AIM: To assess the clinical outcomes and compare the segmental range of motion (ROM) at the implanted L4-L5 level, the cranial and caudal adjacent levels, and the ROM of the whole lumbar spine after semi-rigid lumbar fusion with 2 different devices.

MATERIAL and METHODS: Patients with neurogenic claudication, due to grade 1 spondylolisthesis and spinal stenosis at levels L4-L5, were treated either Bio-flex® (n = 28) and Cosmic® (n = 23); discectomy was not performed at any level. The clinical outcomes were compared between the 2 groups. All patients underwent neutral, flexion, and extension radiography before the surgery and after 2 years postoperatively. ROM was assessed at the level of L4-L5, L3-L4, L5-S1, and at the whole lumbar spine.

RESULTS: According to clinical outcomes, 82% and 78% of patients in the BioFlex and Cosmic groups, respectively, had a good or excellent result. In both groups, there was significant reduction of the segmental ROM at the implanted L4-L5 level (p = 0.039 and 0.011).

CONCLUSION: These outcomes may play a role in decreasing the risk of ASD after dynamic stabilization, at least 2 years after surgery.