A 40-year-old man was referred to our clinic with a 23-year history of AS who presented with acute back pain after a slight fall 21 months ago. On examination, the patient presented with significant percussion tenderness over the T11-T12 spine, and although the neurological examination was negative, the activity of the whole spine was restricted. CT images showed "bamboo-like changes" in the spine, and the fresh three-column fracture of T12 was characterized by no marked displacement and reduction in vertebral body height (Figure 1A). He was treated conservatively, which included a brace, rest, physiotherapy, and a regimen of intramuscular methotrexate (10 mg/week), sulfasalazine (1000 mg twice daily), and oral NSAIDS (nimesulide 0.1 g twice daily). However, he did not take his medicines regularly and experienced a more stooped position. The symptoms gradually worsened. Six months after the initial trauma, the patient returned to the outpatient clinic and complained of persistent low back pain with no neurological signs. CT images revealed pseudarthrosis with marked sclerosis at T12, and the upper part of the T12 vertebral body was irregularly damaged, with lesions identified as ALs (Figure 1B). We recommended surgery, but the patient refused and continued conservative treatment. Nine months after the initial trauma, the patient returned again and presented with progressive thoracolumbar pain without neurological symptoms. CT showed that the lesion involved the intervertebral space and the lower part of the T11 vertebral body, with pseudarthrosis and obvious hyperplasia (Figure 1C). Considering the history of progressive back pain, no neurological deficits, and progressive kyphosis at pseudarthrosis, we recommended surgery, but the patient still refused. Twelve months after the initial trauma, the patient was admitted to our hospital after presenting with unbearable back pain, hypoesthesia in the perineal area, walking weakness, and increases in urinary frequency and urgency. CT demonstrated that the scope of the lesions had extended, and there was severe thoracolumbar kyphosis and spinal canal stenosis (Figure 1D). The patient reported no history of tumor or tuberculosis. On examination, his legs showed weakness and numbness and hypoesthesia of the skin in the perineal area. His key muscle strength was grade IV, the deep reflexes were weakened, and the Babinski sign was negative. Laboratory examination showed that the erythrocyte sedimentation rate and C-reactive protein were 24 mm/h and 148.4 mg/l, respectively. The HLA-B27 results were positive; antinuclear antibodies and tuberculosis screening test (T-SPOT. TB) were negative; and blood counts and other serum chemicals were normal. The patient agreed to under surgery. Debridement and interbody fusion via the posterior pedicle lateral approach were performed. Postoperative CT showed great positioning of pedicle screw fixation, obvious correction of kyphosis and adequate intervertebral bone grafting (Figure 1E). Histopathologic analysis showed degenerative fibrocartilage tissue calcification, necrotic intervertebral disc tissue, and fibrovascular hyperplasia, and focal accumulation of inflammatory cells (Figure 2). When discharged, the back pain was significantly relieved, and the patient could walk independently with a brace. During the 9-month follow-up, the symptoms were significantly improved. CT showed that there was no screw loosening or fracture, no loss of kyphosis correction, and good ALs segmental bone graft fusion (Figure 1F).