Page 22 - Read Online

Palmer et al. Plast Aesthet Res 2020;7:2 I http://dx.doi.org/10.20517/2347-9264.2019.34 Page 3 of 8

native mandible. The concept of hybrid occlusion has since been extended to include cases where
the native dentoalveolar structure is the maxilla, and the mandible is being transplanted [4,10] . Single-
jaw transplantation resulting in hybrid occlusion has been utilized extensively in clinical cases of face
[11]
transplantation . Proponents of this technique argue that poor occlusive outcomes may arise with single-
jaw as well as with bimaxillary transplantation, but only the more conservative approach accounts for
the risk of graft failure by preserving functional recipient anatomy [12,15] . Furthermore, these individuals
[12]
suggest that occlusion can be improved with subsequent orthognathic and orthodontic interventions .
Those advocating for bimaxillary transplantation in cases of single-jaw defects cite the importance of
adequate postoperative occlusion in restoring vital patient functions such as mastication and speech and
suggest that preserving the donor occlusal relationship may optimize these outcomes [4,11] . Additionally,
by obviating the need to find a donor jaw that properly fits the recipient’s native jaw anatomy, bimaxillary
[11]
transplantation may expand the possible donor pool . No studies have directly compared single-jaw with
bimaxillary transplantation, and the number of patients receiving these grafts is still relatively small; at this
point, arguments for one strategy over the other based on functional outcomes remain experiential and
speculative [4,11] .

In both mandible-only and bimaxillary transplantation, the next consideration is where to dissect the
[16]
mandible. The earliest facial allotransplantation to utilize donor mandible included only the chin .
Subsequent procedures included donor mandible from angle to angle, which is now a common practice [16,17] .
The bilateral sagittal split osteotomy of the mandible, a common procedure in traditional orthognathic
surgery that involves splitting the mandible posterior to the alveolar process, has been widely incorporated
into facial transplantation because it offers maximal donor-to-recipient bony contact [8,18] . Furthermore, this
technique is favored over including only a portion of the mandibular tooth bed because incorporation of
the entire donor alveolar structure is thought to better allow establishment of occlusion [10,18] . The exact path
of bilateral sagittal split osteotomy can be customized for an individual recipient by using computer surgical
planning techniques that are discussed below.

An exciting concept in the field currently is the prospect of transplanting the temporomandibular joint
(TMJ) along with the mandible. Individuals with injuries warranting consideration of facial transplantation
[19]
often have significant impairment of the TMJ . Traumatic injuries themselves can cause scarring and
other articular pathologies, and reconstructive efforts may similarly contribute to or exacerbate these
[19]
conditions through scarring, reduction of jaw mobility, and subsequent muscle shortening . Together,
jaw injury and surgery may significantly impact a patient’s quality of life by imposing difficulties opening
[19]
the mouth, chewing, and speaking . Donor mandibles void of articular anatomy, such as those prepared
with the bilateral sagittal split osteotomy, do not alone address the potential for TMJ dysfunction in this
[16]
population . While it is possible to identify and treat TMJ pathology before facial transplantation, clinical
evidence in the face transplant population suggests this strategy does not offer a definitive solution [4,19] .
This fact is further complicated by the observation in at least one facial transplant candidate that TMJ
[19]
impairments may not be apparent on preoperative imaging . In cases where jaw dysfunction persists
postoperatively, secondary revisions such as coronoidectomy and condylectomy are viable options that have
been described in the literature with acceptable results [4,16,20] . In any case, transplantation with an allograft
including the TMJ represents an alternative treatment option for these patients that may eventually offer
[16]
comparable or superior functional outcomes and the possibility of fewer revision surgeries .

The feasibility of TMJ transplantation and associated outcomes are still being elucidated. To date, there
has been one case reported in the scientific literature of unilateral mandibular condyle inclusion in a facial
allograft [6,16] . The patient in this case received a graft including donor mandible from right angle to left
condyle to treat a large mandibular defect and known left TMJ ankylosis secondary to radiation therapy [6,16] .
The transplantation was successful, and, although the patient demonstrated only 10 mm of mandibular