The impact-absorbing effects of facial fractures in closed-head injuries

Transcription

1 J Neurosurg66: , 1987 The impact-absorbing effects of facial fractures in closed-head injuries An analysis of 2 l0 patients K. FRANCIS LEE, M.D., LOUS K. WAGNER~ PH.D., Y. EUGENIA LEE, M.D., JUNG HO SUH, M.D., AND SEUNG RO LEE, M.D. Departments of Radiology and Ophthalmology, University of Texas Health Science Center, Houston, Texas; Yonsei University Medical Center, Seoul, Korea; and Department of Radiology, Hanyang University Medical Center, Seoul, Korea ~" A series of 210 patients with facial fractures sufficiently severe to require cranial computerized tomography (CT) to evaluate suspected closed-head injury (CHI) was studied. The injuries were separated into five grades of severity based on neurological examination, including cranial CT. The injuries were also grouped into three categories based on facial regional involvement, using chi-square contingency table analysis. The data demonstrated that patients with upper facial fractures were at greatest risk for serious CHI. Injuries to both the mandibular and the midfacial regions with no upper facial involvement more frequently resulted in mild CHI with a modest likelihood of no neurological deficits. Trauma to only the mandibular region or to only the midfacial region was least likely to involve CHI. KEY WORDS 9 facial bone fracture 9 closed-head injury 9 computerized tomography B ETWEEN December 1, 1980, and November 30, 1985, more than 1500 patients were treated at the Herman Hospital Trauma Center, University of Texas Health Science Center at Houston. Of these, 210 patients with major facial injuries underwent cranial computerized tomography (CT) to investigate the possible occurrence of closed-head injuries (CHI's). A surprisingly large number of patients with severe facial injuries demonstrated either minor or no CHI on CT scans. The purpose of this study was to correlate these severe regional facial fractures with the occurrence of CHI, as determined from CT findings and neurological examination. Biomechanical Aspects of Facial Trauma In motor-vehicle collisions, the head is often subjected to forces many times that of gravity. The force of gravity is often expressed as a G force. The force of impact (F) can be determined from the equation F = MA, where M represents mass and A acceleration. It is easy for an adult human head to be subjected to an 80- G force in a collision at 30 mph (50 km/hr). If the head weighs 15 lbs, the force on the face in this situation is 15 lbs x 80 = 1200 lbs, which exceeds the fracture limits of most of the facial skeleton as derived from impact experiments on cadavers (Fig. 1).1~'~8"22"27'28 The types of craniofacial injuries resulting from a motor-vehicle accident depend on the following: 22'28 l) force and direction of the collision; 2) impact interface geometry (shape and texture of opposing surfaces); 3) energy-absorbing characteristics of the opposing objects; and 4) use of restraints such as seat belts. Protruding areas with lower tolerance are most likely to sustain injury in motor-vehicle accidents. Thus, the nasal bones are most commonly injured, followed by the zygomaticomaxillary bones, the orbital rims, and the mandible. 4'19"26 Females have lower impact tolerance levels than males. 22 The frontal bone is the area most resistant to injury. 18'22 AS fractures occur, the facial skeleton absorbs some of the impact and cushions the brain against some of its violent effects. 9'21,25 The triplanar arrangement of the facial bones (Table 1) in the horizontal, sagittal, and coronal planes 7,8 may act as an effective cushion against violent forces to the cranium. Complex midfacial fractures have been classified as orbitoethmoidal, zygomaticomaxillary, and Le Fort I, II, and III. 1"3"10"14'15"19 As the nature of motor-vehicle 542 J. Neurosurg. / Volume 66/April, 1987

2 Effect of facial fracture in head injury TABLE 1 Osseous architecture of facial skeleton in three planes* Level of Coronal Plane Struts Horizontal Plane Struts Sagittal Plane Struts Impact upper face midface lower face (mandible) anterior facial: frontal bone, frontal sinus, supraorbital ridge posterior facial: posterior maxillary sinus wall, pterygoid plate nasal bones zygomaticofrontal: anterior maxillary sinus wall, anterior alveolar ridge symphysis * Modified from the data of Gentry, et al. 7 fovea ethmoidalis/cribriform plate orbital roof orbital floor zygomatic arch hard palate body angle ramus median: crista galli parasagittal: cribriform plate lateral: frontozygomatic median: nasal septum parasagittal: medial orbital wall, medial maxillary sinus wall lateral: lateral orbital wall, lateral maxillary sinus wall, lateral alveolar ridge median: symphysis lateral: body, angle, ramus, coronoid, condyle accidents in the past few decades has changed with high-velocity travel, previously unusual combinations of facial fractures have become increasingly common. 3,~9 Most important among these combinations are frontomaxillary fractures which are characterized by disjunction of parts of the frontal bone, the orbital roof, or even the sphenoid bone, so that both the midface and anterior base of the skull are separated from the main body of the cranium. 19'23 These are unlike a Le Fort III fracture, which is a dislocation of the midface from the base of the skull. Injuries of sufficient force and magnitude to produce a Le Fort III fracture usually result in fractures of the Le Fort II and I distribution as well ("total facial smash"). 4'5'1~176 Over 75 % of the patients in this study sustained high- G trauma (such as in motor-vehicle, motorcycle, autopedestrian, and industrial accidents). Under 25% of them were injured by low-g impacts (for example, in assaults, falls, and sporting accidents) (Table 2). TABLE 2 Cause of facial fractures in 210 patients Cause Cases No. % motor-vehicle accidents assaults & falls sporting accidents industrial accidents miscellaneous unknown Clinical Material and Methods Major facial fractures were documented on plain radiography, panradiography, CT, and physical examination in the 210 patients in this series. The age distribution of these patients is given in Fig. 2. The male:female ratio was 3.1:1. A total of 596 craniofacial CT examinations were performed, for an average of 2.8 examinations per patient. A GE 8800 CT scanner (320 x 320 matrix) was used between 1980 and 1983, and two GE 9800 scanners (512 x 512 matrix) were used in 1984 and 1985 for the facial and cranial CT examinations.~5'~6 For the facial bones, multiple axial sections with a slice thickness of 5 or 3 mm were performed, and reformatted images in the sagittal and coronal planes were also obtained in the majority of the patients. When the patients' condition permitted, direct coronal CT scans with a slice thickness of 5 or 10 mm were obtained. With the fast scanner, the entire CT examination in the axial and coronal planes could be FIG. 1. Tolerances of the facial bones to violent forces. A 30-mph collision can easily result in an 80-G force, which is sufficiently large to cause fractures of the nasal bones, zygoma, mandibular ramus, and frontal sinus. (Reproduced with permission from Luce EA, Tubb TD, Moore AM: Review of 1,000 major facial fractures and associated injuries. Plast Reconst Surg 63:26-30, 1979.) J. Neurosurg. / Volume 66/April

3 K. F. Lee, et al. TABLE 3 Incidence of various facial fractures in 210 patients Facial Fracture Group* Cases No. % 1 (lower third) (middle third) 3 (upper third) (lower& middle thirds: 1 + 2) 5 (lower& upper thirds: 1 + 3) (middle& upper thirds: 2 + 3) 7 (lower, mid, & upper thirds: ) * For an illustration of facial segments see Fig. 3. FIG. 2. Age distribution of 210 patients with facial fractures. The highest incidence was noted in the 20- to 29-yearold group, followed by the 30- to 39-year-old and the 10- to 19-year-old groups. completed within 20 minutes. Cranial CT scans with a slice thickness of 8 mm for children and 10 mm for adults were also obtained without injection of contrast material. The clinical status of the patients was classified into five grades based on the CT findings combined with the Glasgow Coma Scale. 2"6"12't3'17'24'29 The CHI was classified according to severity into the following grades: Grade 0 (negative); Grade I (mild); Grade II (moderately severe); Grade III (severe); and Grade IV (grave or fatal). The etiology of craniofacial fractures varied; the great majority of the patients in this series were injured in motor-vehicle accidents (Table 2). Results The highest incidence (39 %) of severe facial fractures was noted in the 20- to 29-year-old age group (Fig. 2). The median age was 26 years. Facial fractures were divided into seven groups depending on the area involved (Fig. 3 and Table 3). Group 1 fractures involved the lower third of the facial skeleton (the mandible). There were 15 cases in this group. Thirteen of these had fractures involving more than one of the following areas: condyle, symphysis, angle, alveolar process, ascending ramus, mandibular dentition, corpus or body, and coronoid process. Group 2 injuries involved the middle third of the facial skeleton (the midface). There were 35 cases in this group. Multiple fractures were demonstrated in the following areas: nasal bone and septum; pterygoid plates; orbit; zygoma; zygomatic arch; and maxilla, including the alveolar process and maxillary dentition. Complex fractures such as Le Fort II and III fractures were observed in 54% of cases. Group 3 fractures involved the upper third of the facial skeleton (forehead). There were 33 cases in this group. Fractures were noted in one or more of the following areas: supraorbital ridge, glabella (frontal sinuses), and frontal bone. Group 4 fractures involved a combination of Group 1 (mandible) and Group 2 (midface) injuries, and were found in 41 cases. Group 5 fractures included a combination of Group 1 (mandible) and Group 3 (forehead) injuries, and were found in 12 cases. Group 6 fractures comprised a combination of Group 2 (mid- FIG. 3. Schematic drawing of the classification system for regional facial fractures. Group 1: lower third facial (If) or mandibular fractures; Group 2: middle third facial (mf) or midfacial fractures; Group 3: upper third facial (uf) or forehead fractures; Group 4: combination of mandibular (1) and midfacial (m) fractures; Group 5: combination of mandibular and upper facial fractures; Group 6: combination of midfacial and upper facial fractures; and Group 7: combination of mandibular, midfacial, and upper facial fractures. 544 J. Neurosurg. / Volume 66/April, 1987

4 Effect of facial fracture in head injury TABLE 4 Computerized tomography findings in 210 cases of craniofacial trauma* Fracture No. of Subdural Epidural ICH HRC SAH Midline TTH Edema Pneumocephalus IVH Miscellaneous Group Cases Hematoma Hematoma Shift total * ICH: intracerebral hematorna; HRC: hemorrhagic contusion; SAH: subarachnoid hemorrhage; TTH: transtentorial herniation; IVH: intraventricular hemorrhage. For definition of fracture groups see Table 3. face) and Group 3 (forehead) injuries, and involved 43 cases. Group 7 fractures included injuries from Groups 1, 2, and 3 combined, and were found in 31 cases. Thus, middle third (midface) and upper third (forehead) combination fractures (Group 6) were seen most commonly (20%), while the lower third (mandible) and upper third (forehead) fracture combination (Group 5) was observed least frequently (5.7%). The cranial CT findings in each group of facial fractures are summarized in Table 4. The following CT findings were noted in order of decreasing frequency: hemorrhagic contusion (77), midline shift (41), subdural hematoma (40), cerebral edema (36), intracerebral hematoma (32), pneumocephalus (31), intraven- tricular hemorrhage (18), subarachnoid hemorrhage (16), epidural hematoma (14), transtentorial herniation (nine), and miscellaneous findings in four. Table 5 and Fig. 4 show each fracture group with the incidence of CHI classified according to the cranial CT findings in conjunction with neurological examinations. Chi-square contingency table analysis revealed that the CHI grade distributions of Groups 1 (mandibular fractures) and 2 (midfacial fractures) were not significantly different (p < 0.35). Similarly, CHI grade distributions in Groups 3 (upper facial fractures), 5 (mandibular and upper facial fractures), 6 (middle and upper facial fractures), and 7 (mandibular, middle, and upper facial fractures) were not significantly different 80% 60% GRAt~ 0 e~jativel 60% GRAD~ I (mild) 60% GRAD~ II (moderate) l 40% 40% i 20% 20% %IG %IG %IG % 20% 10% r-i GRAI~ III severe) GRADE IV (grave/fatal) G-l: mandibular fractures G-2: midfacial fractures G-3: upper facial fractures G-4: ~ a r & midfacial ~ G-5: mandibular & upper facial 20% G-6 : middle and upper facial G-7: mandilmllar,mid & upper(total) I-I [7 R %IG FIG. 4. Regional facial fractures and severity (grading) of closed-head injuries (CHI's) in 210 patients with major facial fractures. For definition of CHI grade see Table 5. J. Neurosurg. / Volume 66/April,

5 K. F. Lee, et al. o wz 80% ~ 6o~ E 40, 2O% I I Mandibular or Midfaeial Fxs Mandibular & Midfacial Fxs Upper Facial Area Fxs d I I I I I 0 I II Ill GRADE OF INTRACRANIAL INJURIES (210 cases) FIG. 5. Regrouping of the seven regional facial fractures into three categories based on contingency table analysis (see text for p values). Severe closed-head injury (CHI) was more frequently observed in patients with upper facial fractures, while the majority of patients with mandibular or midfacial fractures alone demonstrated no CHI or minor CHI. Fxs = fractures. (p < 0.5). The CHI grades associated with Group 4 fractures (mandibular and midfacial fractures) were marginally different from those found with Group 1 and 2 fractures (p < 0.05) and significantly different from the grades in patients with Group 3, 5, 6, and 7 fractures (p < 0.001). The CHI grades in Group 1 and 2 fractures were significantly different from those associated with Group 3, 5, 6, and 7 fractures (p < 0.001). The seven groups presented in Table 3 can therefore be reclassified into three categories of CHI. The first category involves fractures to only the mandibular region or only the midfacial area (Groups 1 and 2). The second category involves fractures of both the mandibular and midfacial areas with no upper facial involvement (Group 4). The third category includes all fractures involving the upper facial area (Groups 3, 5, 6, and 7). A plot of the distribution of these three categories is shown in Fig. 5. Discussion This study of 210 patients whose facial injuries were sufficiently severe to require CT for possible CHI demonstrated the following association with neurological deficits. Fractures involving only the mandibular or the midfacial areas (Groups 1 or 2) were most likely correlated with Grade 0 CHI (62% of cases with that level of fracture) with a modest likelihood of a Grade I injury (24% of cases). More severe injuries were less likely to be found in this group of patients (14% of cases). Combined fractures to the mandibular and midfacial areas (Group 4) were most likely to be associated with Grade I CHI (54% of patients with that fracture group), with a modest likelihood of Grade 0 CHI (32% of IV Incidence TABLE 5 of closed-head injuries in facial trauma* Fracture No. of Grade Grade Grade Grade Grade Group Cases 0 I II III IV (80%) 2 (13%) 1 (7%) (54%) 10(29%) 4(11%) 2(6%) (12%) 9(27%) 16 (48%) 3 (10%) 1 (3%) (32%) 22 (54%) 5 (12%) 1 (2%) (8%) 2 (17%) 5 (42%) 3 (25%) 1 (8%) (2%) 12 (28%) 23 (54%) 6(14%) 1 (2%) (3%) 14 (45%) 13 (42%) 3(10%) 0 * For definition of fracture groups see Table 3. Grade 0: Normal computerized tomography (CT) without significant neurological deficit; Grade I: Minor CT findings with slight neurological deficit; Grade II: Moderately severe CT and neurological findings; Grade III: Severe CT and neurological findings; Grade IV: Grave CT findings with fatal outcome. cases). More severe injuries had a lower likelihood of occurring in this fracture group (14% of cases). Any fracture involving the upper facial area (Groups 3, 5, 6, or 7) was most likely to be a Grade II CHI (48% of cases with this fracture level) with a modest incidence of Grade I injury (31% of cases). Grade 0, III, and IV CHI's occurred less frequently (21% of cases). The compressible air-filled energy-absorbing facial bones serve as a decelerating cushion to protect intracranial structures located behind them. This may be a major reason why extensive crushing injuries of the facial bones are frequently sustained with little apparent damage to the brain. In order to prevent serious injury to the brain in an accident involving facial injury, it is best to protect the areas of the forehead and the skull since injury to these areas is more likely to result in serious CHI than is injury to other areas of the face. References 1. Brant-Zawadzki MN, Minagi H, Federle MP, et al: High resolution CT with image reformation in maxillofacial pathology. A JR 138: , Cooper PR, Maravilla K, Moody S, et al: Serial computerized tomographic scanning and the prognosis of severe head injury. Nenrosurgery 5: , Crusec CW, Blevins PK, Luce EA: Naso-ethmoid-orbital fractures. J Trauma 20: , Dolan KD, Jacoby CG: Facial fractures. Semln Roentgenol 13:37-51, Dolan KD, Jacoby CG, Smoker W: The radiology of facial fractures. Radiographics 4: , French BN, Dublin AB: The value of computerized tomography in the management of 1000 consecutive head injuries. Surg Neurol 7: , Gentry LR, Manor WF, Turski PA, et al: High-resolution CT analysis of facial struts in trauma: 1. Normal anatomy. AJR 140: , Gentry LR, Manor WF, Turski PA, et al: High-resolution CT analysis of facial struts in trauma: 2. Osseous and softtissue complications. AIR 140: , Halazonetis JA: The "weak" regions of the mandible. Br J Oral Surg 6: J. Neurosurg. / Volume 66/April, 1987

6 Effect of facial fracture in head injury 10. Harris JH, Ray RD, Rauschkolb EN, et al: An approach to mid-facial fractures. CRC Crit Rev Diag lmag 21: , Huelke DF, Harger JH: MaxiUofacial injuries: their nature and mechanisms of production. J Oral Surg 27: , Jennett B, Bond M: Assessment of outcome after severe brain damage. A practical scale. Lancet 1: , Kishore PRS, Lipper MH, Becker DP, et al: Significance of CT in head injury: correlation with intracranial pressure. AJNR 2: , 1981; AJR 137: , Le Fort R: Experimental study of fractures of the upper jaw. Part III. Plast Recanst Surg 50: , Lee KF, Yeakley JW: Computed tomography of craniofacial trauma, in Wilder RJ (ed): Multiple Trauma. Progress in Critical Care Medicine, Vol 1. Basel: S Karger, 1984, pp Lee KF, Yeakley JW, Patchell LL: Computed tomography of intracranial traumatic lesions, in Wilder RJ (ed): Multiple Trauma. Progress in Critical Care Medicine, Vol 1. Basel: S Karger, 1984, pp Lipper MH, Kishore PRS, Enas GG, et al: Computed tomography in the prediction of outcome in head injury. A JR 144: , Luce EA, Tubb TD, Moore AM: Review of 1,000 major facial fractures and associated injuries. Plast Reconst Sarg 63:26-30, Matras H, Kuderna H: Combined cranio-facial fractures. J Maxillofac Surg 8:52-59, McCoy FJ, Chandler RA, Magnan CG, et al: An analysis of facial fractures and their complications. Plast Reconst Surg 29: , Murray JF, Hall HC: Fractures of the mandible in motor vehicle accidents. Clin Plast Surg 2: , Nahum AM: The biomechanics of maxiuofacial trauma. Clin Plast Surg 2:59-64, Nakamura T, Gross CW: Facial fractures. Analysis of five years of experience. Arch Otolaryngol 97: , Narayan RK, Greenberg RP, Miller JD, et al: Improved confidence of outcome prediction in severe head injury. A comparative analysis of the clinical examination, multimodality evoked potentials, CT scanning, and intracranial pressure. J Neurosurg 54: , Salem JE, Lilly GE, Cutcher JL, et al: Analysis of 523 mandibular fractures. Oral Snrg 26: , Schultz RC: One thousand consecutive cases of major facial injury. Rev Surg 27: , Schultz RC, Oldham RJ: An overview of facial injuries. Surg Clin North Am 57: , Swearingen JJ: Tolerances of the Human Face to Crash Impact. Oklahoma City: Office of Aviation Medicine, Federal Aviation Agency, Teasdale G, Jennett B: Assessment of coma and impaired consciousness. A practical scale. Lancet 2:81-84, 1974 Manuscript received March 28, Accepted in final form September 11, The data presented here have recently been published in a somewhat different form in Lee KF: High resolution computed tomography of facial trauma associated with closedhead injuries, in Toombs BD, Sandier CM (eds): Computed Tomography in Trauma. Philadelphia: WB Saunders, Tables 2, 3, 4, and 5 and Figs. 2, 3, and 4 of this text are adapted from the WB Saunders text with permission of the publisher. Address reprint requests to: K. Francis Lee, M.D., University of Texas Health Science Center, 6431 Fannin, Houston, Texas J. Neurosurg. / Volume 66/April,