Column, Line-of-Sight, Margins, Ring: A Framework for Planning En Bloc Spondylectomies

En bloc spondylectomies are essential for controlling malignant spinal tumors, but existing classification systems are often complex and impractical. This study introduces the Column, Line-of-Sight, Margins, Ring (CLiMR) framework, a novel system simplifying and standardizing en bloc spondylectomy planning and classification.

A retrospective review of patients who underwent single- or multistage en bloc spinal tumor resections was conducted at a single academic center (October 2019-December 2024). The CLiMR framework assigns scores to 4 components: Column (osteotomies/diskectomies for tumor release), Line-of-Sight (approach for circumferential access), Margin (adjacent structures sacrificed), and Ring (size of the vertebral ring window for safe delivery of neural tissue). Scores were applied using operative notes and imaging.

Column scores ranged from 0.5 to 4.5. Of the patients included, 40.9% underwent sagittal split osteotomies, 22.7% radical diskectomies, 18.2% horizontal osteotomies, and the remaining 18.2% combinations of previous osteotomies . A posterior-only approach (Line-of-Sight score = 1) was used in 45.4% of cases, whereas 45.4% required a multistage approach (score = 2). Margin scores reflected increasing morbidity: 31.8% (n = 7) involving chest wall/pleura resection (grade 3), 40.9% (n = 9) requiring eloquent nerve sacrifice (grade 6), and 9.1% (n = 2) necessitating limb sacrifice (grade 7). The majority (86.4%, n = 19) of ring scores were grade 1, requiring laminectomies/facetectomies. The mean CLiMR score was 9.36 ± 2.43, with higher scores correlating with longer hospital stays (R = 0.64, P = .0012), longer case durations (R = 0.61, P = .0023), and increased blood loss (R = 0.40, P = .067). Patients with local recurrence, positive margins, or complications trended toward greater CLiMR scores.

The CLiMR framework provides a novel, user-friendly method for planning and communicating en bloc spondylectomies. By addressing technical complexities and morbidity, CLiMR enables standardized assessment, facilitates surgical decision-making, and supports future research. This study demonstrates feasibility and lays the foundation for future validation studies.