This study aimed to biomechanically investigate a change in the stability of decompressed segments in the degenerative lumbar spine. Cyclic loading tests to the cadaveric spinal unit were conducted in compressive and bending directions with a stepwise resection of the posterior elements such as wide fenestration (partial laminotomy), unilateral and bilateral facetectomy with the intact supra- and interspinous ligaments and spinous process. Flexion stability did not decrease significantly, and may reflect the fact that the aforementioned ligamentous structures were preserved throughout the resection process. After wide fenestration, the loss of compression stiffness amounted to only half that of bilateral facetectomy, and extension stiffness dropped to this same level. Lateral bending stiffness was maintained until unilateral facetectomy was performed. We recommend restricted decompression surgeries for a single-level central stenosis in the degenerative lumbar spine.