Fig. 1

Preoperative CT and MRI, CT at 3 months after operation, CT at 6 months after operation, local B-ultrasound and CT at 12 months after operation of NO.20. a–d Bone marrow edema under the left sacroiliac joint, bone destruction under the sacroiliac joint, narrow joint space, irregular and slightly longer T2 signal of the soft tissue below the sacroiliac joint. e, f Left sacroiliac joint bone graft stability. g, h Left sacroiliac joint The fusion of the iliac joint was further strengthened, and the left gluteus maximus, gluteus medius, and left piriformis were swollen, and there were sheet-like low-density changes inside. i, j The visible range of the left buttocks muscle gap was found to be 8.0 in the B-ultrasound 6 months after the operation. 2.3 cm hypoechoic area, 2.4 cm from the body surface. k–m CT and 3D reconstruction at 12 months after surgery showed obvious fusion of sacroiliac joints. n, o Pathological biopsy showed tuberculous chronic granulomatous inflammation of the left sacroiliac joint with caseation necrosis