oral surgery oral medicine oral pathology wth
secrions on
oral andmaxillofacial radiology and endodontics
oral surgery Editor: ROBERT B. SHIRA, DDS
School of Dental Medicine Tufts University 1 Kneeland Street Boston, Massachusetts 021 I I
Retrospective analysis of low-velocity gunshot wounds to the mandible Edward A. Neupert III, LCDR, DC, USN,a and Scott B. Boyd, DDS, PhDeb Dallas, Tex., and Detroit, Mich. UNIVERSITY
OF TEXAS AND HENRY
FORD HOSPITAL
A retrospective study was conducted of 32 patients with mandibular fractures resulting from low-velocity gunshot injuries. Airway management was required in 25% of the patients, and 9% sustained major vessel injury. Patients were divided into two groups, depending on site of mandibular fracture: condyle, ramus, and coronoid (n = lo), and angle, body, and symphysis (n = 22). All patients in the condyle, ramus, coronoid group achieved clinical union without infection. Average postinjury maximal mandibular opening was restricted (28 mm), but the average follow-up period was relatively short (2 months). In the angle, body, symphysis group the infection rate was 27%, and in 18% of patients a continuity defect of the mandible developed. The average length of follow-up in this group was 5.4 months with a mean maximal mandibular opening of 36 mm. (ORAL SURC ORAL MED ORAL PATHOL
1991;72:383-7)
S
everal reports have described surgical management of gunshot wound injuries to the face.‘-1° However, few investigations examined outcome after therapy. The purpose of this retrospective study was to evaluate treatment outcome after low-velocity missile injuries to the mandible. METHODS
The sample group in this retrospective study consisted of patients admitted to Parkland Memorial BFormerly Resident, Division of Oral and Maxillofacial Surgery, University of Texas, Southwestern Medical Center, Dallas, Tex.; now Lieutenant Commander, Dental Corps, United States Navy. bDivision Head, Oral and Maxillofacial Surgery, Henry Ford Hospital, Detroit, Mich. 7112123831
Hospital, Dallas, Tex., between 1983 and 1988 for low-velocity gunshot wounds to the mandible. A total of 32 patients with complete medical charts and radiographic records were identified during the designated time period. Data was obtained from these records in four categories: demographics, initial assessment,surgical management, and treatment outcome. Initial assessmentvariables included airway patency, presence of vascular injury, caliber of weapon, site(s) and severity of mandibular fracture, and concomitant injuries. Surgical treatment variables reviewed included method of fracture reduction, type of fixation, and use of drains. A preliminary survey of the data revealed a clear difference in management, depending on the site of injury. On this basis patients were divided into one of two groups: condyle, 383
384
Neupert and Boyd
ORAL SCRC ORAL MED ORAL PATHOI October I99 I
Table I. Distribution of patients within groups CRC and ABS with respect to treatment of postsurgical
findings CRC group No. of patients Open reductions No. of infections Continuity defects MM0 (mm)
Follow-up(mo)
IO I 0 0 28 2
~ ,
A BS group 22 18 6 4 36 5.4
ciated injuries involved both regional (globe, neck, cervical spine, cranium) and distant (abdomen, chest) structures. Fig. 1. Diagrammatic representation of 47 anatomic sites of fracture in 32 patients with gunshot wounds to mandible. ramus, and coronoid (CRC), (n = 10) and angle,
body, and symphysis (ABS) (n = 22). Patients injured in both regions were placed in the ABS group. Treatment outcome variables included incidence and severity of infection, clinical and radiographic evidence of fracture healing, mandibular range of motion, and length of follow-up. RESULTS
Initial assessment
The study group was predominantely young men (81%). The mean age of the group was 26 years with a range from 4 to 50 years. Suctioning of the oral cavity and patient positioning were all that was required to maintain airway patency for the majority of patients (72%, 23/32). The remaining nine patients received either endotracheal intubation (five patients) or tracheostomy (four patients) for airway control. The majority of patients (74%) who preoperatively required only airway observation were extubated within 48 hours after surgery. In contrast, most persons (78%) undergoing preoperative intubation or tracheostomy had airway control maintained more than 48 hours after surgery. Most patients (94%, 30/ 32) were normotensive on presentation to the emergency room. Arteriography was performed on 20 patients (62.5%); 15% (3/20) of the arteriograms were positive for major vessel injury. More than half the patients (56%, 18/3 1) were injured with a weapon of unknown caliber. In those cases where the weapon was identified, a .38 caliber (n = 9) handgun was used most commonly. Fractures were observedthroughout the mandible, with no site of preferential injury (Fig. 1). Multiple sites of fracture occurred in 32% of patients, with a total of 47 fractures noted for the entire group. Concomitant gunshot injuries not involving the mandible occurred in 13 patients (41%). These asso-
Surgical management
Patients in the CRC group were treated by either observation (4/10) or closed reduction (5/10) with stabilization by dental (3/10) or extraskeletal pin fixation (2/10). One patient underwent open reduction for removal of a bullet within the temporomandibular joint. No internal fixation techniques for fracture stabilization in the CRC group were used. Wound debridement (20%) and drain placement (10%) were infrequently performed. In general, patients in the ABS group had more extensive surgical treatment than the CRC group. Open reduction with conservative debridement of devital bone and teeth, with primary closure of soft tissue wounds, was performed in most patients (82%). Drains were placed in some persons (32%). Dental fixation was applied in the vast majority of patients (91%) for dentoskeletal stabilization. Other methods of fracture stabilization included extraskeletal pin fixation (41%) and internal fixation with wire osteosynthesis (23%). Treatment
outcome
No infections occurred in the CRC group. All CRC patients went on to clinical union without evidence of malunion. The mean maximal mandibular opening (MMO) was 28 mm (+ 12.4), with a range from 10 to 45 mm; however, the average length of patient follow-up was relatively short (2 months) (Table I). Infection developed in about one fourth (27%) of the ABS group during the course of treatment. Most of these infections were localized to dentoalveolar structures and were managed successfully by relatively simple measures consisting of oral or intravenous antibiotics, extraction of indicated teeth, and local sequestrectomy. A continuity defect developed in four patients in the ABS group. Continuity defects were the result of either the initial injury (2/4) or extensive surgical debridement (2/4). These four patients subsequently underwent mandibular recon-
Volume Number
72 4
struction with autogenous bone grafting, which successfully restored mandibular continuity in each case. The mean MM0 was 36 mm (+9.4), with a range from 15 to 50 mm. The average length of follow-up (5.3 months) was more than twice as long as that of the CRC group. DISCUSSION
Low-velocity gunshot wounds of the mandible produce a characteristic pattern of injury consisting of a small entrance wound with minimal soft tissue injury and comminution of bone and teeth.* Mortality from low-velocity gunshot wounds to the mandible seldom occurs, and no fatalities were observed in this study. Wound ballistics studies indicate that wounding capacity is related to kinetic energy of the missile.’ l-l3 Kinetic energy is calculated by the formula KE = ‘/2 MV*, which indicates that velocity plays a more important role in determining kinetic energy than mass. This relationship has been used as the basis for categorizing the severity of gunshot wound injuries as either low- or high-velocity wounds. Low-velocity injuries from handgun bullets travel at less than 1000 ft/sec, compared with high-velocity rifles, which can reach a muzzle velocity of 2000 ft/sec or greater. Although velocity undeniably plays an important role in wounding capacity, there are several other important considerations in determining the severity of injury and, consequently, the treatment approach. Major determinants in the wounding mechanism from a ballistics perspective include distance traveled by missile, fragmentation or deformation of the projectile, muzzle velocity versus terminal velocity, and bullet yaw while penetrating the tissue.‘* Tissue elasticity and vascularity of tissues are also important anatomic considerations. It is important to consider the aggregate of these variables in assessingeach individual patient and not to rely exclusively on velocity as the sole determinant of wounding capability. The vast majority of persons sustaining missile wounds in this study were young men (81%) in the second through fourth decades of life. This demographic profile is nearly identical to previous studies*,3,s and emphasizesthe prevalence and unfortunate impact of civilian firearm injuries on young urban men. Recognition and emergent management of airway obstruction in the patient with a maxillofacial gunshot wound is an essential component of care. Failure to recognize acute airway obstruction can lead to disastrous results, with at least one reported case of death.8 After careful assessmentmost persons (75%) in this study were able to maintain an adequate airway by the conservative measuresof suctioning of the oral cavity, patient positioning, and occasionally protraction of the tongue. The remainder of patients re-
Gunshot wounds to mandible
385
quired emergent control of the airway. When acute or impending airway obstruction is identified, endotracheal intubation is the treatment of choice.14Nasoendotracheal intubation is preferred becauseit obviates the need for changing the route of intubation at the time of definitive treatment of the mandible fracture. Becauseoropharyngeal edema leading to airway obstruction may take several hours to develop, prophy lactic intubation in an equivocal case is the prudent course of action. If endotracheal intubation is unsuccessful or if there are contraindications to tube placement, a cricothyrotomy is the emergent treatment of choice.r4 When indicated, tracheostomy is best performed in the operating room only after initial airway control by either intubation or cricothyrotomy. Not unexpectedly, the timing of postoperative extubation or decannulation depends on preoperative airway status, with those patients requiring preoperative airway control maintaining control for more than 48 hours postoperatively. During surgical treatment patency of the airway should be carefully assessedby direct observation because this provides important clinical information used to formulate a plan for postoperative airway control. Indications for prolonged postsurgical intubation are significant trauma to the oral pharynx, major injury to the tongue, or presurgical intubation for respiratory distress. Besidesthe established criteria for extubation,i5 the patient should be free of significant oral pharyngeal edema. One way to assesspharyngeal swelling is to have the patient breathe around the deflated cuff of the endotracheal tube. If a patient fulfills these guidelines, he or she is usually ready for extubation; if not, the airway should be reassessedin 12 to 24 hours. The treating practitioner should have a high level of suspicion of vascular injury even in the face of relatively innocuous-appearing injury. Indications for obtaining invasive vascular studies are predicated on proximity of the path of the missile to major vessels. In this study arteriograms were performed on more than half the group (62%), with positive findings in 15% of those studied. Two of these patients received neck explorations, whereas one received no surgical treatment. No complications associated with arteriography were noted. Only two patients received transfusions, which were primarily the result of concomitant cardiothoracic injuries and not of maxillofacial trauma. Definitive evaluation and treatment is completed after emergent care and resuscitation. This includes a radiographic survey minimally consisting of plain film radiographs that delineate the full extent of dentoskeletal injuries. This is particularly important when planning placement of pins for an extraskeletal fixation appliance, becausemandibular fractures fre-
388
Neupert and Boyd
quently occur in a complex stellate pattern. A preliminary assessmentof the severity of injury can be determined by clinical examination in the emergency room setting in combination with appropriate radiographs, but the definitive treatment plan should be carried out only after careful wound assessmentin the operating room with the patient under general anesthesia. This study examined treatment outcome of gunshot wounds after application of a modification of principles of conservative management as outlined by Walker and Frame2 and others.7,8 Whenever possible, closed reduction of mandibular fracture(s) with the application of Erich-type arch bars for dental fixation was used for stabilization. The ability to use dental fixation alone dependson the site of injury and presence of adequate dentoalveolar segments. The condyle, coronoid, and ramus areas are most amenable to this form of fixation. In addition to stabilizing the jaws, arch bars are important in controlling the occlusion during the postoperative physiotherapy phase of treatment. When the patient is edentulous or significant loss of dentoalveolar structure occurs, extraskeletal pin fixation was used. Extraskeletal fixation has the added advantage of reducing or eliminating the need for mandibular immobilization. Open fracture reduction was reserved for caseswith large fragments of displaced bone, fractured teeth without osseous support, and for any situation in which a closed reduction would achieve a less than desirable occlusal result. Wound debridement was generally performed in a conservative manner with the primary objective of removing nonvital bone, teeth, and bullet fragments that were easily accessibleor that impeded function (i.e., bullet in temporomandibular joint). Missile fragments located in inaccessible areas or close to vital structures were left undisturbed. Rarely wasit necessaryto debride soft tissue, and all attempts were made to leave comminuted bone with periosteal supply undisturbed. The most difficult decision in wound debridement is the extent to which dental, osseous, and soft tissues are debrided. An overly aggressive debridement may create a continuity defect requiring secondary bone grafting. In half the continuity defects in this study (2/4), review of the medical records indicated that the defect was at least partially the result of overly aggressive wound debridement. In contrast, inadequate debridement may retain nonvital tissue, providing a nidus for infection. Soft tissue lacerations were closed primarily. This usually involved minimal soft tissue debridement and occasional local soft tissue undermining to achieve primary closure. Extraoral drain placement in a dependent position was used in extensive injuries. Intravenous antibiotic coverage (penicillin or a first generation ephalosporin) was provided during the pe-
ORAL SURC ORAL
MED ORAL PATHOL October 199 1
rioperative period and oral antibiotics were used for 7 to 10 days after surgery. With the principles enumerated previously, patients in the CRC group were treated primarily by closed reduction and did not require wound debridement, because there was no involvement of dentoalveolar structures or the oral cavity. No postsurgical infections developed in the CRC group, and all patients showed clinical union of the mandible without evidence of malunion. Application of the principles of conservative wound management resulted in a successful treatment outcome with restoration of mandibular continuity and preinjury occlusion. Patients in this group achieved a less than ideal functional result as measured by MMO. In comparison with mean values from normal young adult males,i6 the mean MM0 of 28 mm is about half the expected MM0 (58 mm). There are several possible explanations for poor outcome in this important but frequently overlooked aspect of care. Direct trauma to the major muscles of mastication occurs in the CRC group, because the masseter, medial pterygoid, and temporalis muscles all have their sites of insertion in the CRC regions of the mandible. A secondconsideration is the poor follow-up of this group. The average length of follow-up of 2 months was about half that for the ABS group. For compliant CRC patients, a rigorous long-term (as long as 6 months) program of physiotherapy including both passiveandactive rangeof-motion exercises usually resulted in satisfactory mandibular mobility (>40 mm). An improved level of mandibular mobility could be expected by improved patient education regarding the potential for mandibular dysfunction, early institution of vigorous passive and active exercises, and possibly the use of stabilization devices that allow early mandibular mobilization. The most remarkable difference between the CRC and ABS groups was the higher infection rate in the ABS group. In the ABS group postsurgical infections, which accounted for all infections in this study, developedin six patients. The higher infection rate of the ABS group may be attributable to numerous factors. Patient injured in the ABS group generally had larger bony and soft tissue injuries, which required more extensive surgery. Four of the six patients with infections had extraoral drains placed. This finding questions the necessity of drains, and future studies should examine this question more closely. In four patients in the ABS group a continuity defect developed (Table I). Initial stabilization of the continuity defect was approached with definitive treatment in mind, with extraskeletal pin fixation. This had the advantage of positioning the mandibular segments in appropriate final position, allowing early mandibular function, and minimizing or elimi-
Gunshot wounds to mandible
Volume 72 Number 4
nating the need for periosteal elevation. Recent advancesin stabilization, most notably bone plate and screw fixation, would accomplish the same goals, except more extensive wound dissection would be necessary. Becauseextensive wound exploration and debridement violates one of the basic tenets of conservative wound management, this form of stabilization was not used in this study. It is understood that in some injuries bone plate fixation may be advantageous. This includes mandibular fractures without significant comminution or soft tissue injury. All four patients with continuity defects received autogenous bone grafts for mandibular reconstruction. Cancellous bone from the iliac crest provides an excellent source of osteogeniccells for reconstruction. Superior and inferior cortical struts were used as a crib to support the cancellous bone graft. The graft was also stabilized with the original extraskeletal fixation appliance or a bone plate. The patients receiving bone grafts had restoration of mandibular continuity and facial form. Although none of the patients received dental implants, each would have been an excellent candidate becausesufficient volume of bone existed for implant placement. CONCLUSIONS
In initial assessmentof patients with low-velocity gunshot wounds to the mandible, airway distress and major vessel injury occurred in 25% and 9% of patients, respectively. Patients injured in the nontooth-bearing areas of the mandible achieved complete healing by treatment of closed reduction, primary wound closure, and maxillomandibular fixation. No infections occurred in this group. Follow-up and MM0 in this group tended to be poor. Patients injured in the tooth-bearing areas of the mandible often required open reduction with a combination of fixation techniques. These patients more frequently had infections and continuity defects, which were
387
managed successfully with secondary procedures. The MM0 of this group approached an acceptable range, and their follow-up time was longer than that of patients injured in the non-tooth-bearing areas. REFERENCES
1. Zide MF, Epker BN. Short-range shotgun wounds to the face. J Oral Surg 1979;37:319-30. 2. Walker RV, Frame JW. Civilian maxillo-facial gunshot injuries. Int J Oral Surg 1984;13:263-77. 3. May M, Cutchavaree A, Chadaratana P, West J. Mandibular fractures from civilian gunshot wounds: a study of 20 cases. Laryngoscope 1973;83:969-73. 4. Osborn DB. Intermediate and reconstructive care of maxillofacial missile wounds. J Oral Surg 1973;31:429-37. 5. Yao ST. Vanecko RM. Corlev RD. Stuteville OH. Shoemaker WC. Gunshot wounds’of the face: J Trauma 1972;12:523-8. 6. Grimes WR, Morris DM, Deitch EA. Shotgun wounds involving the head and neck. Am J Surg 1988;155:776-9. 7. Kendrick RW. Management of gunshot wounds and other urban war injuries. Oral Maxillofac Surg Clin North Am 1990;2:55-68. 8. Banks P. Gunshot wounds. In: Maxillofacial injuries. Edinburgh: Churchill Livinnstone. 1985:561-694. 9. Al-Shawi A. Experience in the treatment of missile injuries of the maxillofacial region in Iraq. Br J Oral Maxillofac Surg 1986;24:244-50. 10. Marshall WG. An analysis of firearm injuries to the head and face in Belfast 1969-1977. Br J Oral Maxillofac Sure. 1986: 24:233-43. 11. DeMuth WE. Bullet velocity as applied to military rifle wounding capacity. J Trauma 1969:9:27-38. 12. Fackler ML.’ Wound ballistics. JAMA 1988;259:2730-6. 13. Barach E, Tomlanovich M, Nowak R. Ballistics: a pathophysiologic examination of the wounding mechanisms of firearms: part I, II. J Trauma 1986:26:225-35.374-81. 14. Committee on Trauma, American College of Surgeons, eds. Advanced trauma life support program, 1988:36. 15. Ihde JK, Jacobsen WK, Briggs-BA, eds. Principles of critical care. Philadelnhia: WB Saunders. 1987:171. 16. Agerberg G. Maximal mandibular movements in young men and women. Swed Dent J 1974;67:81-100. Reprint requests:
Scott B. Boyd, DDS, PhD Division of Oral and Maxillofacial Suraerv - _ Henry Ford Hospital 2799 W. Grand Blvd. Detroit, MI 48202-2689
secrions on
oral andmaxillofacial radiology and endodontics
oral surgery Editor: ROBERT B. SHIRA, DDS
School of Dental Medicine Tufts University 1 Kneeland Street Boston, Massachusetts 021 I I
Retrospective analysis of low-velocity gunshot wounds to the mandible Edward A. Neupert III, LCDR, DC, USN,a and Scott B. Boyd, DDS, PhDeb Dallas, Tex., and Detroit, Mich. UNIVERSITY
OF TEXAS AND HENRY
FORD HOSPITAL
A retrospective study was conducted of 32 patients with mandibular fractures resulting from low-velocity gunshot injuries. Airway management was required in 25% of the patients, and 9% sustained major vessel injury. Patients were divided into two groups, depending on site of mandibular fracture: condyle, ramus, and coronoid (n = lo), and angle, body, and symphysis (n = 22). All patients in the condyle, ramus, coronoid group achieved clinical union without infection. Average postinjury maximal mandibular opening was restricted (28 mm), but the average follow-up period was relatively short (2 months). In the angle, body, symphysis group the infection rate was 27%, and in 18% of patients a continuity defect of the mandible developed. The average length of follow-up in this group was 5.4 months with a mean maximal mandibular opening of 36 mm. (ORAL SURC ORAL MED ORAL PATHOL
1991;72:383-7)
S
everal reports have described surgical management of gunshot wound injuries to the face.‘-1° However, few investigations examined outcome after therapy. The purpose of this retrospective study was to evaluate treatment outcome after low-velocity missile injuries to the mandible. METHODS
The sample group in this retrospective study consisted of patients admitted to Parkland Memorial BFormerly Resident, Division of Oral and Maxillofacial Surgery, University of Texas, Southwestern Medical Center, Dallas, Tex.; now Lieutenant Commander, Dental Corps, United States Navy. bDivision Head, Oral and Maxillofacial Surgery, Henry Ford Hospital, Detroit, Mich. 7112123831
Hospital, Dallas, Tex., between 1983 and 1988 for low-velocity gunshot wounds to the mandible. A total of 32 patients with complete medical charts and radiographic records were identified during the designated time period. Data was obtained from these records in four categories: demographics, initial assessment,surgical management, and treatment outcome. Initial assessmentvariables included airway patency, presence of vascular injury, caliber of weapon, site(s) and severity of mandibular fracture, and concomitant injuries. Surgical treatment variables reviewed included method of fracture reduction, type of fixation, and use of drains. A preliminary survey of the data revealed a clear difference in management, depending on the site of injury. On this basis patients were divided into one of two groups: condyle, 383
384
Neupert and Boyd
ORAL SCRC ORAL MED ORAL PATHOI October I99 I
Table I. Distribution of patients within groups CRC and ABS with respect to treatment of postsurgical
findings CRC group No. of patients Open reductions No. of infections Continuity defects MM0 (mm)
Follow-up(mo)
IO I 0 0 28 2
~ ,
A BS group 22 18 6 4 36 5.4
ciated injuries involved both regional (globe, neck, cervical spine, cranium) and distant (abdomen, chest) structures. Fig. 1. Diagrammatic representation of 47 anatomic sites of fracture in 32 patients with gunshot wounds to mandible. ramus, and coronoid (CRC), (n = 10) and angle,
body, and symphysis (ABS) (n = 22). Patients injured in both regions were placed in the ABS group. Treatment outcome variables included incidence and severity of infection, clinical and radiographic evidence of fracture healing, mandibular range of motion, and length of follow-up. RESULTS
Initial assessment
The study group was predominantely young men (81%). The mean age of the group was 26 years with a range from 4 to 50 years. Suctioning of the oral cavity and patient positioning were all that was required to maintain airway patency for the majority of patients (72%, 23/32). The remaining nine patients received either endotracheal intubation (five patients) or tracheostomy (four patients) for airway control. The majority of patients (74%) who preoperatively required only airway observation were extubated within 48 hours after surgery. In contrast, most persons (78%) undergoing preoperative intubation or tracheostomy had airway control maintained more than 48 hours after surgery. Most patients (94%, 30/ 32) were normotensive on presentation to the emergency room. Arteriography was performed on 20 patients (62.5%); 15% (3/20) of the arteriograms were positive for major vessel injury. More than half the patients (56%, 18/3 1) were injured with a weapon of unknown caliber. In those cases where the weapon was identified, a .38 caliber (n = 9) handgun was used most commonly. Fractures were observedthroughout the mandible, with no site of preferential injury (Fig. 1). Multiple sites of fracture occurred in 32% of patients, with a total of 47 fractures noted for the entire group. Concomitant gunshot injuries not involving the mandible occurred in 13 patients (41%). These asso-
Surgical management
Patients in the CRC group were treated by either observation (4/10) or closed reduction (5/10) with stabilization by dental (3/10) or extraskeletal pin fixation (2/10). One patient underwent open reduction for removal of a bullet within the temporomandibular joint. No internal fixation techniques for fracture stabilization in the CRC group were used. Wound debridement (20%) and drain placement (10%) were infrequently performed. In general, patients in the ABS group had more extensive surgical treatment than the CRC group. Open reduction with conservative debridement of devital bone and teeth, with primary closure of soft tissue wounds, was performed in most patients (82%). Drains were placed in some persons (32%). Dental fixation was applied in the vast majority of patients (91%) for dentoskeletal stabilization. Other methods of fracture stabilization included extraskeletal pin fixation (41%) and internal fixation with wire osteosynthesis (23%). Treatment
outcome
No infections occurred in the CRC group. All CRC patients went on to clinical union without evidence of malunion. The mean maximal mandibular opening (MMO) was 28 mm (+ 12.4), with a range from 10 to 45 mm; however, the average length of patient follow-up was relatively short (2 months) (Table I). Infection developed in about one fourth (27%) of the ABS group during the course of treatment. Most of these infections were localized to dentoalveolar structures and were managed successfully by relatively simple measures consisting of oral or intravenous antibiotics, extraction of indicated teeth, and local sequestrectomy. A continuity defect developed in four patients in the ABS group. Continuity defects were the result of either the initial injury (2/4) or extensive surgical debridement (2/4). These four patients subsequently underwent mandibular recon-
Volume Number
72 4
struction with autogenous bone grafting, which successfully restored mandibular continuity in each case. The mean MM0 was 36 mm (+9.4), with a range from 15 to 50 mm. The average length of follow-up (5.3 months) was more than twice as long as that of the CRC group. DISCUSSION
Low-velocity gunshot wounds of the mandible produce a characteristic pattern of injury consisting of a small entrance wound with minimal soft tissue injury and comminution of bone and teeth.* Mortality from low-velocity gunshot wounds to the mandible seldom occurs, and no fatalities were observed in this study. Wound ballistics studies indicate that wounding capacity is related to kinetic energy of the missile.’ l-l3 Kinetic energy is calculated by the formula KE = ‘/2 MV*, which indicates that velocity plays a more important role in determining kinetic energy than mass. This relationship has been used as the basis for categorizing the severity of gunshot wound injuries as either low- or high-velocity wounds. Low-velocity injuries from handgun bullets travel at less than 1000 ft/sec, compared with high-velocity rifles, which can reach a muzzle velocity of 2000 ft/sec or greater. Although velocity undeniably plays an important role in wounding capacity, there are several other important considerations in determining the severity of injury and, consequently, the treatment approach. Major determinants in the wounding mechanism from a ballistics perspective include distance traveled by missile, fragmentation or deformation of the projectile, muzzle velocity versus terminal velocity, and bullet yaw while penetrating the tissue.‘* Tissue elasticity and vascularity of tissues are also important anatomic considerations. It is important to consider the aggregate of these variables in assessingeach individual patient and not to rely exclusively on velocity as the sole determinant of wounding capability. The vast majority of persons sustaining missile wounds in this study were young men (81%) in the second through fourth decades of life. This demographic profile is nearly identical to previous studies*,3,s and emphasizesthe prevalence and unfortunate impact of civilian firearm injuries on young urban men. Recognition and emergent management of airway obstruction in the patient with a maxillofacial gunshot wound is an essential component of care. Failure to recognize acute airway obstruction can lead to disastrous results, with at least one reported case of death.8 After careful assessmentmost persons (75%) in this study were able to maintain an adequate airway by the conservative measuresof suctioning of the oral cavity, patient positioning, and occasionally protraction of the tongue. The remainder of patients re-
Gunshot wounds to mandible
385
quired emergent control of the airway. When acute or impending airway obstruction is identified, endotracheal intubation is the treatment of choice.14Nasoendotracheal intubation is preferred becauseit obviates the need for changing the route of intubation at the time of definitive treatment of the mandible fracture. Becauseoropharyngeal edema leading to airway obstruction may take several hours to develop, prophy lactic intubation in an equivocal case is the prudent course of action. If endotracheal intubation is unsuccessful or if there are contraindications to tube placement, a cricothyrotomy is the emergent treatment of choice.r4 When indicated, tracheostomy is best performed in the operating room only after initial airway control by either intubation or cricothyrotomy. Not unexpectedly, the timing of postoperative extubation or decannulation depends on preoperative airway status, with those patients requiring preoperative airway control maintaining control for more than 48 hours postoperatively. During surgical treatment patency of the airway should be carefully assessedby direct observation because this provides important clinical information used to formulate a plan for postoperative airway control. Indications for prolonged postsurgical intubation are significant trauma to the oral pharynx, major injury to the tongue, or presurgical intubation for respiratory distress. Besidesthe established criteria for extubation,i5 the patient should be free of significant oral pharyngeal edema. One way to assesspharyngeal swelling is to have the patient breathe around the deflated cuff of the endotracheal tube. If a patient fulfills these guidelines, he or she is usually ready for extubation; if not, the airway should be reassessedin 12 to 24 hours. The treating practitioner should have a high level of suspicion of vascular injury even in the face of relatively innocuous-appearing injury. Indications for obtaining invasive vascular studies are predicated on proximity of the path of the missile to major vessels. In this study arteriograms were performed on more than half the group (62%), with positive findings in 15% of those studied. Two of these patients received neck explorations, whereas one received no surgical treatment. No complications associated with arteriography were noted. Only two patients received transfusions, which were primarily the result of concomitant cardiothoracic injuries and not of maxillofacial trauma. Definitive evaluation and treatment is completed after emergent care and resuscitation. This includes a radiographic survey minimally consisting of plain film radiographs that delineate the full extent of dentoskeletal injuries. This is particularly important when planning placement of pins for an extraskeletal fixation appliance, becausemandibular fractures fre-
388
Neupert and Boyd
quently occur in a complex stellate pattern. A preliminary assessmentof the severity of injury can be determined by clinical examination in the emergency room setting in combination with appropriate radiographs, but the definitive treatment plan should be carried out only after careful wound assessmentin the operating room with the patient under general anesthesia. This study examined treatment outcome of gunshot wounds after application of a modification of principles of conservative management as outlined by Walker and Frame2 and others.7,8 Whenever possible, closed reduction of mandibular fracture(s) with the application of Erich-type arch bars for dental fixation was used for stabilization. The ability to use dental fixation alone dependson the site of injury and presence of adequate dentoalveolar segments. The condyle, coronoid, and ramus areas are most amenable to this form of fixation. In addition to stabilizing the jaws, arch bars are important in controlling the occlusion during the postoperative physiotherapy phase of treatment. When the patient is edentulous or significant loss of dentoalveolar structure occurs, extraskeletal pin fixation was used. Extraskeletal fixation has the added advantage of reducing or eliminating the need for mandibular immobilization. Open fracture reduction was reserved for caseswith large fragments of displaced bone, fractured teeth without osseous support, and for any situation in which a closed reduction would achieve a less than desirable occlusal result. Wound debridement was generally performed in a conservative manner with the primary objective of removing nonvital bone, teeth, and bullet fragments that were easily accessibleor that impeded function (i.e., bullet in temporomandibular joint). Missile fragments located in inaccessible areas or close to vital structures were left undisturbed. Rarely wasit necessaryto debride soft tissue, and all attempts were made to leave comminuted bone with periosteal supply undisturbed. The most difficult decision in wound debridement is the extent to which dental, osseous, and soft tissues are debrided. An overly aggressive debridement may create a continuity defect requiring secondary bone grafting. In half the continuity defects in this study (2/4), review of the medical records indicated that the defect was at least partially the result of overly aggressive wound debridement. In contrast, inadequate debridement may retain nonvital tissue, providing a nidus for infection. Soft tissue lacerations were closed primarily. This usually involved minimal soft tissue debridement and occasional local soft tissue undermining to achieve primary closure. Extraoral drain placement in a dependent position was used in extensive injuries. Intravenous antibiotic coverage (penicillin or a first generation ephalosporin) was provided during the pe-
ORAL SURC ORAL
MED ORAL PATHOL October 199 1
rioperative period and oral antibiotics were used for 7 to 10 days after surgery. With the principles enumerated previously, patients in the CRC group were treated primarily by closed reduction and did not require wound debridement, because there was no involvement of dentoalveolar structures or the oral cavity. No postsurgical infections developed in the CRC group, and all patients showed clinical union of the mandible without evidence of malunion. Application of the principles of conservative wound management resulted in a successful treatment outcome with restoration of mandibular continuity and preinjury occlusion. Patients in this group achieved a less than ideal functional result as measured by MMO. In comparison with mean values from normal young adult males,i6 the mean MM0 of 28 mm is about half the expected MM0 (58 mm). There are several possible explanations for poor outcome in this important but frequently overlooked aspect of care. Direct trauma to the major muscles of mastication occurs in the CRC group, because the masseter, medial pterygoid, and temporalis muscles all have their sites of insertion in the CRC regions of the mandible. A secondconsideration is the poor follow-up of this group. The average length of follow-up of 2 months was about half that for the ABS group. For compliant CRC patients, a rigorous long-term (as long as 6 months) program of physiotherapy including both passiveandactive rangeof-motion exercises usually resulted in satisfactory mandibular mobility (>40 mm). An improved level of mandibular mobility could be expected by improved patient education regarding the potential for mandibular dysfunction, early institution of vigorous passive and active exercises, and possibly the use of stabilization devices that allow early mandibular mobilization. The most remarkable difference between the CRC and ABS groups was the higher infection rate in the ABS group. In the ABS group postsurgical infections, which accounted for all infections in this study, developedin six patients. The higher infection rate of the ABS group may be attributable to numerous factors. Patient injured in the ABS group generally had larger bony and soft tissue injuries, which required more extensive surgery. Four of the six patients with infections had extraoral drains placed. This finding questions the necessity of drains, and future studies should examine this question more closely. In four patients in the ABS group a continuity defect developed (Table I). Initial stabilization of the continuity defect was approached with definitive treatment in mind, with extraskeletal pin fixation. This had the advantage of positioning the mandibular segments in appropriate final position, allowing early mandibular function, and minimizing or elimi-
Gunshot wounds to mandible
Volume 72 Number 4
nating the need for periosteal elevation. Recent advancesin stabilization, most notably bone plate and screw fixation, would accomplish the same goals, except more extensive wound dissection would be necessary. Becauseextensive wound exploration and debridement violates one of the basic tenets of conservative wound management, this form of stabilization was not used in this study. It is understood that in some injuries bone plate fixation may be advantageous. This includes mandibular fractures without significant comminution or soft tissue injury. All four patients with continuity defects received autogenous bone grafts for mandibular reconstruction. Cancellous bone from the iliac crest provides an excellent source of osteogeniccells for reconstruction. Superior and inferior cortical struts were used as a crib to support the cancellous bone graft. The graft was also stabilized with the original extraskeletal fixation appliance or a bone plate. The patients receiving bone grafts had restoration of mandibular continuity and facial form. Although none of the patients received dental implants, each would have been an excellent candidate becausesufficient volume of bone existed for implant placement. CONCLUSIONS
In initial assessmentof patients with low-velocity gunshot wounds to the mandible, airway distress and major vessel injury occurred in 25% and 9% of patients, respectively. Patients injured in the nontooth-bearing areas of the mandible achieved complete healing by treatment of closed reduction, primary wound closure, and maxillomandibular fixation. No infections occurred in this group. Follow-up and MM0 in this group tended to be poor. Patients injured in the tooth-bearing areas of the mandible often required open reduction with a combination of fixation techniques. These patients more frequently had infections and continuity defects, which were
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managed successfully with secondary procedures. The MM0 of this group approached an acceptable range, and their follow-up time was longer than that of patients injured in the non-tooth-bearing areas. REFERENCES
1. Zide MF, Epker BN. Short-range shotgun wounds to the face. J Oral Surg 1979;37:319-30. 2. Walker RV, Frame JW. Civilian maxillo-facial gunshot injuries. Int J Oral Surg 1984;13:263-77. 3. May M, Cutchavaree A, Chadaratana P, West J. Mandibular fractures from civilian gunshot wounds: a study of 20 cases. Laryngoscope 1973;83:969-73. 4. Osborn DB. Intermediate and reconstructive care of maxillofacial missile wounds. J Oral Surg 1973;31:429-37. 5. Yao ST. Vanecko RM. Corlev RD. Stuteville OH. Shoemaker WC. Gunshot wounds’of the face: J Trauma 1972;12:523-8. 6. Grimes WR, Morris DM, Deitch EA. Shotgun wounds involving the head and neck. Am J Surg 1988;155:776-9. 7. Kendrick RW. Management of gunshot wounds and other urban war injuries. Oral Maxillofac Surg Clin North Am 1990;2:55-68. 8. Banks P. Gunshot wounds. In: Maxillofacial injuries. Edinburgh: Churchill Livinnstone. 1985:561-694. 9. Al-Shawi A. Experience in the treatment of missile injuries of the maxillofacial region in Iraq. Br J Oral Maxillofac Surg 1986;24:244-50. 10. Marshall WG. An analysis of firearm injuries to the head and face in Belfast 1969-1977. Br J Oral Maxillofac Sure. 1986: 24:233-43. 11. DeMuth WE. Bullet velocity as applied to military rifle wounding capacity. J Trauma 1969:9:27-38. 12. Fackler ML.’ Wound ballistics. JAMA 1988;259:2730-6. 13. Barach E, Tomlanovich M, Nowak R. Ballistics: a pathophysiologic examination of the wounding mechanisms of firearms: part I, II. J Trauma 1986:26:225-35.374-81. 14. Committee on Trauma, American College of Surgeons, eds. Advanced trauma life support program, 1988:36. 15. Ihde JK, Jacobsen WK, Briggs-BA, eds. Principles of critical care. Philadelnhia: WB Saunders. 1987:171. 16. Agerberg G. Maximal mandibular movements in young men and women. Swed Dent J 1974;67:81-100. Reprint requests:
Scott B. Boyd, DDS, PhD Division of Oral and Maxillofacial Suraerv - _ Henry Ford Hospital 2799 W. Grand Blvd. Detroit, MI 48202-2689
