Early radiological and perioperative outcomes of a boomerang-shaped expandable cage versus static cages in single-level minimally invasive transforaminal lumbar interbody fusion
Year: 2026
Type: article
Study design: Observational Study
Abstract: Background: Expandable cages have been reported to improve intervertebral disc height and segmental lordosis in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF); however, their advantages over static cages remain controversial. This study compared the early radiological and perioperative outcomes of a boomerang-shaped expandable cage and conventional static cages in single-level MIS-TLIF.Methods: This retrospective observational study included 91 consecutive patients who underwent primary single-level MIS-TLIF for degenerative lumbar disease between September 2022 and October 2025. Patients were divided into an expandable cage group (E-group, n = 47) and a static cage group (S-group, n = 44). Lumbar lordosis (LL), segmental lordosis (SL), and intervertebral disc height (DH) were evaluated preoperatively and at 3 months postoperatively. Operative time, blood loss, early cage subsidence, and endplate breach were also assessed. Because preoperative DH differed between the groups, an additional multiple linear regression analysis was performed with postoperative DH as the dependent variable and cage group, preoperative DH, and their interaction as predictors.Results: SL increased significantly in the E-group but not in the S-group. The increase was greater in the E-group (+2.14° ± 4.15° vs. +0.12° ± 2.31°, P = 0.005). DH increased significantly in both groups, with a greater increase in the E-group (+2.83 ± 1.68 mm vs. +2.09 ± 0.90 mm, P = 0.010). Preoperative DH was greater in the E-group (8.1 ± 1.8 vs. 7.1 ± 2.2 mm, P = 0.029), and a significant group-by-preoperative DH interaction was observed (P < 0.001). At the overall mean preoperative DH of 7.607 mm, postoperative DH was estimated to be 1.14 mm greater in the E-group than in the S-group (95% CI, 0.72–1.57 mm; P < 0.001). The change in LL did not differ significantly between groups (+1.10° ± 6.39° vs. −0.32° ± 4.78°, P = 0.231). Operative time was not significantly different (81.9 ± 14.6 vs. 77.4 ± 11.2 min, P = 0.108), whereas median blood loss was greater in the E-group [150 (IQR, 100–220) vs. 60 (IQR, 48.8–100) mL, P < 0.001]. Early cage subsidence occurred in 4 of 47 (8.5%) and 8 of 44 patients (18.2%), respectively (P = 0.222), and no endplate breach was identified in either group.Conclusions: Use of the boomerang-shaped expandable cage was associated with greater early restoration of segmental lordosis and disc height than the paired static cage strategy. However, the absolute radiological differences were modest, global lumbar lordosis correction did not differ, and intraoperative blood loss was greater. The clinical significance of these early radiological differences remains uncertain in the absence of validated patient-reported outcome measures.
Source: Journal of Spine Surgery
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7221768797