Enhanced Recovery After Surgery (ERAS) is a multidisciplinary, multimodal approach aiming to improve surgical outcomes. This study compares the length of hospital stay of patients undergoing single-level posterior lumbar arthrodesis and treated with the ERAS protocol with the hospital stay of patients treated according to the standard protocol.

Hundred and ten patients scheduled for single-level posterior lumbar arthrodesis (PLIA) will be randomized to be treated by the standard protocol or the Enhanced Recovery After Surgery (ERAS) protocol. The ERAS protocol differs from the standard protocol in 4 phases: pre-operative counseling and intake, day of surgery, the pre-operative patient preparation, the per-operatively used analgesic and anesthetic drug combination, and the post-operative care consisting of a more intensive physical therapy in the ERAS group. It is the objective the mobilize patients more rapidly without compromising the comfort in terms of pain.

Inclusion Criteria:

• Scheduled for a single level PLIA as treatment of mono segmental degenerative instability, as seen on dynamic X-rays, after the failure of 6 months conservative therapy Capable of understanding the provided information Giving informed consent

Exclusion Criteria:

• Revision surgery Arthrodesis for trauma, neoplasms, infection, or listhesis due to lysis. High dose opioid use (step 3 of the WHO pain ladder) Diabetes Cognitive impairment (baseline dementia, cognitive dysfunction, or inability to consent to participate).

Known kidney insufficiency: GFR <30 mL/min/1.73 m2 Allergy/intolerance/contraindication to any medication or component included in the ERAS pathway protocol Patients with a risk factor for reflux

The interventions described in the patient information brochure make masking impossible