Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Treatment of Traumatic Mandibular Fractures The mandible is reportedly the most commonly fractured bone in facial trauma. The injury is found predominantly in males in the 20 to 30 year old age group and occurs with highest frequency in the summer months. The mandible is composed of a thick outer plate of bone and a compact inner plate of cortical bone separated by trabeculated medullary bone. The mandible is divided into the alveolar tooth-bearing process, the symphysis, the body, the angle or gonion, the ramus, the coronoid, and the condylar processes. The inferior alveolar nerve enters at the mandibular foramen and exits at the mental foramen at the interspace between the first and second premolars. There are 32 adult teeth which are numbered according to the ADA universal classification system. The upper right third molar is #1, the upper left #16, lower left third molar #17, lower right third molar is #32. Occlusion is classified according to Angle's system, which is absed on the relationship of the retrobuccal cusp of the upper first molar to the buccal groove of the lower first molar. In normal class I occlusion, the mesiobuccal cusp of the maxillary first molar occludes exactly with the mandibular first molar buccal groove. In class II occlusion the mesiobuccal cusp is mesial or anterior to the mandibular first molar buccal groove. An overjet of more than 4 mm creates a "buck tooth" appearance. In class III occlusion, the mesiobuccal cusp is distal to the buccal groove. The incisiors are either edge to edge or with a negative overjet. The anatomic distribution of fractures varies with etiology. Condylar and subcondylar fractures make up 26% to 36%; angle fractures, 20% to 26%; symphyseal and parasymphyseal fractures, 14% to 23%; body, 11% to 21%; ramus, 25 to 3%; and coronoid fractures, 1 to 2%. Fractures are often termed favorable or unfavorable depending on their tendancy towards distraction by the masticatory musculature. A horizontally unfavorable fracture is one directed anterior superior to posterior inferior. The posterior fragment of the mandible will be pulled cephalad by the musculature causing distration of the fracture segments. If the fracture was directed anterior inferior to posterior superior, the cephalad pull of the musculature will squeeze the fragments together making this a favorable fracture. A vertically unfavorable fracture is one directed anterior medial to posterior lateral. The mylohyoid pulls the posterior segment medially causing distraction. A fracture running anterior lateral to posterior medial is squeezed together by the medial pull of the mylohyoid. The treatment of mandible fractures can be divided into open and closed techniques. Closed treatment refers to external fixation devices and intermaxillary fixation (IMF) which is based on the principle that when the teeth of a fractured segment are in correct occlusion, then the bone fragments to which they are attached will, in most cases, also be satisfactorily reduced. Healing of the bone occurs by secondary intention with callus formation in the same way as a long bone in a cast heals. The mandible must be immobilzed for 4-6 weeks for most fractures. The average weight loss is 10-15 pounds. IMF is the primary teatment for condylar and subcondylar fractures. Unilateral condylar fractures with good occlusion can be managed with close observation and liquid diet. IMF for 2 to 3 weeks is recommended for those with continued pain, malocclusion, or bilateral condylar fractures. Open treatment is reserved for special cases. External fixation devices such as Hoffman pins, and the Morris Biphase apparatus are useful for certain cases. The indications include severe traumatic loss of bone, severely atrophic mandibles that prevent the use of plates, fractures complicated by osteomyelitis, infected nonunion, and loss of bone to be repaired with subsequent bone graft or free flap. Open techniques of mandible repair are divided into rigid and semi-rigid fixation. Wire osteosynthesis is a form of semi-rigid fixation using 0.35mm stainless steel wire to secure the fractured segments. A small amount of movement of the proximal and distal segments occurs causing healing with periosteal callus formation. This technique is useful for superior border wiring. In true rigid fixation, healing occurs primarily, without callus formation allowing early return of function. Dynamic compression plates (DCP) are based on the concept of preload and friction at the fracture site. These plates cause compression of the fracture segments resulting in preload and friction. The preload prevents distraction of the segments as long as the static compression is greater than the dynamic tension caused by the masticatory musculature. The friction stabilizes against torsional forces. Together these allow primary bone healing to occur. The dynamic compression plates cause compression through the spherical gliding principle. As the screws are tightened the spherical undersurface of the screw glides down the horizontally directed cylindrical plate hole converting a downward movement into a horizontal one. The bone fragment to which the screw is attached moves horizontally against the plate towards the opposite fragment which is moving horizontally in the opposite direction. Anatomically, the dental roots and the inferior alveolar nerve require that the DCP must be placed at the inferior border of the mandible. If used alone, the DCP would cause compression at the inferior border with distraction and gapping at the superior border. The tension band principle prevents this from occurring. A device such as an arch bar or plate can be placed on the alveolar or tesion side of the mandible to restore anatomic alignment before the DCP is applied, allowing even compression along the entire length of the fracture. Monocortical miniplate systems are based on an entirely different principle. Masticatory muscle function normally produces tension at the upper border of the mandible with compressive forces at the lower border. In addition, torsional forces are produced in the area anterior to the canines. In a series of experiments, Champy was able to define ideal lines of osteosynthesis. Monocortical "tension banding" osteosythesis results in neutralization of distracting and torsional forces exerted on the fracture during physiologic stress, while the normal compressive forces at the basilar aspect of the mandible are restored. Posterior to the mental foramen a single plate is placed below the dental roots and above the inferior alveolar nerve. Anterior to the mental foramina two plates are necessary to neutralize the torsional forces. The advantage of monocortical miniplates is that they can applied nearly anywhere in the mandible via an intraoral approach. The lag screw technique is another method of rigid fixation. An oversized or gliding hole is drilled through the near cortex with a diameter greater than the thread diameter of the screw. A countersink hole is drilled at the outer end of this hole to accommodate the screw head. The distal portion of the hole is drilled with a diameter corresponding to the core diameter of the screw. As the screw is tightened its distal end engages the threaded hole of the distal fragment. The undersurface of the screw head contacts the countersink hole and pulls the distal fragment against the proximal fragment causing compression. A lag effect can only occur if the screw can pass freely through the gliding hole. Lag screws are most appropriate for oblique fractures. 2-3 lag screws are needed to ensure stability. The ASIF recommends drilling holes so that the axis of the holes bisects the angle formed by the fracture and the cortical surface to prevent shearing. The last form of fixation to be discussed is the reconstruction plate. These plates are a form of internal surgical splint. They serve to buttress fragments against displacent and to absorb the functional load while healing occurs. The plate holes are designed for neutral screws. These plates are particularly useful for the treatment of multiple segmental fractures. The fracture segments are held together with wires or miniplates. The reconstruction plate is than contoured and secured with two screws in each stable lateral segment. The segmental fragments are then secured to the plate. Case Presentation A 37-year-old Latin American woman, was asleep in bed when she sustained a single gunshot wound to the face. Fired by an unknown assailant outside the patient's house, the bullet had passed through one wall before striking the patient. She was taken by ambulance to Ben Taub General Hospital where she was received in stable condition without signs of respiratory distress. She had an entry wound just above the right oral commissure. Intraoral examination revealed tooth destruction of the right maxillary and mandibular arches and malocclusion. A large caliber bullet was extracted from the right maxillary alveolar process. A slight weakness of the right marginal mandibular branch of the facial nerve was also noted. The rest of her examination was essentially normal. Past medical history was non-contributory. Radiographic examination revealed a left mandibular parasymphyseal fracture and multiple tooth loss. The patient was taken to the operating room where she underwent: debridement of the right alveolar processes of the maxilla and mandible; extraction of residual roots of teeth numbers 5, 6, 28, 29, 30, 31; placement of arch bars; and open reduction and internal fixation of a left oblique parasymphyseal fracture with two lag screws and a reduction screw. The patient remained intubated for twelve hours following the procedure because of floor of mouth edema and was then extubated without complication. Postoperative examination revealed good occlusion without the necessity of IMF. The patient was instructed to maintain a soft diet for four weeks. Her arch bars were removed after two weeks. In follow-up, serial postreduction panorexes revealed maintenance of the reduction. Bibliography Anderson T, Alpert B. Experience with rigid fixation of mandibular fractures and immediate function. J Oral Maxillofac Surg 1992;50:555-560. Ardary WC. Plate and screw fixation in the management of mandible fractures. Clin Plast Surg 1989;16:61-67. Ardary WC. Prospective clinical evaluation of the use of compression plates and screws in the management of mandible fractures. J Oral Maxillofac Surg 1989;47:1150-1153. Beck RA, Blakeslee DB. The changing picture of facial fractures: 5-year review. Arch Otolaryngol Head Neck Surg 1989;115:826-829. Clark WD. Management of mandibular fractures. Am J Otolaryngol 1992;13:125-132. Coleman JJ III, Wooden WA. Mandibular reconstruction with compositie microvascular tissue transfer. Am J Surg 1990;160:390-395. Creasman CN, Markowitz BL, Kawamoto HK, Cohen S, Kioumehr F, Hanafee WN, et al. Computed tomography versus standard radiography in the assessment of fractrues of the mandible. Ann Plast Surg 1992;29:109-113. El-Degwi A, Mathog RH. Mendible fractures - medical and economic considerations. Otolaryngol Head Neck Surg 1993;108:213-219. Ellis E III, Ghali GE. Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 1991;49:13-21. Ellis E III, Ghali GE. Lag screw fixation of mandibular angle fractures. J Oral Maxillofac Surg 1991;49:234-243. Fridrich KL, Pena-Velasco G, Olson RAJ. Changing trends with mandibular fractures: a review of 1,067 cases. J Oral Maxillofac Surg 1992;50:586-589. Friedman CD, Costantino PD. Facial fractures and bone healing in the geriatric patient. Otolaryngol Clin North Am 1990;23:1109-1119. Hidding J, Wolf R, Pingel D. Surgical versus non-surgical treatment of fractures of the articular process of the mandible. J Cranio-Maxillofac Surg 1992;20:345-347. Klotch D. Use of rigid internal fixation in the repair of complex and comminuted mandible fractures. Otolaryngol Clin North Am 1987;20:495-518. Leonard MS. The use of lag screws in mandibular fractures. Otolaryngol Clin North Am 1987;20:479-493. Levine PA. AO compression plating technique for treating fractures of the edentulous mandible. Otolaryngol Clin North Am 1987;20:457-477. Levy FE, Smith RW, Odland RM, Marentette LJ. Monocortical miniplate fixation of mandibular angle fractures. Arch Otolaryngol Head Neck Surg 1991;117:149-154. Maloney PL, Welch TB, Doku HC. Early immobilization of mandibular fractures: a retrospective study. J Oral Maxillofac Surg 1991;49:698-702. Prein J, Kellman RM. Rigid internal fixation of mandibular fractures - basics of AO technique. Otolaryngol Clin North Am 1987;20:441-456. Raveh J, Vuillemin T, Lädrach K, Roux M, Sutter F. Plate osteosynthesis of 367 mandibular fractures: the unrestricted indication for the intraoral approach. J Cranio-Maxillorac Surg 1987;15:244-253. Reitzik M, Schoorl W. Bone repair in the mandible: a histologic and biometric comparison between rigid and semirigid fixation. J Oral Maxillofac Surg 1983;42:215-218. Rood SR, Gallia LJ, Johnson JT, Myers EN. Treatment of mandibular fracures. Washington D.C.: American Academy of Otolaryngology - Head and Neck Surgery Foundation, Inc., 1983. Rowe NL, Williams, JL. Maxillofacial injuries, Volume 1. Edinburgh: Churchill Livingstone, 1985. Rudderman RH, Mullen RL. Biomechanics of the facial skeleton. Clin Plast Surg 1992;19:11-29. Shetty V, Caputo A. Biomechanical validation of the solitary lag screw technqiue for reducing mandibular angle fractures. J Oral Maxillofac Surg 1992;50:603-607. Shetty V, Freymiller E. Teeth in the line of fracture: a review. J Oral Maxillofac Surg 1989;47:1303-1306. Siegel MB, Wetmore RF, Potsic WP, Handler SD, Tom LWC. Mandibular fractures in the pediatric patient. Arch Otolaryngol Head Neck Surg 1991;117:533-536. Takenoshita Y, Ishibashi H, Oka M. Comparison of functional recovery after nonsurgical and surgical treatment of condylar fractures. J Oral Maxillofac Surg 1990;48:1191-1195. Thaller SR, Mabourahk S. Pediatric mandibular fractures. Ann Plast Surg 1991;26:511-513. Thaller SR, Reavie D, Daniller A. Rigid internal fixation with miniplates and screws: a cost-effective technique for treating mandibular fractures? Ann Plast Surg 1990;24:469-474. Thorén H, Iizuka T, Hallikainen D, Lindqvist C. Different patterns of mandibular fractures in children: an analysis of 220 fractures in 157 patients. J Cranio-Maxillofac Surg 1992;20:292-296. Wenig BL, Keller AJ. Microvascular free-tissue transfer with rigid internal fixation for reconstruction of the mandible following tumor resection. Otolaryngol Clin North Am 1987;20:621-633. Yaremchuk MJ, Gruss JS, Manson PN, editors. Rigid fixation of the craniomaxillofacial skeleton. Boston: Butterworth-Heinemann, 1992. Zide MF. Open reduction of mandibular concyle fractures. Indications and technique. Clin Plast Surg 1989;16:69-76. Zorman D, Godart PA, Kovacs B, Andrianne Y, Daelemans P, Burny F. Treatment of mandibular fractures by external fixation. Oral Surg Oral Med Oral Pathol 1990;69:15-19. Grand Rounds Archive | Department Home page BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2006 Baylor College of Medicine
|