Fig. 2

X-rays and CT before and after surgery of NO.5. a–c Preoperative X-rays d–f Preoperative CT showed the joint space disappeared. Strip calcification can be seen in the spinal canal behind the lumbar 4–5 vertebral body, and the spinal canal is narrowed behind the corresponding intervertebral space. The bone density of the right sacroiliac joint and sacrum is uneven, and multiple worm-like bone destructions can be seen, and multiple spot-like high-density shadows can be seen inside. Similar oval, slightly hypodense shadows in the right psoas muscle, multiple punctate calcifications can be seen on the edge of the lesion and in its interior. The right iliacus muscle was swollen, and punctate high density was seen in the musculature around the pelvic floor. g, h Postoperative X-ray. i, j postoperative CT. k, l X-rays 6 months after surgery. m, n CT 1 year after operation: the sacroiliac joint is fused, and the joint space disappears. o, p CT and X-ray films 2 years after surgery showed irregular shape of the right sacroiliac joint, fusion of the sacroiliac joint and disappearance of the joint space. q Examination results of surgically removed pathological tissue