In 1992, McCarth et al. first reported four cases of extraoral traction lengthening of the mandible, introducing distraction osteogenesis (DO) to the field of oral and maxillofacial surgery in the first place. The application of distraction osteogenesis in the mandible is more mature, but its application in the maxilla and mid-facial skeleton is more limited due to the complex anatomy of the mid-facial region and its morphological and structural differences with the long bones. Since 1993, some traction osteogenesis techniques have been reported for the treatment of midface deformities and defects caused by cleft lip and palate, trauma, surgery and craniofacial syndrome.
1. Correction of congenital deformities of the maxilla
The application of DO in the midface was first reported in 1993 by Rachmiel et al. They applied the traction osteogenesis technique to successfully sagittally lengthen the midface skeleton in adult sheep and made a series of studies on the traction process, imaging and histological examination, and postoperative recurrence. In 1995, Cohen et al. reported the use of an orthodontic arch expander adapted for traction osteogenesis in children with half of the facial hypoplasia and confirmed the vertical and sagittal lengthening of the maxilla and the formation of new bone with the aid of 3D CT. They then performed anterior maxillary traction after LeFort I osteotomy in two children with cleft lip and palate secondary to maxillary hypoplasia.
The treatment of maxillary hypoplasia secondary to cleft lip and palate is by far the most used area of maxillary traction osteogenesis, and Mofid et al. concluded that such patients accounted for about 40% of the midface traction osteogenesis in 3278 cases. Since the mid-1990s, the Rigid external distractor (RED) has been used extensively in the treatment of maxillary osteogenesis in patients with cleft lip and palate with satisfactory results. The most commonly used REDs are the KLS Martin and Jacksonvile products. These external retractors can adjust the traction direction and angle during the traction process according to the needs, and can meet the needs of Le Fort I or Le Fort II or III traction and multidirectional traction by relying on the joint connection between different components and the combination of different components. At present, KLS Martin’s RED II system is the most representative extracranial traction device. According to the experience of our department since the 1990s, the maxillary built-in retractor is less used at present because of the inability to control the direction of traction and the need to keep the bilateral position parallel when placing the retractor, but it is more difficult to operate, and it is not easy for the patient to perform traction during traction because the traction bar is located in the patient’s mouth during traction, and it needs to be removed in the second stage of surgery. Of course, the external retractor also has its disadvantages, its device is more complicated, and it has a greater impact on the patient’s normal social life, especially during sleep, such as the use and care of not only, it is easy to lead to secondary infection, and even retractor breakage, fracture and other accidents.
Although the traditional orthognathic surgery forward displacement of the maxilla adopts a strong internal fixation technique, the magnitude of the forward displacement of the maxilla is still limited due to the large amount of scar contraction in the palate, and the risk of recurrence is higher if the forward displacement distance is too large. In contrast, anterior maxillary traction can significantly reduce the recurrence rate of maxillary anterior displacement in cleft lip and palate patients due to new bone production in the osteotomy gap, and osteogenesis while correspondingly lengthening the surrounding soft tissues and avoiding problems such as increased palatopharyngeal closure after orthognathic surgery. In contrast, Chanchareonsook et al. studied the effect of conventional Lefort I orthognathic surgery with anterior displacement versus DO anterior displacement on the short-term postoperative palatopharyngeal closure function in a randomized group of patients with cleft lip and palate requiring anterior displacement of the maxilla, and no abnormalities were found between the two groups. evaluation.
In cases of severe maxillary lateral hypoplasia, surgically assisted cortical osteotomy is generally used to assist in the expansion of the arch, which is actually part of the traction osteogenesis category. In the late 1980s, a bone-supported maxillary arch expander was first applied abroad for rapid arch expansion (Transpalatal distrator, TPD), thus effectively avoiding the shortcomings of the traditional tooth-supported arch expander such as tooth tilting, root exposure, alveolar bone resorption, and higher recurrence rate, and it should be said that the bone-supported maxillary rapid arch expander is the future trend for the treatment of maxillary The trend of lateral underdevelopment.
In addition, Monasterio et al. performed simultaneous maxillary and mandibular traction after Le Fort I osteotomy and mandibular ascending osteotomy for patients with hemifacial dysplasia, and obtained good treatment results by fixing the maxilla and mandible with intermaxillary ligatures and then traction as a whole to maintain the original occlusal relationship.
2.Craniomaxillofacial deformity orthopedic treatment
The common craniomaxillofacial deformities often involve multiple anatomical regions in the middle of the face, and the traction osteogenesis of the middle of the face involves not only the maxilla, but also the nasal bone, zygomatic bone, frontal bone, etc. Generally, it is necessary to perform Lefort II or III osteotomy, and many scholars have researched in this area. The results demonstrated that simultaneous traction osteotomy of the midface in multiple directions could correct complex midface deformities.
Cedars et al. performed LeFort III osteotomy and traction osteogenesis in 14 patients with severe midfacial depression deformity. They also conducted a series of studies on postoperative complications, changes in x-ray cephalometric measurements, respiratory, phonological, and visual changes. In the 1-year postoperative follow-up of 7 patients with preoperative OSAS, they found that all 7 patients showed significant improvement in their symptoms, including 3 patients who relied on continuous positive airway pressure (CPAP) before surgery, and 1 of 2 patients who underwent tracheostomy for severe OSAHS before surgery had the cannula successfully removed after surgery and their OSAHS symptoms disappeared. The other patient also showed significant improvement in postoperative hypoxia. Lu et al. reported a patient with Crouzon syndrome with OSAHS treated by Lefort III and modified Lefort I osteotomy with a maximum anterior displacement of 35 mm and significant postoperative improvement. Since severe maxillary and midface hypoplasia often cause OSAHS due to upper airway obstruction, DO is a highly desirable option for severe midface hypoplasia with OSAHS symptoms.
For the treatment of some complex deformities with severe craniomaxillofacial syndromes, such as Crouzon syndrome mentioned above, as well as Apert syndrome and Treacher Collins syndrome, DO has been increasingly emphasized by clinicians and plays a very important role.
Mu Xiongzheng et al. reported 8 patients with Crouzon syndrome and Apert syndrome who underwent Lefort III osteotomy anterior traction surgery using the RED II system, with an average anterior displacement of 9 mm and a drop of 1.5 mm in the midface, with no significant recurrence at 5 months of postoperative follow-up. Mezzini et al. followed up 17 children who underwent Lefort III DO (mean age at surgery 7.3 years) for up to 10 years (mean 6.1 years) and found stable long-term outcomes. Holmes et al. performed Le Fort III traction osteogenesis in seven patients with craniomaxillofacial syndrome using an internal retractor, resulting in different degrees of midface lengthening in multiple directions. Mealing et al. also reported 7 cases of Lefort III osteotomy with internal retractors, with a mean anterior displacement of 23 mm, and the main postoperative complications were nasal septal deviation, temporary dentition in one case, and postoperative tearing in one case.
Our experience in mid-facial DO surgery is that Lefort II osteotomy can be performed with a traditional coronal incision or a small facial incision combined with an intraoral incision, whereas Lefort III osteotomy is generally performed with a coronal scalp incision, which is more traumatic. The external retraction device is easy to control the direction, and the angle and direction of retraction can be adjusted according to the treatment needs in time during retraction, and the control of bone movement is better. In addition, we also found that the fixation force of the built-in retractor was poor during internal traction, and the bone in the middle of the face had a tendency to move downward by gravity after disconnection, and this unplanned displacement might affect the effect of traction. The external retractor has a stronger fixation force, but it is easier to develop secondary skin infection at the skull fixation.
3.Orthodontic treatment of acquired deformity in the middle of the face
Trauma and tumor resection are one of the common causes of mid-facial bone defects, and bone graft repair is currently the more commonly used method for correction. However, due to the complicated and traumatic technique of bone grafting, which is restricted by the bone source, the function of the graft area is often impaired after autologous bone extraction, and the grafted bone is also prone to necrosis, displacement and resorption, therefore, how to develop a less traumatic and more effective repair method is a common concern for oral and maxillofacial surgeons and plastic surgeons. Tissue engineering techniques are still some time away from real clinical application, and traction osteogenesis as an “endogenous tissue engineering technique” has become one of the ways to reconstruct jaw defects. However, because the maxilla lacks a relatively regular morphological structure similar to that of the mandible, DO repair of maxillary defects has yet to be further improved in basic theory and practice, and is currently limited to the treatment of smaller maxillary defects such as alveolar process defects and small maxillary defects.
In 2001, Henkel et al. reported the application of DO on a porcine alveolar process cleft model to close the cleft and apply it to clinical use; Jensen et al. increased the vertical height by traction for patients with alveolar ridge defects to meet the need for implantation; Hong Kong scholar Zhang Qian et al. reported the animal experiment of using transfer disc traction to reconstruct the posterior maxillary defect in monkeys, and because of the similarity between monkeys and human species, the experiment provided a basis for clinical application The experiments provided a certain feasibility basis for clinical application. We established a model of anterior maxillary defect in goats (average defect 12.7 mm), and traction was used to reconstruct the anterior maxillary defect after making the anterior maxillary transfer disc and installing the traction device at the same time, and the quality of bone formation was observed by 3D CT and histological examination after surgery.
For the treatment of acquired defective deformity in the middle of the face, our department’s experience is mostly limited to partial maxillary defects (defect area less than 1/2). If DO repair is used, it is usually necessary to design individualized retractors to adapt to the characteristics of different parts of the maxillary defect morphology, and because the maxillary morphology has curved characteristics, the retraction course is long, and it is often difficult to achieve the repair treatment needs with general finished retractors. We have performed individualized DO treatment for several patients with partial maxillary defects and achieved relatively satisfactory results. For DO repair of alveolar fissures, the clinical application is less frequent due to the irregular fissure morphology, partial accompanying oronasal fistula, and insufficient amount of soft tissue. Reviewing the literature, traction repair of larger maxillary or mid-facial defects has not been reported. In view of the advantages of traction osteogenesis, although the practical application of traction osteogenesis for maxillary defect reconstruction is still immature, traction osteogenesis provides a new way of thinking for the reconstruction of maxillary defects.
4.Progress of mid-facial DO
Computer-assisted surgery has become increasingly mature and has become one of the directions of development in the field of oral and maxillofacial surgery, which also covers the field of anterior traction osteogenesis in the midface. Samehukou et al [18] simulated the process of mandibular traction lengthening and widening by means of a calculator and concluded that the traction direction of the tractors on both sides of the mandible must be parallel to avoid adverse biological forces, which is also applicable to the traction osteogenesis of the maxilla. Gateno et al. reported a computer simulation of seven patients with jaw deformities caused by hemifacial hypoplasia, Nager syndrome, and Treaeher Collins syndrome, and analyzed the required osteotomy line, the optimal position of the retractor placement, the angle of the retractor attachment and the direction of retraction for multi-directional retraction in different patients during the actual treatment process. This provides an important reference basis for the accuracy of the actual operation. Zhu Min et al. also used the CASSOS system to simulate and predict the changes of soft and hard tissues before and after maxillary traction osteogenesis, and the predicted results showed a high similarity with the comparison of the results after surgical fainting. Computer-aided surgical techniques can perform 3D image analysis of the maxilla and midface, design of osteotomy lines, design and placement of individualized traction osteotomies, simulation of the traction osteogenesis process, and prediction of the results, etc. By simulating and predicting the surgical process and results, the blindness caused by experience alone can also be overcome. Currently, with the continuous development of software technology and stereoscopic photography, the prediction of the three-dimensional shape of the facial soft tissues after the movement of the jaws and the real-time three-dimensional facial shape, the so-called “four-dimensional” prediction, are being developed and applied.
Rapid prototyping technology allows surgeons to obtain a 3D prototype of the patient’s skull before surgery, analyze the characteristics of the defect on the model, design the traction osteotome and treatment plan, which is conducive to more accurate treatment planning, and largely avoid unnecessary expansion of the scope of surgery and trauma caused by the lack of understanding of the real situation of the patient’s jaws before surgery, and achieve personalized treatment. For patients with complex craniomaxillofacial deformities or defects, preoperative rapid prototyping has become one of our routine treatment tools.
The development of resorbable materials is also being applied to the field of distraction osteogenesis, and in 2001, Cohen et al. reported the use of a built-in distraction osteogenesis device using the MID system in combination with biodegradable materials for the DO treatment of patients with Crouzon syndrome. The traction device was removed at the end of the traction period, and a resorbable polylactic acid mesh plate was used to provide fixation and protect the new bone. The strength was reduced to approximately 70% after 9 months, 50% after 12 months, and completely degraded by hydrolysis after l8 to 36 months. The results demonstrate that the application of resorbable materials to some extent overcomes some of the existing disadvantages of the built-in traction osteotomies. In the mid-facial region, especially the Lefort III osteotomy traction can be used to replace the now commonly used metal retractors. However, due to the strength of the resorbable material, it may be more beneficial in pediatric patients.
The endoscopic-assisted Lefort I osteotomy with built-in maxillary retraction was reported as early as 2001, but similar studies have been rare this year, but with the concept of minimally invasive surgery gaining popularity, it is believed that endoscopic-assisted and computer-assisted navigation surgery will be applied to craniomaxillofacial traction osteogenesis in the near future.
The current theory of maxillary traction osteogenesis basically follows the tension-tension rule proposed by Ilizalov. However, the jaw bone differs greatly from the long bone in structure, blood supply, and growth pattern, and some scholars have proposed differences in the biological mechanism of jaw traction osteogenesis, traction rate, and other aspects of traction osteogenesis from the long bone. Weinzweig et al. also confirmed in animals that there was no significant difference in the quality of osteogenesis and postoperative recurrence with or without a pre-traction interval. Therefore, the basic theory of traction osteogenesis of the jaws still needs further study and improvement.
Although most reports suggest that postoperative complications are significantly lower than those of conventional orthognathic surgery, there are potential risks. We also had a case of skull fracture after RED II traction. It is important for clinicians to consider how this technique can be used more safely.