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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5184_Библиотеки_им_академика_М_И_Перельмана.pdf
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Imaging oftheCommon Conditions oftheTemporomandibular Joint
71
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H. Demirturk and A. Potluri
e
Fig. 5 Coronal (a and b), sagittal (c and d), and 3D vol-
ume rendering (e) CBCT images show right condylar
hyperplasia accompanied by hemimandibular elongation
resulting in transverse plane asymmetry, leading to chin
deviation toward the contralateral side. Right condylar
process is large (a and c) compared to the normal left side
(b and d) with normal cortical borders and subchondral
bone
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Imaging oftheCommon Conditions oftheTemporomandibular Joint
73
Fig. 6 CBCT images illustrate a bid condyle in a
mediolateral orientation. The coronal image (a) depicts a
heart-shaped condyle, while the sagittal image (b) reveals
3. Bid condyle
Bid condyle is characterized by the
presence of a groove or depression of varying depth on the mandibular condyle, resulting in partial division of the condyle
(Fig.6). Condition is usually observed unilaterally, although there have been reports
of bilateral bid condyles. Trid condyles
have also been documented, but they are a
rare phenomenon compared to bidity.
attening and minor depression in the center of the superior aspect of the right condyle
in the anteroposterior case, they appear as
two condyles, one located anterior to the
other in sagittal reformat images.
• Mandibular fossa can undergo remodeling
to adapt to the changed condylar
morphology.
• Traumatic causes may lead to bony
ankylosis.
• Condyle appears lobulated in panoramic
radiograph.
Bidity’s cause is still debated, with theories ranging from possible embryonic origins tied to limited blood supply to the
3.2 TMJ Internal Derangements
condylar head, trauma, or microtrauma
from sources like birth-related injuries or
condylar head fractures to factors such as
genetic or systemic conditions, infections,
and radiotherapy.
Imaging:
• Depression or notch on the superior condylar surface or a complete duplication with
continuous cortex.
• Orientation of the condyles can be either in
the mediolateral or in the anteroposterior
plane. In the mediolateral case, they resemble a heart shape in coronal images, while
Internal derangements, characterized by alterations in the disc’s morphology or position within
the TMJ, can be triggered by factors such as
trauma, malocclusion, ligament laxity, or other
conditions that exert pressure on the disc causing
it to shift from its normal location. Once the disc
is displaced, it initiates a breakdown in the usual
joint function. The following discussion will outline the progression from internal derangement to
degenerative joint disease, along with the different forms of these derangements and the various
stages of degenerative joint disease.
74
H. Demirturk and A. Potluri
Disc displacement is considered to have four
clinical stages:
• Stage I (disc displacement with reduction):
The articular disc is displaced when the mouth
is closed but returns to its normal position
when the mouth is opened; the central narrow
zone of the disc is in contact with the condylar
head and articular eminence when the mouth
is opened.
• Stage II (disc displacement with reduction
with intermittent locking): The disc is displaced when the mouth is closed and intermittently locked in position when the mouth is
opened.
• Stage III (disc displacement without reduction): The disc is displaced when the mouth is
closed and does not return to its normal position when the mouth is opened. This condition
is sometimes referred to as a “closed lock.”
• Stage IV (disc displacement without reduction): In the nal stage, the disc is permanently
displaced and does not return to its normal
position, with perforation of the disc or posterior (band) attachment tissues.
Degree of Disc Displacement: Disc displace-
ment can manifest as either partial or complete.
In cases of partial displacement, the disc undergoes morphological changes, adopting either a
biplanar appearance (characterized by the attening of the posterior band) or a biconvex shape
(associated with thickening of the posterior band,
typically observed when the condyle is positioned posteriorly). Conversely, a completely displaced disc that has been acutely displaced retains
its biconcave appearance (Figs. 7 and 8).
However, over time, it may gradually lose its
original shape and anteroposterior length, eventually leading to atrophy (Fig.9).
Direction of Disc Displacement: Disc dis-
placement can be presented in multiple directions. The most common form is anterior disc
displacement (Figs. 7, 8, 9, and 10). Other
forms include anterior rotational displacement
where the disc slides off of just one pole while
maintaining a normal relationship with the
remaining portions of the condyle (Fig. 11),
sideways displacement in either a purely lateral
or medial direction (Fig.12), or posterior displacement which should be distinguished from
the thickening of the intermediate posterior
attachment, also referred to as “pseudodisc formation” (Fig.9).
Disc Displacement with Reduction
(DDWR): DDWR is among the most prevalent
intra-articular disorders. DDWR can be found in
approximately 33% of asymptomatic individuals.
In individuals with DDWR, the disc is displaced
relative to the condyle when the mouth is closed.
However, when the mouth is opened, the disc
returns to the intermediate position between the
condyle and the articular tubercle. The disc
returns to its displaced state once again upon
closing the mouth (Figs.10 and 13).
Following the reduction of the disc during
condylar translation, there is typically no restriction in the range of motion. However, mandibular
movements may not exhibit the same level of
smoothness as in a normal condition due to the
momentary sliding of the condyle on and off the
disc. Nevertheless, once the mouth reaches the
fully open position, the ultimate alignment of the
condyle and the disc in a joint with DDWR is
nearly identical to that in a joint without displacement. Clinically, DDWR is associated with TMJ
noise. The movement of the disc onto and off of
its proper position can produce clicking, snapping, and/or popping sounds, collectively known
as opening and closing “clicks.”
Disc Displacement Without Reduction
(DDWOR): In the closed-mouth position, the
disc is displaced relative to the condyle, and the
disc does not return to its normal position with
mouth opening. The displaced disc mechanically
hinders the condyle’s translation, resulting in
restricted jaw opening and a jaw deviation toward
the affected side.
Signs encompass a maximum assisted mouth
opening of less than 40mm, mandibular deection to the ipsilateral side during opening and
protrusion, and limited movement toward the
contralateral side. Symptoms may involve sharp,
sudden, and intense pain localized around the ear
area and a sudden reduction in mandibular movement due to the “closed lock.” As time passes and
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Imaging oftheCommon Conditions oftheTemporomandibular Joint
75
Fig. 7 Sagittal T1WI closed-mouth image (a) shows
anterior disc displacement, with the disc (white arrow)
positioned inferior to the crest of the articular eminence
and the condyle situated posteriorly within the mandibular
fossa. Assessment of the condylar position should consider its relationship with the fossa and the disc, not just
the disc’s relation to the condyle. In the sagittal T1WI
open-mouth image (b), the disc (white arrow) exhibits a
slight anterior movement yet remains inferior to the crest
of the eminence, while the condyle remains positioned
posterior to the crest of the eminence, indicating anterior
disc displacement without reduction and limited mouth
opening. The disc relatively retains its biconcave shape
and anteroposterior dimension, suggesting an acutely displaced disc. (Courtesy P.Celenk, DDS)
Fig. 8 (a) and (b) show anterior disc displacement with-
out reduction on sagittal closed (a) and open (b) PD MR
images. In the closed position, the condyle is positioned
posteriorly in the mandibular fossa, and the disc (arrow) is
slightly posterior to the crest of the articular eminence. In
the open position, the condyle translates posterior to the
crest of the articular eminence, and the disc (arrow) is
anterior to the condyle and anteroinferior to the crest of
the articular eminence. The disc maintains its biconcave
appearance and anteroposterior dimension suggestive of
an acutely displaced disc
76
Fig. 9 The sagittal closed T1 MR image reveals osteophyte, sclerosis, and vertical height loss of the condyle,
and attening of the eminence consistent with degenerative joint disease, as well as a chronically anteriorly displaced disc (arrow) that has altered shape. A pseudodisc
formation (thin arrow) can be seen posterior to the displaced disc and superior to the condyle. The thickening
and brosis of the posterior attachment create a disclike
appearance, which in some instances may be misinterpreted as a posteriorly displaced disc. (Courtesy ST
Gokdeniz and K.Orhan, DDS)
tissues adapt, the range of motion is gradually
regained, leading to a subsiding of symptoms
(Figs.7 and 8).
3.2.1 Bone Marrow Edema andJoint
Eusion
During growth, the composition of bone marrow
in the mandible undergoes a transformation, initially being predominantly hematopoietic marrow and gradually transitioning to mostly fatty
marrow. On imaging sequences like T1WI and
uid-sensitive images such as T2WI with fat saturation or STIR, the signal intensity of the temporal and mandibular bones reects the changing
proportions of hematopoietic and fatty marrow.
In infants, bone marrow signal intensity appears
low on T1-weighted images (similar to muscle)
and intermediate on uid-sensitive sequences
(appearing brighter than muscle but darker than
uid). As individuals age and the proportion of
fatty marrow increases, the signal intensity eventually becomes the same as subcutaneous fatty
tissue across all imaging sequences.
H. Demirturk and A. Potluri
In acute trauma cases, the bone marrow can
become edematous, resulting in a high signal
intensity in the subchondral bone on T2WI.This
signal is typically intermediate to low on T1WI
or PDWI.
Joint Fluid
Similar to other synovial joints, the TMJ also
contains a small quantity of joint uid. This uid
is derived from plasma through a process known
as dialysis and is secreted by the synovial membrane. Normal, physiological amount of joint
uid may not be apparent on T1WI.However, it
becomes easily detectable on T2WI, where it
appears as an area with high signal intensity,
similar to other uids (i.e., showing an isointense
signal compared to cerebrospinal uid). Small
dots or lines of high signal intensity within the
joint recesses, not exceeding 1mm in width, can
be considered a physiological amount of joint
uid. These should not be misinterpreted as joint
effusion, which typically involves a larger uid
accumulation and can indicate an underlying
medical condition.
Synovitis and the resulting joint effusion are
best seen on T2WI, presenting as regions of
increased signal intensity (hyperintensity)
(Fig. 14). This uid accumulation can happen
within a single compartment or affect both, creating an “arthrographic effect” that accentuates the
disc shape (Fig.14).
If there is effusion in just one joint compartment, it can reveal a perforation in the disc or its
attachments when the uid leaks into the other
compartment. Additionally, this uid can demonstrate movement within a compartment during
jaw opening, aiding in visualizing the detachment of the temporal posterior attachment (TPA)
from the glenoid fossa. In cases of acute microor macro-trauma, the bone marrow can exhibit
edematous changes, leading to a high signal
intensity in the subchondral bone on T2-weighted
images, while appearing intermediate to low signal intensity on T1- or PD-weighted images.
3.2.2 Subluxation
The most frequent TMJ subluxation or dislocation in a non-fractured mandible involves bilat-
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Imaging oftheCommon Conditions oftheTemporomandibular Joint
77
Fig. 10 Sagittal PD MR images show anterior disc displacement with reduction: In the closed view (a), the posterior band of the disc is located at the 9 o’clock position
relative to the condyle. In the open view (b), the condyle
translates to a position slightly posterior to the crest of the
eminence, and posterior band of the disc is located
between anterosuperior aspect of the condyle and posterior slope of the articular eminence consistent with partial
reduction and slightly limited opening. (c) Sagittal view
shows anteriorly displaced disc in the closed position.
Upon opening (d), the condyle translates to a position just
inferior and posterior to the articular eminence’s crest
suggestive of mild decrease in the range of motion, while
the disc, situated between the joint surfaces, corresponds
to the junction between the anterior band and the intermediate zone. In open-mouth position, the point of intersection between intermediate zone and anterior band should
be positioned between the articular surfaces
78
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H. Demirturk and A. Potluri
Fig. 11 PDWI sagittal images show anterior rotational
disc displacement. (a) The central area of the TMJ displays a relatively normal disc-condyle relationship (11
eral dislocation of the mandibular heads anteriorly
to the articular tubercles without spontaneous
reduction.
o’clock position). (b) Meanwhile, in the lateral region of
condyle
ography, CBCT, and MRI.These diagnostic procedures can help to rule out facial fractures and
give information for further treatment plans.
The condyle is situated in an anterior and
superior position relative to the crest of the eminence. Within this context, the part of the disc
located between the bony elements is referred to
as the anterior band, and it often sits between the
posterior aspect of the condyle and the anterior
slope of the eminence (Figs. 13 and 15). This
hypermobility can be observed in patients with
Ehlers-Danlos syndrome and joint laxity. In addition to neurological and neuromuscular conditions, the absence of posterior support due to
advanced tooth loss is considered a predisposing
factor for TMJ dislocation.
Typically, individuals in the age range of
25–45years are affected. The most common triggers are routine activities that involve wide mouth
opening, such as yawning, laughing, or biting.
During clinical examination, an empty TMJ
socket can be observed. Additionally, long-term
dislocation may manifest signs of malnutrition in
some cases.
Patients with symptoms that could suggest
other differential diagnoses should undergo
imaging examinations, including panoramic radi-
3.2.3 Disc Adhesion
To achieve a full range of jaw movement, it is
essential for the condyle to rotate, moving along
the inferior part of the disc. Furthermore, the
mandibular condyle/disc pair must glide
smoothly along the posterior aspect, vertex, and
lower portion of the articular eminence. This
arrangement provides wide mouth opening, lateral movement, protrusion, and retrusion.
Disc adhesion refers to the bands of connective tissue that connect the disc with the intracapsular structures. The brous connection of the
disc can happen either in the superior compartment (which is more common and restricts
motion to a greater extent) or in the inferior compartment. Jaw may deviate to the affected side
during mouth opening. In cases of superior compartment adhesions, when the jaw opens, the condyle moves, but the position of the disc remains
unchanged in comparison to its closed position
(Fig.16).
Adhesion of the disc to the articular fossa can
eventually prevent the gliding of the disc, result-
Imaging oftheCommon Conditions oftheTemporomandibular Joint
a b
c d
79
Fig. 12 PDWI coronal and sagittal images show sideways disc displacement: (a
signal medial portion of the disc (black arrow), which is
folded over the medial pole while the lateral superior portion is lacking the disc (white arrow). (b) Sagittal image
depicts the absence of a posterior band of the disc superior
to the condyle in the lateral portion of the TMJ (white
) Coronal image reveals a low-
ing in a signicant restriction of mouth opening.
This attachment could mark the initial phase of a
progression that may develop into anterior displacement with adhesion or even progress to
osteoarthritis.
arrow). (c) Sagittal image reveals a low-signal disc that is
folded over the lateral pole in the lateral aspect of the TMJ
(black arrow). (d) T1WI coronal view in a different patient
illustrates anteromedial disc displacement. Medial portion
of the disc folded over the medial pole (white arrow)
while the lateral pole lacking the disc (black arrow).
(Courtesy T Gokdeniz and K Orhan, DDS)
3.2.4 Functional Remodeling
oftheTemporomandibular
Joint
Functional remodeling of the TMJ denotes the
adaptive adjustments in the joint due to changes
80
H. Demirturk and A. Potluri
a
c
b
d
Fig. 13 T1WI (a) and PDWI (b–d) sagittal images show
bilateral hypermobility and anterior disc displacement
with reduction. In the closed-mouth position, the right
condyle is centered (a), while the left condyle is posteriorly positioned (c) within the fossa, and the disc is anteriorly displaced on both sides. In the open-mouth position
in functional requirements or conditions (Fig.17).
This dynamic phenomenon encompasses the
modication of different components within the
TMJ, such as the joint surfaces, articular discs,
and related ligaments.
Functional remodeling can be prompted by
various factors, such as muscle activity, patterns
of jaw movement, and occlusion (bite) alterations. For instance, when there is an irregular jaw
movement or abnormal bite, the TMJ may adap-
(b and d), both condyles translate to a point anterior and
superior to the crest of the eminence. The intermediate
zone of the disc is positioned between the posterior aspect
of the condyle and the anterior slope of the eminence
(arrows)
tively change to accommodate these functional
requirements. These adaptations may involve
modifying the position and form of the joint surfaces, remodeling the articular disc, and adjusting
the alignment and tension of the related
ligaments.
Functional remodeling is a multifaceted process that can differ based on individual factors
like genetic makeup, age, and overall health.
Functional remodeling is a normal occurrence