Mandibular Trauma

Radiographic Evaluation
To adequately screen for the presence of a
mandibular fracture, at least two views at
right angles to each other are necessary. A
panoramic radiograph and a reverse
Towne’s view (Figure 22-11) are adequate
screening studies for this purpose. If only
one view is used, fractures can easily be
missed.28 In the multiple-trauma patient
for whom panoramic radiographs are not
possible, lateral oblique views may be substituted.
Other radiographic views that
may be useful depending on the circumstances
are posteroanterior mandibular,
mandibular occlusal, and periapical. Linear
tomographies of the temporomandibular
joints can also be useful in the evaluation
of fractures at the level of the condylar
process. However, intracapsular fractures

of the condylar head are often difficult to
visualize accurately on plain films.
The typical radiographic findings
when a condylar fracture is present are the
following: a shortened condylar-ramus
length; the presence of a radiolucent fracture
line or, in the case of overlapped segments,
the presence of a radiopaque
double density (Figure 22-12); and evidence
of premature contact on the side of
the fracture if the radiograph was taken
with the patient in occlusion. If more
accurate information of the involvement
of the temporomandibular joint is
required, axial and coronal computed
tomography (CT) scans offer an excellent
opportunity to study the fracture details.


Indications for CT scans are the
following:
1. Significant displacement or dislocation,
particularly if open reduction is
contemplated
2. Limited range of motion with a suspicion
of mechanical obstruction caused
by the position of the condylar segment
3. Alteration of the surrounding osseous
anatomy by other processes, such as
previous internal derangement or
temporomandibular joint surgery, to
the degree that a pretreatment baseline
is necessary
4. Inability to position the multipletrauma
patient for conventional radiographs
(CT scans may be the only
useful radiograph that can be obtained)


Chayra and colleagues reviewed the
need for a complete series of films.29 They
concluded that the initial screening of
patients could be effectively undertaken
with a panoramic radiograph alone.Ninetytwo
percent of fractures were seen on a
panoramic radiograph alone, compared
with only 66% on a routine radiographic
series without a panoramic view. However,
in order to accurately visualize displacement
it is recommended that the standard
mandibular views consist of a panoramic
radiograph, a posteroanterior mandibular
view, and reverse Towne’s view (Figure 22-
13). The latter view allows for visualization
of the degree of medial or lateral displacement
of the fracture and unveils injuries in
which only subtle deviation is present, such
as is seen in greenstick fractures, which are
not readily evident on panoramic view.


The panoramic radiograph usually
requires the patient to be able to stand
upright and also requires accurate patient
positioning for good-quality films. In the
severely traumatized patient, this may be
difficult to achieve with some machines.
Further, mesiolateral displacement in the
ramus and body and anteroposterior displacement
in the symphyseal regions may
also be difficult to visualize. The traditional
lateral oblique views of the mandible can be
used when panoramic films are not possible.
They require accurate positioning of
the patient and film to obtain useful views,
particularly in the condylar area. A transcranial
temporomandibular view may be a
good addition in these circumstances.


Accurate assessment of symphyseal
fractures may be problematic with the
standard views. A mandibular occlusal
view is particularly useful in this scenario.
It also aids in the assessment of the fracture
of the lingual plate, particularly in
very oblique fractures. Periapical views
may also be necessary for evaluation of the
teeth on either side of the fracture line to
assess root fractures, periapical and periodontal
pathology, and the relationship of
the fracture line to the periodontal ligament
of each tooth.


Classification
The first step in the development of an
appropriate treatment plan is to establish
a clear understanding of the type of
injury the patient has suffered, in order
to provide an adequate surgical solution.
In the diagnostic work-up phase, the lack
of standardized ways to assess and characterize the nature and severity of
the orofacial injury engenders variation
in practice patterns.30 Probably the most
basic question one should ask at the initial
evaluation is whether the fractures
are displaced or nondisplaced. Depending
on the amount of energy transmitted
to the facial skeleton and the vector in
which such force is directed, there will be
more or less disruption of the normal
anatomic structures. Muscle attachment
and their counteracting forces also play a
primary role in the pattern and direction
of the fractures. It is the displacing forces
of the muscles of mastication that influence
favorableness (Figures 22-14 and
22-15). The principle of favorableness is
based on the direction of a fracture line
as viewed on radiographs in the horizontal
or vertical plane. A horizontally favorable
fracture line resists the upward displacing
forces, such as the pull of the masseter and temporalis muscles on the
proximal fragment when viewed in the
horizontal plane. A vertically favorable
fracture line resists the medial pull of the
medial pterygoid on the proximal fragment
when viewed in the vertical plane.
In the parasymphyseal region of the
mandible, the combined action of the
suprahyoid and digastric muscles on a
bilateral fracture can pull on the distal
fragment inferiorly in unfavorable fractures,
putting the patient at risk for acute
upper airway obstruction.


The first concern is whether there are
indeed fractures present, and if there are,
where they are located anatomically.
Mandibular fractures may be further classified
by the pattern of fracture (Figure 22-
16) present and by anatomic location.


Many systems of classification have
been applied to fractures involving the
mandibular condyle.24,31–35The recommended
classification parallels the comprehensive
classification set forth by Lindahl.
24 As mentioned before, it is
imperative that radiographs be taken of
the suspected injury in two planes at right
angles to each other. The following major
relations are noted: the level of the fracture;
the relation of the condylar fragment
to the mandible, termed the degree
of displacement; and the relation of the
condylar head to the fossa, or the degree of
dislocation.


Anatomic Location
The following classification has been modified
from Kelly and Harrigan’s epidemiologic
study in which they divided
mandibular fractures based on their
anatomic location36:
• Dentoalveolar fracture: Any fracture
that is limited to the tooth-bearing
area of the mandible without disruption
of continuity of the underlying
osseous structure
• Symphysis fracture: Any fracture in
the region of the incisors that runs
from the alveolar process through the
inferior border of the mandible in a
vertical or almost vertical direction
• Parasymphysis fracture: A fracture that
occurs between the mental foramen and
the distal aspect of the lateral mandibular
incisor extending from the alveolar
process through the inferior border
• Body fracture: Any fracture that occurs
in the region between the mental foramen
and the distal portion of the second
molar and extends from the alveolar
process through the inferior border
• Angle fracture: Any fracture distal to
the second molar, extending from any
point on the curve formed by the
junction of the body and ramus in theretromolar area to any point on the
curve formed by the inferior border of
the body and posterior border of the
ramus of the mandible
• Ascending ramus fracture: A fracture in
which the fracture line extends horizontally
through both the anterior and
posterior borders of the ramus or that
runs vertically from the sigmoid notch
to the inferior border of the mandible
• Condylar process fracture: A fracture
that runs from the sigmoid notch to
the posterior border of the ramus of
the mandible along the superior
aspect of the ramus; fractures involving
the condylar area can be classified
as extracapsular or intracapsular,
depending on the relation of the fracture
to the capsular attachment


Pattern of Fracture
The following classification is based on pattern
of fracture (see Figure 22-16):
• Simple fracture: A simple fracture consists
of a single fracture line that does
not communicate with the exterior. In
mandibular fractures this implies a
fracture of the ramus or condyle or a
fracture in an edentulous portion with
no tears in the periosteum.
• Compound fracture: These fractures
have a communication with the external
environment, usually by the periodontal
ligament of a tooth, and involve all fractures
of the tooth-bearing portions of
the jaws. In addition, if there is a breach
of the mucosa leading to an intraoral
communication or a laceration of the

skin communicating with the fracture
site, edentulous portions of the
mandible may be involved.
• Greenstick fracture: This type of fracture
frequently occurs in children and
involves incomplete loss of continuity
of the bone. Usually one cortex is fractured
and the other is bent, leading to
distortion without complete section.
There is no mobility between the
proximal and distal fragments.
• Comminuted fractures: These are
fractures that exhibit multiple fragmentation
of the bone at one fracture
site. These are usually the result of
greater forces than would normally be
encountered in simple fractures.
• Complex or complicated fracture: This
type of injury implies damage to structures
adjacent to the bone such as major
vessels, nerves, or joint structures. This
usually implies damage to the inferior
alveolar artery, vein, and nerve in
mandibular fractures proximal to the
mental foramen and distal to the
mandibular foramen. On rare occasions
a peripheral branch of the facial nerve
may be damaged or the inferior alveolar
nerve injured in subcondylar fractures.
• Telescoped or impacted fracture: This
type of injury is rarely seen in the
mandible, but it implies that one bony
fragment is forcibly driven into the
other. This type of injury must be disimpacted
before clinical movement
between the fragments is detectable.
• Indirect fracture: Direct fractures arise
immediately adjacent to the point of
contact of the trauma, whereas indirect
fractures arise at a point distant
from the site of the fracturing force.
An example of this is a subcondylar
fracture occurring in combination
with a symphysis fracture.
• Pathologic fracture: A pathologic fracture
is said to occur when a fracture
results from normal function or minimal
trauma in a bone weakened by
pathology. The pathology involved

may be localized to the fracture site,
such as the result of a cyst or metastatic
tumor, or as part of a generalized
skeletal disorder, such as osteopetrosis.
• Displaced fracture: Fractures may be
nondisplaced, deviated, or displaced.
A nondisplaced fracture is a linear
fracture with the proximal fragment
retaining its usual anatomic relationship
with the distal fragment. In a
deviated fracture, a simple angulation
of the condylar process exists in relation
to the remaining mandibular
fragment, without development of a
gap or overlap between the two segments.
Displacement is defined as
movement of the condylar fragment
in relation to the mandibular segment
with movement at the fracture site.
The fragment can be displaced in a lateral,
medial, or anteroposterior direction.
In displaced fractures the articular
surface of the condyle remains
within the glenoid fossa and does not
herniate through the joint capsule.
• Dislocated fracture: A dislocation
occurs when the head of the condyle
moves in such a way that it no longer
articulates with the glenoid fossa.
When this is associated with a fracture
of the condyle, it is termed a fracture
dislocation. Fracture dislocations are
discussed more completely later in this
chapter. The mandibular condyle may
also be dislocated as a result of trauma
without an associated condylar fracture.
Dislocations can occur anteriorly,
posteriorly, laterally, and superiorly.
• Special situations: Other types of fractures
that do not readily fit the above
classification include grossly comminuted
fractures or fractures involving
adjacent bony structures, such as the
glenoid fossa or tympanic plate; open
or compound fractures; and fractures
in which a combination of several different
types of fractures exist. Open
fractures of the condyle are usually
caused by missiles such as bullets.


Nonfracture Injuries of the
Articular Apparatus
The most commonly documented result of
trauma to the articular apparatus and
mandibular condyle is fracture. Other
injuries occur as well and must be considered
in the differential diagnosis (Table 22-1).
Anterior dislocation occurs when the
condyle moves anterior to the articular
eminence. This is by far the most common
situation and represents a pathologic forward
extension of the normal translational
movement of the condylar head. Unlike
subluxation, which is also a forward extension
of the condyle, dislocation is not selfreducing.
Dislocation may be caused by
yawning, oral sex, phenothiazine use, and
trauma. Traumatically induced anterior
dislocation is most commonly bilateral,
but it may occur unilaterally (particularly
if associated with a concomitant fracture
elsewhere in the mandible). The diagnosis
of an anteriorly dislocated mandible is
made by the following clinical features: an
anterior open bite with the inability to
close the mouth; severe pain in the region





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