Article Type : Case Report
Authors : Ivory JW, Jenzer AC and De Latour F
Keywords : Distraction osteogenesis; Mandible; Condyle; Hemifacial microsomia; Craniofacial deformities
An
active duty solider, a 21-year-old male, was evaluated in the summer of 2017
for significant facial asymmetry. He was referred by his orthodontist for
surgical treatment evaluation and planning. The patient has an unremarkable
medical history with no surgeries, medications, allergies, or tobacco use. His
chief complaint was “I am interested in having my bite corrected with braces
and I have some pain and noises in my jaw joint.”
The patient’s
physical exam revealed a significant cant of the dentition due to left
mandibular condylar and ramus hypoplasia with associated facial asymmetry
(Figure 1). His facial fifths, besides the obvious mandibular asymmetry, were
otherwise equal, he displayed 2mm of maxillary tooth show in repose with
maxillary midline coincident with the mid-sagittal plane, with 5mm of maxillary
tooth show in animation. His mandibular midline was 3mm to the right of the
mid-sagittal plane. He displayed balanced animation (Figure 2) with full buccal
corridors and a noticeable cant. From a lateral perspective, he demonstrated a
straight facial profile with equal facial thirds, with associated
classifications of a Fitzpatrick 3, Glogau 1, and Dedo 1 (Figure 3).
Figure 1: Photo demonstrating the patient in frontal repose.
Figure 2: Photo with patient in frontal animation. Note the significant cant.
Figure 3: Patient in lateral profile.
Intra-orally, he was missing teeth 1,4,13,16,17,32, demonstrated a Class II molar – Class I canine relationship, and had good oral and periodontal hygiene (Figure 4).
Figure 4: Intra-oral photo demonstrating centric occlusion.
His
temporomandibular joints were unremarkable except for rare, minor, pain on the
left side, later determined due to hyperfunction on that side because of his
hypoplastic growth on the right. A panoramic image and medical grade CT scan
revealed a mandibular cant of 6mm (Figures 5 and 6). A scintigraphy scan was
performed to rule out left condylar hypertrophy which was negative.
Figure 5: Reconstructed panoramic radiograph. Note mandibular asymmetry.
Figure 6: 3D CT reconstruction demonstrating significant deformity.
The
patient was diagnosed with a dentofacial asymmetry secondary to right
mandibular condylar and ramus hypoplasia. The case was presented to the local
dentofacial deformity board and treatment plans created and reviewed with the
patient to include doing nothing, orthognathic surgery with anticipated lefort
I osteotomy and bilateral mandibular split osteotomies with a custom allograft
implant to the left mandible with consideration for a genioplasty, distraction
osteogenesis to the left mandible followed by orthognathic surgery, and a left
sided custom temporomandibular joint replacement with a left single sided split
osteotomy with lefort/genioplasty. After multiple treatment planning meetings
with the patient and careful review of the risks and benefits and advantages
and disadvantages of each option, the patient elected to proceed with the
distraction osteogenesis option.
The surgery was then
virtually planned by the team and a custom distractor and cut guides were
fabricated (Figures 7- 9). The cut and distraction device were planned to
maximize control of the vectors of force.
Figure 7: Pre-operative virtual surgical planning for custom distraction device.
Figure 8: Pre-operative virtual surgical planning showing device and cut guide.
By
creating an L shape and distracting in a vertical direction, the L shape
ensured continued bony contact which would help maintain the vectors in the
correct orientation.
In February of 2018 the patient was brought to the main operating room where, under general anesthesia, a retromandibular approach was completed and the custom cut guide used to direct the precise cuts of the mandible with placement of the device (Figures 10-12).
Figure 9: Pre-operative virtual surgical planning demonstrating screw depths.
Figure 10: Intra-operative osteotomies completed using cut guide. Note additional corocotomies completed to aid in maximizing blood flow to the area.
Figure 11: Intra-operative device placement.
Figure 12: Intra-operative device placement posterior view.
The operation went smoothly with no complications or issues and the patient was discharged to home the next day. The device could rest passively for a latency period of seven days before an activation phase of nineteen days during which the mandible was distracted at a rate of 1.0-1.5mm per day. The distraction device was maxed out over the associated time period and then allowed to consolidate over twelve weeks. A CT scan was obtained at the end of this period demonstrating the gain from the device (Figures 13-16).
Figure 13: Post-distraction phase panoramic image with device in place.
Figure 14: Post-distraction phase CT sagittal cut demonstrating distraction osteogenesis.
Figure 15: Post-operative 3D reconstruction showing vertical height gained from distraction.
Figure 16: 3D reconstruction showing the change in occlusion on the left gained from the increase in vertical height from the distraction osteogenesis.
In
March of 2018, the patient was brought back to the main operating room where he
underwent removal of the distractor arm and placement of an occlusal splint
without complications or issues. The final orthognathic surgical treatment plan
was finalized as the distracted area continued to consolidate. The changes in
the patient’s appearance and occlusion were impressive already currently
(Figures 17-19). The final plan was a lefort I osteotomy, genioplasty, and
removal of the distraction device with placement of the custom plate for
increased strength in the area, with associated three dimensional movements
planned in the (Figures 20-22). The surgery was complete in the main operating
room in June 2018 without complications or issues and the patient was
discharged to home the next day (Figures 23 and 24).
Figure 17a and 17b: Pre-op and post-distraction frontal repose.
Figure 18a and 18b: Pre-op and post-distraction frontal animation.
Figure 19a and 19b: Pre-op and post-distraction central occlusion.
Figure 20: Pre-operative phase 2 virtual surgical planning for device removal and insertion of custom plate, Lefort 1 osteotomy, and genioplasty.
Figure 21: Pre-operative phase 2 virtual surgical planning for device removal and insertion of custom plate, Lefort 1 osteotomy, and genioplasty with cephalometric analysis.
Figure 22: Custom plate to replace the device for increased strength to the area.
Figure 23: Post-operative panoramic image.
Figure 24: Post-operative AP cephalometric image.
Figure
25: Post-operative
final photo in frontal repose.
Figure 26: Post-operative final photo in frontal animation.
Figure 27: Post-operative final photo in lateral profile.
Figure
28: Post-operative
final photo of central occlusion.
The patient then finished his orthodontic treatment and presented for interval exam with a final set of photos in May 2020 (Figures 25-28). The patient was satisfied with the outcome and had no complaints or issues.
Distraction
osteogenesis (DO) is a surgical technique that, while relatively new in its
widespread use, has been around for over 100 years. The first reported case was
an attempt by Alessandro Codivilla in 1905 to length a femoral fracture [1].
In the early 1900s a number cases were reported using DO to treat
congenital craniofacial deformities [2-4]. From there, it gained popularity and
increased use, surging with the publication by Ilizarov in the 1980’s, which
sparked deeper investigation and development [5]. In 1995, Klein et al
published a study on distraction osteogenesis of nine cases of childhood
unilateral and bilateral mandibular hypoplasia with a resulting average of
lengthening of 21mm [6]. As the technology advanced to current day
with custom devices and virtual planning, the significantly increased the
control and predictability of the vectors involved and lead to better surgical
outcomes. In the authors’ opinions, it should be part of the armamentarium of
any surgeon treating complex craniofacial deformities.
The
biology involved in distraction osteogenesis is classically thought of in five
distinct phases: osteotomy, latency, activation, consolidation, and
re-modeling. The initial osteotomy is created with consideration for
minimization of periosteal stripping and tissue reflection in order to best
preserve the blood supply, designing surgery and approaches to minimize chance
of contamination, particularly from intra-oral sources, and minimizing damage
from heat and trauma to tissue and the surrounding area. A gap of 1-2mm is left
open between the bony segments once the device is in place. This osteotomy gap,
over approximately the next week, is the site of the most important part of the
next phase, latency. The initial inflammatory response, with influx of cytokines,
healing, and pro-inflammatory factors, sets the stage for the next phase,
activation. Other techniques describe doing only a cortical osteotomy, which in
turn requires a significantly larger distraction device to apply the necessary
forces to distract bone. For that reason, this technique is not preferred in
the head and neck region [7].
As
the device is activated it is opened at a rate between 0.5mm to 1mm per day,
divided into two to sessions. As the osteotomy gap progressively increases
there is a reciprocal stretch and elongation of the collagen fibers within the
gap. Mesenchymal cells at the periphery of the osteotomies move into the gap
and undergo differentiation into a mix of cells including osteoblasts,
fibroblasts, and chondroblasts [8]. Neovascularization concurrently takes place
from the bony segments and periosteal walls. This milieu of collagen and
healing factors within the distraction chamber allows for lengthening of the
segment while maximizing blood and nutrient flow to the area. This new tissue
forms parallel to the vector of traction [9].
The
next phase is the consolidation portion, where this controlled injury is healed
by the body. Mineralization begins at the bony walls and advances into the
defect until the fibrous inter-zone is, hopefully, fully mineralized. Osteoid
is deposited and woven bone formed with eventual re-modeling to lamellar bone.
This time period is difficult to predict as one considers the factors involved;
age, area, blood supply, systemic and/or local medical conditions, and the
minutiae of bony healing that is yet to be fully elucidated especially in
induvial patients as it pertains to their genetics and immune systems. The last
phase is re-modeling where the distractor is removed, and normal bony forces
and tension allow shaping and continued transformation of the osseous tissue.
The
key to successful distraction osteogenesis is the rate of distraction. During
distraction, as the soft tissue surrounding the bone lengthens along with the
bone. Soft tissue responds to tension through cellular proliferation [10].
A rate that is too slow can result in ossification of the osteotomy,
requiring a second surgery. A rate that is too fast will not allow soft tissues
to proliferate and will likely compromise vascular supply to the surgical site.
Distraction
osteogenesis is a therapy that has a wide range of applications within the
scope of head and neck surgeons. Treatment of congenital syndromes, to include
conditions such as hemifacial macrosomia and Pierre Robin Syndrome to name a
few, is a prime population where this therapy shines, especially in pediatric
patients [11-14]. Augmentation of alveolar bone in the gnathic bones,
particularly for the often difficult to attain vertical ridge augmentation, is
another application where distraction osteogenesis offers a useful therapy
[15].
However,
one must weigh the relative advantages and disadvantages of using this
technique against the unique problem set of each case. The major advantage in
distraction osteogenesis is that often allows for greater movements of bone
when compared to an osteotomy alone. It brings along soft tissue and vascular
supply generally resulting in greater soft tissue and bone bulk [16]. The
resulting bone is already fully vascularized and can preclude the need for
further augmentation surgeries. Specific for cases such as described above,
treatment of hemifacial microsomia, often greater symmetry can be achieved as
compared to orthognathic surgery alone, since as the mandibular ramus is
lengthened, it results in a more balanced symmetry at the gonial angles,
avoiding the need for a later implant at the aforementioned site. With virtual
surgical planning and custom devices fabricated to the patient and the plan,
the surgeon can control all aspects of the case, from osteotomy and placement
in order to avoid vital structures like the inferior alveolar nerve, tooth
roots, etc., while maximizing control of the vectors to increase predictability
of a favorable result.
There
are, of course, disadvantages as well. The discomfort and social stigma
associated with having the device protruding through the skin, if an external
device is used, combined with the longer length of time, and most commonly, a
second procedure to remove the device as well as any subsequent surgeries, are
all relative disadvantages. Facial scarring can occur secondary to the surgical
approaches and the protruding device. Patient acceptance and buy-in, for these
reasons, can be difficult. Relapse is another potential issue that many studies
have looked at, for example Strijen et al. showed that in fifty patients, high
angle patients have a significantly higher relapse than low angle patients
[17].
Some
of these relative disadvantages can be mitigated by considering vectors. The
vector is based on the mandibular shape and the desired end goal [18]. Treating
a multi-vector case with a single vector device has been a studied source of
criticism and debate. However, Singh demonstrated that this can be overcome
with careful preoperative planning [19]. Internal vector control and
distraction is possible with newer devices and remains and interesting area of
future exploration and is definitely a viable option of exploration depending
on the patient and based on the specifics of the case.
Overall,
distraction osteogenesis is an excellent therapy that should be part of any
head and neck surgeon’s armamentarium of treatment modalities.