Background: The use of expandable cages in lumbar spine surgery is seen more frequently than in cervical cases, both a higher cost and a paucity in evidence surrounding their use may have contributed to this disparity.
Methods: A database search was carried out to identify the literature detailing outcomes from expandable and non-expandable cages in the cervical spine. These were screened using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) protocol.
Results: Fifty-five studies were included. Fixed and random-effects models were used with a 95% confidence interval. The Freeman-Tukey double arcsine transformation was utilised for proportion-based outcomes to allow for inclusion of studies with zero events. The mean subsidence was significantly greater for the non-expandable cages (2.63 mm; CI, 2.52–2.73 mm vs. 2.12 mm; CI, 1.90–2.34 mm; P<0.001). Mean change in segmental lordosis was significantly greater in expandable cages but change in cervical lordosis was greater in the non-expandable cages (segmental: 10.48°; CI, 10.34–10.62° vs. 2.01°; CI, 1.95–2.07°; P<0.001), (cervical: 3.12°; CI, 2.76–3.84° vs. 3.86°; CI, 3.77–3.96°; P<0.001). Improvement in neck pain was significantly greater in non-expandable cages (3.57; CI, 3.55–3.58 vs. 2.56; CI, 2.45–2.67; P<0.001). Change in JOA score was significantly higher in non-expandable cages (4.57; CI, 4.54–4.60 vs. 2.78; 2.57–3.00; P<0.001). No significant difference was found in the number of complications (P=0.58), reoperations (P=0.28) or fusion rate (P=0.43).
Conclusions: The use of expandable cages may carry improved radiological outcomes than that of non-expandable cages in the cervical spine, however as the clinical outcomes show little difference between the two, it remains unclear whether the heightened expense of using expandable cages is justified.
