Functional structure
of the skull
and
Fractures of the
skull
Functional structure of the skull
According to strain and produced forces on
the skull bones we have thickened and
thinner parts of the skull.
- the transmission of masticatory forces,
traction of nuchal and cervical muscles …
- fracture predilection
Functional structure of the skull Facial
buttresses system
▪ thin (fragile) segments of bone are encased
and supported by more rigid framework of
"buttresses"
▪ The midface is anchored to the cranium
through this framework
▪ It is formed by thickened parts of frontal,
maxillary, zygomatic and sphenoid bones and
their attachments to one another
▪ The buttress system
absorbs and transmits
forces applied to the
facial skeleton
▪ Masticatory forces are
transmitted to the skull
base and skull vault
primarily through the
vertical buttresses, which
are joined and
additionally supported by
the horizontal buttresses
Vertical buttress
▪ nasomaxillary
▪ zygomaticomaxillary
▪ pterygomaxillary
Horizontal buttress
▪ glabella
▪ orbital rims
▪ zygomatic processes
▪ maxillary palate
„framework“ of the skull
2 nasomaxillary butt. (1-4)
3 zygomaticomaxillary butt.
(5-6)
4 pterygomaxillary butt.(7,8)
1
4
3 2
Maxilla
Base of proc. alv. – upper
basal arch (1), together with
the hard palate forms the socalled
palatinal plate, into
which the system of pillars is
embedded.
Strain that occurs from mastication /or trauma/ is
transferred from the inferior of the mandible also
via various trajectory lines (thickened patrs)
→ to the condyles → articular fossa → temporal
bone (small part of masticatory forces)
1. dentale
2. basilare
3. posticum
4. marginale
5. praeceps
6. copolans
7. transversum
1
2
3
4
5
6
7
Mandibula
Short columns protrude from the lower teeth to the lower
basal arch (tr. basilare) and through crista colli
mandibulae to caput mandibulae.
Trajectorium:
Vault - Thickened parts:
▪ tubera frontalia
▪ tubera parietalia
▪ protuberantia occipitalis ext. et int.
▪ linea temporalis
▪ margin of sulcus sinus sagitalis sup.
et transversus
Cranial base Thickened
parts:
Base centre and the most
solid part - pars
basilaris ossis
occipit.
▪ sagittal line
▪ ventral lateral line
▪ dorsal lateral line
.
Thinner parts of
splanchnocranium
➢ Sinus maxillae
➢ Orbita
➢ Nasal cavity
Thinner parts of
skull base
▪ articular fossa
▪ cribriform plate
▪ foramines, canals and
fissures
▪ anterior, medial and
posterior cranial fossa
Transmission of chewing pressure
Periodontal ligaments connecting the root of the tooth with the wall of
the alveolus by their pull on the adjacent bone cause the formation of
bone beams and the formation of so-called trajectories. These
trajectories deviate from the tips of the roots in a fan shape, they
capture small movements of the teeth in the alveolus during chewing,
they act against tensile forces from the periodontium.
Thickened beam - the pillars transmit and neutralize the masticatory
pressures from the upper dental arch to the base and vault of the skull,
they are anchored in the bone plate (formed by the hard palate and the
upper part of the alv.proc. The task is to put resistance to the pressure
that the lower jaw exerts on the upper jaw during the bite and to
transmit the chewing pressures from the splanchnocr. to neurocr.
The pillars run regardless of the anatomical boundaries of the individual
bones. The compact and beams of spongiosis are reinforced - arranged
in the direction of the load. The maxillary sinus is located in the
mechanically empty area of splanchnocr.
▪ When external
forces are applied,
these components
prevent disruption
of the facial
skeleton until a
critical level is
reached and then
fractures can occur
Fractures of the skull
We can divide:
➢ Infraction / fracture without dislocation /
dislocated fracture
➢ Simple / multiple (more fracture lines in one bone) /
comminuted fr. (more irregular fr.lines)
➢ Closed / open – compound (associated with soft
tissue injury, where the fractured bone is in direct
communication with the outside environment)
➢ Primary / secondary
■ hit hard by a moving object
■ the impact of the head on a stationary hard object
■ compression effect (between 2 subjects)
■ pulse mechanism without direct mechanism of
action on the skull (alternation of acceleration and
deceleration - traffic accidents)
Etiology of injury
Alternation of tensile
and compressive forces
acting on the brain
■ dimensions, weight, shape, consistency and
elasticity of the object
■ direction, speed and magnitude of the force
of the blow
■ movement of the head after hit
■ place of violence (bone thickness, curvature)
■ skull elasticity, age
■ fractures due to a patholog. processes
The type and extent of skull
fractures depends on:
II. Craniofacial
fractures
I. Neurocranial
fractures
I. Neurocranial fr. of the cranial vault
▪ A break in the skull bone generally occurs as a
result of a direct impact
▪ If the force and deformation is excessive, the
skull fractures at or near the site of impact
▪ Uncomplicated skull fractures themselves rarely
produce neurologic deficit, but the associated
intracranial injury may have serious
neurologic consequences !
1. Linear skull fracture
▪ Most common
▪ Involve a break in the bone
but no displacement
▪ Usually the result of low-energy transfer
▪ Due to blunt trauma over a wide surface area
of the skull
▪ Are usually of little clinical significance
Linear skull fracture
2. Depressed skull fractures
A fracture is clinically
significant and sometimes
requires surgical elevation of
the fragments
Closed or compound (open)
Compound fractures may occur
when they are associated with a
skin laceration or when the fracture
extends into the paranasal sinuses
or the middle-ear structures
Depressed fractures
are usually
comminuted,
with broken
portions of bone
displaced inward and
may require
surgical intervention
to repair underlying
tissue damage
Depressed fracture
3. Basilar skull fractures
▪ A basilar skull fracture is a break of a bone in the
base of the skull.
▪ Usually indirect force
▪ Basilar fractures are the most serious!
▪ Can be isolated or together with fractures of
cranilal vault / calvaria
▪ Fracture lines often occur at predilection sites
Spreading of the fracture lines
Basilar fractures
characteristic signs:
- blood in the sinuses
- a clear fluid - cerebrospinal fluid (CSF) leaking
from the nose (rhinorrhea) or ears (otorrhea)
- periorbital ecchymosis often called 'raccoon eyes
- retroauricular ecchymosis known as "Battle's
sign„
- pneumocephalus
Symptoms and complications of
skull fracture
▪ Otorrhea, rhinorrhea, epistaxis, bleeding
▪ Battle´s sign, Raccoon eyes
▪ Cranial nerve lesion …
▪ Pneumocephalus
▪ Intracranial hemorrhage: extradural / epidural
subdural
subarachnoideal
intracerebral
▪ Damage of the brain, brain oedema, hypoxy,
posttraumatic epilepsy, meningitis …
Rhinorrhea Otorrhea
A cerebrospinal fluid (CSF) leak occurs in about 20% of
cases of a basilar skull fracture and can result in fluid
leaking from the nose or ear
High risk of infection!
Battle´s sign
Battle's sign, also known as mastoid ecchymosis, is an indication of
fracture of middle cranial fossa of the skull. These fractures may be
associated with underlying brain trauma.
Battle's sign consists of bruising over the mastoid process as a result of
extravasation of blood along the path of the posterior auricular artery
Raccoon eyes –
periorbital ecchymosis
They are most often
associated with
fractures of the anterior
cranial fossa
Raccoon eyes (also known in the United
Kingdom and Ireland as panda eyes) or
periorbital ecchymosis is a sign of basal
skull fracture
Cranial nerve lesion
I. (Olfactory n.) - loss of smell
(anosomia)
II. (Optic n.) - loss of vision,
abnormal pupillary reflex
III. (Oculomotor n.) - loss of
accommodation, lateral strabism
VI. (Abducens n.) - medial strabism
VII. (Facial n.) - paralysis
VIII. (Auditory n.) - hearing loss
➢ presence of
intracranial gas /
air
➢ is most commonly
encountered
following trauma or
surgery
Pneumocephalus
NOTE! Extradural = epidural
Extradural hemorrhage
▪ An arterial bleeding from a
middle meningeal artery
accumulates and forms a
hematoma
▪ Between the inner skull
table and dura matter
▪ The temporal bone is
usually the thinnest part of
the skull
Dura mater
Arachnoidea
Pia mater
Bone
Epidural hemorrhage
Subdural hemorrhage
▪ tears of the small veins that bridge the gap between the
dura and the cortical surface of the brain
▪ Between the dura matter and arachnoid
Subarachnoid hemorrhage
▪ A result of a ruptured of intracranial arterial aneurysm or
trauma
Intracerebral hemorrhage
▪ A result of a ruptured
atheromatous intracerebral
arteriole, vasculitis, ruptured
intracranial arterial aneurysm, or
trauma
▪ Traumatic intracerebral
hemorrhage is usually due to
extension of hemorrhage from
surface contusions deep into the
substance of the brain
Subdural
IntracerebralSubarachnoid
Epidural
II. Craniofacial Fractures
1. Mandible
2. Lower mid-face
3. Upper mid-face
1. Fracture of the mandible
Body fractures
▪ Between the distal aspect of the canines and a
hypothetical line corresponding to the anterior
attachment of the masseter, proximal to the third
molar
▪ The actions of the masseter, temporalis, and
medial pterygoid muscles distract the proximal
segment superomedially
▪ The mylohyoid muscle and anterior belly of the
digastric muscle may contribute to the displacing
the fractured segment posteriorly and inferiorly
Bilateral fracture in the canine location
Dislocation of the chin part dorsocaudally by the pull of
depressors -> the root of the tongue sinks back to
the oropharynx
Symphyseal and parasymph. fractures
▪ In the midline of the mandible are
classified as symphyseal
▪ When teeth are present, the
fracture line passes between the
mandibular central incisors
▪ fr. not in the midline, are classified
as parasymphyseal
Angle fractures
▪ Occur in a triangular region between the
anterior border of the masseter and the
posterosuperior insertion of the masseter,
distal to the third molar
▪ The actions of the masseter, temporalis, and
medial pterygoid muscles distract the
proximal segment superomedially
Condylar process fractures
▪ Classified as extracapsular, intracapsular and subcondylar
▪ The lateral pterygoid muscle tends to cause anterior and
medial displacement of the condylar head
Lower mid-face
Upper mid-face
2. Lower midfacial fracture
Le Fort I or low horizontal fractures:
From nasal septum to the lateral pyriform rims horizontally
above the teeth apices
→ below the zygomaticomaxillary junction,
and traverses the pterygomaxillary junction
to interrupt the pterygoid plates
3. Upper midfacial fracture
a) Naso-orbitoethmoid Fractures
b) Zygomaticomaxillary Complex
c) Orbital fractures
d) Le Fort II
e) Le Fort III
a) Naso-orbitoethmoid Fractures
▪ The NOE complex represents a bony
fractures that separate the nasal, orbital,
and cranial cavities (the nasal, frontal,
maxillary, ethmoid, lacrimal, and sphenoid
bones)
▪ If there is bilateral comminution and
displacement, the nasofrontal ducts are
disrupted - predisposes the patient to
future mucocele formation
▪If the fracture
segments are
displaced, nasal
bones and frontal
process of the
maxilla may be
telescoped
posteriorly beneath
the frontal bone
▪In patients with comminution, the bony segments may
spread medially into the nasal cavity, superiorly to the
anterior cranial fossa, and laterally into the orbit
Damage of the angulus med. dx.
-> enlargement of the interorbital
distance
= telecanthus
Isolated fractures of nasal bones
b) Zygomaticomaxillary Complex
▪ Fracture lines usually run through
the infraorbital rim, involve the
posterolateral orbit, and extend to the
inferior orbital fissure
▪ The fracture line then continues to
the zygomatic sphenoid suture area
and on to the frontozygomatic suture
line
▪ All zygomatic complex fractures
involve the orbit, making visual
complications a frequent occurrence
c) Orbital Fractures
The fractures of orbital skeleton include blow-out
(hydraulic) fr.
Fractures associated with other fractures of the facial
skeleton (zygomaticomaxillary, naso-orbito-ethmoid,
frontal-sinus, Le Fort II, and Le Fort III fracture)
Orbital apex fractures - associated with damage to
the neurovascular structures of the superior orbital
fissure and optic canal
SYMPTOMS:
▪ Periocular ecchymosis and oedema
▪ The position of the globe should be assessed
▪ Enophthalmos is rarely evident in the first days after
injury because of edema of the orbital tissues
▪ A degree of proptosis is evident early
▪ Hypoglobus may be seen with severe floor
disruption with a subperiosteal hematoma of the roof
▪ Epistaxis, cerebrospinal fluid leakage, lacrimal
drainage problems
▪ Diplopia
Isolated blow- out (hydraulic) orbit fr.
CT
Blow-out orbital fracture
d) Le Fort II fractures (pyramidal)
below the nasofrontal suture
→ the frontal processes of the maxilla
→ the lacrimal bones and inferior orbital floor
and rim
→ the inferior orbital foramen
→ the anterior wall of the maxillary sinus
→ the pterygomaxillary fissure
→ the pterygoid plates
e) Le Fort III fractures (transverse)
The nasofrontal and frontomaxillary sutures
→ along the medial wall of the orbit
→ through nasolacrimal groove and ethmoid bones
→ along the floor of the orbit
→ along the inferior orbital fissure
→ through the lateral orbital wall, zygomaticofrontal
junction and the zygomatic arch
Intranasally: through the base of the perpendicular
plate of the ethmoid, through the vomer, and
through the interface of the pterygoid plates to the
base of the sphenoid
In clininical access we distinguish:
1. fractures with traumatic changes of occlusion
(fr. of alveolar proces maxillae;
Le Fort I, II, III; …)
2. fr. without traumatic changes of occlusion
(isolated fr. of nasal bones, nasal setum fr.,
blow out fr., … )