David B. Powers and Eduardo D. Rodriguez

Outline

Causes of Avulsive Injuries of the Maxillofacial Complex

The description of injury can be summarized simply as the effects of energy overcoming inertia. Our study of physics, and the work of Sir Isaac Newton, has shown that the velocity of a body remains constant unless the body is acted on by an external force. To quote Haug, “In the case of maxillofacial trauma, the object is the specific maxillofacial body part, and kinetic energy is provided by the wounding agent, either bullet, bludgeon, or motor vehicle.⁵ When considering avulsive defects of the maxillofacial complex, a sufficient quantity of energy must be delivered to the body part to remove it from its native bed. Kinetic energy (KE) is related as  mv² (where m = mass and v = velocity), but Cunningham has hypothesized that softer tissues, such as brain and muscle, are associated with a lower exponent of injury (0.5) than harder tissues, such as bone, which would have a higher exponent (2.5) and therefore a higher likelihood of permanent injury. Thus, the corrected formula for estimating wounding capacity by kinetic energy would be as follows:

depending on the location of the trauma.⁶

Incidence

Historically underreported in the craniomaxillofacial trauma literature, or noted primarily in case reports from periods of military conflict, avulsive defects to the maxillofacial region have been recognized to occur infrequently and are perceived to have a poor prognosis in regard to an acceptable cosmetic and functional repair.5,20,21–30 In the civilian literature, the decade-long experiences of Clark et al at one of the busiest and premier level I trauma centers in the United States, have identified approximately 1.5 cases/year of avulsive tissue loss to the craniomaxillofacial region.²⁴ Considering the reported volume of over 6700 unique trauma patient identifiers at the shock trauma center annually, the relative infrequency of this occurrence becomes apparent.³¹ Clark et al noted that approximately 46.6% of these injuries involve the mandible, maxilla, and orbit; 26.6% involve the mandible and maxilla; and 26.6% involve the mandible alone. Haug et al have reported a 1% occurrence of avulsive maxillofacial injuries (5 of 475patients) during a review of experiences at a civilian trauma center in Cleveland, with most cases involving self-inflicted gunshot wounds with shotguns in a suicide attempt.²⁷ In a survey of over 9400 patients treated during the Vietnam conflict, Osbon had previously noted that 9.4% exhibit an avulsion of a notable portion of their mandible.²⁵ Because Vietnam represented the first armed modern conflict against nonconventional military forces, the avulsive loss of mandibular anatomy was not previously experienced to the degree as seen in this conflict.²⁹ Dobson outlined classic forms of warfare to include: minor conventional warfare, major conventional warfare, rural attack, and terrorist attack.³²

Rural attacks, minor conventional warfare, and major conventional warfare displayed remarkably similar historical incidences of head and neck injury, with 16%, 16%, and 15% for British, Commonwealth, and military personnel, respectively, since 1914. Terrorist attacks, however, displayed a statistically higher incidence of 21%. In the only known paper published during Operation Iraqi Freedom–Operation Enduring Freedom (OIF-OEF) with reported battlefield conditions consistent with classic military combat, Montgomery et al noted the incidence of head and neck casualties as 25% for U.S. military personnel, which is consistent with the previously reported historic norms for U.S. conflicts.³³ Dobson et al³² have described terrorist attacks as highlighted by the unconventional use of improvised explosive devices (IEDs), which correlates with the injury pattern of the IED as used by insurgents in OIF-OEF. Most hard tissue facial injuries were sustained in the mandible due to its prominence from the facial skeleton. This was also noted in Lew et al’s study of maxillomandibular fixation (MMF) and open reduction and internal fixation (ORIF) of mandible fractures being the second and fourth most commonly reported surgical procedures.²⁹ The placement of IEDs, usually well below the level of the head and neck, would obviously place the anterior-inferior aspect of the mandible at increased risk as the explosive force and associated shrapnel would proceed in a superior vector, striking the lower face. Modern body armor plays a significant role in the overall survivability of wounded military personnel, but Dobson et al’s observations offer a unique perspective and potential additional cause for the increased craniomaxillofacial injuries seen in OIF-OEF.

Assessment and Initial Medical Management

Obviously, avulsive injuries to the craniomaxillofacial complex are potentially life-threatening (Fig. 31-4). Compromise of the airway through anatomic collapse, hemorrhage, foreign body obstruction, or aspiration are acknowledged as known risks, requiring immediate intervention to provide for continued oxygenation of the patient. As prescribed in the current Advanced Trauma Life Support (ATLS) protocols, securing the airway definitively should be accomplished by conventional oral or nasal endotracheal intubation, intubation of a visible component of a traumatically exposed trachea, or cricothyroidotomy or surgical tracheostomy.²¹ After the airway has been established, attention should be directed to a thorough analysis of the patient for potentially lethal injuries and appropriate interventions initiated. Control of hemorrhage should be established with simple pressure to the site by compression dressings or manual palpation, ligation of visible sources of active bleeding, or use of hemostatic dressings impregnated with components such as chitosan or similar compounds.³³ Injuries to the deep vessels of the head or neck, or those not visible from routine surgical access, may require interventional approaches to gain control of the hemorrhage.³⁴ During the course of fluid resuscitation, particular attention should be paid to the head and neck region because seemingly benign scalp lacerations, or those not recognized due to lack of hemorrhage secondary to hypovolemia, have been associated with exsanguinating hemorrhage as the patient’s mean arterial pressure is increased.³⁵ If the head and neck region is covered under surgical drapes due to ongoing therapy in other areas of the body, this unrecognized source of bleeding can confound anesthesia providers and surgeons, or potentially be lethal.

After all life-threatening injuries have been recognized and successfully managed, identification of the avulsive facial defects can be accomplished. Computed tomography (CT) scans with three-dimensional reconstruction are the minimum baseline studies required for the treatment planning of avulsive craniomaxillofacial defects (Fig. 31-5). Most avulsive soft tissue injuries, and all avulsive hard tissue injuries, will be definitively treated in an operating room environment. After stabilization, medical management should commence with appropriate early nutritional and psychiatric support for the patient, with antibiotic therapy directed toward cutaneous, oral, pharyngeal, nasal, and sinus contaminants.^33,36 Because these wounds are typically contaminated, and may exhibit vascular compromise, consideration should be given to the administration of the appropriate tetanus prophylaxis (Table 31-1) and, in the case of animal bites, rabies prophylaxis (Fig. 31-6).

Classification

Initial Surgical Management of Avulsive Maxillofacial Injuries

After initial stabilization and resuscitation, the patient may be transported to the operating room for their first surgical procedure. The goals of the initial operation are as follows:

Because of the likely multitude of surgical interventions and concurrent soft tissue edema that the patient will experience, not only due to the primary injury but as a tissue response to initial and subsequent fluid resuscitations, strong consideration should be given to performing an elective surgical tracheostomy if not done previously. Wound exploration for transected vessels should be performed with identification and definitive control established through ligation or cautery. Efforts should be directed to preservation of all hard and soft tissues, including those with questionable vitality, because they may be able to be preserved or surgically reattached through conventional or microsurgical techniques. Soft tissue is generally repaired from inside-out, with stable reapproximation of the deep tissues. Identification of clinically significant soft tissue injuries, including transection of the facial nerve or salivary ducts, should be performed under magnification with surgical loupes or microscope, and primary repair attempted, if feasible. The recognition of facial nerve injury is a critical finding for the rehabilitation of the patient because the determination for facial reanimation surgery and the timing for repair options have a finite period for intervention.41,42 Hard tissue repair can be accomplished by beginning with the mandible and reestablishment of the occlusion, followed by the midface and upper facial third. The frame of the midface and upper face should be established from the supraorbital bar, lateral orbital rims, malar buttresses, and arch projection first, followed by the central midface of the naso-orbital-ethmoid (NOE) region, with final corrections of the dentoalveolar unit at the Le Fort I level accomplished last. Although the mandible-first protocol generally is applied most often, if the midface or upper facial third is minimally injured, and a more accurate reconstruction for the surgical foundation can be accomplished in those areas, reconstruction should commence in those regions.

The initial surgical procedure should not be considered as a definitive reconstruction, but as an examination under anesthesia, with the primary focus being to identify which structures have been lost and which remain, and to prevent further progressive or iatrogenic loss of additional hard and/or soft tissue. The existing identifiable bone should be located, identified, and rigidly fixed in an anatomic position with surgical reconstruction plates, with the reestablishment of a functional occlusion being the ultimate goal. The remaining soft tissue wound edges are arranged in as close an anatomic approximation as possible, even if tension at points of closure or blanching of the tissue occurs, and a comprehensive evaluation under anesthesia should commence, identifying as accurately as possible the avulsed or injured soft and hard tissue components.

After this primary surgery, the patient should undergo a complete CT imaging survey to evaluate anatomic reduction or fixation, better identify tissue loss, and assist with treatment planning for an early reconstruction. As described by Powers and Robertson and others, the patient will likely require frequent returns to the operating room at 2- to 3-day intervals to control infection, decontaminate and/or débride necrotic tissue, and reassess vitality in the remaining tissues.33,43 Good mucosal coverage with adequate vascularity of the osseous structures internally, and similar cutaneous coverage externally, will help prevent infection and mitigate hard tissue necrosis.

Reconstruction of Avulsive Soft Tissue Injuries

Initial determinations of reconstructive options for avulsive soft tissue injuries are aligned under the decision to proceed with prosthetic reconstruction, or native soft tissue utilization. As previously described by Haug and Carlson, the necessity for adjunctive therapy of native soft tissue rehabilitation is determined by the following parameters: temperature, color, oximetry, and capillary refill.⁵

Unimpeded vascular supply provides nutrients and warmth to a body part, so comparing the temperature of the reapproximated avulsed segment with its surrounding tissue allows for a qualitative assessment of adequate arterial circulation. Color is an acceptable evaluator of blood flow—venous congestion will appear blue or purple and arterial insufficiency will appear pale or white when compared with surrounding soft tissue. Pulse oximetry may provide another measure for determining the adequacy of vascularity to a reconstructed segment. Although no specific guidelines are found in the literature, the SaO₂ of a repaired component of soft tissue should probably be at least 80% for predictable survivability. Capillary refill is a useful clinical tool to assess venous congestion versus arterial compromise of partial avulsions of facial soft tissue. Capillary refill of facial soft tissue should be about 2 to 3 seconds. Prolonged capillary refills longer than 3 seconds suggest arterial insufficiency and rapid capillary refills shorter than 1 to 2 seconds indicate venous congestion. Appropriate identification of the need for adjunctive procedures to assist with maintenance of vascularity can be achieved by following these recommendations.