DISCUSSION
Cleft lip and palate is considered the most prevalent congenital
craniofacial birth defect and is the second most common congenital
malformation of the human body, second only to
clubfoot.15 Fusion of several structures and processes
of the neonatal face result in development of both the lip and palate
between the 4th to 12th week of
gestation. A failure of fusion due to genetic or environmental causes
may lead to the development of cleft lip and palate.16
ABG forms a fundamental component of the treatment protocol of alveolar
clefts in patients with cleft lip and palate. The main objectives of ABG
are to: establish continuity of the dental arch, facilitate closure of
oro-nasal fistulae, correction of the nasal alar bases and to provide
solid bone for tooth migration and dental implant placement. Although
its use has increased, certain aspects of the surgical technique are
shrouded in controversy.5 The timing at which ABG is
performed is one such dilemma with two possible approaches having been
proposed: primary bone grafting during infancy or secondary bone
grafting during the mixed dentition period.17Recently, some consensus seems to have been reached with most surgeons
opting for secondary ABG between 8 to 10 years of age due to lower
incidences of complications such as maxillary growth restriction which
have been reported frequently after primary ABG.9,18However, the current debate revolves around the choice of ideal source
of bone graft material which may be even more controversial than the
timing issue of ABG.
The ideal bone graft sites can be grouped into either extra-oral sites
such as the iliac crest, proximal tibia and ribs or intra-oral sites
such as the mandibular symphysis and mandibular
ramus.5 The selection of a particular donor site is
dependent upon the size of the defect being repaired, ease of harvest,
donor site morbidity and the experience and preference of the
surgeon.11 The various donor sites also provide the
surgeon with a choice of either endochondral cancellous bone (extra-oral
sites) or intramembranous cortico-cancellous bone (intra-oral
sites).9 For many years it has been believed that
endochondral bone is far more superior to intramembranous
bone.9,11 However, due to the increased cortical bone
content in intramembranous bone harvested from intra-oral sites, it
undergoes delayed resorption and therefore maintains its volume for a
prolonged period of time compared to endochondral
bone.14 Additionally, intramembranous grafts have
shown to develop up to 166% more new bone around the graft site, which
is significantly higher than endochondral grafts.12
The maxillary tuberosity contains an appreciable amount of
intramembranous bone which can be used to reconstruct small to medium
alveolar clefts. After careful patient assessment, the amount of bone
obtained can be enhanced further by also harvesting bone from
odontectomy sites of the wisdom molars. If all these sites are utilized,
there is a potential of harvesting up to 30 cc of bone, which can
satisfy extensive grafting requirements.19 Other
salient advantages of using these sites as a source of bone graft lies
in their convenient anatomical location, a single surgical site in the
same region of the body as opposed to two sites away from one another,
minimal post-operative complications, hidden scars and a much shorter
hospital stay.5
We therefore strongly recommend that clinical examination of these
regions be a part of the routine evaluation of patients when selecting a
donor site for ABG.13 During pre-operative assessment,
Cone Beam Computed Tomography (CBCT) can be implemented to make an
accurate 3-dimensional analysis of the maxilla and mandible for the best
sites of bone graft material. Additionally, the timing of removal of the
wisdom teeth should ideally coincide with repair of the clefts. It seems
that the use of these sites can be a simple and valuable alternative
technique for alveolar cleft reconstruction with fewer intraoperative
difficulties and post-operative complications. In the event that the
maxillary antrum is exposed during bone harvesting, primary immediate
repair can be done.19 Since some of these patients
present after having undergone unsuccessful repair of oro-nasal
fistulae, advancement of local flaps to close the defects will not be
successful. A well designed pedicled tongue flap is the best alternative
for soft tissue repair of such defects.
In the present case, ABG was successful based on the clinical and
radiographic findings (figure 6). There was establishment of good
maxillary arch form with stabilization of the premaxillary segment.
There was also complete closure of oro-nasal fistulae, significant
improvement in the patient’s occlusion and facial profile. Overall, a
satisfactory aesthetic outcome was achieved.