Letter to editor: Radiological outcomes of static and expandable cage placement in minimally invasive oblique lumbar interbody fusion: a retrospective study

Aanchal Sharma; Reema Rasotra

doi:10.31616/asj.2025.0504.r1

To the Editor,

We read with great interest the recent article by Seaton et al. [1] titled “Radiological outcomes of static and expandable cage placement in minimally invasive oblique lumbar interbody fusion: a retrospective study.” While the study provides useful insights into cage selection in oblique lumbar interbody fusion (OLIF) procedures, several methodological and interpretive concerns warrant consideration.

Sample size and follow-up

The study analyzed 36 patients with expandable cages and 41 with static cages; however, the expandable group had a markedly shorter follow-up (27.6±14.1 months vs. 42.9±29.4 months). This imbalance may underrepresent late-onset complications such as cage subsidence or adjacent segment degeneration.

Radiographic versus clinical outcomes

Although radiographic improvements were documented, no patient-reported outcome measures (PROMs) were included. Lin et al. [2] found that expandable cages in transforaminal lumbar interbody fusion significantly improved anterior and foraminal disc heights and Oswestry Disability Index scores, but showed no significant differences in fusion or subsidence rates compared with static cages. This suggests radiological gains may not consistently translate into functional benefits.

Subsidence and surgical technique

Seaton et al. [1] reported lower subsidence with expandable cages (4% vs. 20%), yet broader evidence shows that subsidence is strongly influenced by factors such as bone quality, surgical level, and cage geometry. Wu et al. [3] highlighted that poor bone quality, multilevel procedures, and narrow/tall cages substantially increase endplate injury and subsidence risk. Without controlling for these variables, direct comparisons between cage types may be confounded.

Measurement reliability and generalizability

Radiographic measurements were reported without intra- or inter-rater reliability testing, which is crucial for reproducibility. Furthermore, the single-surgeon, single-center design limits generalizability. Larger multicenter studies would improve external validity.

In conclusion, while the study adds meaningful data to OLIF literature, its limitations require cautious interpretation. Future work should integrate PROMs, ensure adequate follow-up, stratify analyses by bone quality and surgical technique, and report measurement reliability. We commend the authors’ contribution and encourage further research to refine evidence on cage selection in OLIF.