Follow‐Ups and Outcomes of Interest

All patients were followed up after the initial admission. The follow‐up time points included 6 weeks post‐surgery, 12 weeks post‐surgery, and 52 weeks post‐surgery. The primary outcome was the ordinal change in the AIS grade. The secondary outcomes included the surgical time, volume of surgical bleeding, rate of admission to the ICU, length of ICU stay, duration of mechanical ventilation, length of hospital stay, and postoperative complications. And the elapsed time of patients transported to hospital by ambulance at different phases was recorded, including the transfer, inspection or examination and the others. Whether the Chinese trauma treatment systems is used or not will also be recorded.

The AIS is the international gold standard for evaluation of spinal cord injuries ²³ . The AIS is a standardized examination consisting of a myotomal‐based motor examination, dermatomal‐based sensory examination, and an anorectal examination. The AIS further classifies injuries as a complete or incomplete spinal cord injury. A complete spinal cord injury is defined as the absence of all motor and sensory functions, including sacral roots, distal to the site of injury. These injuries are designated as being Grade A on the AIS. Incomplete injuries are defined as those with some degree of retained motor or sensory function below the site of injury. Patients with AIS Grade B injuries have some sensory function but no motor function. AIS Grade C injuries have a motor grade less than 3 below the neurologic level of injury while AIS Grade D injuries have a motor grade of at least 3 below the neurologic level of injury. Patients with Grade E injuries have normal motor and sensory examinations, but still may have abnormal reflexes or other neurologic phenomena.

The surgical time was from the time the skin was cut through to the time the wound was closed at the end of the operation.

Volume of surgical bleeding was defined as intraoperative blood loss, as the amount of fluid in the aspirator minus the amount of rinsed water.

The rate of admission to the ICU was the proportion of patients admitted to the ICU immediately after surgery.

Length of ICU stay was defined as the period of confinement of a patient to the ICU.

Duration of mechanical ventilation referred to the time that the patient needs to use mechanical ventilation after surgery due to medical factors.

Length of hospital stay was defined as the period of confinement of a patient to the hospital.

Postoperative complications were defined as the pathologic processes that affect patients after surgery, including infection, cardiovascular complication, poor wound healing, and so on.

The transfer phase referred to the time between the patient's call to the ambulance and the patient's arrival at the hospital. The inspection or examination phase was defined as the physical examination and ancillary examination that must be completed prior to surgery.