A patient with sacrum adherence of cyst hydatic, the nightmare of all orthopaedists. Cavity walls were matured with 4 weeks of albendazol use before the surgery. Then we debrided the cavity and abscess in the muscle with posterior approach. We washed it with 3 litres of 3% NaCl. After the process, we filled the cavity with radio-opaque material and took scopy image. Especially on the pron-lateral graphy, the width of debridement towards the pelvis can be seen.