Early mechanical outcomes of two expandable interbody cages in minimally invasive TLIF: a comparative single-surgeon study

Background: Expandable transforaminal lumbar interbody fusion (TLIF) cages permit low-profile insertion followed by in situ restoration of disc height and segmental lordosis. Mechanical failure, including secondary collapse of the expansion mechanism and endplate subsidence, has been reported with some expandable designs. We compared early secondary cage collapse and, secondarily, subsidence between the Catalyft PL and X-PAC expandable TLIF cages in a consecutive single-surgeon minimally invasive surgery (MIS) cohort.

Methods: We retrospectively reviewed 168 consecutive patients (224 cages) undergoing one- or two-level MIS TLIF: 112 patients (144 cages) received Catalyft PL and 56 patients (80 cages) received X-PAC during sequential, non-overlapping periods. Surgical technique, disc preparation, grafting, and pedicle screw-rod instrumentation were comparable between cohorts. Standing lateral radiographs obtained postoperatively and during follow-up were independently reviewed by three reviewers, with discrepancies resolved by consensus. The primary endpoint was patient-level secondary cage collapse, defined as >2 mm loss of implant height relative to baseline imaging. Cage-level analyses were supportive; clustered generalized estimating equation (GEE) models accounted for within-patient correlation. Fisher’s exact test was used for categorical comparisons, with a Bonferroni-corrected threshold of α=0.008 across six pre-specified comparisons.

Results: Secondary collapse occurred in 23/112 Catalyft PL patients (20.5%, 95% CI: 14.1–28.9%) versus 1/56 X-PAC patients [1.8%, 95% confidence interval (CI): 0.3–9.4%] (relative risk 11.5, 95% CI: 1.6–83.0; P=0.001), remaining significant after Bonferroni correction. At the cage level, collapse occurred in 24/144 Catalyft PL cages (16.7%) versus 1/80 X-PAC cages (1.2%) (P<0.001); clustered GEE analysis was consistent with this association (odds ratio 15.2, 95% CI: 2.0–116.0). Subsidence was more frequent with Catalyft PL at both the patient level (32.1% vs. 14.3%) and cage level (28.5% vs. 10.0%), but the patient-level comparison did not survive Bonferroni correction (P=0.02). The cohorts also differed substantially in cage footprint (approximately 273 vs. 384 mm²) and multilevel proportion (28.6% vs. 42.9%); subsidence is therefore considered exploratory. Pseudarthrosis occurred in 2 Catalyft PL patients (1.8%) and no X-PAC patients (P=0.55), an underpowered comparison.

Conclusions: In this single-surgeon MIS TLIF series, Catalyft PL was associated with a significantly higher rate of early secondary collapse than X-PAC. Because the cohorts were treated sequentially and differed in cage geometry, these findings demonstrate association rather than a causal effect of expansion mechanism. The collapse findings are consistent in direction and magnitude with an independent published series and with a 2025 US Food and Drug Administration class 2 recall of the Catalyft PL system, and warrant cautious device selection and independent prospective validation.