The causes of swelling after back surgery are blood clots and infections, states the University of Maryland Medical Center. Infections occur in the incision area, either at the surface or in the deep tissue, and are accompanied by redness, swelling, heat, drainage and fever. Although infections are rare, antibiotics or draining the infection can treat them.
Blood clots, such as thrombophlebitis, can occur after back surgery, usually forming in the legs, explains UMMC. The blood clots start in the calf veins and work their way up the legs, causing swelling. If a blood clot breaks off, it can travel to the lungs and cause a pulmonary embolism or obstruct blood flow to the lungs. Because this can cause death, doctors like to get patients moving after a surgery to help the blood circulate and prevent clotting and give patients drugs that inhibit blood clotting. Most cases of thrombophlebitis arise after pelvic or leg surgery.
Other complications following back surgery include anesthesia reactions, lung problems, implant complications and spinal cord injury, according to UMMC. Because the spinal cord is riddled with nerves, back surgery can accidentally damage these nerves, resulting in paralysis and numbness. The implants or hardware can break or move immediately after surgery. The lungs can have trouble working properly after anesthesia.