KEY WORDS
Ameloblastoma - fibula free flap - jaw neoplasms - mandibular reconstruction - non-vascularised
bone graft - segmental mandibulectomy
INTRODUCTION
Ameloblastomas (also known as Adamantinoma; Eve's disease) are uncommon tumours of
the jaw constituting 1%–3% of all jaw tumours.[1] While the term ‘Giant ameloblastoma of the mandible’ has been used quite liberally
in the literature, a unanimous definition of the word ‘Giant’ remains elusive. A literature
review performed using the keywords ‘giant mandibular ameloblastoma’ and ‘giant ameloblastoma
of the mandible’ revealed that the available information on giant mandibular ameloblastomas
(GMA) is largely anecdotal and sparse, majority of which is limited to case reports[2]
[3]
[4] typically describing unusually large mandibular growths that are truly ‘giant’,
even to the untrained eye. The authors feel that the term ‘giant’ can be better utilised
to describe those mandibular ameloblastomas demonstrating certain characteristics
that warrant special considerations from a clinical perspective rather than its current
usage in portraying peculiarly large, ‘reportable’ cases of these tumours. Doing so
will allow for a rational way to approach and manage this entity which until now has
been sidelined as a medical aberration.
Based on our experience with mandibular ameloblastomas and a review of the established
literature on the subject, we recommend clinically pertinent objective criteria for
the classification of mandibular ameloblastomas that is simple enough for use in everyday
clinical practice, promotes better doctor communication and most importantly, has
a direct influence in decision-making and management. Furthermore, the treatment and
outcome of GMA presenting at our institute and as identified by the new set of criteria
have been evaluated, in terms of aesthetic and functional results, patient satisfaction
and long-term recurrence.
PATIENTS AND METHODS
From a treatment standpoint, the following sets of inclusion and exclusion criteria
were proposed for a GMA.
Inclusion criteria
Exclusion criteria
-
Tumours that are more than 5 cm in its longest dimension but with a narrow base (requiring
either a marginal mandibulectomy or a segmental mandibulectomy creating a horizontal
defect of <6 cm)
-
Exclusive lateral defects, irrespective of the size of the defect.
Reconstruction of large defects in the lateral aspect of the mandible has provided
comparable results with vascularised bone grafts, non-vascularised bone grafts (NVBGs)
or with only soft-tissue flaps.[5]
[6]
[7]
[8]
[9]
[10] Hence, vascularised bone grafts in such situations are not proven to be significantly
better than other modalities.
We report a retrospective analysis of 16 patients of mandibular ameloblastomas presenting
at our institute from August 2012 to September 2016, of which eleven were categorised
as GMA consistent with the described criteria [Table 1]. Accordingly, these patients received radical treatment in the form of segmental
resection and primary reconstruction with vascularised bone flaps (VBF), NVBGs with
local flaps and reconstruction plate with condylar prosthesis.
Table 1: Clinical summary of all patients treated for giant mandibular ameloblastomas
Five of these patients were excluded based on our exclusion criteria. In one instance,
although the gross tumour (expanded along the alveolus with a narrow base) measured
>5 cm in greatest dimension, the post-resection mandibular defect that needed to be
reconstructed was <6 cm. This patient, however, wanted an autologous bony reconstruction
and therefore, received a free fibula flap for reconstruction. In the remaining four
instances, the defects either did not involve the central segment at all or did not
extend significantly across the midline. These patients were reconstructed variously
with free fibula flaps (n = 2), NVBG (n = 1) and reconstruction plate with attached metallic condylar prosthesis (n = 1) as studies showed that non-microsurgical methods were as good as vascularised
bone transfers for lateral segment defects.[5]
[6]
[7]
[8]
[9]
[10]
Pre-operatively, the patients were evaluated clinically and diagnosis established
with biopsy. Imaging studies including panoramic X-ray and computed tomography (CT)
facial skeleton with three-dimensional (3D) reconstruction were utilised to facilitate
surgical planning.
Segmental mandibular defects were classified according to the ‘HCL’ method described
by Jewer and later by Boyd et al.[11] Post-operative results were evaluated by the primary author based on two sets of
questionnaires, one related to appearance and the other function specific (including
speech, chewing and swallowing and drooling of saliva). The approach followed for
the management of cases of mandibular ameloblastomas presenting at our institute is
depicted in [Figure 1].
Figure 1: Algorithm depicting step-wise approach to mandibular ameloblastomas. 1A long, thin rim of residual mandible that is prone to fracture may be supported by
the judicious use of reconstruction plates. NVBG: Non-vascularised bone graft, VBF:
Vascularised bone flap, GMA: Giant mandibular ameloblastomas
RESULTS
Of a total of 16 patients with ameloblastoma of the mandible presenting at our institute
during the study period, 11 patients were identified as having GMA as per the criteria
proposed [Table 1].
The defects in the mandible following segmental resection ranged from 7 cm to 11.5
cm in length (mean: 9.3 cm). The left side fibula was consistently used for the transfer
for the ease of harvest and patient preference.
All flaps were viable apart from one (90.90%) (Patient No. 1) who had partial flap
necrosis of her skin paddle measuring 8 cm × 5 cm. All resected specimens were subjected
to a histopathological examination which showed complete removal of the tumours. Except
for Patient No. 1, whose discharge was delayed because of partial flap loss and subsequent
development of a small oro-cutaneous fistula that healed on conservative treatment
with regular dressings and oral hygiene and Patient No. 4, who developed a surgical
site infection of the flap donor site with subsequent graft loss, hospital stay was
<2 weeks in the rest of the patients. Complications did not require a return to theatre
and were treated conservatively. They did not affect the final result regarding cosmesis
and function. At 2–3 months of follow-up, all were tolerating a normal diet and were
able to speak coherently and had good oral competence. Although great toe flexion
was weak in Patient No. 7 with Patient No. 2 even developing a flexion contracture
of her great toe, it did not hamper ambulation. No clinical or radiological evidence
of tumour recurrence was found during a mean follow-up period of 10.7 months (range:
2–28 months).
Because of its subjective nature, aesthetic results were assessed by questionnaire-based
serial evaluations. Three patients were more than satisfied (score 8–10), six patients
were satisfied (score 4–7) and two were not satisfied (score 1–3) with their cosmetic
outcomes. The questionnaire was elementary, largely focussing on the patient's ability
to integrate socially. Unfortunately, although patients were aggressively counselled
post-operatively, none of our patients received dental rehabilitation in the form
of dental implants.
Patients
Patient 1 – A 33-year-old female presented with expansion of the lower jaw for 8 years.
The swelling was slow growing, painless and hard in consistency, measuring 12 cm ×
9 cm in greatest dimensions. A CT of the facial skeleton with 3D reconstruction showed
a multiloculated lesion with mixed radiolucent and radiopaque areas. Cortical thinning
of the inferior mandibular border along with expansion of the alveolus were noted
on clinical and radiological examination. A segmental mandibulectomy performed via
a submandibular approach with 1 cm margins extending from L 3rd molar to R 2nd premolar resulted in a 9 cm ‘LCL’ bone defect [Figure 2]. Resection of the overlying mucosa lead to an intraoral lining defect as well. Reconstruction
was achieved with a free fibula osteoseptocutaneous flap (FFOSC flap). The flap skin
paddle measuring 8 cm × 5 cm was used to restore the intraoral lining.
Figure 2: (a). Case 1– a 33-year-old female with 10 cm × 15 cm mandibular swelling. (b and
c) Facial computed tomography showing the multiloculated lesion, anterior and lateral
views. (d) Specimen following segmental mandibular resection from the left third molar
to right second premolar
Patient 6 – A 19-year-old male presented with a swelling arising from the lower jaw
which was slow growing, painless and long-standing (>10 years), measuring 13 cm ×
10 cm. The swelling was associated with malocclusion and exfoliation of teeth. An
orthopantomogram indicated a bony lesion affecting the R mandible with mixed radiolucent
and opaque areas along with alveolar bone destruction. A segmental mandibulectomy
was performed through a submandibular approach in combination with a lip-split incision.
The resultant 11 cm ‘LC’ defect, extending from R angle to L canine was reconstructed
with a FFOSC flap [Figure 3]. At 6 months of follow-up, he was tolerating a normal diet and could speak coherently.
Figure 3: (a). Case 6-slow growing mandibular tumour in a 19-year-old male. (b) Alveolar expansion
with malocclusion. (c) Orthopantograph showing exfoliation of teeth. (d) Intra-operative
photograph displaying the reconstructed mandible with fibula osteocutaneous flap
DISCUSSION
Although Chaine et al.[12] attempted to define GMA, they did not elucidate the reasons for their criteria.
Their criterion of ‘large size (>5 cm in length)’ is suboptimal because an ameloblastoma
often substantially expands and balloons out the mandibular cortex while remaining
narrow at its base. Consequently, rather than the size of the ameloblastoma, which
may be misleading, the length of the actual defect following its removal with a healthy
margin is what is clinically relevant. Furthermore, terms such as ‘considerable jaw
expansion’ seemed arbitrary and lacking clinical significance.
Treatment of ameloblastomas with simple curettage and enucleation is associated with
an unacceptably high rate of recurrence.[13] Currently, it is agreed that a radical resection is associated with the lowest recurrence
rates on long-term follow-up.[14] Therefore, mandibular resection with a 1–2 cm margin of healthy bone[15]
[16] is the recommended strategy. This radical resection can be in the form of a segmental
or a marginal mandibulectomy.
Performing a marginal resection with preservation of the inferior or posterior mandible
border, whenever possible, simplifies the reconstruction, especially with regard to
the central mandibular defect.[16] A segmental resection should be favoured when the tumour expands the inferior or
posterior border or when provisions for close follow-up are lacking.[15]
In an article by Pogrel et al.[7] the authors state that NVBGs >6–9 cm in length are associated with a graft failure
rate of 20% or more. Similarly, Foster et al.[6] showed that the percentage of patients achieving bony union following free fibular
flap was almost double (95% vs. 44%) compared to NVBGs when performed for mandible
defects 6–10 cm in length. Bearing in mind that free fibula flap failure rates, in
general, are <5%–10%,[17] the use of NVBGs to reconstruct mandibular defects >6–9 cm would not be prudent.
Unlike periosteum covering the mandible elsewhere, the alveolar mucoperiosteum does
not form an effective barrier to the spread of ameloblastoma. This is evidenced by
a lack of capsule formation in this region along with direct contact of the tumour
with mucosa (‘collision phenomenon’) and finally, an infiltrative pattern of growth
vis-a-vis the smooth contours seen in the rest of the mandible.[18] As a consequence, invasion and expansion of the alveolus by the tumour would necessitate
inclusion of the overlying oral mucosa in the resection.
Based on a review of cases of mandibular ameloblastomas treated at our institution,
a step-wise approach for the management of this entity is illustrated in [Figure 1]. The decision-making process in the treatment of mandibular ameloblastomas begins
with an evaluation of inferior or posterior mandibular border expansion. In its absence,
a marginal mandibulectomy can be safely carried out as part of radical treatment while
significantly reducing operative complexity, costs and patient morbidity.[15]
[16] The tumours those fit into the proposed criteria as listed in the ovals implies
a GMA and warrants microsurgical expertise for adequate reconstruction.
Tumours that demonstrated alveolar bone invasion and expansion, as determined by clinical
and radiological examination, were subjected to excision of the overlying alveolar
mucosa followed by reconstruction with the skin paddle of the FFOSC flap. For lateral
defects being reconstructed with NVBG or bridging plates, the use of local soft-tissue
flaps such as the submental and the facial artery myomucosal flaps can provide alveolar
lining in such cases.
Because of the numerous studies in existence, that show that non-microsurgical reconstructive
options such as bridging plates and NVBG are adequate modalities for reconstructing
lateral mandibular defects,[5]
[6]
[7]
[8]
[9]
[10] we did not feel the need to compare results of VBF reconstruction with other forms
of reconstruction and would leave it to the discretion of the treating surgeon to
choose the appropriate treatment modality for such defects.
In the light of the present evidence, instead of simply using arbitrary criteria such
as size >5 cm for defining GMA, we would instead recommend categorising as GMAs those
tumours that will need segmental resection leaving a bone defect of >6 cm and involving
the central segment, thereby necessitating reconstruction with a VBF.
The authors, therefore recommend, that while non-GMA tumours may be treated with a
variety of reconstructive approaches including free fibula flaps (based on the surgeon's
preference), GMA tumours must be reconstructed with free fibula flaps for optimum
outcomes.
Although patients presented with a variety of complaints including but not limited
to pain, skin ulceration and dental problems such as malocclusion and loosening of
teeth, the primary reason for presentation was a change in appearance. Moreover, all
patients retained sufficient oral function which posed a challenge during the reconstructive
effort to ensure oral function was not significantly altered. In contrast, based on
the authors’ experience, oral cancer patients requiring mandibulectomy and mandibular
reconstruction (T4b) tend to have more functional problems such as pain, trismus,
difficulties in speech and swallowing.
Even though not performed by us, consideration can be given to a double barrel fibula
flap[19] to allow easier placement of osseointegrated dental implants. Osseointegrated dental
implants will be required for optimal dental rehabilitation.[20] Alternatively, in areas with financial and infrastructure constraints, a more practical
and inexpensive option would be the use of removable partial dentures or similar prostheses.[21] Following central mandibular segment resection, the genioglossus (prevents tongue
fallback) and digastric (jaw depressor) are inadvertently detached. These detached
muscles were sutured to empty miniplate holes or around the screws which are then
tightened after coiling the suture around them to avoid tongue fall back and lower
face and lip sagging[22] in the early post-operative period.
While alternative options for vascularised osteocutaneous flap transfers do exist
including circumference iliac osteocutaneous flap and osteocutaneous radial forearm
free flap, the free fibula flap was preferred since it offers clear-cut advantages
in mandibular reconstruction.[23] Similar to Yadav et al.[24] we felt that choosing one leg over the other as a donor site for flap harvest did
not influence the final result. Hence the left leg was consistently used for ease
of harvest, intra-operative instrumentation and personnel set-up as well as patient
preference.
In most of the patients, because of the large tumour size, often extending to the
opposite side, standard techniques for achieving an aesthetically contoured neo-mandible
such as pre-plating techniques and CT tracings were difficult to employ. In addition,
intermaxillary fixation was not possible in the majority owing to extensive resection
of the tooth-bearing mandibular segment. A preformed bent wire template was used to
best match the defect. However, the use of dedicated DICOM image processing software
such as OsiriX® (Pixmeo; Bernex, Geneva) available for Mac OS (Apple Inc., California) may be of
benefit in assisting with pre-operative planning for mandibular reconstructions.[25]
CONCLUSIONS
The clinical presentation, investigation protocols, treatment and follow-up considerations
are significantly different for GMA as compared to non-GMA tumours. We believe that
infusing the term ‘GMA’ with the new set of criteria will allow logical segregation
of these lesions from non-GMA lesions, thereby facilitating better communication and
decision-making among treating reconstructive surgeons. Chiefly, recognising a mandibular
ameloblastoma as a GMA should precipitate an early referral to a centre with microvascular
expertise thereby expediting the treatment process.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
