Functional structure of the skull and Fractures of the skull MUDr. Anna Rábová 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 rám_lebka 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) pilíře_maxilla 1 4 3 2 Maxilla Base of proc. alv. – upper basal arch (1), together with the hard palate forms the so-called palatinal plate, into which the system of pillars is embedded. Trajektorie odstupují vějířovitě od oblasti hrotů kořenů zubů. Při bazi alv. výběžku je kostní tkáň zesílena v tzv. horní bazální oblouk. Připojením tvrdého patra k oblouku vzniká patrová deska, ze které se žvýkací tlak přenáší na lebku 3 hlavními žvýkacími tlakovými pilíři: 1. Špičákový – vychází od dna alveolu 3 a 4, přebírá i tlaky z oblasti 1,2. Probíhá kraniálně po med. okraji sinus max., pokračuje v pr. frontalis až na os frontale. 2. Zygomatický – vychází z oblasti aveolu M1, probíhá v crista infrazygomatica a pr. zygomaticus maxillae přechází do os zygomaticum, kde se dělí na rameno a) svislé rameno (pr. frontalis ossis zyg. a dále do os frontale po zevním zesíleném okraji orbity). b) horizontální rameno pokračuje směrem do arcus zygomaticus a vyzařuje do squama ossis temporalis. Stejně jako špičákový, i zygomatický pilíř má vztah k lat. stěně sinus maxillaris, kde se často projeví jako zesílená hrana, vyčnívající do lumina sinusu – tzv. septa. 3. Pterygoidní vzniká srůstem zadní a med. plochy maxily s dolní ½ pr. pterygoideus a s lamina perpendicularis ossis palatini. Začíná v oblasti alveolu M2-3, zajišťuje přenos tlaků od zadních zubů na tělo kosti klínové. Tento pilíř zesiluje zadní plochu stěny sinus max. Pterygoidní pilíř se spojuje s jařmovým pilířem v oblasti zadního hrbolu čelisti – tuberculum articulare a tvoří kostní vyvýšeninu v oblasti foramen ovale. 4. zadní, mastoidní vychází z pr. mastoideus a ze zadního okraje foramen magnum. V oblasti patra probíhají tahy kolmo na okraje alv. výb. V předním oddíle patra mají průběh podélně obloukovitý, v zadním odíle spíše příčný. 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: Trajektorie odstupují vějířovitě od oblasti hrotů kořenů zubů a v dolní čelisti směřují ke stěně canalis mandibulae, kde se nachází trajectorium dentale. V zesílené části dolního okraje mandibuly je pak další trajektorium basilare (dolní bazální oblouk) Jak basální oblouk, tak i trajektorium dentale přechází do proc. condylaris přes crista colli mandibulae a přes caput mandibulae (stěna fossa mandib. je však tenká - hlavní přenos žvýkacího tlaku tudy proto nejde !) Vault - thickened parts: § tubera frontalia § tubera parietalia § protuberantia occipitalis ext. et int. § linea temporalis § margin of sulcus sinus sagitalis sup. et transversus zesílená_místa 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 Ø ØSinus maxillae ØOrbita ØNasal cavity Ø rám_lebka zesílená_místa 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 cranial 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 bone 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. pilíře_maxilla § 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: ØInfraction / fracture without dislocation / dislocated fracture Ø ØSimple / multiple (more fracture lines in one bone) / comminuted fr. (more irregular fr.lines) Ø ØClosed / open – compound (associated with soft tissue injury, where the fractured bone is in direct communication with the outside environment) Ø ØPrimary / 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 image 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 Figure 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 DepressedSkullFracture49 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 § frbase4 frbase3 frbase1 fr frbase2 Spreading of the fracture lines Basilar fractures Øcharacteristic signs: Ø Ø- blood in the sinuses Ø- a clear fluid - cerebrospinal fluid (CSF) leaking Ø from the nose (rhinorrhea) or ears (otorrhea) Ø- periorbital ecchymosis often called 'raccoon eyes Ø- retroauricular ecchymosis known as "Battle's Ø sign„ Ø- 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%27_sign2 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 Brýlový hematom 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 Øpresence of intracranial gas / air Øis most commonly encountered following trauma or surgery Pneumocephalus NOTE! „Extradural“ = epidural Epidural 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 § Beneath arachnoid 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 Subdural2 Subdural ANd9GcRapECmyQFbEgPOLzcBkUr8eA0GTPxE5hGaNoPnQLBKWJ5LLS3KmA large-intracerebral-hemorrhage Intracerebral Subarachnoid Epidural II. Craniofacial Fractures 1. Mandible 2. Lower mid-face 3. Upper mid-face 1. Fracture of the mandible Jaw Fracture - Facial Trauma 84611-84613-132 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 frmandib 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 frakturaDČ 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 ex3 Elefort1 3. Upper midfacial fracture a) Naso-orbitoethmoid Fractures b) b) Zygomaticomaxillary Complex c) c) Orbital fractures d) d) Le Fort II e) 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 ex7 §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 36e5ed30 Damage of the angulus med. dx. -> enlargement of the interorbital distance = telecanthus Isolated fractures of nasal bones nasal_fracture_241x411oct11_010 nasal_fracture_oct17_040 nasal_fx_oct11_014 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 TripodFxAPBig: 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. BlowoutFx: CT Entrapment_of_right_inferior_rectus_muscle_ENT_026 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 lefort3 ex5 ex5 Ø In clininical access we distinguish: Ø1. fractures with traumatic changes of occlusion Ø (fr. of alveolar proces maxillae; Ø Le Fort I, II, III; …) Ø Ø2. fr. without traumatic changes of occlusion Ø (isolated fr. of nasal bones, nasal setum fr., Ø blow out fr., … ) Ø ØReferences: Ø •Čihák, R.: Anatomie 1,2,3, Praha, Grada, 2001 •Netter, F.: Atlas of HumanAnatomy, 4th ed., Elseviesr, USA, 2006 •Naňka, Elišková: Přehled anatomie. Galén, Praha 2009 •Seidl et al.: Radiologie pro studium i praxi, Grada publishing, 2013 •Mrázková, Doskočil: Klinická anatomie pro stomatology, Alberta, Praha, 1994 •Brand, Isselhard: Anatomy of orofacial structures, 8th edition, Elsevier, USA, 2019 •Fehrenbach, Herring: Illustrated anatomy of the head and neck, 5th edition, Elsevier, USA, 2017 •Moore, Dalley: Clinically oriented anatomy, 5th edition, USA, 2006 Ø