Textbook of Oral and Maxillofacial Surgery PDF

Textbook of Oral and Maxillofacial Surgery Gustav O Kruger (The C V Mosby Company, St Louis, Toronto, London, 1979) Fifth Edition Chapter 19...

Textbook of Oral and Maxillofacial Surgery Gustav O Kruger (The C V Mosby Company, St Louis, Toronto, London, 1979) Fifth Edition Chapter 19 Fractures of the jaws Gustav O Kruger General discussion Etiology Fractures of the jaws occur most often because of automobile collisions, industrial or other accidents, and fights. Since the mandible is a hoop of bone articulating with the skull at its proximal ends by two joints, and since the chin is a prominent feature of the face, the mandible is prone to fracture. The mandible has been compared to an archery bow, which is strongest at its center and weakest at its ends, where it breaks often. The chin is a convenient feature at which an adversary can aim. It is interesting to note that often the patient will not identify his adversary to the oral surgeron or to the police after a fight. He prefers to gain revenge in like manner later. This philosophy increases the number of jaw fractures, and if the patient has not had 6 months of good healing before the second altercation, he himself may be a candidate for a bone graft to the original site of injury. A recent survey of 540 fractured jaw cases at District of Columbia General Hospital revealed that physical violence was responsible for 69% of the fractures, accidents for 27% (including automobile accidents, 12%, and sports, 2%), and pathology for 4%. Men experienced 73% of the fractures, whereas women experienced only 27%. Private hospitals in the same are report a preponderance of automobile accidents as the main cause of jaw fractures. Hospitals in industrial cities report a high incidence of industrial accidents. The automobile has made serious injury to the face and jaws commonplace. Violent forward deceleration causes injury to the head, face, and jaws. When the car stops quickly, the head hits the dashboard, steering wheel, rearview mirror, or the windshield. A middle face fracture can result, in which the maxilla, nose, zygoma, and perhaps the mandible are fractured. The National Safety Council, automobile manufacturers, and other groups have instituted various safety features, including seat and shoulder belts, dashboard padding, rearview mirror of different design, telescoping steering wheel, push-away windshield, dashboard with recessed or absent knobs, and air bags. It seems sensible to insist that children always ride in the back seat, since fewer major facial fractures occur to back-seat riders. The most dangerous seat in the automobile is the front seat next to the driver. A fracture can occur more easily in a jaw that has been weakened by predisposing factors. Diseases that weaken all bones can be factors. Examples include endocrine disorders 1 such as hyperparathyroidism and postmenopausal osteoporosis, developmental disorders such as osteopetrosis, and systemic disorders such as the reticuloendothelial disease, Paget's disease, osteomalacia, and Mediterranean anemia. Local disorders such as fibrous dysplasia, tumors, and cysts can be predisposing factors. A patient turning over in bed can experience a pathological fracture if the jaw is weak enough. Classification Fractures are classified into various types, depending on the severity of the fracture and whether or not the fracture is simple, compound, or comminuted. A simple fracture is one in which the overlying integument is intact. The bone has been broken completely, but it is not exposed to air. It may or may not be displaced. A greenstick fracture is one in which one side of a bone is broken, the other being bent. It is difficult to diagnose sometimes, and it must be differentiated on the roentgenogram from normal anatomical marks and suture lines. It requires treatment, since resorption of the bone ends will occur during the healing process. Functioning of the member and muscular pull can result in a nonunion during healing if the bone ends are not held rigidly in place. However, the time required for healing usually is minimal. This type of fracture is seen often in children, in whom the bone will bend rather than break through. A compound fracture is one in which an external wound is associated with the break in the bone. Any fracture that is open to the outside air through the skin or mucous membrane is assumed to be infected by outside contaminants. Unfortunately, almost all jaw fractures that occur in the region of the teeth are compounded. The jaw will respond to stress by fracturing through its weakest part. Rather than fracture through the full thickness of the bone at an interdental space, it will separate through a tooth socket and then extend from the apex of the socket to the inferior border. The periodontal membrane and the thin alveolar mucosa are broken to a point adjacent to the tooth. The edentulous mandible will harbor a simple fracture more frequently. Even though the fracture may be displaced so that a "hump" appears on the ridge, the periosteum and overlying tissues can "give" a little, since the tissues have no close attachment to the teeth. The oral surgeon is accustomed to dealing with fractures that are compounded into the mouth. Antibiotics have aided in controlling the potential infection. The bones of the jaws appear to have a degree of natural resistance to oral infection. A fracture that is compounded through the outside skin is more difficult to manage, and an osteomyelitis may develop more readily. The orthopaedic surgeon finds that compounded fractures of the long bones are much more difficult to manage than simple fractures. This is partly the result of the introduction of plain dirt as well as outside organisms and partly of the fact that the fractured bone ends are more distracted so that one end of the bone can penetrate the skin. A comminuted fracture is one in which the bone is splintered or crushed. It may be simple (that is, not open to outside contaminants) or compounded. Fractures of the vertical of the mandible are composed sometimes of ten or more fragments, and yet, because of the splinting action of the masticatory muscles, no displacement occurs, and compounding is not present. If comminution occurs in the body of the mandible, the treatment is sometimes revised. Although an open reduction might be done normally (in which the bone is exposed surgically, joles are drilled, and wires are placed to hold the fragments in place), such a procedure would force stripping of the periosteum from the many small bone fragments, and 2 healing would be delayed. A closed procedure may be substituted to ensure viability of the fragments. Gunshot wounds are usually compound comminuted fractures, and usually bony substance is lost where the missile has traversed. The District of Columbia General Hospital survey found the following incidence of jaw fractures: simple fractures, 23%; compound fractures, 74%; and comminuted fractures, 3%. Examination Every patient who has suffered a head or face injury should be examined for the possibility of a jaw fracture. Not infrequently a leg fracture is treated and facial wounds are sutured only to discover several days or weeks later that a jaw fracture exists. Fractures are more difficult and in some cases impossible to treat satisfactorily at the later date. In most large hospitals every head injury is examined routinely by the oral surgery service while the patient is still in the emergency room. The general condition of the patient and the presence or absence of more serious injuries are of prime concern. Asphyxia, shock, and hemorrhage are conditions that demand immediate attention. Extensive soft tissue wounds of the face are cared for before or concomitantly with the reduction of bony fractures, except in the few cases in which the fractures can be treated by direct wiring before soft tissue closure is accomplished. However, treatment of minor facial wounds is delayed until intraoral arch bars have been placed, since a beautiful skin closure can be reopened by the stresses imposed by the intraoral procedure. A history should be written as soon as feasible. If the patient cannot give a good history, the relative, friend, or police officer should be asked for a statement. Relevant details of the accident should be placed in the record. The events that took place between the time of the accident and the time of arrival at the hospital should be recorded. The patient should be questioned regarding loss of consciousness, length of unconscious period if known, vomiting, hemorrhage, and subjective symptoms. Medications given before arrival at the hospital are recorded. Questions regarding past illnesses, current medical treatment immediately preceding the accident, drugs being taken, and known drug sensitivity should be asked now. If the patient is uncomfortable, the detailed medical history can be deferred until later. Routine physical examination can be done now or later, according to the judgment of the examiner. When examining the patient to determine if jaw fracture is present and its location, it is well to look for areas of contusion. This will provide information about the type, direction, and force of the trauma. The contusion sometimes can hide severely depressed fractures by tissue edema. The teeth should be examined. Displaced fractures in dentulous areas are demonstrated by a depressed or raised fragment and the associated break in the continuity of the occlusal plane, particularly in the mandible. Usually a tear in the mucosa and concomitant bleeding are noted. A characteristic odor is associated with a fractured jaw, which perhaps results from a mixture of blood and stagnant saliva. If no obvious displacement is present, manual examination should done. The forefingers of each hand are placed on the mandibular teeth 3 with the thumbs below the jaw. Starting with the right forefinger in the retromolar area of the left side and with the left forefinger on the left premolar teeth, an alternate up-and-down motion is made with each hand. The fingers are moved around the arch, keeping them four teeth apart, and the same movement is practiced. Fracture will allow movement between the fingers, and a peculiar grating sound (crepitus) will be heard. Such movement should be kept to a minimum, since it traumatizes the injured site further and allows outside infection to enter. The anterior border of the vertical ramus and the coronoid process should be palpated within the mouth. The mandibular condules should be palpated on the side of the face. The forefingers can be placed in the external auditory meatus with the balls of the fingers turned forward. If the condyles are situated in the glenoid fossae, they can be palpated. Unfractured condyles will leave the fossae when the jaw is opened. This maneuver should be done carefully and sparingly. The patient will experience pain on opening the jaw and inability to open properly if a fracture is present. The unilateral condylar fracture is suspected in the presence of a shift of the midline toward the affected side on opening. A step sometimes is noted on the posterior or lateral borders of the vertical ramus of the jaw in a low condylar neck fracture if edema has not obscured it. The maxilla is examined by placing the thumb and forefinger of one hand on the left posterior quadrant and rocking gently from side to side, following with the same procedure on the right posterior quadrant and then on the anterior teeth. If a complete fracture is present, the entire maxilla might move. An old fracture or one that has been impacted posteriorly will not move. The latter will be reflected in a malocclusion. In a unilateral fracture, one half of the maxilla will move. This must be differentiated from an alveolar fracture. The unilateral maxillary fracture usually will have a line of ecchymosis on the palate somewhere near the midline, whereas the alveolar fracture will be confined to the alveolar ridge. If a maxillary fracture is demonstrated, the facial aspect of the maxilla and the nose should be observed. A pyramidal fracture extending upward in the nasal area may be present. Besides loose bones, the patient usually will have a nosebleed (epistaxis) and black eyes. All patients with facial injury should be examined for a transverse facial fracture. These fractures are overlooked sometimes because of facial edema and soreness. The examining finger should palpate the infraorbital ridge. A step in this area indicates a fracture. The normal ridge has a roughened area here, which should not be mistaken for a fracture. The lateral aspect of the bony orbit should be palpated next. Careful examination may reveal a separation of the frontozygomatic suture line. It is found usually if the infraorbital ridge is fractured. The arch of the zygoma should be palpated. A fracture may be found here even if no other facial or jaw fracture is present. If the infraorbital and lateral orbital areas reveal fractures, the body of the zygoma is detached from the maxilla, and, frequently, one or more posterior fractures are present in the zygomatic arch. Careful palpation may reveal the fracture. A dimple over the course of the zygomatic arch is pathognomonic of a fracture. Overlying edema may make the clinical diagnosis difficult. By standing in front of the patient and pressing a tongue blade from the center of the zygoma to the lateral aspect of the 4 temporal bone on each side, the examiner will note a difference in angulation between the blades that will aid in the diagnosis of a depressed zygomatic arch. A depressed body of the zygoma may allow a gravitational depression of the orbital contents. The edge of a tongue blade held in front of the pupils of the eyes will incline away from a horizontal plane if one eye is lower than the other. When a maxillary fracture is suspected, several signs should be looked for before proceeding with manual examination as just described. 1. Bleeding from the ears. This requires differentiation between a middle cranial fossa fracture, a fracture of the mandibular condyle, and even a primary wound in the external auditory canal. A neurosurgical consultation is necessary to help differentiate these conditions. Other neurological signs are present with the cranial fracture. However, the experienced oral surgeon can diagnose the condylar fracture and thereby facilitate the neurological examination. The patient with a suspected or diagnosed cranial fracture is the responsibility of the neurologist or neurosurgeon. Fractures or other wounds are treated only when he considers the patient to be out of danger, which in some cases may be a week or two later. 2. Cerebrospinal rhinorrhea. If the cribriform plate of the ethmoid bone is fractured in a complicated maxillary fracture, cerebrospinal fluid will leak out the external nares. Quick diagnosis can be made by placing a handkerchief under the nose for a moment and then allowing the material to dry. Mucus associated with a head cold will starch the handkerchief, whereas cerebrospinal fluid will dry without starching. If doubt exists, test the collected material for glucose. A commercial paper reagent test will identify sugar in normal cerebrospinal fluid; it is not accurate, however, in the presence of significant amounts of blood. Movement of the maxilla of any type in the presence of cerebrospinal rhinorrhea is dangerous. Infectious organisms can be pushed up into the dura, and a meningitis may result. A few years ago the neurologist insisted that time be allowed for a granulation tissue covering to form over the distracted bone ends so that infection could not enter the meninges when maxillary fracture reduction was attempted. Complete reduction often was not possible by that time. With antibiotics, the reduction is now allower earlier. Properly reduced bones allow earlier and better soft tissue healing over them with less bridgings of voids between distracted bone ends. 3. Neurological signs and symptoms. Lethargy, severe headache, vomiting, positive Babinski reflex, and a dilated and widely fixed pupil or pupils are signposts that point to possible neurological trauma. Neurological consultation should be sought. Radiographic examination. A patient should be examined radiographically if indications suggest that a fracture exists. Three extraoral are films routinely made: posteroanterior jaw and right and left lateral oblique jaws. The films should be examined immediately with particular attention paid to the bone borders, where most fractures appear. If a fracture is suspected in the vertical ramus or in the condyle, the oblique lateral view on that side can be remade to concentrate on the suspected area. A lateral temporomandibular radiograph can also be made. If necessary, the x-ray beam can be directed posteriorly through the orbit to a cassette held to one side of the back of the head to obtain a proximolateral view of the condyle head. 5  In suspected maxillary fractures, a Waters view (nose-chin position taken from a posteroanterior exposure) should be made. If a zygomatic fracture is suspected, a "jug-handle" view is made with the tube near the patient's umbilicus and the cassette at the top of the head. Maxillary fractures are difficult to diagnose on the radiograph even by the trained oral surgeon or the radiologist. When a definite conclusion cannot be reached, a lateral skull radiograph should be made. If the frontonasal suture line is opened on the radiograph, the possibility is strong that a maxillary fracture exists. The absence of this sign, however, does not eliminate the possibility of maxillary fracture. In cases in which a fracture is demonstrated, intraoral radiographs should be made at fracture sites before definitive treatment is given. Extreme trismus or a severly injured patient would preclude this. Intraoral views generally provide excellent definition because of the proximity of bone to the film. They sometimes show fractures that are not seen on the standard views, notably alveolar process, midline maxilla, and symphyseal fractures. The condition of adjacent teeth and detailed information about the fracture can be obtained by this procedure. The diagnosis of a double fracture at one site, particularly in the mandible, should be made guardedly. A lateral jaw radiograph is not often so made that the fractures of the lateral cortex and the medical cortex superimpose exactly. The two fractured cortical plates may be interpreted mistakenly as two fractures through the body of the bone. From a medicolegal point of view, a permanent record in the form of radiographs is necessary. In any case in which a fracture might be suspected, it is better to err on the safe side and make the minimum extraoral radiographs, that is, the posteroanterior jaw and right and left lateral oblique jaw films. In children or young adults in whom consideration of the total amount of radiation is a factor, a leaded rubber sheet can be used to cover the gonads and neck. First aid The primary consideration is to have a live patient. Accordingly, immediate measures should be taken to assure that his general condition is satisfactory. Specific treatment of fractures in the severely injured patient is given anytime from hours to weeks later. If the airway is not patent, the fingers should be placed at the base of the tongue and the tongue pulled forward. Dentures, broken-off teeth, and foreign objects should be removed carefully if the finger can reach them. Suction should be employed for secretions and blood. A rubber airway can maintain a patent airway temporarily, or a suture can be placed through the midline of the tongue and tied to the clothing or affixed to the chest wall with adhesive tape. Mandibular fractures may involve the muscular attachment of the tongue with attendant posterior displacement and resultant asphyxia. If serious consideration is given to performing a tracheostomy, it should be done. An emergency tracheostomy may be needed, or, if time and facilities are available, an elective tracheostomy can be done. However, in a surprisingly large number of cases of temporary airway embarrassment, an intratracheal tube will provide adequate relief until the fracture can be reduced, thus making a tracheostomy unnecessary. Usually, the tube is placed first, and then a tracheostomy is performed only if the tube is found to be inadequate. 6  Shock is treated by placing the patient in shock position, with the head slightly below the level of the feet. Warm blankets are placed over him. Excessive heat in the form of hot- water bottles is as dangerous as cold. Whole blood is given for definitive treatment of major shock. Hemorrhage is rarely a complication of jaw fractures unless deep vessels in the soft tissues (for example, maxillary artery, facial vessels, lingual vessels) are involved. Even if the inferior alveolar vessels are severed in the bony canal, the hemorrhage is not severe. Hemorrhage from other wounds, however, demands immediate attention. In most cases the proper pressure point can be held with finger pressure until the vessel can be clamped and tied. Patients with head injury should not receive morphine, except possibly in case of severe pain. Morphine may complicate further the function of the respiratory center. Tetanus antitoxin is given after a sensitivity test if the skin is broken, provided the patient has not been immunized. If the patient has been previously immunized, then a 1 mL booster dose of tetanus toxoid is given. This is done in the emergency room. The possibility of spinal cord injury concomitant with cervical fracture or dislocation should be considered. Movement of the head in this instance can cause permanent injury to the spinal cord. Cervical radiographs should be made first if pain is present in the neck or if muscle weakness is present in the extremities. The best treatment for jaw fractures is immediate intermaxillary fixation. Ideally, the permanent fixation that will be used to treat the fracture should be placed within hours after the injury. In a good many large hospitals the resident is instructed to place intermaxillary fixation immediately after clinical and radiographic examination, regardless of the time of day or night. The patient then is sedated further, given antibiotics and other necessary supportive measures, and ice packs are placed on the face. If these procedures are done soon after admission, the patient is more comfortable. The broken ends of bone are not moving or in malposition, and therefore, the nerve is not traumatized. The organization of the blood clot, which takes place in the first few hours, will not be disrupted by further manipulation in the majority of instances. Intraoral wiring is more difficult to apply the next morning when edema and the trismus associated with reflex spasms of the muscles have occurred. If further treatment is necessary, it is discussed after the immediate measures have been instituted and adequate postoperative radiographs are available for interpretation. Temporary fixation should be placed if definitive fixation is not feasible. Some type of fixation should always be placed to keep the patient comfortable and to keep the fragments in as good as position as possible. A head bandage is the most simple form of fixation. The four-tailed bandage is one method that can be used. Ivy loops can be placed as temporary measures. A method that has been valuable is to string No 4-0 dress clamps on thin, 28-gauge stainless steel wire. Four of these can be placed in as many minutes, and elastics are stretched between them. Treatment The treatment of fractures is directed toward placing the ends of the bone in the proper relation so that they touch and maintaining this position until healing occurs. The term used for positioning the bone is reduction of the fracture. The term used for maintaining the position is fixation. 7  Closed reduction. Several methods of reduction are available. The simplest method is closed reduction, that is, manipulation without surgically exposing the bone to view. In closed reduction of long bones, the orthopedic surgeon pulls or manipulates the bone under the intact skin until the fracture is in proper position. The story is told of an old Scottish physician who had a bucket of sand in the corner of his office. A patient suffering a wrist fracture would be directed against his will to pick up the bucket. In so doing, the fractured parts would align themselves perfectly, and a plaster cast was applied. Most early jaw fractures can be reduced manually. In older fractures in which the bony segments are not freely movable, traction supplied by rubber bands between the jaws exerts a powerful, continuous force that will reduce an obstinate fracture in 15 minutes to 24 hours. The elastic traction overcomes three factors: the active muscular pull that distracts the fragments (the main cause for malposition), the organized connective tissue at the fracture site, and the malposition caused by the direction and force of the trauma. A maxillary fracture often is pushed back by force, and it must be brought forward by manual manipulation or elastic traction. Rarely do the bones require surgical separation except in the case of delayed treatment when a fracture has healed in malposition (malunion). Open reduction. It is not feasible to reduce all fractures satisfactorily by closed procedures. The often-encountered fracture at the angle of the mandible is difficult to reduce because it is difficult to counter the powerful pull of the masticatory muscles in that area. In the case of the angle fracture, however, open reduction is done more for fixation that for reduction. When the bone is surgically exposed, holes are drilled on either side of the fracture, wire is crossed over the fracture, and the bone ends are brought into good approximation. Besides good fixation, the fracture can be reduced exactly by direct vision. Perfect approximation is not always present after closed procedures. It might be stated in passing, however, that jaw fractures occurring within the dental arch are reduced to a fraction of a millimeter by the action of the dental facets of one arch guiding the other arch into the preexistent occlusion. This is not so likely to be true in fractures in other parts of the body, where manipulation is necessarily done through large muscle masses. Reduction in these latter instances need not be as critical as in jaw fractures, which must present an exact occlusion. Another advantage of open reduction, particularly in a late fracture, is the opportunity for the surgeon to clean out the organizing connective tissue and debris between bone ends that would delay healing in the new position if left interposed. Disadvantages of open reduction are: (1) the surgical procedures removes the natural protective clot at the site, and the limiting periosteum in incised; (2) infection is possible even with extreme aseptic procedures and antibiotics; (3) a surgical procedure is necessary, which increases time in the hospital and other hospital costs; and (4) a skin scar is present. Fixation. The orthopedic surgeon reduces a simple fracture of the long bones by a closed procedure and then employs a plaster cast for fixation. The oral surgeon frequently combines the two procedures by the use of one apparatus. When the bones of the jaws contain teeth, the occlusion of the teeth can be used to guide the reduction. By placing wires, arch bars, or splints on the teeth and then extending elastic bands or wires from the mandibular to the maxillary arch, the bones are held in proper position through proper and harmonious interdigitation of the teeth. Plaster casts are not necessary or feasible. The fixation of jaw fractures is approached in graduating steps. Usually intermaxillary fixation by means of wires, arch bars, or splints is the first step. In many cases that is all that 8 is needed. If this is insufficient, however, direct wiring through holes in the bone is done by an open procedure. This is done in addition to the intermaxillary fixation. Methods other than open reduction and direct bone wiring have been employed to manage the angle fracture. Distal extensions from intraoral splints and external extensions from plaster headcaps to a hole in the proximal fragments have been discarded by and large. Fixation by medullary pins is used sometimes. The parts are reduced, and a long, sharp, stainless steel pin is drilled into the length of the bone, crossing the fracture line. The pin is used more often in mandibular symphysis fractures and rather infrequently in mandibular angle fractures. Skeletal pin fixation is used often. In simplest form, a screw pin, 8 cm long with a diameter of 2 mm, is drilled into the lateral aspect of the jaw through the skin and subcutaneous tissues, through the outer bone cortex, the spongiosa, and just through the inner bone cortex. Another pin is drilled on the same side of the fracture. Two pins are drilled on the other side of the fracture. The pins are attached to each other by a connecting apparatus, and the two connecting units are united across the fracture by a stout metal rod. This is a closed procedure that is simple, but many failures are associated with it. If it is performed by an inexperienced person, the pin will not engage the inner cortex, and the entire assembly will become loose at an inopportune time. Maxillary fractures must be maintained against the base of the skull. A plaster headcap with extensions has been used for years. Recently, internal wiring has been used more often. Wires are suspended over the intact zygomatic arches or holes are drilled into an unfractured bone superior to the fracture, such as the infraorbital ridge or the bone just above the zygomaticofrontal suture line. Wires are passed then beneath the skin, and the maxilla thereby is supended. Since this suspension is not visible, the patient can go about his business during recovery. Less chance exists for movement of the fracture during healing than with the plaster headcap. It is interesting to note changes in the thinking of the profession over the years regarding open reduction. In the years before World War II, open operations on bones frequently resulted in osteomyelitis. Complicated jaw fractures were treated by all manner of gadgets. Bicycle spokes, fancy castings, and "man-from-Mars" outfits were used. In the years since the beginning of World War II, the popular procedure has been the open reduction. Antibiotics, the introduction of metals tolerated by the tissues, and more predictable results were largely responsible. The gadgets had been uncomfortable to the patient and sometimes inefficient in approximating the bony segments, and the surgeon never knew when one would slip at a crucial moment. The trend is beginning to regress a bit at present. Largely responsible are the occasional infection of the open wound that is resistant to many antibiotics and the fact that results are not always that much better despite the increased amount of surgery. A tremendous backlog of experience with open procedures can be compared now with conservative procedures. The fractured mandibular condyle is an exmaple. A few years ago almost every fractured condyle was considered for open reduction. Now only a selected few are done. However, many indications exist for open procedures if no other method will give a comparable satisfactory result. Open reduction is still preferable to most of the modern gadgets. 9  Healing of Bone Healing of bone can be divided into three overlapping phases. Hemorrhage occurs first, associated with clot organization and proliferation of blood vessels. This nonspecific phase occurs during the first 10 days. Callus formation occurs in the next 10 to 20 days. A secondary callus in which the haversian systems form "in every which way" forms in 20 to 60 days. Functional reconstruction of the bone is the third phase. Mechanical forces are important here. The haversian systems are lined up according to stress lines. Excess bone is removed. The shape of the bone is molded to conform with functional usage so that bone may be added to one surface and removed on another side. It takes 2 to 3 years, for example, to completely reform a fracture of the human femur. Weinmann and Sicher divide the healing of fractures in six stages: 1. Clotting of blood of the hematoma. When a fracture occurs, blood vessels of the bone marrow, the cortex, the periosteum, the surrounding muscles, and adjacent soft tissues rupture. The resultant hematoma completely surrounds the fractured ends and extends into the bone marrow as well as into the soft tissues. It coagulates in 6 to 8 hours after the accident. 2. Organization of blood of the hematoma. A meshwork of fibrin is formed in the organizing hematoma. The hematoma contains fragments of periosteum, muscle, fascia, bone, and bone marrow. Most of these fragments are digested and removed from the scene. Inflammatory cells, which are so necessary for the hemorrhagic phase of bone healing, are called forth by this diseased tissue rather than by bacterial organisms. Capillaries invade the clot in 24 to 48 hours. Fibroblasts invade the clot at about the same time. The proliferation of blood vessels is a characteristic of the early organizing hematoma. A good blood supply is important. The capillary beds in the narrow, cortex, and periosteum become small arteries to supply the area of fracture. As they become more tortuous, a slower flow results in a richer blood supply. At this stage, proliferation of capillaries occurs throughout the hematoma. The hyperemia associated with the slow flow of blood through tortuous vessels is responsible for mesenchymal proliferation. Protein building blocks created by the richer blood supply form the basis for mesenchymal proliferation. Resorption of bone is a characteristic of an older hematoma. The torrents of blood running through the area of active hyperemia, and not disuse atrophy, cause resorption of bone. When the blood gets into the actual site of fracture where the capillary bed lies (which Johnson likens to a "swamp"), the flow is slowed. This area of passive hyperemia is associated with proliferation of bone. Calcium ion level is increased in this swamp area by the capillary bed. 3. Formation of fibrous callus. The organized hematoma is replaced by granulation tissue ordinarily in 10 days. The granulation tissue removes necrotic tissue primarily by phagocytic activity. As soon as this function is completed, the granulation tissue develops into a loose connective tissue. The end of the hyperemic phase is characterized by a decrease in the number of white cells and partial obliteration of the capillaries. The fibroblasts are now most important. They produce numerous collagenous fibers, which are termed fibrous callus. 4. Formation of primary bony callus. Primary callus forms between 10 and 30 days after fracture. Structurally it has been compared to a crudely woven burlap. The calcium content is so low that primary callus can be cut with a knife. It is for this reason that primary 10 callus cannot be detected on the roentgenogram. It is an early stage that serves only as a mechanical prop for the formation of secondary callus. Primary callus has been considered in different categories, depending on location and function. Anchoring callus develops on the outside surface of the bone near the periosteum. It extends some distance away from the fracture. Young connective tissue cells of the fibrous callus differentiate into osteoblasts, which produce this spongy bone. Sealing callus develops on the inside surface of the bone across the fractured end. It fills the marrow spaces and goes out into the fracture site. It forms from endosteal proliferation. Bridging callus develops on the outside surface between the anchoring callus on the two fractured ends. This callus is the only one that is primarily cartilaginous. The question has been raised whether true bridging callus forms in the healing of mandibular fracture, since the mandible is one of the bones formed originally in membrane rather than by replacement of cartilage. However, cartilage cells have been identified in such areas of healing in the mandible. Uniting callus forms between the ends of bones and between areas of other primary calluses that have formed on the two fractured parts. It does not form until the other types of callus are well developed. It forms by direct ossification. Extensive resorption of the bone ends has occurred by this time. Therefore, rather than merely ossifying the interposed connective tissue at the fracture site, the uniting callus forms in the area of resorption as well. A well-united fracture is the result. 5. Formation of secondary bony callus. Secondary bony callus is mature bone that replaces the immature bone of the primary callus. It is more heavily calcified, and therefore it can be seen on the roentgenogram. It differs from other skeletal bone, however, by the fact that the pseudohaversian systems are not formed in any uniform pattern. It is composed of laminated bone that can withstand active use. Therefore fixation can be removed when secondary callus is seen on the roentgenogram. Formation of secondary callus is a slow process, requiring from 20 to 60 days. 6. Functional reconstruction of the fractured bone. Reconstruction proceeds over months or years to the point where the location of the fracture usually cannot be detected histologically or anatomically. Mechanics is the major factor in this stage. As a matter of fact, if a bone is not subjected to functional stress, true mature bone will not form. True haversian systems that are oriented by stress factors replace the non-oriented pseudohaversian systems of secondary callus. The secondary callus that is formed in abundance is sculptured to conform with the size of the remainder of the bone. The entire bone is molded by mechanical factors if the healing has not taken place in exact alignment. Steps are reduced on the one side, and deficiencies are filled in on the other side. This process seems to take place in alternative waves of osteoclastic activity and osteoblastic activity. 11  Fractures of the Mandible Causes Two principal components are involved in fractures of the mandible: the dynamic factor (blow) and the stationary factor (jaw). Common causes for setting in motion the dynamic factors have been discussed at the beginning of the chapter. Physical violence and automobile accidents lead the list in a municipal hospital administering to a preponderance of indigent patients. However, in studies conducted in private hospitals, industrial accidents rate as a close second to automobile accidents. In these hospitals the incidence of physical violence is extremely low, usually about 10%. The dynamic factor is characterized by the intensity of the blow and its direction. A light blow may cause a greenstick or simple unilateral fracture, whereas a heavy blow with "follow through" may cause a compounded, comminuted fracture with traumatic displacement of the parts. The direction of the blow largely determines the location of the fracture or fractures. A blow to the right of the chin may result in a fracture of the mental foramen region on that side and a fracture of the angle of the mandible on the other side. Force applied to the point of the chin might result in symphysis and bilateral condylar fractures. Severe force may push the condylar fragments out of the glenoid fossa. The stationary component has to do with the jaw itself. Physiological age is important. A child, with his growing bones, can fall out of a window and experience a greenstick fracture or no fracture at all, whereas an elderly person, whose heavily calcified skull can be compared to a flower pot, can trip over a rug and suffer a complicated fracture. Mental and physical relaxation prevents fractures associated with muscular tension. A bone that has severe tensions placed on it by all-out contractions of its attached muscles requires only a slight blow to fracture it. On the other hand, intoxicated persons have fallen from rapidly moving vehicles only to suffer bruises. The muscle masses serve as tissue cushions when relaxed, but the same muscles under tension form strain patterns in the bones. Vulnerability of the jaw itself varies from one individual to another and from time to time in the same individual. A deeply impacted tooth will make the angle of the jaw vulnerable, as will physiological and pathological conditions such as osteoporosis or a large cyst. Heavier deposition of calcium in the trained athlete will reduce jaw fractures. Jaw fractures in boxers are almost nonexistent because of increased calcification, the use of padded boxing gloves and rubber mouthguards, and a training factor. Location In the series quoted previously, the following incidence of fracture, by sites, occurred in the mandible. Angle 31% Symphysis 8% Condyle 18% Cuspid 7% Molar region 15% Ramus 6% Mental region 14% Coronoid process 1%. The most common bilateral fracture was in the angle-mental regions. 12  Displacement The displacement of a fracture of the mandible is a result of the following factors. Muscle pull. The intricate musculature attached to the mandible for functional movement distracts the fragments when the continuity of the bone is lost. The action of balances between sets of muscles is lost, and each muscle group exerts its own force unopposed by another muscle group. The "sling of the mandible", that is, the masseter and medial pterygoid muscles, displaces the posterior jaw fragment upward, aided by the temporal muscle. The opposing force, that is, the suprahyoid muscles, displaces the anterior fragment downward. These forces would balance themselves if attached to an intact bone. The posterior fragment usually is displaced medially, not because of lack of muscular balance as much as because the functional direction of pull is medial. The medial pterygoid muscle is largely responsible. The superior constrictor of the pharynx exerts medial pull from its multicentric origin on the mylohyoid ridge, pterygomandibular raphe, and hamular process to its insertion on the occipital bone. The lateral pterygoid muscle attached to the condyle will help, and in the case of the condylar fracture, it will tend to displace the condyle medially. Fragments situated in the anterior portion of the jaw can be displaced medially by the mylohyoid muscle. Symphysis fractures are difficult to fixate because of the bilateral posterior and slight lateral pull exerted by the suprahyoid and digastric muscles. Direction of line of fracture. Fry anmd associates classified fractures of the mandible as "favorable" and "unfavorable", depending on whether or not the line of fracture was in such direction as to allow muscular distraction. In the mandibular angle fracture, the posterior fragment will be pulled upward if the fracture extends forward toward the alveolar ridge from a posterior point on the inferior border. This is termed unfavorable fracture. However, if the inferior border fracture occurs further anteriorly and the line of fracture extends in a distal direction toward the ridge, a favorable fracture is present. The long angle of the anteroinferior portion will lock the posterior fragment mechanically to withstand upward muscular pull. These distractions are in a horizontal plane, and so the terms horizontal unfavorable and horizontal favorable are used. Most angle fractures are horizontal unfavorable. Medial displacement can be considered in similar fashion. Oblique fracture lines can form a large buccal cortical fragment that will prevent medial displacement. If the mandible could be viewed directly downward from the upper jaw so that the occlusal surfaces of the teeth are seen in button fashion, a vertical unfavorable fracture line extends from a posterolateral point to an anteromedial point. No obstruction to medial muscular pull is present. A vertical favorable fracture extends from an anterolateral to a posteromedial point. Medial muscular displacement is prevented by the large buccal cortical fragment. Force. Factors such as the direction of the blow, the amount of force, the number and location of fractures, and the loss of substance as in gunshot wounds are not as important in displacing mandibular fractures as they are in maxillary fractures except insofar as they form the basis for later muscular distraction. Force on itself can displace fractures by forcing the bone ends away, impacting the bone ends, or pushing the condyles out of their sockets, but secondary displacement by muscular pull is stronger and more significant in mandibular fractures. 13  Force that compounds a fracture or comminutes it serves to complicate the treatment. Events that follow the initial fracture can also complicate it. An initially undisplaced fracture may be displaced by trauma (such as rolling) in the same accident. Placing the patient face down on a stretcher or injudicious and unskilled examination may displace bone segments. Lack of temporary support of the jaw, particularly in the case of a fractured skull, often leads to functional and muscular displacement, which is painful and difficult to treat later. Signs and symptoms 1. History of injury is invariably present, a possible exception being a pathological fracture. 2. Occlusion indirectly offers the best index of recently acquired bony deformity. 3. Abnormal mobility with bimanual palpation of the mandible is a reliable sign of fracture. By this procedure, separation between mandibular fragments is differentiated from mobility of teeth. 4. Pain with movements of the mandible or on palpation of the face often is a significant symptom. When condylar movements are restricted and painful, a condylar fracture should be suspected. 5. Crepitus with manipulation or mandibular function s pathognomonic of a fracture. However, this is elicited with considerable pain to the patient in many cases. 6. Disability is manifested by the patient's inability to masticate because of pain or abnormal motility. 7. Trismus is seen frequently, especially in fractures through the angle or in the ramus region. This is a reflex spasm mediated through the sensory pathways of the disrupted bone segments. 8. Laceration of the gingiva may be seen in the region of the fracture. 9. Anesthesia may be noted, especially in the gingiva and lip up to the midline, when the inferior alveolar nerve is injured. 10. Ecchymosis of the gingiva or mucosa on the lingual or buccal surfaces may be suggestive of a fracture site. 11. Salivation and foetor of breath. Treatment methods Treatment of the fracture consists of reduction and fixation. In the case of long bones, this is often done in two stages, particularly if much manipulation is necessary for reduction. In simple mandibular fractures, reduction and fixation are accomplished together. The apparatus that is used to keep the jaws together during healing will often reduce the fracture as well. If multiple-loop wiring is placed, no attempt is made to reduce the fracture until the wiring on each jaw is complete. When the jaws are brought together and intermaxillary elastic traction is placed, the occlusion of the teeth will help to orient the fractured parts into good 14 position. Exceptions occur, of course. Fractures that occur beyond the tooth-bearing portion of the mandible, such as the angle, will not be reduced if initially displaced. Other examples are edentulous jaws and old fractures that are partially healed, which require continuous elastic traction for reduction. Intermaxillary fixation, that is, fixation obtained by applying wires or elastic bands between the upper and lower jaws to which suitable anchoring devices have been attached, will successfully treat most fractures of the mandible. The main methods for such fixation are wiring, arch bars, and splints. Wiring Multiple-loop wiring. The armed services and many civilian institutions use this method almost exclusively. The four posterior quadrants are wired. Preparation. Local anesthesia with sedation or sedation alone is used. General anesthesia is used occasionally when further treatment is necessary after the wiring. Even then it is better to have the interdental wiring completed the day or night before the operation so that the time of the operating room personnel and prolonged general anesthesia are not needlessly required. The wiring is done in a dental chair if possible. A local anesthetic can be given by two pterygomandibular blocks in the mandible and simple infiltration in the maxilla. Bilateral block anesthesia combined with sedation in a patient who later will be put on his back in bed can be dangerous because of lingual anesthesia. The patient should sit in a chair until the anesthesia has disappeared. If the contact points of the teeth are not too tight and broad, and if the interdental gingival tissue is not too close to the contact points, no anesthesia is necessary. Sedation alone is adequate if care is taken that the fracture zone is not traumatized by undue movement. Premedication with either meperidine hydrochloride (Demerol), 50 to 100 mg, or pentobarbital sodium (Nembutal), 100 to 200 mg, parenterally is adequate generally. For severe pain or to render the patient almost completely insensible to manipulative pain for 20 minutes, 75 to 100 mg of meperidine hydrochloride can be given intravenously to an average adult. This must be administered slowly over a 2-minute interval. Armamentarium. The materials used for multiple-loop wiring are as follows: Wire, 26-gauge stainless steel, cut into lengths of 20 cm and placed in a cold- sterilizing solution 20 minutes before use; wire cut on a bevel so that the bevel can act like a needle point if it must go through tissue. Solder, soft No 20 resin core. Hegar needle holders (two). Wire cutters. Blunt-nosed crown and bridge pliers. Discoid dental instrument. 15