The cause of fever after lumbar internal fixation surgery may be absorption heat or infection. 1. Absorption of heat: due to the lumbar internal fixation surgery can lead to tissue damage around the surgery, the damaged tissue in the repair process will produce aseptic inflammatory substances, this substance is absorbed into the blood vessels can cause a reaction and fever phenomenon, fever is generally below 38.5 ℃. 2. Infection: because of the poor physical condition after the surgery, sometimes it is easy to get cold and have a cold, etc. If there is redness, swelling and heat in the wound, causing wound infection, fever can also occur. Fever after lumbar internal fixation surgery may also have other reasons, and should be promptly judged by the doctor according to the symptoms, signs and auxiliary examination to determine the specific cause, and give the correct treatment for the cause.