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29 Tissue Engineering andRegenerative Medicine inOral andMaxillofacial Surgery: TheMost Important…
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progenitor cells. Scaffolds have been composed
with a variety of natural or synthetic biomaterials
(see above); their functions are to provide a structural support to the cells, to be a reservoir of
growth factors, and to offer a exible spatial
environment for tissue remodeling. The properties of the ideal scaffold include biocompatibility,
appropriate mechanical strength, and suitable
degradation. Furthermore, porosity, permeability,
and interconnectivity are also important features
for an effective and efcient diffusion of gases
and nutrients; these characteristics inuence cell
adhesion, migration, and proliferation within the
scaffold. In a pilot study, focused on the biological compatibility of innovative dental biomaterials, the behavior of DPSCs grown was evaluated
on silicon nanoporous and mesoporous matrices;
as a result, among the 28 matrices examined, silicon scaffold functionalized with (3-aminopropyl)
trimethoxysilane/toluene was found to better
support the proliferation of DPSCs [44].
Depending on the clinical target, different
potential tissue engineering methods could be
performed. A general inductive technique consists in the delivery of soluble signaling molecules to the adjacent tissues; in this approach,
growth factors are carried by a bioactive scaffold
and are exploited to attract cell movement and to
organize cellular behavior.
The guided tissue regeneration approach is
extensively used for the treatment of periodontal
diseases; in this conductive approach, the scaffold acts as a submissive tridimensional mechanical support to which cells can connect and
propagate.
For the treatment of huge tissue defects, cell
transplantation is more suitable. This procedure
typically includes cell harvesting from a donor
source and in vitro handling of the donor cells
that are directly seeded onto polymers typically
made up with the physical forms of ber-based
mesh, sponge, or hydrogel. The cells residing
into the scaffold proliferate, forming a regenerated tissue that is subsequently established into
tissue-decient areas.
Summarizing, the bioengineered tissue constructs recapitulate the physiology, natural architecture, dynamic conditions, intercellular matrix,
and cell-extracellular matrix interactions; such
exvivo constructs found extremely large application, for example, is employed for pharmacokinetic and pharmacodynamic analyses of drugs, as
preclinical models for high-throughput drug
screening and device testing. The advantages
offered by these man-made tissues include high
reproducibility and accurate control over culture
conditions; these techniques represent a powerful
tool in regenerative medicine; therefore, they are
particularly important in medical research.
29.3 Discussion
Regenerative medicine has been dened as the
application of scientic principles to the design,
production, modication, and growth of living
tissues using cells, growth factors, and biomaterials, either alone or in combination [45]. These
three central elements, stem and progenitor cells,
growth factors, and appropriate biological scaffold, have been thoroughly discussed. Tissue
engineering involves the use of matrices or scaffolds that guide the implanted cells and also the
host’s surrounding cells during tissue regeneration or restoration.
The use of more undifferentiated cell types
such as stem cells or early mesenchymal progenitors that retains self-renewal and multi-lineage
potential is preferable to that of terminally differentiated cells. Differentiation of stem and progenitor cells can be obtained invitro by changing
the culture conditions after their expansion or by
providing a new physiological microenvironment
in the transplanted area invivo.
Adult stem cells harvested from donor tissues could be further expanded in culture and
then associated with biomaterials to form a scaffold. A biomaterial should easily integrate with
the adjacent tissues and favor new tissue
ingrowth (e.g., osteoconduction in bone regeneration). It should allow colonization by the host
blood vessels and should be biocompatible and
resorbable. Polymers include collagen that can
be prepared in solution or shaped into membrane lms, bers, sponges, and hydrogels.
Synthetic polymers allow a better control of
346
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M. Tatullo et al.
physicochemical properties and delivery kinetics. They also reduce the risk of potential
biohazardous complications. Biodegradable
scaffolds supply the initial structure and stability
for new tissue formation but degrade as tissue
forms, providing three- dimensional space for
matrix deposition and tissue growth, in the aim
to mimic the extracellular matrix in a regenerating environment. Thus, scaffolds have to be
instructive to the cells as well as provide mechanical support. Biomaterial can be used alone or in
combination with growth factors.
Growth factors are cytokines that are secreted
by many cell types and function as signaling molecules; as an example, the members of the TGF-β
family, particularly bone morphogenetic
proteins, are mostly relevant to bone tissue
engineering; in fact, BMPs promote the proliferation of mesenchymal stem cells and induce their
chondrogenic and osteogenic differentiation. For
this signicant role in bone development, BMPs
have been quite often incorporated into tissue
engineering scaffolds and delivery systems.
The choice of the cell sources depends on
accessibility and frequency of cells. Oral tissues
are a very accessible and abundant source of
highly immature mesenchymal stem cells, with
great proliferation rate and different broad range
of specialized tissue, with special regard to their
innate propensity to neural differentiation.
Dental-derived stem cells could be easily initiated to osteo- and odonto-differentiation; therefore, these cells represent an interesting powerful
tool for oral and maxillofacial regeneration.
29.4 Conclusions
Oral and maxillofacial surgery is focused on
treatment of traumatic or degenerative diseases.
Scientist efforts initially were based on guided
tissue regeneration and on the use of several biomaterials as graft substitutes and in the employment of a variety of growth factors; subsequently,
stem cell-based transplantation and new techniques based on recruitment of host cells (cell
homing) improved previous technology. The discovery of even more accessible sources of mes-
enchymal stem cells, such as oral tissues, allows
to reduce patient’s morbidity in the view of cooperating in the collective purpose to recapitulate
the microenvironmental niche, for understanding
cellular behavior, and moving to an integrated
approach to better create innovative and effective
regenerative medicine products.
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Reconstruction ofPost-Traumatic
https://t.me/medicina_free
Maxillary Ridges Using aRadial
Forearm Free Flap andAllogeneic
Tissue-Engineered Bone Grafts
JamesC.Melville, HuyQ.Tran, JonathanW.Shum,
RamzeyTursun, andRobertE.Marx
30
30.1 Introduction
Many options are available to the surgeon when
considering maxillofacial reconstruction. Since it
was rst introduced in the literature, the reconstructive ladder has upheld a solid foundation for
the novice and veteran surgeons (Fig.30.1). At the
very top of the ladder, free tissue transfer is often
the preferred choice for large maxillofacial defects
due to the ability to reconstruct both soft and bony
J. C. Melville (*) · H. Q. Tran · J. W. Shum
Department of Oral and Maxillofacial Surgery,
University of Texas Health Sciences Center at
Houston, Houston, TX, USA
Department of Oral and Head and Neck Oncology
and Microvascular Surgery, School of Dentistry,
University of Texas Health Sciences Center at
Houston, Houston, TX, USA
e-mail: James.C.Melville@uth.tmc.edu;
Huy.Q.Tran@uth.tmc.edu; Jonathan.Shum@uth.tmc.edu
R. Tursun
Department of Oral and Maxillofacial Surgery,
University of Texas Health Sciences Center at
Houston, Houston, TX, USA
Department of Oral and Head and Neck Oncology
and Microvascular Surgery, School of Dentistry,
University of Texas Health Sciences Center at
Houston, Houston, TX, USA
University of Miami, Jackson Memorial Hospital,
Miami, FL, USA
R. E. Marx
University of Miami, Jackson Memorial Hospital,
Miami, FL, USA
e-mail: rmarx@med.miami.edu
Distant flap
Local flap
Skin graft
Primary closure
Fig. 30.1 Traditional reconstructive ladder
tissues simultaneously. In 1989, the bula free
ap was rst received as a novel way of reconstructing mandibles [1]. Since then, it has
remained the workhorse for reconstruction of
tumor-resected maxillomandibular defects [2]. In
one systematic review, the author found a 99%
survival rate and 95% dental implant success rate
for vascularized bular free ap [3]. Despite its
success, an osteocutaneous free ap is an invasive
technique associated with serious morbidities [4].
As such, it may be inappropriate to harvest a bula free ap to reconstruct smaller segments of
defects when other alternatives can be explored.
In consideration of reconstructing posttraumatic maxillary alveolar ridge defect, a traditional block bone graft or an onlay graft is usually
© Springer Nature Switzerland AG 2019
D. Duscher, M. A. Shiffman (eds.), Regenerative Medicine and Plastic Surgery,
https://doi.org/10.1007/978-3-030-19958-6_30
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the rst treatment choice [5]. It requires adequate
soft tissue for coverage, a requirement that
patients of maxillofacial trauma often lack. Any
communication to the intraoral environment
almost certainly means a death sentence to the
graft. At the other end of the spectrum, one can
quickly advance the reconstructive ladder by
turning to osteocutaneous microvascular aps
such as bula free ap as an alternative. As mentioned before, they are by far the most invasive
options, are too bulky, and have incorrect geometric shape for the defect [6]. Additionally, a
history of surgery or trauma to the donor site is a
contraindication to ap harvest.
In 1982, Song et al. [7] published the rst
reported case of cutaneous radial forearm free
ap. The ap has long since remained one of the
most reliable options for reconstruction of maxillofacial soft tissue defect. It brings the advantages of shape versatility, being thin and pliable
with large- and long-caliber vessels, low donor
morbidity, and relatively simple ap harvest [8].
With such tool in the bag, we can further our
reconstructive approach by incorporating the
concept of tissue engineering. Bone marrow
aspirate has long been studied in orthopedic literature but is a relatively new concept in maxillofacial surgery [9, 10]. In immediate
reconstruction of benign tumor extirpations,
study showed excellent success rate in using a
combination of cadaver bone, bone marrow
aspirate concentrate (BMAC), and recombinant
human bone morphogenetic protein 2 (rhBMP-
2) [11, 12]. Unlike an open approach such as
iliac crest harvest, bone marrow aspiration is far
less invasive and is associated with less morbidity. In this study, all patients present with excellent regenerated bone volume and were good
candidates for dental implants during their
6-month follow-up.
30.2 Indications
1. Maxillofacial defects lacking considerable
soft tissue and bony structures.
2. Patient is not a candidate for onlay block graft
due to signicant soft tissue deciency.
3. When bula free ap is too excessive and results
in inadequate esthetic and functional results.
4. Patient is not a candidate for vascularized bula free ap due to peripheral vascular disease, other comorbidities, and previous
trauma/surgery to the lower extremities.
30.3 Contraindications
30.3.1 To Radial Forearm Harvest
1. History of trauma/surgery to both arms
2. Negative modied Allen’s test and/or abnormal duplex ultrasound
30.3.2 To BMAC Harvest
1. Bone diseases: congenital (osteogenesis
imperfecta), metabolic (osteopetrosis), and
malignant (multiple myeloma)
2. History of trauma or radiation to harvest site
30.4 Preparation ofBone Marrow
Aspirate Concentrate
The concept of tissue engineering revolves
around three familiar principles: osteoconduction, osteoinduction, and osteogenesis [13, 14].
First, the allogenic bone chips provide a conductive scaffold for the process of bone regeneration.
Second, the rhBMP-2 provides the activation signal for bone regeneration and recruiting signal
for migrating osteogenic cells. Last, the BMAC
can provide signicant amount of mesenchymal
stem cells that are capable of differentiating into
osteocytes and osteoblasts [15].
The bone marrow can be aspirated from the
anterior ilium, the posterior ilium, or the tibia. In
this chapter, we will explore the anterior iliac
approach.
The patient is rst positioned in the supine posi-
tion. Adequate padding at pressure points is needed
to avoid nerve compression and postoperative pain
and numbness. The anterior spinal iliac crest (ASIC)
is marked and the iliac crest is outlined. The surgical
site is then surgically prepped and draped.
A Nick incision using a #11 blade is made at
least 2cm posterior to ASIC.Care must be taken
to avoid dissecting anteriorly to the ASIC to
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prevent damage to the lateral femoral cutaneous
nerve, which may lead to debilitating complications such as meralgia paresthetica. Using a
hemostat, blunt dissection is done to create a pathway through several layers of the abdominal wall
until contact with the bone. A BMAC trocar system, wetted with a heparin concentrate of 1000U/
mL, is then inserted into this pathway and directed
to engage the ilium. A drill can then be used to
engage the trocar tip into the medullary cavity. At
this point, the bone marrow is ready to be collected. The inner trocar is removed, and the outer
aspirating sleeve is left in the cavity. One milliliter
of the heparin solution is rst loaded onto each
syringe to prevent coagulation during collection
and processing. The heparin solution is injected
into the bone marrow cavity prior to aspiration. At
least 60mL of the bone marrow should be aspirated for sufcient quantity of mesenchymal stem
cells and osteoprogenitor cells [16]. This can be
done with two distant harvest sites to maximize
the amount of cell concentrate. The harvest sites
can be approximated with a deep dermal suture
and closed with the surgeon’s preference of subcuticular or simple running suture.
The bone marrow aspirate is then processed
immediately after collection. The aspirate must pass
through a lter into conical tubes to remove microscopic clots and debris. Subsequently, the tubes
containing the aspirate are then centrifuged twice.
The rst centrifugation at 2400 rpm for 10 min
serves to separate the acellular plasma layer from
the cellular concentrate, with the latter transferred
into another conical tube. Another centrifugation of
3400rpm for 6 min serves to isolate the pellet of
BMA/white cell concentrate. The pellet is then
resuspended, and a nal hemanalysis and complete
blood count with differential are performed [10].
Once the radial forearm is harvested and anastomosed, the BMAC is then mixed with rhBMP-2
protein and crushed corticocancellous bone. The
mixture is packed into the alveolar ridge defect
with a resorbable mesh for stability.
30.5 The Radial Forearm Free Flap
The radial forearm free ap relies on the radial
artery for its blood supply and a dual venous system for drainage through the cephalic vein or
venae comitantes [
the volar forearm skin, the antebrachial fascia,
and the intermuscular fascia.
Preoperatively, it is important to assess any
history of trauma or surgery to the donor arm.
Modied Allen’s test (MAT) is performed to
determine the vascularity of the donor site. A
positive MAT indicates adequate dual arterial
supply of the hand by the radial artery and the
ulnar artery, such that harvesting the former
would not result in ischemia of the hand. A negative result, however, is an absolute contraindication to manipulation of radial artery. A secondary
test such as duplex ultrasound can be used for
conrmation in those with abnormal result.
Fifteen percent of the population can be expected
to have a positive MAT result, and approximately
11.6% of those will show abnormal duplex ultrasound examination [
using the donor arm for IV access.
Utilizing the Doppler ultrasound, the ap
design is drawn on the volar forearm with careful
outlining of the vessels. The distal margin of the
ap is 3cm proximal to the wrist crease, and the
proximal margin is dependent on the size needed
for reconstruction. A tourniquet of 250 mmHg
can be used for exsanguination of the arm. The
uptime is recorded at this point. The incision is
made using the ap outline. The dissection begins
at the distal margin through the skin and subcutaneous tissue. Blunt dissection technique is carried down until recognition of the exor tendons.
The dissection is then advanced proximally with
attention to identify the vascular pedicle commonly found in the septum between the brachioradialis and the exor carpi radialis muscles. The
deep branches of the radial artery can be ligated
and divided to release the deep margin of the
vascular pedicle. The proximal margin of the ap
can then be incised, and at this point, the dissection can advance distally and subdermally. After
locating the intersection of the brachioradialis
and exor carpi radialis, the two muscles are
retracted. The intermuscular septum can then be
further isolated up to the antecubital fossa. Any
attached fascia or perforators should be ligated
and divided. After achieving adequate vessel
length for the recipient site, the tourniquet is
released and downtime is recorded. The ap is
then reperfused for 15min, and the surgeon can
17]. The ap usually includes
18]. It is important to avoid
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J. C. Melville et al.
use this time to verify the patency of the vessels
and its skin perforators using the Doppler ultrasound. Once the recipient site is ready, the vessels can be ligated and divided.
At this time, the radial artery can be anastomosed to an artery of the recipient site (usually
the facial artery) and the vena comitans to a vein
(usually the facial vein). Once the graft is placed
with a resorbable mesh, the radial forearm can be
sutured around and over the graft.
Prior to closure of the donor site, a drain is
placed in the subdermal area. The donor site is
then closed with dermal sutures or staples. Splitthickness skin graft is used to cover the cutaneous defect with overlying wound-VAC therapy
for optimization of wound healing.
30.6 Case Presentation
A 45-year-old female presents for reconstruction
of left maxillary alveolar ridge defect after a
motor vehicle accident 4months prior. The injury
left her with severe vertical and horizontal alveolar bone deciency, as well as missing teeth from
the left maxillary central incisor to the second premolar. After presenting several treatment options,
the patient opted for reconstruction of maxillary
alveolar ridge defect using radial forearm free ap
combined with a tissue-engineered bone graft,
which consists of allogeneic bone, rhBMP-2, and
BMAC. Careful consideration was taken into
account the swelling and edema caused by BMP
on the overlaying radial forearm ap. Due to the
pliability and exibility of the radial forearm skin
and fascia, no venous congestion nor diminished
arterial ow was encountered. We do however
recommend taking a generous amount of the skin
and fascia to compensate for the swelling.
A series of surgeries were planned for the
complete reconstruction of her facial cosmesis,
but the rst planned surgery was to reconstruct
her alveolar bone height and restore her dentition
with endosteal implants. Due to her avulsive
injury to her anterior left maxillary alveolus, she
was missing teeth #9 thru #13 (Fig. 30.2). She
also lacked the soft tissue for a tradition block
bone graft or an only graft.
A thorough discussion of treatment options
includes All-on-4 restoration option versus full
a
b
Fig. 30.2 (a) Loss of the left maxillary alveolar ridge
with teeth #9 thru #13. (b) Post-traumatic defect with
brous scar tissue
mouth extraction and complete dentures versus
bone grafting and placement of implants. The
patient opted to go with the bone graft since she
deferred to have her remaining teeth extracted.
Various osteocutaneous microvascular aps were
considered such as the free bula ap and osteocutaneous radial forearm ap, but all were too
bulky and/or have incorrect geometric shape for
the defect. After careful consideration and a thorough discussion with the patient, we decided on a
novel reconstruction using a radial forearm free
ap combined with a tissue-engineered bone graft
consisting of allogeneic bone, rhBMP-2, and
BMAC.A modied Allen’s test was performed to
see if the ulnar artery had adequate perfusion for
the entire hand, which was positive (normal).
The surgery consisted of two teams, the rst
team exposing and preparing the alveolar defect
as well as harvesting the BMAC from the iliac
crest and the second team harvesting the radial
forearm which is under tourniquet pressure to
minimize blood loss and maximize visualization.
The radial forearm skin paddle and pedicle (radial
artery and vena comitans) were raised in-between
30 Reconstruction ofPost-Traumatic Maxillary Ridges Using aRadial Forearm Free Flap andAllogeneic…
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the brachioradialis muscle and exor carpi radialis to the antecubital fossa to gain adequate pedicle length. Once the radial forearm was harvested,
the radial artery was anastomosed to the left
facial artery and vena comitans anastomosed to
the facial vein. The area of the left maxillary
ridge was denuded of its scar tissue and the
remaining bone was exposed (Fig.30.3). Thirty
milliliter of crushed corticocancellous bone
(University of Miami Tissue Bank, Miami, FL)
and a small rhBMP-2 (Infuse) kit (Medtronic
Sofamor Danek, Memphis, TN) were mixed with
60 BMAC. The tissue-engineered graft was
placed and packed onto the defect with SonicWeld
Resorb-X
®
, a 100% amorphous, noncrystalline
poly-DL-lactic acid (PDLLA) mesh (KLS
Martin, Jacksonville, FL) (Figs.30.4 and 30.5).
The radial forearm was then sutured around and
over the graft (Fig. 30.6). With an uneventful
postoperative course, the patient was discharged
in 6days. After 6months, the bone graft demonstrated ossication and consolidation on CBCT
for placement of dental implants. The ap was
viable with good perfusion and Doppler signal
throughout the 6 months. Clinically the recon-
structed alveolar ridge showed excellent height
and ridge, and the skin of the radial forearm
mucosalized (Figs.
30.6 and 30.7). Three dental
implants were placed in a solid bone (Figs.30.8
and 30.9); at the same time, a vestibuloplasty was
performed with split-thickness skin graft from
the thigh (Fig.30.10). The patient was referred to
a maxillofacial prosthodontist for a xed partial
denture for the reconstructed ridge.
Fig. 30.5 Poly-DL-lactic acid mesh carrier
Fig. 30.3 Orthopantomogram on initial visit demonstrat-
ing decient alveolar bone for dental rehabilitation
Fig. 30.4 Exposure of alveolar defect
Fig. 30.6 BMP+B MAC+allogeneic bone
Fig. 30.7 Radial forearm ap positioned over the tissue-
engineered bone graft
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Fig. 30.8 CBCT 5months post-op imaging demonstrating consolidation and maturation of avascular bone graft underneath radial forearm ap
J. C. Melville et al.
Fig. 30.9 Six months s/p RFFF+bone graft+BMP+BMAC
Fig. 30.10 Debulking of skin paddle showing excellent
ridge formation
Fig. 30.11 Placement of three endosteal implants into
the reconstructed alveolar ridge
Fig. 30.12 CBCT of endosteal implants in reconstructed
maxillary ridge, week postoperative
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