Table 3 In-and exclusion criteria used for the selection of the papers for the three independent observers

1. Patients: Patients who had a spinal surgical intervention above the age of eighteen years.

2. Baseline characteristics: Age, gender, type of spinal surgery, primary or secondary surgical intervention, time of hospitalization.

3. Main determinant: Study compares a physical postoperative outpatient appointment with an intervention (no appointment, digital appointment, telephone consultation).

4. Main outcome measurements: Direct (< 30 days) or late complications related to the surgical intervention and the time interval of occurrence (rate or intensity), time between surgery and complication, measurement of quality of care, time between intervention and postoperative appointment, 6 weeks follow up or longer.

Exclusion criteria

- Patients with complex spinal surgery, spinal surgery after traumatic injury or patients with paraplegia.

- Patients unable to attend a physical post-operative appointment