Quantitative Evaluation of Motor Function Before and After Surgery for Degenerative Lumbar Spinal Stenosis

Inclusion Criteria: Patient: * more than 18 years old * who has provided verbal consent * with acquired arthritic lumbar spinal stenosis * eligible for surgery (pain \> 3 months, resistant to medical treatment) * for whom the neurosurgeon has scheduled nerve decompression without osteosynthesis or instrumentation * able to walk ≥ 10 metres without help Exclusion Criteria: Patient: * Adult under guardianship * Absence of health insurance cover * Pregnant or breast-feeding women * History of lumbar spinal surgery involving posterior or anterior arthrodesis * History of lumbar spinal surgery involving arthroplasty * History of lumbar spinal surgery within the previous 12 months * Locomotor disorders due to causes other than spine disease (orthopaedic, neurological, vascular, cardiac…) that could significantly affect walking speed * patients in whom the surgery could not be done or deferred (intolerance to the ventral decubitus position, infection…) * patients who had revisit surgery before M6 (with the exception of early revisit surgery during the first month post-intervention) * patients in whom osteosynthesis or the implantation of instruments was decided and done during the surgery