Surgical Treatment of Lumbar Hyperextension Injury in Ankylosing Spondylitis
A 43-year-old man was admitted for severe low back pain after slipped down on the icy roads. He had a history of AS. Findings from the physical examination consisted in tenderness to palpation of the lumbar spine at L1. The neurological findings were normal. Plain radiographs of the lumbar spine revealed a bamboo spine typical for AS, with a visible fracture line in the L1-2 spine. A whole spine computed tomography (CT) confirmed the presence of a transcorporeal bony fracture of the L2 lumbar spine. By magnetic resonance imaging (MRI), the T2 sequence disclosed high signal intensity from the body and neural arch of L2, consistent with a recent fracture. MRI also demonstrated injury of posterior interspinous ligaments and there was no thecal compression and cord signal change (). This fracture in a patient with AS involved all three spinal columns and was therefore considered unstable. We decided to perform the surgical treatment due to highly unstable fracture condition.\nPreoperative evaluation was done for general anesthesia. He had cardiovascular and pulmonary disease; aortic regurgitation, mitral valve disease and fibrous disease in the lung apex. We had to consider the patient's medical disease. When performing intubation, we did it fiberoptically in the awakening state due to typical kyphotic bamboo spine.\nAt first, we performed the posterior fixation of T12, L1, L2, L3. Post posterior surgical management, the disalignment was detected on L1-2 in the plain radiography. After that, we did anterior approach using the expendable cage. Performing combined posterior and anterior approach, the patient showed left lower extremity weakness in hip flexion of grade 2 and left knee extension of grade 1. From the retrospective review, we noticed that disalignment at the fracture site was happened in prone positioning for posterior fixation. Postoperative computed tomography revealed that the left L2 root was compressed between disaligned lamina and pedicle (). The patient was put under absolute bed rest and administrated intravenous steroid. On the first postoperative day, we performed root decompression and the patient showed improvement on the neurologic examination as the motor grade 3 of Lt. knee extension and hip flexion. After 2 days of absolute bed rest, the patient received rehabilitation treatment with the aid of orthosis for two months. On the follow-up radiographs obtained 1 and 2 months after surgery, the cage subsidence was shown gradually. But the cage subsidence was not aggravated after the last 2 months radiographs.