The mandibular joint facilitates complex movements of the lower jaw. It consists of the lower and upper parts, divided by the articular disc (discus articularis). The pit is located at fossa mandibularis near divergence of processus zygomaticus ossis temporalis. The head is a part of processus articularis of the lower jawbone. A ligamentous cartilage equilibrates incongruence of the joint surfaces which are covered with a cartilage as well. During the initial phase of mouth opening process, the head turns at the lower part of the joint at the disc pit; then during a continuing movement of the jaw the head shifts together with the disc to the upper part of the joint - from fossa mandibularis along the planum tuberculum forward to tuberculum articulare - which makes a solid obstacle to further movement out of the pit. The articular capsule together with ligaments complete the whole structure of the joint.
Mechanism of luxation.
If the head leaves the pit by shifting in front of tuberculum articulare, the lower jaw luxation appears. Luxation without a bone damage happens at excessive mouth opening (yawning, screaming, cramps, vomiting), or during a forceful passive mouth opening (medical treatments: intubation, insertion of probe etc.). Recurring luxations appear at predisposed individuals (shallow tuberculum, loose articular capsule). Traumatic luxations happen upon forceful effects on the lower jaw’s edge (a hit, rarely after falling).
Classification of luxations.
acute luxations at the ventral direction (with no bone damage)
recurring luxations at the ventral direction (habitual luxations)
traumatic central luxations, happen by penetration of the mandibular condyle through damaged glenoid fossa into the middle cranial space (intracranial hemorrhage)
traumatic luxations at medial or lateral directions (extremely rare, mostly appear as luxation fractures of processus articularis mandibulae)
Manifestations and examination.
The basic sign is a patient’s mouth open that cannot be closed. Pain and tension are felt in chewing muscles and the mandibular joint. Saliva may leak from the mouth, since swallowing is difficult. During attempts to close the mouth, a resistance of tight chewing muscles can be felt. An empty pit of the mandibular joint can be felt upon palpation through the auditory canal. X-ray images show the head’s position in front of tuberculum articulare.
Therapy for the lower jaw luxations.
Timely repositioning of luxated lower jaw is crucial for a feasibility to use a simple maneuver. Soon, a spasm of chewing muscles causes a very strong resistance that can be surpassed under general anesthesia and after muscular relaxation only.
Repositioning can be commonly made by the Hippocratus grip: fingers of both hands embrace the lower jaw body with thumbs laid on the lower molars. By pushing thumbs downwards, the chewing muscles resistance is overridden and by pushing against the chin by rest of fingers, the head is placed into the fovea.
After a successful repositioning the jaw should be fixed by an external sling bandage or a simple wire intermaxillar bond for several days. A patient has to receive soft foods and be aware of wide mouth opening.
Opening of the mouth is then slowly rehabilitated; a physical therapy or muscular spasmolytics can be used. Recurring or habitual luxations require a surgical treatment that adjusts the joint path and removes obstacles (ablation of tuberculum articulare).
10.5 Injuries of the Middle Third of the Face
The middle third of the face is at its upper part divided from the neurocranial part of the skull by a line that connects both zygomatic-frontal sutures with front-maxillar sutures and naso-frontal sutures. On sides, it is bordered by lines running from the zygomatic-frontal towards the zygomatic-temporal suture and further back to tuber maxillae and pterygoid process of the sphenoid bone. The bottom boundary is formed by the occlusal plane of the upper teeth.
The basic structure of this part of face is body of the upper jaw. The upper jaw together with the hard palate span above the oral cavity and form the bottom of nasal and orbital cavities. Similar to the lower jaw that determines shapes of chin and lower lip, the upper jaw influences formation of the mouth, upper lip, nose and position and size of orbits.
Extension of an injury to the skull’s base.
The boundary between the middle and upper thirds of face, formed by the frontal, sphenoid and ethmoid bones that moreover encompass the pneumatic system of secondary nasal sinuses, enables for fractures affecting the middle third to extend to the skull’s base (craniomaxillar fractures) with all consequences of such an injury (liquorrhea, infection of brain meninges, pneumo-cephalus etc.).
Fractures of the middle facial third.
Fractures of the middle third of face differ from fractures of the lower jaw. Reasons include both different anatomical layout of this area and composition of bones. The lower jawbone is a movable bone with a thick cortical bone tissue and well developed spongy tissue. Skeleton of the facial middle third is firmly connected to the skull and it is formed by thin bony lamellas reinforced at certain places by bony trabeculae. Except the maxilla and palatal processes of the upper jaw, there is no developed compact bone. At this region, it is very rare to find isolated injuries of particular bones (except the nasal skeleton), more often groups of bony structures (complexes) are damaged, that break up as a whole unit. Fractures are often of a comminuted character. The presence of the nasal cavity and secondary nasal sinuses whose epithelium can easily be damaged during fractures, make all injuries of the facial middle third to be open fractures with a risk of infection. A honeycomb structure of bones of the middle face with its large periosteum make all healing processes to proceed very rapidly. Dislocated fragments may get fixed at wrong positions that makes later reposition difficult. Serious functional and cosmetic malformations appear as a result.
Skeleton of the facial middle third is composed of many bones (the upper maxilla, palatal bone, nasal bones, lachrymal bone, vomer, ethmoidal bone, upper, middle and lower ethmoturbinal conchae, zygomatic bone, sphenoid bone, zygomatic arches). Bones are held together by sutures to form one unit, with bony lamellae closing various cavities. The skeleton of the facial middle third protects important sensorial organs (vision, hearing, olfaction) and it is a place where airways and alimentary tract begin.
Mechanisms of injuries.
The upper jaw is exposed to shocks from the lower jaw during chewing. The upper jaw’s teeth absorb shocks from occlusal teeth and distribute them along the skull’s base. Pillars that are made by thicker and stronger lamellae at walls of cavities are positioned in such a way to allow for this absorption. The core and hub of pressures at the middle third is the sphenoid bone that transfers shocks and distributes them to all lamellae, processes and cavities. The bone itself participates at formation of walls of all cavities of this facial region. The middle third skeleton is very resistant to forceful hits at direction from the bottom upwards but it is less resistant to hits coming from the front and sides. Majority of fractures are caused by impacts at horizontal direction. A direction and strength of an impact that causes fractures influence character of fractures and dislocation of fragments. A muscle tonus does not play a role. A reason that participates at fragments dislocation is their own weight. In case of the whole middle third breaking off the neurocranium it may drop down and cause breathing problems by airways closure and dislocation backwards at the direction of causative force. The face then obtains a shape of inverted dish or bowl (a dish face). Most frequent causes of injuries are impacts of moving head onto a barrier. An extent and location of injury are determined by the head position (turn) at the moment of impact and the size of area onto which a force acts. With increased kinetic energy of an impact the extent and comminuted character of injuries of bony structures magnify. An impact of a moving object to the face has a similar effect. A force of a hit by fist directed at the nasal or cheek bones areas already causes an extensive destruction of bones.
10.5.1 Classification of Fractures of the Middle Facial Third
At the beginning of the 20th century, anatomist who lived in Paris, René Le Fort described and classified 3 basic types of fractures of the maxilla , based on experimental studies on heads of corpses. As technology progressed and speed of transportation increased, kinetic energy of moving persons or objects become higher. Placement of fracture lines has changed as well. Despite that, the classical division is still in use and has its own firm place among systems of classification of fractures of the facial middle part.
The facial middle third can be divided into central and lateral (side) parts. The division line goes from the nasofrontal suture along the inner edge of orbit towards the foramen infraorbitale, and towards the connecting point of a zygomatic bone with the maxilla ’s body (this is the fracture line Le Fort type II.). Injuries of the central part are often accompanied by serious complications.
Fractures of the central part.
lower (suborbital) layer: fractures do not affect orbits, they are located underneath them.
fractures of the alveolar ridge
fractures Le Fort type I, lower sub-zygomatic fracture
sagittal fracture of palatal bones and maxilla s
upper (sub-basal) layer: fractures affect orbits, as well as the ethmoidal bone at the inter-orbital area.
isolated fracture of nasal bones
fracture of the naso-maxillar complex
fracture Le Fort type II., upper sub-zygomatic fracture
Fractures of the lateral part.
zygomatic arch fracture
fracture of the zygomatic-maxillar complex
Combined fractures of central and lateral parts.
fracture Le Fort type III., supra-zygomatic fracture.
Fractures of the alveolar ridge.
The incisal edge of the upper incisor teeth protrudes forward when head is at upright position. That is why this area is exposed to injuries to a greater extent. If a great force is applied to a large area, the alveolar ridge breaks off together with the teeth which remain mostly undamaged. Vertical fracture lines run between tooth sockets and a horizontal line goes at the level of tooth apexes or just above it. If a force acts towards a single tooth, its isolated damage occurs (subluxation, luxation, breakage of tooth parts). A fragment is usually dislocated at the palatal direction, or downwards by its own weight, in case it is completely detached.
Fracture Le Fort type I. (lower sub-zygomatic fracture).
If a force acts against a large area of a lower part of the middle facial third, a breaking off appears, whose fracture line runs above the teeth root tips and begins at the lateral edge of apertura piriformis nasi. The breakage descends into the fossa canina and declines backwards under the thickened part of the maxilla ’s processus zygomaticus, it crosses the lateral wall of the maxillary sinus and continues to the back edge of the maxilla . At this place, it usually goes down to tuber maxillae, or goes further towards the pterygoid process of the sphenoid bone. It thus runs above the palatal plate at base of the maxillary sinus. If the lateral wall of nasal cavity is broken as well, and if the cartilaginous septum is detached from the vomer, movability of the whole complex can be clinically proven easily by pulling on the upper incisor teeth.
Sagittal fractures of maxilla s and palatal bones.
Isolated injuries of these bone structures is very rare, they are usually combined with other fractures of this facial part. A fracture line runs in most cases through the suture connecting palatinal processes of both maxilla s and horizontal lamellae of palatal bones. At the front part, it runs through foramen incisivum and between alveoli of the upper middle incisor teeth. Widening of the palatal suture causes the periosteum, that is firmly attached to bones, to break off thus creating an oro-nasal connection.
A sagittal fracture occurs most often upon a force acting from below to the lower jaw and by transfer of impact to the upper teeth that causes the aforementioned breakage at the palatal suture.
Nasal bones fractures.
A position of the nose skeleton at the face predisposes it to frequent injuries. An isolated damage may occur, however, adjacent bones are often damaged as well or the whole bone complexes are broken off.
Nasal bones get detached from the frontal processes of the maxilla s, or a frontal process is broken on one side and nasal bones are heaved at medial direction. If such an injury appears on both sides, nasal bones form a roof-like overlap. At the same time, nasal cartilaginous structures may be damaged, too.
An upper subzygomatic fracture Le Fort II.
If a force acts from the front, from upper rims of orbits down to alveolar ridges, a possibility arises that maxilla s and nasal bones will be broken off on both sides. Dislocation backwards appears and a decline downwards may be present. An X-ray image taken at postero-anterior projection shows an apparent lengthening of craniocaudal distance of orbits entrances. A fracture line affects nasal bones at their thinnest parts - under nasofrontal sutures. The maxillary frontal process and lacrimal bone are often damaged as well. The fracture line reaches towards fissura orbitalis inferior parallel to canalis infraorbitalis. Around the canal’s exit on the front surface of the maxilla it crosses the lower orbital edge at the point where maxilla and a zygomatic bone are jointed, and runs downwards to the lateral wall of the maxillary sinus. From here, it proceeds backwards - similarly to a Le Fort type I fracture - to tuber maxillae or onto the sphenoid bone.
Fractures of the zygomatic arch.
Rarely appear as isolated fractures, occur together with fractures of the zygomatic-maxillar complex. Its causes include a direct impact (or falling onto a sharp edged or rod-like barrier) to the arch area. The arch, due to its shape is affected by breaking off a part of its curvature (two breakages) thus forming a middle fragment that gets heaved at medial direction, towards the temporal bone.
Fractures of the zygomatic-maxillar complex.
These are far the most common fractures of the facial middle third. A characteristic configuration of the face is formed by prominence of zygomatic bones at the latero-ventral direction. A side impact onto this area causes not only an isolated damage of a zygomatic bone (very rarely), but it gets also broken off the surrounding bone structures due to its rigidity. Those structures get damaged as well thanks to their anatomical forms. Fracture lines thus often run across bone structures. A cranial loosening appears at the zygomatic-frontal suture, from where a line runs on the outer surface of an orbit along the connection of zygomatic bones with large alae of the sphenoid bone towards fissura orbitalis inferior. A breakage crosses from here to the connection of zygomatic bones with orbital parts of the maxilla. Around the lower orbit’s edge it runs at the site of zygomatic-maxillar suture nearby foramen infraorbitale from the front surface of maxillary sinus to its lateral wall where several fracture lines are formed. The wall is shattered into many fragments, and the zygomatic-alveolar crista is damaged, too. This crista makes a lateral reinforcement of the facial middle third and transfers a mastication pressure upwards. The fracture line proceeds on the lateral side upwards to fissura orbitalis inferior again. The malar arch is usually broken as well. The most frequent causes include a direct impact of head turned aside to a barrier or hitting by an object (fist) on a zygomatic bone’s body. Dislocations at various directions occur, depending on intensity of a causal force. If the whole bone complex gets broken off, backwards and downwards dislocations are mostly found.
Supra-zygomatic fracture Le Fort type III.
While the above described fractures have fracture lines that run below the zygomatic bones which stay firm, a combined fracture of the central and lateral parts exhibits the whole middle part of the skull detached from the skull’s base. A fracture line runs below nasofrontal sutures and further through frontal processes of the maxilla and proceeds above and behind the lacrimal bones to the orbital part of the ethmoid bone, from where it descends laterally towards the lower orbital fissure. It further proceeds to pterygoid processes of the sphenoid bone that get interrupted. A second fracture line runs from the lower orbital fissure laterally towards the link of the zygomatic bone orbital part with large pterygoid processes, it crosses the temporal wall of an orbit and divides the zygomatic bone from the frontal bone near the suture zygomatic-frontal. From this suture, a fracture line declines downwards onto the sphenoid bone infratemporal surface at the pterygoid processes base. The malar arch is also broken near the zygomatic-temporal suture. Dislocation backwards occurs, as well as downwards due to the whole part’s weight. It results in articulation of distal molars only and an unclosing bite at the front part occurs.
Signs of fractures.
An injured patient’s examination should always begin with a careful anamnesis. A description of events during an injury can help to elucidate its extent and location, providing a patient can recall it.
Soft tissues swelling, changes of physiognomy.
An apparent sign of the middle skull skeleton injuries during the palpation are notably large swollen soft tissues. It appears very shortly after an injury, sometimes the whole face gets swollen (the face resembles a soccer ball). At another cases, such as flattening of a prominent cheek area during zygomatic-maxillar complex fractures, swelling of soft tissues masks a facial area deformation. If the whole middle third gets dislocated downwards and the face gets elongated which can be observed at the nose and the inner eye corners that are limp. During injuries at the nose base or orbital area with breakage of lig. canthus med., the distance between eyes widens (post - injury hypertelorism).
Bite and occlusion maladies.
Damaged occlusion or bite occur after dislocation of fragments. A patient can bite together at the distal molars only and an unclosing, frontally open bite is the result. In case of one-sided injury, a decrease occurs resulting in a traumatic bite on an affected side. If the lower jaw pushes up forcefully, the deformation disappears, but only until the mouth is opened again. In such cases, it is important to examine the hard palate inside the mouth, since an oro-nasal communication may be formed that is a sign of a sagittal fracture of palatal bones.
Bleeding and hemorrhages.
Soft tissue and bony structures damages are accompanied by bleeding. A direct bleeding from the nasal cavity is most frequent, although blood can partially accumulate at secondary nasal sinuses forming blood clots that show up as an obscured maxillar sinus at an X-ray image (at semi-axial projection). Hematomas form at soft tissues. Hematomas of lower or upper eye lids, conjunctiva or the face skin often help to locate affected parts. Hematomas of eye lids are very common, they can close the eye and hamper vision. An “eyeglasses-like” hematoma can develop as a sign of the skull’s base fracture ( it has to be confirmed on an X-ray exam).
Bony structures deformation.
Palpation with gentle and careful touching can revise bony structures shape and location, providing a developed tissue edema or hematoma allows it. At typical places where bone fractures often appear, a physician can sense irregularity, a step or a bone is missing completely as a result of breaking off and shifting away (a dislocated fragment). Places suitable for such examination by palpation are the following: lower and lateral edges of orbits, nose base, hard palate, lateral edge of maxillary sinus (zygomatic-alveolar crista). In cases of widened fractures, these are: the upper edges of orbits, frontal area. A typical sign of fractures in these areas is a subcutaneous emphysema, resulting from air being blown under pressure into the subcutis from secondary nasal sinuses through broken bone walls.
Pathological mobility of fragments or parts of the middle facial third.
During a palpation examination, a movability of bony parts can already be felt, initiated by a slight pressure onto a fragment. It can be used for determination of an injury type and presence or absence of a fracture.
Impairment of vision, mobility of eyeballs or eye-lids.
Vision impairment, hampered eyeballs and eye-lids movability may occur at injuries to bone structures of orbits. Position of both eyeballs can be readily observed by eyes (aspection). An eyeball can be dislocated at different types of injuries ventrally, dorsally, or caudally (dorsally and caudally in cases of breakage of the orbit’s base which happens during isolated hydraulic fractures of orbits). Traumatic enophthalmus occurs as well. On the contrary, an exophthalmus occurs at ventral dislocation. In cases of fractures of an orbital base, an eyeball moves downwards, the eye optical axes shift and double vision - diplopia - appears.
Double vision may occur in cases of trapping an eye moving muscle into a fracture line. For this reason, movability of eyeballs should be examined at all directions in order to identify, at what direction the movement is impaired. If a fracture line runs over the upper orbital fissure, impairment of functions at regions innervated by one of the head nerves (n. oculomotorius, trochlearis and abducens) that are located at these areas may happen.
Non-dislocated fractures or parts of bone complexes that break off incompletely do not require any fixation, just protection from further impacts, lying head at unhurt side, eating mushy food and anti-inflammatory treatments. The following fractures can be fixed by mono-fixation (a splint at injured jawbone) or by inter-maxillar immobilization: fractures of the alveolar ridge, one-sided fractures Le Fort I., sagittal fractures of maxilla s. The above described dental splints (Sauer’s splint) or wire fixtures reinforced by resin or composite materials, are used for those purposes. At some cases, fixation is preceded by a simple repositioning that puts fragments firmly together.
Surgical ways of therapy.
Surgical ways of repositioning and fixation are used more often at injuries of the middle facial third than those of the lower jawbone. Most often, a direct bone suture is applied. Osteosuture is performed either from the outside (skin) approach, often through soft tissue wounds, or from intra-oral side, to the front surface of maxilla, zygomatic-alveolar crista, hard palate or alveolar ridge. Surgical ways of therapy offer an advantage of repositioning of fragments under direct visual control, achieving their perfect toilet and correction, repositioning into proper positions and fixating them with sufficient firmness. An adaptive osteosuture serves the purpose of getting fragments close to each other and hold them at proper positions, not connecting them rigidly. Rigid connection is achieved with aid of bone splints and screws.
Loose parts of the middle facial third or whole level descend downwards by their weight and get dislocated backwards by an impact. The aim of therapy is to connect them back to the firm upper third (neurocranium) by a wire sling that ensures a good contact of broken surfaces and long-term rest which is not disturbed by chewing movements of the lower jaw. A hinge has to be selected and positioned in such a way so that it does not cause inconvenience to a patient, i.e. not on the outside, but rather underneath the skin or tissues. These requirements are met by the Adams’ hinges (1942). A high sling is placed at the zygomatic process of the frontal bone above zygomatic-frontal suture. Low slings are fit at undamaged zygomatic arches or the lower edge of nasal base (apertura piriformis nasi). With the aid of Kostečka’s needle or other inserting tools, wires are drawn into the oral cavity and fixated to the upper or lower dental splints. By fastening the wires, required fixation is achieved. The fixture stays at place for 7 weeks and is removed after that.
A rigid fixation:
At the middle facial third, only bone mini- or microsplints and corresponding screws of various lengths should be used. Gracile splints are rigid enough and inert for an organism (made of pure titanium). Besides high requirements on technical parameters of splints utilized, it is mandatory that a splint is positioned at the right place and fitted beforehand.
The traditional Le Fort’s classification of fractures determines also the most common placement of bone splints. They are positioned above particular breakages at fractures of nose, as well as the palate fractures.
Fractures of the zygomatic-maxillar complex are fixed by splints positioned at lateral edges of orbits at the zygomatic-frontal suture area and inside the oral cavity to the zygomatic-alveolar crista. If a lower orbit’s edge gets significantly dislocated, a well fitted splint has to be placed at this area as well. Suprazygomatic fractures (Le Fort III.) have to be fixed on both sides at lateral edges of orbits and at the nose root.
Repositioning and fixation of zygomatic-maxillar complex fractures:
These most frequent fractures of the middle facial third are successfully treated shortly after a dislocated injury (1 week after an injury) by one-time transcutaneous repositioning using a sharp hook, introduced beneath the zygomatic bone body through a cheek. Pulling out and entanglement of fragments can be checked by straightening of a step-like deformation on the orbit’s lower edge. Fragments fit into each other and no further fixation is required. Highly dislocated fractures, comminuted fractures and those fractures found long time after an injury cannot be repositioned by a bone hook alone. If the orbit’s lateral edge got damaged at the place of zygomatic-frontal suture followed by shifting of fragments, an osteosuture or fixation by a bone splint are applied. Repositioning of the zygomatic bone body is performed through the oral cavity -trans-antrally- by an elevator and fixation at a proper position is achieved by an acrylic column pushed against the firm wall of the antrum medial wall. If an acrylic column is fitted in the middle with an orthodontic screw, its length can be adjusted by turning it thus improving support and fixation. The screw can be later (after 7 weeks) removed easily after shortening it by turning and replacement the support from beneath the zygomatic bone body.