Spinal cord firearm injury

　　First, Etiology

　　Spinal cord injury caused by bullets or shrapnel.

　　Second, Pathogenesis

　　In firearm injuries to the spinal cord, the injury capacity of the bullet is directly determined by its mass and speed (E=1/2MV^2), and the effect of speed is more significant relative to mass. The projectiles in wartime are mostly high-speed bullets or shrapnel, with a flight speed greater than 1000 m/s, while in peacetime, low-speed bullets are mainly used. Low-speed flying objects cause relatively mild spinal cord injury, commonly involving direct impact, compression, and laceration. High-speed flying objects advance in a rolling manner, causing more severe direct tissue damage. When they hit bone, they can become secondary projectiles. Particularly prominent is the strong lateral impact force they generate in the wound channel, which can reach 135 kg/cm^2, affecting the spinal cord far away from the wound channel. Spinal cord injury caused by high-speed bullets can even occur without direct impact on the spine, causing contusion without spinal fracture, penetration, or shrapnel retention. In addition, the special mechanism of injury is the instant tearing of the posterior and lateral columns of the spinal cord when the bullet hits the arm from the nerve.

　　1. Penetrating injury caused by high-energy bullets passing through the vertebral body or spinal canal, which can be divided into the following types:

　　(1) Transverse: The projectile贯通 the spinal canal, breaks the spinal cord, or transmits energy to the spinal cord after piercing the vertebral body, causing it to break. The defect is 1 to 1.5 cm, the ends are irregular, and the dura mater is often damaged. Within 1 to 2 cm of the ends, the central gray matter hemorrhages and gradually spreads outward, resulting in complete necrosis of the section after 42 hours.

　　(2) Complete contusion and laceration: The missile passes through the wall of the spinal canal or adjacent areas, the shock wave bruises the spinal cord, but its appearance is still intact, the dura mater is mostly intact, and fractures often occur. The changes are similar to those mentioned above, but more severe and progress faster.

　　(3) Incomplete contusion: The bullet passes through the paravertebral area and intervertebral disc, and the shock wave acts on the spinal cord. Its appearance is normal. Under the microscope, multiple hemorrhagic foci are seen in the gray matter, with no significant white matter changes, or only slight degeneration.

　　(4) Mild contusion: The trajectory is slightly away from the spinal canal (such as passing through the spinous process), and the spinal cord shows no significant change, with central punctate hemorrhage visible under the microscope.

　　2. When the speed of the blind missile is slow, it can stay inside or on the wall of the spinal canal, and the degree of spinal cord injury is one level lower than that of the penetrating injury at the same location.

　　The prominent complication of spinal fire weapon injury is infection. Infection can occur in the wound, within the spinal canal (epidural or intradural), and the focus of prevention and treatment is on thorough debridement, sufficient drainage, and extensive use of antibiotics. The retention of bullets may cause lead poisoning, especially when the shrapnel is in direct contact with cerebrospinal fluid or forms pseudocysts. The lead component in the shrapnel may decompose and cause chronic lead poisoning, mainly manifested as abdominal pain, dementia, headache, memory loss, muscle weakness, etc. Treatment can be carried out with chelating agents such as ethylenediamine tetraacetic acid (EDTA) and dimercaprol (BAL).

　　1. Wound condition

　　Mostly located in the thoracic segment, followed by the lumbar and cervical segments, and the sacral segment is the least. This is related to the length of each segmental segment. The wound is heavily contaminated, and cerebrospinal fluid or spinal cord tissue may exude.

　　2. Characteristics of spinal cord injury

　　Due to the shock and contusion areas outside the primary wound channel of fire weapon injury, the level of neurological function damage at the time of injury may be several segments higher. With the recovery of this pathological change, the damaged level may decrease, so when performing early lumbar plate incision and spinal cord exploration, this should be taken into consideration. Similar to spinal blade injuries, complete injuries account for the majority.

　　3. Complications

　　The neck can be accompanied by major blood vessels, trachea, and esophagus injury, half of the cases have complications such as hemothorax, pneumothorax, abdominal organ injury, or retroperitoneal hematoma, so the incidence of shock is high.

　　This disease is mostly caused by sudden situations with no effective preventive measures. Pay attention to health, do a good job in safety protection, reduce and avoid accidental injuries, which can play a certain preventive role. In case of onset, active treatment and proactive intervention should be taken to prevent the occurrence of complications.

　　1. X-ray film

　　Observe the retained position of bullets or shrapnel in the spinal canal and paravertebral area, whether there is a fracture, and estimate the severity of spinal cord damage according to the location of vertebral bone damage.

　　2. CT scan

　　When the condition of spinal cord damage on the X-ray film is not clear, performing axial CT scan can indicate the location of the fracture, whether there is a fracture fragment or metal fragment in the spinal canal, and pay attention to the presence of spinal cord hematoma.

　　3. MRI

　　MRI can accurately show the condition of spinal cord damage and has an irreplaceable advantage, but whether to use MRI examination in spinal fire weapon injury, especially when there may be shrapnel in the spinal cord, should be cautiously analyzed. The strong magnetic field generated during MRI scanning may cause the shrapnel in the spinal cord to displace, causing more serious damage, and metal foreign bodies can also cause artifacts in the examination. When there is no metal bullet or shrapnel left in the wound, especially in the spinal canal, MRI examination can most accurately show the state of spinal cord damage.

　　1. Diet for spinal fire weapon injury

　　A balanced diet, eating more fruits and vegetables and high-fiber foods, and more high-protein foods such as eggs and soybeans, with attention to light and savory food, and appropriate exercise can be done.

　　2. It is best to avoid certain foods for spinal cord firearm injuries.

　　Avoid smoking, alcohol, spicy food, coffee, and other irritant foods.

　　I. Treatment

　　1. Open spinal cord injuries generally do not affect spinal stability and have no special requirements for transportation.

　　2. Prioritize the treatment of associated injuries and actively treat shock.

　　3. Early systemic administration of high-dose broad-spectrum antibiotics and TAT to prevent infection.

　　4. Debridement should be performed within 6 to 8 hours after injury. The principle is to eliminate necrotic tissue and visible foreign bodies, and free bone fragments along the wound track. The debridement of wounds on the chest wall is limited to the soft tissue and does not enter the thoracic cavity.

　　5. Indications for Laminectomy

　　(1) Foreign bodies, bone fragments in the spinal canal compressing the spinal cord or the presence of factors that are likely to cause infection (such as bullets piercing the intestinal tract before entering the spinal canal).

　　(2) Hematoma in the spinal canal compressing the spinal cord.

　　(3) Severe cerebrospinal fluid leakage.

　　(4) Incomplete injury patients show symptoms of deterioration during observation, and the Quincke test suggests obstruction within the spinal canal. Generally, another incision should be made. The purpose of the surgery is to debride the spinal canal, remove foreign bodies, bone fragments, and blood clots from the spinal canal. If the dura is not damaged, it generally should not be incised to avoid contamination of the spinal cord tissue; if it is damaged, it should be incised widely to explore the spinal cord, remove foreign bodies, and gently aspirate the damaged spinal cord. After removal, the dura should be sutured and repaired.

　　6. Spinal instability secondary to low-speed bullet fire weapon injuries is rare. The reasons for the instability are mostly iatrogenic, often due to incorrect or excessive pursuit of decompression effects, leading to multiple vertebral plate resection and decompression. Therefore, there should be sufficient awareness of this before the vertebral plate resection operation.

　　II. Prognosis

　　Spinal cord firearm injuries are often accompanied by life-threatening visceral injuries and shock. According to the famous British spinal cord injury expert Ludwig Guttmann, the mortality rate during World War I was as high as 70% to 80%. After that, due to the strengthening of anti-shock treatment, the wide application of antibiotics, the improvement of conditions for the transport of patients, and the establishment of spinal cord injury centers, the mortality rate gradually decreased to less than 15% by the late stage of World War II.