Distraction Osteogenesis Versus Orthognathic Surgery: Demystifying Differences in Concepts, Techniques and Outcomes

Abstract

Introduction

The popularity and interest evoked by orthognathic surgery and distraction osteogenesis are undisputed in the field of oral and maxillofacial surgery. However, questions regarding the individual identities of either of them with clarity in their concepts, techniques and outcomes have remained unanswered. The aim of this review is to shed light on these questions.

Methods

This review is structured as a narrative review of thirty years of literature available in the specialities of orthognathic surgery and distraction osteogenesis.

Conclusion

The authors present a review of existing literature combined with contrasting experience gained over the years in providing an overview of the merits and demerits of the two surgical techniques which will aid the clinician in justifying the use of one technique over the other.

Background for This Review

In the United States of America, there were about a hundred thousand patients operated for orthognathic surgery within a timespan of 9 years [1]. Since the first published case of Orthognathic surgery in 1849 [2] and the first report of Distraction osteogenesis in humans in 1992 [3], these surgical techniques have evolved significantly in many ways.

Precious et al. [4] remarks that, “Orthognathic surgery consists of a constellation of procedures that permit differential alteration and repositioning of bone, cartilage, muscle, teeth, gingiva, mucosa, and skin”, while distraction osteogenesis is described as a biologic process of new bone formation between the surfaces of bone segments that are gradually separated by incremental traction [5].

About 18 years ago, the first publication on the long-term results of distraction osteogenesis was published by McCarthy et al. [6], in which he elucidated his 11-year experience with mandibular distraction osteogenesis and summarized that it produced clinically favourable results. Later, Shaw et al. [7] did a critical appraisal of 88 studies on distraction osteogenesis and found that almost all publications were based on retrospective studies, with short-term evaluation of a limited samples from heterogeneous patient populations, lacking controls. He proposed the need for a prospective registry, for objective distraction osteogenesis research.

Distraction osteogenesis (DO) and orthognathic surgery (OGS) have been widely indicated in many deformities of the craniofacial region. However, there still is great uncertainty as to which is the ideal choice of correction, especially in terms of clinical indications, patient-related outcomes, such as stability, long-term influence on growth, socio-psychological implications and quality of life. This also needs to be studied with variations in satisfaction and social support among different ethnic groups [8]. Given the lacunae in literature for well-designed clinical trials and publications with higher levels of evidence, we undertook this literature review to present a comprehensive report of how various parameters fare when comparing distraction osteogenesis and orthognathic surgery. This is a unique literary review that undertakes a comprehensive comparison of pre-operative, intra-operative and post-operative parameters involved with both treatment modalities. The aim is to present the plethora of evidence appraised regarding vital parameters to be considered prior to decision making between distraction osteogenesis and orthognathic surgery.

Pre-operative Planning

Age

Distraction osteogenesis is versatile and can be performed at any age, from neonates to adults as long as the patient is physiologically capable to undergo surgery [9]. The common indication for neonatal mandibular distraction osteogenesis (MDO) is to ameliorate the difficulties encountered during breathing and feeding in patients with Pierre Robin sequence (PRS) [10–12] and Treacher Collins syndrome (TCS). Distraction osteogenesis has shown predictable success in children and adolescents [13, 14] and can be safely performed even in older ages [15].

Orthognathic surgeries are not performed in neonates and young children and are generally recommended only after the skeletal growth completion occurs [16], as there might be growth spurt variabilities, which will probably necessitate future interventions. In rare instances, they may be performed early.

Pre-operative Imaging and Planning

Distraction osteogenesis warrants computed tomographic (CT) scanning for pre-operative planning. CT scans divulge the finer details of the anatomic variations, which allow proper planning of the vectors, aid in locating the tooth buds, the inferior alveolar nerve, and also in assessing the temporomandibular joint [17, 18]. Stereolithographic models can be fabricated and the distractors can be adapted pre-operatively to reduce operative time. There are no patient-specific or customized distractors that have been developed.

Radiographs like orthopantomograms, lateral cephalograms and postero-anterior cephalograms suffice in the treatment planning for orthognathic surgeries, unless the procedure is planned with computer-aided design/computer-aided manufacturing (CAD/CAM) technology to fabricate customized splints, cutting guides and patient-specific implants (PSI).

Distraction osteogenesis doesn’t mandate complex virtual pre-operative planning to simulate three-dimensional (3D) movements, whereas in case of osteotomies that involve 3D movements of maxillomandibular complex, virtual planning software that incorporate DICOM data are commonly employed [19], in recent times.

Movements

Quantum of Bone Movement

When an acute movement of bone is performed through orthognathic surgeries, advancements of more than 7 mm are not advisable and those of more than 10 mm are considered to be with an elevated risk of relapse [20, 21]. The lack of immediate adaptation of soft tissue envelope around the new position of bone influences the stability by the stretch mechanisms and possible proprioceptive functions. Movements of more than 7 mm, involving LeFort I or higher-level advancements, have a propensity for non-union and relapse, therefore, definitely warrant bone grafting to make them more stable and achieve primary healing [22–24].

Distraction osteogenesis is a popular modality for larger advancements of 10 mm or more [25], as it remains relatively stable [26]. In patients with syndromes or with cleft maxillary hypoplasia, who present with higher magnitude of deficiencies, distraction osteogenesis is the preferred method of choice, due to excellent post-operative stability [27–30] and the concomitant histogenesis [29], thereby producing superior aesthetic and functional results.

Prediction of Bone Movement

Vector control is crucial in the planning for distraction osteogenesis [31], where the placement of the distractor dictates the primary vector. External distraction devices offer flexible vector control and better predictability, when compared to internal devices, due to the ability of vector change during the distraction period [11, 29, 32]. With internal distractors, the vector is difficult to manoeuvre during distraction period, except for a few multi-vector internal distractors [33]. When moving large composite segments like LeFort II or III, the combined use of external and internal distractors is advised, for superior vector control and stability after osteotomy. The activation of the distractor by 1 mm should ideally yield a movement of the same quantum. However, while external devices maintain higher accuracy of vectors in linear advancements, internal devices may induce rotational movements [34].

Orthognathic surgery offers, in most instances, predictable movements through precise pre-operative planning [4, 19] and intra-operative usage of splints to optimize the bone position [35]. Shirota et al. published that a mean error of < 1.03 mm on the 3 axes was observed between pre-operative simulation and post-operative CBCT images with intra-operative navigation surgery [36], which suggest that simulation-guided navigation makes accurate post-operative outcomes possible in orthognathic surgeries.

Directions of Bone Movement

A major drawback of distraction is that impaction, setback or compression of bone is not possible [37].

Orthognathic surgery provides the possibility of bone movements in multiple directions in space [27], including retraction, and correction of discrepancies like vertical maxillary excess [4].

Three-Dimensional Bimaxillary Movements

Kim et al. remarked that orthognathic surgery can offer complete movement of the entire maxillomandibular complex, which acts as a rigid body with six degrees of freedom in 3D space. The movements include translations in the anteroposterior, lateral, vertical directions and rotations around the x-, y- and z-axes, commonly called the pitch, roll and yaw rotations. They can be evaluated by a 3D surgical treatment objective (STO), which can be done precisely and as a single step through CAD/CAM technology [19].

It is difficult to manipulate 3D movements of the maxillomandibular complex, in a single stage through distraction osteogenesis [11, 29]. Multiple distractors may be used combined or sequentially; however, precise vector control may be challenging, as in facial asymmetry cases.

Surgical Procedures

DO as Interim Procedure

Distraction osteogenesis can be used as a part of a staged surgical treatment plan to achieve early correction from childhood, to minimize the deformities in patients with severe skeletal discrepancies [11, 29]. It does not induce permanent growth in the regions of genetically determined growth centre deficits [14]. Hence, it can be used as an interim procedure to minimize the quantum of deformity, providing a socially acceptable appearance.

Orthognathic surgery has limitations and cannot be used as an interim procedure and is preferred after growth completion [38]. Osteotomies in the growing patients will necessitate future interventions, as growth spurts would produce changes in the final maxillomandibular relationship.

Composite Distraction Versus Multiple Osteotomies

Multiple independent distraction of the bone segments in the naso-maxillary zygomatic complex aren’t commonly performed.

Orthognathic surgery offers the possibility of movements of the bone segments in the naso-maxillary zygomatic complex through simultaneous LeFort I and LeFort III osteotomies, followed by fixation separately [39].

Calvarial Deformity Correction

While correcting calvarial deformities in paediatric patients with osteotomies, there is an absolute necessity of intervening bone/cartilage grafts and resorbable plates to be used [40], as indicated in brachycephaly and craniosynostosis.

Procedures like LeFort III distractions or frontoparietal (monobloc) distractions [41], negate the use of interpositional grafts. Posterior cranial vault distraction offers considerable advantage over posterior vault osteotomies in craniosynostosis patients and the usage of internal, resorbable distractors nullify the need for an additional surgery [42].

Multiple Segmentations

Orthognathic surgery offers the possibility to address the segmental discrepancies of maxilla or midface, by separating them into predetermined segments during surgery [27], and requires intricate planning and intra-operative splints.

Three or four pieces of segmentalization is not an option while performing distraction osteogenesis [37], because they will make the distraction segments unstable [33].

Obstructive Sleep Apnoea

Paediatric

In severe forms of syndromic mandibular deficiencies and maxillary hypoplasia, distraction osteogenesis is the initial modality of treating obstructive sleep apnoea (OSA) [11].

In temporomandibular joint (TMJ) ankylosis, pre-release distraction has been advocated [43] to correct OSA for immediate airway improvement and better vector control of distal mandibular segment against stable proximal ankylosed ramus component.

Orthognathic surgeries don’t have a role in paediatric OSA management.

Adults

Though maxillomandibular orthognathic rotation advancements are mostly preferred for OSA correction, distraction of isolated mandible/maxillomandibular complex is performed prior to ankylotic release similar to the paediatric group.

Transverse Skeletal and Dental Discrepancies

Distraction osteogenesis is the best option for transverse skeletal discrepancies, as it obviates the need for extractions and proximal stripping, to gain space in the upper and lower arches [27] and to achieve facial fullness.

Orthognathic surgeries require transverse discrepancy management and space gain before surgery; hence, extractions and proximal stripping play a vital role in planning [44].

Segmental Defects

Transport distraction osteogenesis offers the possibility of reconstructing continuity defects of the maxillofacial region [45]. It can be achieved through incremental movement of one (bifocal distraction), two (trifocal distraction) or three (quadrifocal distraction) viable bone segments across a defect [46].

Orthognathic surgeries cannot replicate this movement and are not indicated for bridging segmental defects.

Irradiated Cases

Distraction osteogenesis has been successfully performed in conditions with compromised vascularity like irradiated mandibles. Confirmation of bone viability and the condition of surrounding soft tissues are vital parameters in ensuring the success of distraction in irradiated cases [47].

A conference abstract was the only mention of a bimaxillary osteotomy performed for correction of obstructive sleep apnoea, 2 years after radiation to the mandible. They report no long-term results [48].

Compromised Bone Quality

Bone regeneration has been observed after distraction osteogenesis, in suboptimal clinical situations like scarred tissues wherein the native periosteum had been destroyed [49].

Orthognathic surgeries can be performed only in situations, wherein there are no disruptions of periosteum and with healthy soft tissue cover. Osteotomy cuts raise the risk of unfavourable fractures and bad splits in patients with low bone mineral density disorders like osteoporosis [50, 51].

Condylar Hyperplasia/Hypertrophy

Distraction osteogenesis has no role in managing situations like condylar hypertrophy/hyperplasia, as it doesn’t influence the growth centre, which is actually the etiological factor. As mentioned earlier, distraction is futile when impaction, reduction or compression movements are required.

Surgical interventions for condylar hyperplasia either in isolation or with maxillomandibular osteotomies are the treatment of choice in such pathologies at appropriate age [52].

Neo-condyle Rehabilitation

In patients with TMJ ankylosis, after resection of the ankylotic segment, reconstruction can be done with neo-condyle distraction using the ramus segment [53]. Animal studies have demonstrated that the biomechanical properties of neo-condyle, under functional loading are equal to that of physiologic condyle. Histological analysis has revealed the distraction gap filled with collagen fibrous tissue gets gradually replaced by mature bone after 24 weeks postdistraction [54]. A pseudo-meniscus is formed by the fibrocartilaginous cap at the advancing front of distraction, replicating a normal anatomic form.

Orthognathic surgery can also be employed as a modality to achieve this by vertical sliding ramus osteotomies, where the stump of the posterior ramus can replace the condyle [55]; however, there is no formation of a fibrocartilaginous cap which will act as a pseudo-meniscus. Though there were reports of complete anatomic remodelling and stable function, diminution of the angle was one disadvantage that was observed [56].

Comparison of Costs

The procedure of distraction osteogenesis is more expensive [4, 57] than orthognathic surgery, due to costs associated with the distractors [28, 57] and the need for an additional surgery to remove the distractor [37, 57, 58]. In our experience, we have observed that there is a need for a longer stay in the hospital, for cases of transport distraction, which magnifies the cost.

Single jaw or genioplasty surgeries are performed as day care procedures, and hence, they cost considerably lower. Bimaxillary surgery with ancillary procedures like bone graft harvesting, necessitate a longer admission time when compared to single jaw procedures [59]. However, this is only comparing surgical costs and not the need for pre/post-operative orthodontics and possible functional appliances over time. Recent advances like customized surgical guides, splints and patient-specific implants could contribute to additional expenditure in orthognathic surgery.

Training and Learning Curve

Surgeons who wish to master distraction osteogenesis techniques will realize that there is a learning curve associated with it. While the technique and devices have undergone several changes over the years, it is imperative to have a thorough understanding of the process. This learning process has evoked the need to modify the existing distraction devices and creating newer ones, for better results with lesser complications [60]. To understand paediatric distraction and its outcome, the patients would need to be followed long term until growth cessation.

Orthognathic surgeries are still the workhorse for oral and maxillofacial surgeons and are in routine practice in more centres around the world when compared to distraction osteogenesis. This in turn may offer more opportunities for trainee surgeons to view them more frequently when compared to DO. Newer advancements like virtual 3D pre-operative planning [61], which produces more accurate results, might require additional training.

Intra-operative Factors

Anaesthetic Considerations

For placement of internal distractors, nasal intubation is preferred to prevent the interferences caused by the oral endotracheal tube. For placement of extra oral distractors, oral intubations can be practised. For distractor placement in TMJ Ankylosis, fibre optic intubation is ideal, due to lack of mouth opening and inability to visualize the vocal cords [62].

Nasal intubation is preferred in orthognathic procedures to facilitate the assessment of desired occlusion on table. Certain centres report submental intubation for orthognathic surgeries, for better intra-operative assessment of maxillary positioning and nasal profile [63]; however, there is no general consensus among surgeons.

Osteotomy Design

Distraction osteogenesis involves linear bicortical osteotomy separation but it can also be performed in certain instances with cortical scoring [12], like in neonatal distraction of Pierre Robin sequence or Treacher Collins syndrome, to serve the purpose of emergency airway improvement [10, 11].

In orthognathic surgery, specifically designed osteotomy cuts are done, for complete mobilization and movement of the osteotomized segments in different planes [24].

For patients undergoing LeFort I distraction, there is no necessity to down fracture the maxilla, but pterygo-maxillary dysjunction should be performed and the mobility of maxilla in anteroposterior direction should be achieved, to check free movement of the distractors without any interference.

Bone Grafting

As distraction osteogenesis eliminates the need for autogenous bone harvesting and grafting at the site of bone movement [4, 29], there is no donor site morbidity [9, 13, 64]. The only indication for bone grafting after distraction will be in cases of transverse deficiencies, specifically in areas of mandibular ramus or zygoma, to achieve optimal symmetry, if warranted.

In orthognathic maxillary advancements of more than 7 mm, bone grafts are desirable to stabilize the osteotomized segments [22–24]. This autogenous bone grafting has disadvantages like donor site morbidity, infection of the bone graft, resorption and subsequent relapse due to resorption [29]. Immediate bone grafting or the usage of synthetic substitutes for augmentation is an advantage of OGS over DO, as fixation of those can be done simultaneously.

Need for Overcorrection

For growing patients with facial asymmetry, who undergo distraction, mild overcorrection of the segments is advised [65], to catch up with the growth of unaffected side and also to reduce the later discrepancies that might occur during growth. In bilateral mandibular distraction, overcorrection to a skeletal class III maybe done to counter the future maxillary growth.

Overcorrection is not practised for orthognathic surgery patients, as they are operated after growth cessation with final planned occlusion in mind and due to the availability of custom-made calibrated titanium plates to reduce relapse, though in SFA, mandibular movements are performed with a horizontal overcorrection of 2 mm to adjust occlusion to the desired position post-operatively [66].

Necessity for Surgical Splints

When osteotomy cuts are placed in orthognathic surgery, it is imperative to use splints, which serve as an intra-operative guide to establish a pre-surgically planned occlusion. After facebow transfers and mock surgeries, guiding splints are fabricated for accurate intra-operative bone repositioning [35, 67]. CAD/CAM splints are used these days, for better accuracy and precision [35].

Surgical splints are not essential in distraction cases, as it only involves the mobilization of segments, followed by fixation of the devices.

However, in both the techniques, a surgical guide for placement of osteotomy cuts/implant fixation and for positioning of distractors can be used for surgical accuracy [68].

Role for Transfusion

Distraction procedures are less invasive with a lower necessity for post-operative blood transfusion [9, 64], due to minimal manipulation of hard and soft tissues. Bimaxillary orthognathic procedures have an increased propensity for post-operative blood transfusions [69] and authors report that, isolated maxillary orthognathic procedures have a higher rate of requirement for blood transfusions [70].

However, difference in the techniques for Lefort osteotomies and additional usage of tranexamic acid has shown to be very effective in controlling blood loss and thereby preventing the need for transfusion [71, 72].

Duration of Surgery

Incision to closure time for a distraction procedure for maxilla or mandible is lower than a similar procedure performed as an orthognathic surgery [9, 64]. The obvious reasons are that distraction cases don’t require intra-operative positioning in planned occlusion; there is reduced mobilization of segments, decreased blood loss and better visibility of the operating field. The duration of the surgery was found to decrease with increasing expertise to the procedure [28].

Post-operative Issues

Biomechanics of Bone Healing

Histologically, the healing process in sites of distraction osteogenesis differs from osteotomy in two basic aspects. There is an advantage of having a controlled microtrauma and an intramembranous ossification. The controlled microtrauma present during the activation phase of distraction stimulates osteoblast proliferation, bone extracellular matrix (ECM) synthesis and induces growth factors [73].

In orthognathic osteotomy sites, the healing is produced by endochondral processes, similar to fracture healing. The position and condition of the osteotomized bone segments are vital during repair. The cartilage matrix plays a vital role in the regulation of products that determine the maturation or apoptosis of chondrocytes and act as a scaffold for osteoblast progenitors. The vascular endothelial growth factor that is produced by hypertrophic chondrocytes has a fundamental role in the growth and differentiation of endochondral ossification [74].

Post-surgical Imaging

Distraction osteogenesis mandates, regular monitoring of the progress of the distraction regenerate consolidation, direction and dimension of movement, through serial radiographs. However, factors like radiation exposure and increased cost have led to the usage of ultrasonograms for repetitive evaluation, to determine the degree of bone formation [75].

Orthognathic procedures require post-operative radiographs to assess the degree of movement and fixation and will require further investigation should a complication arise.

Assessment of Post-operative Changes

Occlusion

Distraction osteogenesis has a tendency to cause mild to severe occlusal discrepancies as the movements are planned at basal bone level. In children, the changes in the dental occlusion after completion of distraction may be compensated by the appropriate eruption pattern of the permanent dentition. Posterior open bites and anterior cross-bite are the most common occlusal changes [58]. This occurs rapidly, due to the active vertical growth of the maxilla after it is released from the constriction effect of the hypoplastic mandible. In adults undergoing mandibular distraction, there will be severe alteration of dental occlusion, which will require prolonged orthodontic treatment or secondary orthognathic surgery [9, 57, 58].

Orthognathic surgery relies on planning and predictability. The patient undergoes presurgical orthodontics and the intra-operative final position is determined by the splint. After the surgical procedure, the patient is referred to the orthodontist to correct the expected post-operative changes in occlusion [27, 67]. Unexpected intra-operative complications like bad splits, condylar sag or post-operative complications like plate fracture could lead to occlusal discrepancies.

Condylar Position

Long-term studies in orthognathic surgery involving large forward and upward rotations of the maxillomandibular complex have produced a significant decrease in the joint space leading to greater degrees of remodelling in the posterior region of the condyle [76]. The bilateral sagittal split osteotomy is notorious for producing inadequate condylar positioning and displacement, which had led to condylar resorption and subsequent internal derangement [57, 67, 76, 77].

Distraction osteogenesis, which is performed for either anteroposterior or transverse discrepancies of the mandible, has lesser incidences of temporomandibular joint complications when compared with procedures like BSSO [57] or with vertical symphyseal step osteotomies [78]. However, if the vectors of distraction for bilateral mandibular distraction are not kept parallel, they have a propensity to develop lateral flaring of the proximal fragments [25]. In children with Pierre Robin sequence who underwent bilateral mandibular distraction, a significant decrease in the superior joint space was detected. These changes were consistent with the extent of the bone tissue newly formed and with the improvements in coordination and appearance of the children’s facial structures [79].

Velopharyngeal Changes

In patients undergoing maxillary advancement for moderate cleft maxillary hypoplasia of less than 10 mm, distraction osteogenesis has no significant advantage over orthognathic surgery in preventing velopharyngeal incompetence (VPI) or speech disturbances [80–82].

In patients with severe cleft maxillary hypoplasia of more than 10 mm, performing a Le Fort I osteotomy increases VPI in patients with pre-existing borderline VPI [83], but maxillary advancements achieved through distraction osteogenesis have markedly minimal effects on velopharyngeal competence [27].

Distraction offers a distinct advantage due to the ability to monitor VPI during the activation phase to quantify changes and to halt the process if needed.

Concomitant Histogenesis

One of the major advantages of distraction osteogenesis is the concurring distraction histogenesis. This phenomenon explains the simultaneous expansion of the soft tissues [29], including skeletal muscles, nerves, ligaments, fat, skin and gingiva [10], in concert with the lengthened bone, thereby producing excellent aesthetic and functional results [9, 14, 58]. Distraction histogenesis occurs due to the incremental traction of bone, which manipulates the soft tissue envelope around it to stretch, expand and regenerate during the process [49, 84].

In orthognathic surgery, as the facial bones are advanced in an acute fashion and fixed in its new planned position, the adjacent soft tissues are stretched and they tend to displace the bony segments back to their previous positions to a certain degree [77]. Orthognathic surgery changes the functional matrix (Moss functional matrix hypothesis), as muscular and soft tissue tension are altered following the surgical movements in an acute manner. Literature supports acute muscle stretching as a major reason for skeletal relapse following orthognathic surgery.

Additional Interventions

In patients with internal submerged distraction devices, an additional surgery is necessary, to remove the device [29, 37, 57, 58] and to excise the hypertrophic scarred tissue at the site of activation arm [10, 85]. In a few instances, where there are midline deviations and malrotations of the jaws, additional orthognathic procedures will be needed to achieve an optimal final result [86]. Degradable distractors are not popular, as the ability of the biodegradable plates/screws to withstand the muscular forces are not equivalent to titanium plates [87]. Currently, there are no long-term follow-up studies on the use of internal resorbable distractors in the midface [11].

As orthognathic surgery is usually a definitive single-stage procedure, the necessity for additional surgeries is rare. In orthognathic surgeries, fixation is only temporary, until healing occurs and few authors have advocated the removal of these plates after healing [88]. Though there does not appear to be a consensus in agreement for their removal, this is undertaken routinely in some countries [89].The usage of biologically inert and resorbable plates for fixation in orthognathic surgery appears to offer certain clinical advantages over metal plates, by eliminating the need for a second surgery for their removal [90], that might occur due to any untoward post-operative complications.

Patient Compliance

Patients should be briefed of the need to activate the distractor device two or more times per day for the entire period of activation [27, 57], while the patient and their family are to be counselled to overcome the anxiety and distress during this period [11, 91]. External halo distraction devices due to their bulky nature bring great physical and social discomfort to the patient [11, 29]. Internal devices are hence more preferred [29], but the protrusion of the activation arm into the oral cavity may be a source of significant discomfort during speech and food intake [30]. Though the satisfaction rate is high after distraction [82], the pain and the functional impairment during active distraction are a major drawback [92]. Empathetic communication and addressing patient’s queries while assessing their compliance and willingness should be assessed prior to procedure, as not every patient is the same and the surgeon has to decide who is a good fit for distraction.

Orthognathic surgery, unlike distraction, is almost entirely an intraoral procedure which is generally well tolerated with superior patient compliance. The overall satisfaction rate of patients, after orthognathic surgeries, is very high [93]. Soh et al. did an extensive review and reported that patients experienced an improvement in the overall quality of life after orthognathic surgery [94].

Follow-Up Visits

Constant post-operative follow-up visits are mandatory [9] following distraction procedures, to check for regularity in activation, and also to note the occurrence of complications, if any. This is a particular disadvantage in the Indian scenario, as the patient might be coming from a distant place and this might interrupt the regular visits, leading to complications. In distraction osteogenesis patients, discharge is delayed due to post-operative device activation, need for close assessment and vector check, assessment of quantum of movement and prevention of immediate post-operative complications.

Numerous visits are not necessary after an orthognathic surgical procedure [28]. The patients need to have one to two post-operative follow-up visits with the surgeon, after which they are handled by the orthodontist, lest any complication arise.

Duration of Treatment

Distraction osteogenesis entails a prolonged treatment time, lasting at least 3 months [4, 9]. This procedure involves a consolidation period, which lasts for about 8–12 weeks depending upon the quantum of distraction, hence is one of the major disadvantages. Onger et al. reviewed that the acceleration of regeneration by stimulation of callus during the consolidation period would shorten the time for treatment [95]. Low-intensity ultrasound, intermittent parathyroid hormone, calcitonin, zoledronic acid, bone morphogenetic proteins, transforming growth factor, vascular endothelial growth factor, recombinant growth factor, cytokines, extracorporeal shock waves have been used to improve the bone healing and shorten the consolidation period [96, 97].

Orthognathic surgeries are single step procedures, and only the adjuvant orthodontic treatment might cause an increase in the treatment duration. With advancements in orthodontics, a return to normal life is much quicker with an orthognathic option like surgery-first approach (SFA).

Complications

Relapse

Distraction osteogenesis has lower relapse rates with larger advancements [26, 57], as there is decreased force needed to lengthen the bone due to the phenomenon of distraction histogenesis [9]. After mandibular distraction for craniofacial microsomia, there seems to be a continuous loss of the relative height of the ramus with a return towards the original ratio, as the patient grows [98]. Though significant skeletal relapse was noted, it did not worsen the treatment results [99] and this relapse sometimes might be attributed to the muscular forces acting against the direction of the distraction.

In orthognathic surgeries, advancements of more than 10 mm in any direction are considered to be with an elevated risk of relapse [20, 21], while few studies even report relapse after advancements of more than 6 mm [100].

In patients with cleft maxillary hypoplasia, considerable relapse occurred after orthognathic surgeries [101, 102], the causation of which is thought to be the fibrosis of structures around the hypoplastic maxilla, while after distraction, the relapse rate is significantly minimal [30].

Post-operative Infection

The distraction rods that penetrate the oral mucosa are portals of entry for infection [13, 37]. Chronic infections have been reported with mandibular distraction cases [15]. In patients with internal distraction devices, maintenance of oral hygiene is an important factor to prevent the occurrence of infections [30]. There is a tendency for advocating long-term antibiotics in patients undergoing distraction through extraoral devices, as there is an exposure to the external environment.

The infection rates in orthognathic surgery patients are very minimal or even nil, if proper antibiotic regimen is followed [103]. Recent trials suggest that even post-operative antibiotics are unnecessary after orthognathic surgery, if a single dose of perioperative antibiotic prophylaxis had been administered [104]. Maintenance of oral hygiene and preventing food from accumulating along suture lines are some ways to decrease incidence of post-operative infection.

Outcome of Surgical Correction for Facial Symmetry

Symmetrical results are not guaranteed in all cases of distraction especially bilateral where device failure or premature consolidations may cause asymmetrical movements, contrary to what was planned. [18].

This complication is very unlikely to happen with orthognathic surgeries, as bilateral symmetrical movements are achieved through definitive pre-operative planning and appropriate splint usage [35, 67]. There can be post-operative complications like mobility at the osteotomy site and condylar sag, which might produce occlusal discrepancies.

Extra Oral Scarring

External distraction devices anchored by transcutaneous pins are used to transport and stabilize the skeletal fragments [105]. Though there are numerous advantages like less infection rate, easy adjustment of vector and easy removal, these pins are prone to cause scarring of the skin [9], which can be minimized if no puckering of skin is produced in between the pins. To circumvent this, internal distractors are used as there are no skin incisions and they cause no risk to the branches of the facial nerve [105], but there are instances, wherein they too have caused hypertrophic scarring near the activation arm [10, 85].

Orthognathic surgery has no extra oral scarring as the approaches are always made transorally [24], barring a few procedures like extraoral ramus osteotomies and Lefort III osteotomies [97, 106].

Neurological Deficits

The larger incidences of persistent long-term inferior alveolar nerve (IAN) disturbances have been reported following bilateral sagittal split osteotomy (BSSO) [67, 107].

Mandibular distraction has lower incidences of persistent sensory nerve disturbances when compared to orthognathic surgery, between 6 and 10 mm of distraction, as noted in a review by Cheung [28]. Reasons attributed are the gradual stretching of IAN during distraction, allowing better nerve adaptation [108] and secondly the simpler split of the bone segments (green stick type), with less traumatic manipulation of IAN intra-operatively [57].

However, there aren’t many studies to assess nerve injuries in distraction osteogenesis as there are in orthognathic surgery. Risk factors for nerve injury are the quantum of movement and the rate of distraction, where one millimetre a day in fractions is advised for optimal nerve histogenesis.

Complications in Specific Craniofacial Procedures

Frequent and severe complications like cerebrospinal fluid leakage, meningitis, subgaleal haematoma, transection of the infraorbital nerve, strabismus and ptosis have a higher incidence in patients undergoing LeFort III osteotomy than those undergoing LeFort III distraction [41, 109, 110].

In the hands of an experienced surgeon, LeFort III distraction offers minor or no post-operative complications [111]. Complications related to mandibular procedures have been dealt in detail all along this review.

Authors’ Conclusions

This review delineates the similarities and differences between orthognathic surgery and distraction osteogenesis in ideal cases. Currently, there is no concrete evidence to support or refute that either of the technique is superior to the other. However, based on the indications (Table 1) or case specific scenarios, one technique could be considered a better fit than the other. While significant inter-technique variation exists, distraction osteogenesis provides clear benefits in the growing population.

Table 1.

Summary of parameters—DO versus OGS

Parameters	Distraction osteogenesis	Orthognathic surgery
Paediatric patients	✔
Adult patients	✔	✔
Bone movement of less than 8 mm (maxillary complex)	✔	✔ (preferred)
Bone movement of 8–10 mm (maxillary complex)	✔	✔
Bone movement of more than 10 mm (midface/mandible)	✔ (preferred)	✔
Impaction, retraction, compression of bone		✔
Precise 3D movements	✔	✔ (preferred)
Simultaneous movements of the midface complex (two–three procedures)	✔	✔ (preferred)
Existing VPI with movement of more than 10 mm	✔ (preferred)	✔
Calvarial deformity corrections	✔	✔
Multiple segmentations (movements of 2–3 subunits)		✔
Transverse discrepancies	✔ (preferred)	✔
Segmental defects	✔
Irradiated cases	✔
Poor bone quality	✔
Condylar hypertrophy/hyperplasia		✔
Neocondyle rehabilitation	✔ (preferred)	✔
Symmetrical results	✔	✔ (preferred)

There is paucity for quality evidence when drawing comparisons in cleft patients, which necessitates prospective research with a larger sample size that is inclusive of patients with different facial characteristics, to elicit true differences between the interventions. These prospective trials could be conducted in a high-volume centre or as a prospective multi-centre trial, comparing both arms to eliminate bias by patient or surgeon factors.

Advancements in design and material sciences, coupled with the use of CAD–CAM technology, have aided perfecting the placement of distractor, achieving superior vector control, hence, improving results. There is immense scope for research and development of miniature design, patient-specific distractors, improved rotational torque control in curved bone distraction process and innovation of motorized distractors, that could transform distraction into a more acceptable modality for patients and surgeons.

On the other side, OGS has undergone tremendous advancements by CAD–CAM technology usage in simulation surgery and predictions for hard and soft tissues changes, surgical guides, intra-operative splints and patient-specific implants (PSI). Simulation-guided navigation during orthognathic surgery [36] has improved reproducibility of the pre-operative virtual surgical planning and this has created a quantum leap in OGS planning and precision surgery.

There are a few peculiar clinical scenarios, where OGS alone may be used as a precious tool, such as correction of post-traumatic occlusion, access osteotomies in tumour surgery, reverse face lift procedure as simultaneous maxillomandibular advancement to changes the skeletal framework of the face, improving soft tissue support, rejuvenating the middle and the lower third of the face, transgender surgery and ethnic orthognathic surgery [112].

In 1995, Molina and Monasterio posed the golden question: would mandibular elongation by distraction osteogenesis be a farewell to major osteotomies [113]. However, the scenario has not changed much since then. Both the surgical techniques still coexist and thrive all over the world; except for a few overlapping indications, the surgeon still holds the discretion to make the obvious choice.