Expandable interbody cages restore disc height more reliably than static cages, but evidence on spinal alignment and subsidence is mixed, according to an article in the fall 2026 issue of Vertebral Columns.
Four authors from the orthopedics department at New York City-based Hospital for Special Surgery wrote the article, including Nuri Demirci, MD, and Sheeraz Qureshi, MD. They said the evidence is more divided than the pace of adoption suggests.
Five things to know:
1. Expandable cages restored more disc height. A meta-analysis of 15 retrospective studies covering 2,247 patients found static cages produced smaller gains. The same analysis found no difference in segmental lordosis, a measure of spinal curvature.
2. Subsidence findings conflicted. One meta-analysis of 23 studies and 1,838 patients reported subsidence rates of 12.8% with expandable cages and 25.7% with static cages, but only three of those studies compared the designs directly. Another meta-analysis found a trend toward less subsidence with static cages, and a 417-patient single-institution study found 14.1% with expandable cages compared with 6.6% with static cages.
3. Lateral approach results did not match the transforaminal findings. A prospective study of 98 patients found 12-month fusion rates of 94.0% with expandable cages and 82.9% with static cages, but patients were not randomized: the first 50 received static cages and the next 48 received expandable cages, so the authors said period and learning-curve effects cannot be ruled out. A meta-analysis of four comparative lateral studies found no difference in subsidence, disc height or patient-reported outcomes at 24 months.
4. Approach, implant width and bone quality shaped subsidence risk. The authors said subsidence tracked more closely with surgical approach and implant width than with the expansion mechanism. Poor bone quality was the patient factor most consistently linked to it.
5. Higher costs and thin evidence complicate selection. The authors said expandable cages cost substantially more, though the gap has not been consistently quantified. No randomized comparison exists, and both recent meta-analyses said every study they included was retrospective.
The authors said expandable cages are a reasonable default for a collapsed disc space reached through a narrow corridor in a patient with adequate bone, but a poor default for patients with osteoporosis.
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