Characteristics of included studies.
| Study | Location | Study Design | Level of Evidence | Participants(n) | Gender(F/M) | Procedure Type | Duration of Study (mo) | Outcome |
| Kim et al, 201210 | Korea | Prospective cohort | 2 | 31 | 31/0 | Lumbar fusion (lumbar spinal stenosis) | 12 | VAS, ODI |
| Stoker et al, 20135 | US | Cross-sectional | 4 | 313 | 176/137 | Lumbar, thoracic, and cervical fusion (spondylosis and deformity) | 15 | ODI |
| Ravindra et al, 20152 | US | Cross-sectional | 4 | 230 | 129/101 | Lumbar, thoracic, and cervical fusion (pathology unknown) | 12 | ODI |
| Martins et al, 201711 | Brazil | Prospective observational | 2 | 46 | 29/17 | Cervical and lumbar fusion (degenerative pathology, deformity, tumor, infection, and trauma) | 12 | VAS |
| Ravindra et al, 201912 | US | Prospective observational | 2 | 58 | 24/34 | Cervical fusion (cervical spondylotic myelopathy) | 12 | VAS, ODI |
| Donnally et al, 201913 | US | Retrospective | 3 | 150 | 73/77 | Lumbar and thoracic fusion (degenerative pathology, deformity, spondylosis, and lumbar spinal stenosis) | 20 | VAS |
| Xu et al, 202014 | China | Retrospective | 3 | 360 | 212/148 | Lumbar fusion (degenerative pathology, lumbar spinal stenosis, and spondylolisthesis) | 24 | VAS, ODI |
ODI, Oswestry Disability Index; VAS, visual analog scale.