Penetrating trauma to the head and neck from a nail gun: a unique mechanism of injury.

Abstract

Published reports of nail gun injuries to the head and neck are rare. We describe the cases of three patients who sustained nail gun injuries to the head and who were managed at our institution. All patients were treated successfully and all recovered with minimal morbidity. Any physician who is called on to manage a nail gun injury to the head or neck should understand that most likely the patient will have sustained a surprisingly limited amount of tissue injury, owing to the relatively low velocity of the projectile compared with that delivered by firearms. Computed tomography and selective angiography can play a vital role in assessing the integrity of relevant vascular structures. Moreover, catheter angiography with embolization can be a most useful nonsurgical adjunct to control the extent of vascular injury.

Introduction

Penetrating trauma to the head and neck caused by a nail fired from a nail gun is a unique, uncommon, and usually nonfatal injury. The use of nail guns in the construction industry gained popularity during the 1990s and is now widespread.(1,2) This technology has significantly increased productivity, lowered costs, and reduced repetitive stress injuries associated with using a hammer.(2) However, the growing popularity of these tools has been accompanied by a rise in the incidence of nail gun injuries, which are occasionally intentional but primarily accidental.(1-3)

Authors in other specialties have reported nail gun injuries to various parts of the body,(4-6) but few reports have been published of head and neck injuries.(7-9) In this article, we describe three cases of penetrating trauma to the head as a result of nail gun accidents, two of which involved cranial penetration. We also discuss relevant wound ballistics and the benefits of selective angiography (both diagnostically and therapeutically) in this peculiar type of injury. To assist in the writing of this discussion, we determined the average velocity of a 3-inch framing nail (used by carpenters to construct the frame of a wood structure) fired from a nail gun under experimental conditions.

Case reports

Patient 1. A 27-year-old man was referred to the University of Utah Medical Center (UUMC) after he had been struck in the right temporal area by a nail approximately 3 inches in length. The patient had accidentally fired the nail while reloading a nail gun as he was working at a construction site. The nail struck a nearby wall, ricocheted back toward him, and struck him in the head. After sustaining the injury, the patient's only complaint was pain on jaw motion. He did not experience any loss of consciousness, headache, photophobia, or numbness.

The man was taken to an emergency department, where plain radiography revealed that the nail had penetrated the cranium (figure 1, A). Noncontrast computed tomography (CT) demonstrated that the nail had penetrated the squamous portion of the right temporal bone and had traversed the right temporal fossa; the tip of the nail was lateral to the right sphenoid sinus and anterolateral to the right cavernous sinus (figure 1, B). An intraparenchymal hemorrhage was also apparent in the right temporal lobe. The patient was transferred to the UUMC in stable condition.

Physical examination revealed that approximately 2 cm of the nail (the flathead end) protruded from the right temporal area just posterior to the pterion. Findings on neurologic examination were within normal limits except for weakness of the right frontalis muscle. The patient was taken to the radiology suite, where he underwent right cerebral angiography (figure 1, C). Both the external and internal carotid arterial systems were found to be intact. No major intracranial vascular injury was identified.

The patient was taken by the neurosurgery service to the operating room, where he underwent a right temporal craniotomy. The nail was removed and the right temporal lobe was debrided. His postoperative course was uncomplicated, and he was discharged home 6 days later in stable condition.

Patient 2. A 43-year-old man was referred to the UUMC after he had accidentally fired a nail into his left cheek as he pointed a nail gun in the direction of his face. The man had been working as a carpenter at a construction site. Immediately after sustaining the injury, he noticed some mild bleeding from a small wound on his left medial cheek. The bleeding stopped after several minutes and the man continued working, not realizing the nature of his injury. When he eventually arrived home, his wife noticed that he was acting peculiar and making nonsensical statements. He then began to vomit.

The man was taken to an emergency department, where plain radiography revealed the presence of the nail intra-cranially (figure 2, A). CT of the head showed that the nail extended from the floor of the left middle cranial fossa through the frontal lobe superiorly. The patient was transferred to the UUMC in stable condition.

Physical examination detected a 3-mm entrance wound in the left nasolabial fold. Findings on neurologic examination were within normal limits except for mild nuchal rigidity and some mild expressive aphasia. The patient was taken to the radiology suite, where he underwent left cerebral angiography (figure 2, B and C). The angiograms showed that the head of the nail was located below the middle cranial fossa. There was no evidence of injury to the middle or anterior cerebral arteries. The tip of the nail was embedded in the frontal lobe and appeared to be remote from the major cerebral vessels. There was no evidence of dissection, pseudoaneurysm, or venous thrombosis.

The patient was taken by the neurosurgery service to the operating room, where he underwent a left temporal craniotomy with mobilization of the left zygoma and removal of the nail. His postoperative course was uncomplicated. However, because of his mild to moderate cognitive deficits (including memory loss and speech impairment), he was transferred to the rehabilitative medicine service on postoperative day 9. The following day, he refused further treatment and left the hospital against medical advice.

Patient 3. A 16-year-old boy was referred to the UUMC after he had been struck by a nail fired from a nail gun. While working as a construction framer, he was holding a ladder for a coworker. The coworker slipped and accidentally fired a nail into the patient's left face at close range. The victim noted an immediate onset of left facial pain, epistaxis, and trismus.

The patient was taken to an emergency department, where plain film radiography detected the nail in the left pterygomaxillary space. The projectile had entered above the zygomatic arch and its tip rested at the posterior end of the left inferior turbinate. He was transferred to the UUMC in stable condition.

Physical examination revealed that the flat head of a nail 1 cm in diameter was flush with the skin above the left zygomatic arch just posterior to the supraorbital rim. The left nasal cavity contained freshly clotted blood and the patient exhibited moderate trismus. The patient denied any loss of consciousness, nausea, vomiting, dysphagia, or change in vision. The results of his neurologic examination were within normal limits.

The patient was taken directly to the radiology suite for selective catheter angiography of the left external and internal carotid arteries. No significant abnormality involving the left internal carotid artery was identified. However, angiography of the left external carotid artery showed that the tip of the nail was located immediately adjacent to the left distal internal maxillary artery (figure 3, A). Vascular congestion had caused a delay in the clearance of contrast material, which was suggestive of a laceration of a smaller vessel and possible extravasation. The left distal internal maxillary artery was then embolized with Gelfoam pledgets. Repeat catheter angiography confirmed the embolization and also detected an anastomosis between the left facial artery and the distal left internal maxillary artery via the ascending palatine artery (figure 3, B). Gelfoam pledgets were again used to embolize the proximal left facial artery, occluding it as well as the takeoff of the ascending palatine artery. Poste mbolization angiography revealed complete occlusion of both the left distal internal maxillary artery and the left facial artery (figure 3, C).

The patient was taken to the operating room where, under general anesthesia, the nail was grasped with a large hemostat and removed. The patient experienced no significant bleeding. He was observed overnight and discharged the following morning.

Determination of nail velocity

We measured the velocity of experimentally fired nails with a ballistic chronograph (MK III Championship Timer; PACT; Grand Prairie, Tex.). We loaded a nail gun (Craftsman model No. 351-18320; Sears, Roebuck; Garland, Tex.) with a magazine of 3-inch framing nails. Each nail weighed 66.7 grains. A regulated air supply of 110 Ibs/ inch (2) was utilized. The chronograph was positioned so that its lead sensor was approximately 12 inches from the nail gun (muzzle distance). We fired 10 consecutive rounds horizontally through the chronograph toward a 4 x 8-ft upright sheet of 3/4-inch-thick plywood located approximately 15 ft from the nail gun. The velocity of the fired nails ranged from 97.7 to 121.1 ft/sec (mean: 105.5).

Discussion

Certain framing nail guns can project 2- to 3 1/2-inch nails with a driving power that can reach 930 inch-lbs. (10) Lyons distinguished high-velocity from low-velocity nail guns by their mechanism of firing action. (11) High-velocity tools are equipped with an explosive cartridge directly behind the nail, while low-velocity tools use a captive piston that is usually activated by compressed air. The nails are typically loaded in a clip or magazine and joined by wires or resin. Most nail guns are designed with a safety mechanism to prevent unintentional firing. A switch must be engaged before the trigger can be pulled. When a nail gun is carried with its trigger depressed, an inadvertent firing can occur if the switch is accidentally engaged.

The growing popularity of these devices over the past decade has been linked to an increase in injury. (1-3) Baggs et al studied nail gun injuries in Washington State from 1990 through 1998 and reported a rising trend in their incidence." (1,2) They found that nail gun injuries to the finger, hand, and foot accounted for nearly 75% of all nail gun injuries. Eye injuries accounted for 1.4% of the total. No record of injuries specific to the head and neck was made. Each of our three patients was struck in the head at close range.

In the otolaryngology literature, several authors have described the wound ballistics of conventional firearms as they pertain to the head and neck. (12-16) Understanding these principles provides an insight into how our patients survived this type of penetrating trauma. A missile's wounding capability is determined by its kinetic energy (KE) on impact and by the amount of energy that is absorbed by living tissue. (15) To calculate KE, it is necessary to know the missile's mass (m) and velocity (v). KE is measured in ft-lbs, m in grains, and v in ft/sec. The formula:

KE = [mv.sup.2] [DIVIDED BY] 2

The missile velocities of conventional firearms range from 300 ft/sec (0.22- and 0.25-caliber pistols) to 2,200 ft/sec (0.27-caliber hunting rifles). (15) A missile speed of 1,000 ft/sec or less is considered to be low velocity. (13) The military-issue M-16 rifle has a missile velocity of 3,200 ft/sec, and its bullets weigh 55 grains each. (13) Thus, the KE of a bullet as it leaves an M-16 is 2,500 ft-lbs. In terms of KE, a missile's velocity is significantly more important than its mass; doubling the velocity quadruples the KE, while doubling the mass only doubles the KE.

High-velocity missiles create a temporary (pulsating) cavity as they pass through living tissue. (16) This phenomenon explains the significant damage that is sustained by neural and vascular tissues that are not directly in the path of a bullet. A bullet entry can also create a permanent cavity, which can be three to four times larger than the diameter of the bullet itself. (15)

We experimentally determined that 3-inch nails weighing 66.7 grains each fired from a standard nail gun travel at an average velocity of 105.5 ft/sec, thereby qualifying them as low-velocity missiles. The nails fired from our nail gun had a KE of 1.64 ft-lbs, much less than the 2,500 ft-lbs of an M-16 round.

We also noted a pattern of nail imprints on the plywood backstop that indicated that at a distance of 15 ft from the nail gun, there was considerable instability in the trajectory of these nails. A significant number of nails struck the backstop sideways--that is, with the tip and head of the nail parallel to the wood rather than perpendicular to it. The mechanism of injury in our three patients was consistent with this finding. Each patient was hit at close range by a nail (tip first) that had penetrated deeply into either the face or cranium. When living tissues are struck by low-velocity missiles, structures such as vessels, nerves, and facial planes deflect them, which limits damage to the tissues. (16) Only one of our three patients (patient 3) experienced any significant vascular injury: a distal internal maxillary artery laceration that was detected and treated.

CT was obtained for two of our patients (patients 1 and 2). Selective angiography was used diagnostically for all three patients and therapeutically (embolization) for one (patient 3). Angiography has historically been the primary radiographic modality for diagnosing cerebrovascular trauma. (17) Trauma to the cerebrovascular system (both penetrating and nonpenetrating) can cause injuries such as arterial dissection, pseudoaneurysm, arterial or venous rupture or thrombosis, and arteriovenous fistula. (18) In the two patients we treated who experienced intracranial penetration (patients 1 and 2), the integrity of the pertinent cerebrovasculature was confirmed preoperatively by selective internal carotid artery catheter angiography. Although neither patient experienced any major vascular injury, both required craniotomy and debridement secondary to local parenchymal damage.

In a 10-year study at a large urban trauma center, Sclafani and Sclafani found that angiography was a safe and reliable diagnostic and therapeutic modality in 401 patients who were treated for penetrating cervicofacial wounds. (19) Selective angiography and embolization were successfully performed on our patient 3. In this patient, the missile's trajectory went from posterosuperior (above the left zygomatic arch) to anteroinferior (left posteroinferior lateral nasal wall); angiography of his left external carotid artery clearly demonstrated an injury to the distal internal maxillary artery. Once this injury was treated with embolization, the nail was safely removed from a site that was relatively difficult to access surgically; embolization had significantly reduced the risk of hemorrhage during removal.

Our three patients were all treated at the UUMC approximately 10 years ago. Accompanying this article is our suggested diagnostic and therapeutic algorithm for managing nail gun injuries to the head and neck that is based on current technology (figure 4). We emphasize that the prudent use of CT and catheter angiography when necessary might reduce morbidity in these peculiar injuries to the head and neck.

Acknowledgments

The authors extend special thanks to David Krise, DDS, and Mark B. Horton, OD, MD, for their technical support in determining nail velocity, and to John R. Hocker and Constance L. Buchalter for their invaluable assistance in the preparation of this manuscript.

References

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(2.) Baggs J, Cohen M, Kalat J, Silverstein B. Pneumatic nailer injuries: A report on Washington State 1990-1998. Professional Safety 2001; 46:33-8.

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(8.) Sasaoka Y, Kamada K, Matumoto M, et al. [Penetrating injury of the head, neck, and chest by a nail-gun: A case report]. No Shinkei Geka 1995;23:1099-104.

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(10.) Stanley Bostitch "Pneumatic Tools" Brochure AD2648, December 1999.

(11.) Lyons FR. Industrial nail gun injuries. Med J Aust 1983;2:483-7.

(12.) Lubock P, Goldsmith W. Experimental cavitation studies in a model head-neck system. J Biomech 1980;13: 1041-52.

(13.) Jahrsdoerfer RA, Johns ME, Cantrell RW. Penetrating wounds of the head and neck. Arch Otolaryngol 1979;105:721-5.

(14.) Landeen JM. Firearm wounds of the head and neck. Eye Ear Nose Throat Mon 1972;51:222-8.

(15.) Stiernberg CM, Jahrsdoerfer RA, Gillenwater A, et al. Gunshot wounds to the head and neck. Arch Otolaryngol Head Neck Surg 1992;118:592-7.

(16.) Holt GR, Kostohryz G, Jr. Wound ballistics of gunshot injuries to the head and neck. Arch Otolaryngol 1983;109:313-8.

(17.) Gaskill-Shipley MF, Tomsick TA. Angiography in the evaluation of head and neck trauma. Neuroimaging Clin N Am 1996;6:607-24.

(18.) Bula WI, Loes DJ. Trauma to the cerebrovascular system. Neuroimaging Clin N Am 1994;4:753-72.

(19.) Sclafani AP, Sclafani SJ. Angiography and transcatheter arterial embolization of vascular injuries of the face and neck. Laryngoscope 1996;106:168-73.

From the Ear, Nose, and Throat Department, Phoenix (Ariz.) Indian Medical Center (Dr. Buchalter); the Department of Otolaryngology-Head and Neck Surgery, University of Utah Medical Center, Salt Lake City (Dr. Johnson); and the Department of Neurosurgery (Dr. Reichman) and the Department of Radiology (Dr. Jacobs), LDS Hospital, Salt Lake City.

Reprint requests: Gregory M. Buchalter, MD, ENT Department, Phoenix Indian Medical Center, 4212 N. 16th St., Phoenix, AZ 85016. Phone: [phone]; fax: [phone]; e-mail: [e-mail]

Originally presented in part at a poster session during the annual meeting of the American Academy of Otolaryngology-Head and Neck Surgery; Minneapolis: September 1992.