprocessor, which is located within the ECU. The information coming from the rotational encoder is evaluated by the microprocessor, and the run or stop decision is made by the DC motor (Fig. 2). Simulation and analysis of the electronic system were performed using software (Proteus Design Suite; Labcenter Electronics, North Yorkshire, England). The result of this analysis revealed that the circuits need an electrical current of 0.50 μA. The lithium cell battery (3.6 V) was selected as an energy supply unit. The ECU is the electronic component of the EMD. By using the display panel on the ECU, the amount of distraction (distraction distance, D) was
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
Aykan et al
FIGURE 3. The mechanical parts of the EMD. By using different diameter gears, movement resolution and gain of force were improved.
FIGURE 1. Electronical and mechanical components of the EMD.
monitored. The ECU was designed to allow the clinician to adjust the rate and rhythm via the display panel at the beginning of the distraction process. The mechanical part is composed of gear wheels and shaft (Fig. 3). The motion which was provided by the DC motor was transferred to the shaft by gear wheels. All mechanical units were designed by a software (SolidWorks Dassault Systèmes, SolidWorks Corp), and mechanical evaluation of fracture and strength analyses were performed on computer before the application of the EMD.
Surgical Procedure Five adult female sheep (age, 2–3 y; mean weight, 55 kg) were used in this study. All animal experiments were performed in accordance with the approved protocol of the scientific research board and ethics board of animal experiments. Each sheep was operated on under general anesthesia after 14 hours of nutritional abstinence. Anesthesia was induced through intravenous application of midazolam (0.2 mg/kg; Dormicum; Roche, Basel, Switzerland) and propofol (3 mg/kg; 1% Propofol-Lipuro; Braun, Melsungen, Germany), and after endotracheal intubation inhalation, anesthesia with isofluran (Isofluran-Lilly; Lilly, Giessen, Germany) was performed. The submandibular and cheek hairs were shaved using an electrical shaver, and the surgical area was disinfected using 10% povidone-iodine solution. Ten minutes before incision, a regional subcutaneous infiltration with 10 mL of 1% lidocaine (Xylocain; Astra Chemicals, Hamburg, Germany) was applied. The skin flaps were raised to expose the mandibular bone after a 4-cm longitudinal incision in the right submandibular area. The mandibular cortex was cut across the mandible using an electrical saw just 2 cm anterior to the angulus mandible (Fig. 4). The 2 mandibular segments were separated completely at the corticotomy line using a small bone chisel. Four holes were opened at both sides of the osteotomy line using an electrical drill, and pins were inserted. Then, the mechanical part of EMD was placed and fixed using screws. Subcutaneous tissues and skin were reapproximated in layers.
FIGURE 2. Schematic diagram showing the working principle of EMD.
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Postoperative Care Postoperative analgesia was provided with intramuscular injection of 0.01-mg/kg buprenorphine (Temgesic; Reckitt and Colman, Hull, United Kingdom) and 0.8-mL/kg carprofen for 2 days. Antibiotic prophylaxis was administered daily with subcutaneous injections of baytril (5-mg/kg enrofloxacin; Bayer AG, Leverkusen, Germany) for 3 days postoperatively.
Distraction Protocol After 5 days of latency, the ECU was secured on the neck area of the sheep and connected to the mechanical part of EMD (Fig. 5). The ECU was programmed to a distraction rate of 0.30 mm per 8 hours; then, the EMD was activated. The bone was lengthened for 20 days before the device was turned off. During the activation period, the distraction process was observed on the ECU daily without any intervention to the EMD. The ECU was disconnected from the neck area at the beginning of the consolidation period (Fig. 5).
Assessment The animals were killed on the sixth week after the consolidation period, and 5 distracted mandibles were examined through macroscopic observation and radiology. After removing the distractor from the sheep, the distracted mandibles were isolated from soft tissue and periosteum. New callus formation in the distraction gap was evaluated through direct radiography and computed tomography (Toshiba Aquilion). The sagittal volumetric computed tomographic images were obtained with a slice thickness of 0.5 mm, and
FIGURE 4. Intraoperative views of the surgical stages. After the marking of the mandible, monocortical osteotomy was achieved using an electrical saw (upper left). The holes were opened using a drill (upper right). Osteotomy was accomplished using a bone chisel (lower left). Pins were inserted, and the EMD was placed (lower right).
© 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 4, July 2014
FIGURE 5. The ECU was secured to the neck area of the sheep (left). After the distraction period, the ECU was disconnected from the neck area (right).
new callus length was measured by using software (Vitrea 2 4.1.2.0 version imaging software). The mean distraction length was calculated.
RESULTS Surgical procedure and postoperative care were uneventful. The animals were checked daily by veterinarians, and there was no significant change in body weight. Active distraction was painless for the animals and easy to handle. The distraction procedure was completed without any electronical and mechanical problem. The bone movement of bone segments was easily achieved, and there was no failure of the distraction devices.
Macroscopic Evaluation New callus formation was observed on the mandibular distraction gaps after the isolation of soft tissue and periosteum (Fig. 6).
Radiology New callus formation was observed on computed tomographic images (Fig. 6). New callus length was found to be, in average, 18.28 ± 0.19 mm.
DISCUSSION Because of the device-related drawbacks of DO, novel distraction devices were developed by various researchers.12–20 Improved patient compliance and decreased postoperative visit frequency were aimed in all of these experimental studies with self-activating distractors. As mentioned before in the comprehensive review of the distraction devices by Goldwaser et al,21 new designs of automated, continuous distraction would eliminate the need for patient participation in this process. Therefore, we developed a fully automatic EMD for continuous mandibular DO. Various methods of power were chosen for providing the mechanical movement of the device for distraction.12–20 Basically, electrical motors, springs, or hydraulic systems are used for continuous distraction. Because of some of the disadvantages of the spring-driven devices, the motor-driven and hydraulic systems have more potential for future applications.21 The major drawback of spring-driven devices is the generation of force. The force generated by the spring-driven devices is at maximum level when the spring is fully compressed in early distraction but gradually decreases as the spring expands in the later period.21 Moreover, the distraction process is not reversal in the spring-mediated systems and cannot be adjusted once the distraction is activated. The developed hydraulic distractors had functioned successfully in providing continuous distraction.18–20,22 However, when the distraction device is located internally, it still needs a flexible hydraulic tube connection that exits the skin to an extracorporeal steering unit. Although it is an internal device, this hydraulic tube connection may increase the risk for infection. The critically sized bone defect that had been created in the sheep mandible was successfully
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reconstructed with hydraulic distraction device automatically by Ayoub et al.22 Of the 8 sheep, 2 animals were excluded from the study because of postoperative complications. Despite the satisfactory treatment with antibiotics, 4 animals (66.6%) had developed infection between the second and third postoperative days at the site of the connection tube. Similarly, in the study of Wiltfang et al,19 1 animal had developed a local inflammation (16.6%) where the hydraulic tube emerged from the skin and treated with antibiotics. It seems that, although the device was located internally, the flexible hydraulic tube's access site on the skin provides an important foundation for the development of infection. Although the device was located externally, there were no animals that had infection in our study. The EMD was fixated to the bone segments using 4 steel pins, which passed through the skin. Compared with the internally applied hydraulic devices that have only 1 skin opening to the external environment, the EMD had 4 skin openings for stabilization of the device to the bone segments using pins. However, low infection rate in EMD application compared with the hydraulic devices shows that it may not be related only to the skin openings to the external environment. The size of the skin openings and the material composition that passed through the skin may be associated with high infection rates. A flexible tube whose structure is not fully specified in the literature was used for connection between the internal distractor and an external steering unit in hydraulic systems.22 Because of the flexible behavior of the connection tube, it is suggested that the tube is probably composed of plastic material in these designs. This could be facilitating the bacterial adhesion and transmission from external environment. The diameter of the flexible tube that carries the fluid was not indicated in studies. The hydraulic distractor used in the study of Wiltfang et al19 consisted of a cylinder and a piston. The cylinder had an external diameter of 9 mm, and the flexible tube was connected between the external steering unit and cylinder. Accordingly, the diameter of the connection tube that passed through the skin was nearly 1 cm. Similar to other articles, tubes of the same diameters were used as seen in device photographs.18,23 This may provide the substantial amount of skin openings that facilitate the development of infection. Three of the novel distraction devices were motor-driven and successfully generated sufficient force to move the bone fragments in the literature.12–14 However, none of the motorized device allowed the clinician to measure progress without taking radiographs.12–14 The amount of distraction (distraction distance, D) was monitored with our newly developed EMD on the display panel. Moreover, the EMD allowed the clinician to adjust the rate and rhythm via the display panel and the electrical control unit at the beginning of the distraction process. The ECU was designed to provide the distraction rate in millimeters, and distraction periods in days were observed using the digital display located on the ECU. When designing a new device, it is essential to choose a suitable experimental model for preliminary studies. Small-animal models were mostly selected in studies that were subjected to automated
FIGURE 6. New callus formation was observed on the distraction gap (left) and computed tomographic image (right).
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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Aykan et al
mandibular DO in the literature.14–17 Small experimental mandible models for distraction have some advantages in comparison with the larger animal models, including lower cost, easy handling, and simple housing.24 However, these criteria are not suitable for the application of automated distractors to humans. To provide a clinically relevant model, the newly designed automated mandibular distraction device should be tested on animals whose mandibles are more similar to the human mandible. The similarity of the sheep mandible to the human mandible consists of not only anatomic or macroscopic properties but also physiologic properties.25,26 The physiologic similarities of the sheep mandible to the human mandible, in terms of distraction, have been revealed by Knabe et al.25 Growth factor expression after clinical mandibular DO in humans and its comparison with existing animal studies were reported by Knabe et al,25 and the authors found that the expression pattern of growth factors secondary to human DO closely resembled those observed in the sheep model. This similarity was also mentioned in studies performed by Ploder et al13 and Ayoub et al.22 Because of all these similarities, the sheep mandible model was selected in our study. However, the edentulous area between the anterior and posterior teeth on the ramus of mandible was selected as localization for osteotomy by these researchers.13,22 Swennen et al11 presented a comprehensive review about craniofacial DO, and in this review, they reported that, in the clinical setting, mandibular distraction was performed most frequently at the angle of the mandible. Although the location of the ramus of the mandible of the sheep is convenient and an easy area for the procedure, we think that the angulus mandible should be the preferred area for experimental models to create a clinically relevant model. For that reason, contrary to other studies, the angulus mandible was selected in our study. Mandibular DO is performed with external or internal devices in clinical applications, and there are advantages and limitations of each. Placement of intraoral devices reduced facial scarring and dislodgment compared with that of external devices.27,28 Despite the advantages of the internal device in this respect, external devices are used more often today in mandibular DO.11 Similar to clinical practice, we designed this prototype as external device and did not observe any complication. However, it is necessary to reduce the device dimensions for future human application. The effect of high distraction frequency resulted in a more rapid course of osteogenesis, which was shown by Ilizarov in the late 1980s.29,30 In addition, these studies showed that increased frequency of distraction improved the quality of new bone. More recently, similar findings were supported by other studies.19,31 However, the devices available today for clinical applications in the field of DO do not allow continuous distraction. In routine usage, the distraction process is achieved through manual activation of the distractor. To provide the high frequency distraction rate with short distance steps, the device must be manipulated more often. This also increases the probability of physician-dependent error. These problems can be overcome by the development of distraction devices that provide continuous distraction. By using EMD, high distraction frequency with regular intervals was achieved in our study. Moreover, the physician-dependent activation of distraction device was eliminated. The ECU was programmed to a distraction rate of 0.30 mm per 8 hours in our experimental design. However, by using a more advanced engineering design of EMD, higher frequency rate of DO can be achieved in future studies. However, even in the current design, EMD has the potential for high-resolution movement capacity when compared with the human hand.
CONCLUSIONS In this preliminary study, we reported a newly designed EMD that allows the desired period (frequency) and the amount
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of distraction (rate) with high-resolution movement capacity when compared with manual distraction. In addition, humanindependent activation of the EMD was shown to provide great ease for DO. The clinical use of the device will be facilitated by advanced engineering studies that will result in reduced distractor size and weight. Moreover, by the inclusion of the remote data transmission system to the EMD, dependence between the patient and the physician may be completely eliminated during distraction period. ACKNOWLEDGMENTS The authors thank Nisa Cem Oren, MD, and Yalcin Bozkurt, MD, for the evaluation of the radiologic images.
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26. Aykan A, Ozturk S, Sahin I, et al. Biomechanical analysis of the effect of mesenchymal stem cells on mandibular distraction osteogenesis. J Craniofac Surg 2013;24:169–175 27. Shetye PR, Warren SM, Brown D, et al. Documentation of the incidents associated with mandibular distraction: introduction of a new stratification system. Plast Reconstr Surg 2009;123:627–634 28. Davidson EH, Brown D, Shetye PR, et al. The evolution of mandibular distraction: device selection. Plast Reconstr Surg 2010;126:2061–2070 29. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues: I. The influence of stability of fixation and soft-tissue preservation. Clin Orthop 1989;238:249–281 30. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues: II. The influence of the rate and frequency of distraction. Clin Orthop 1989;239:263–285 31. Kessler P, Neukam FW, Wiltfang J. Effects of distraction forces and frequency of distraction on bony regeneration. Br J Oral Maxillofac Surg 2005;43:392–398
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