After verifying the signals collected in the laboratory, the investigators performed a preliminary verification in the surgery, in which the sound pressure signals of lamina milling were collected during the surgery to identify milling status.

The sound of milling cortical bone and cancellous bone were recorded during posterior spinal decompression.

Inclusion Criteria:

1. Patients with myelopathy caused by spinal stenosis who had undergone posterior decompression.

Exclusion Criteria:

1. Receipt of surgery using an anterior approach or circumferential spinal cord decompression through a posterior approach;
2. Experience of trauma;
3. History of spinal tumor;
4. Previous spinal surgery;

Patients with spinal stenosis requiring surgery