Unveiling the role of lumbar intervertebral space morphology: a novel classification and its impact on cage migration in lumbar fusion surgery.

PURPOSE: This study aimed to establish a novel classification system for lumbar intervertebral spaces based on anatomical morphology, to investigate the relationship between intervertebral space types and cage migration risk after transforaminal lumbar interbody fusion (TLIF), and to optimize fusion strategies tailored to different anatomical types. METHODS: A retrospective cohort study was conducted on 103 patients who underwent TLIF between February 2022 and June 2023. Lumbar intervertebral spaces were classified into 3 fundamental types: lordotic, neutral and kyphotic and 2 modified types: normal and degenerative. Clinical outcomes (Visual Analogue Scale [VAS], Oswestry Disability Index [ODI]), and radiographic parameters (Intervertebral Space Angle [ISA], Intervertebral Space Height [ISH], Intervertebral Foramen Height [IFH]) were evaluated. Statistical analyses included t tests, ANOVA, chi-square tests, and logistic regression. RESULTS: VAS and ODI scores significantly improved postoperatively (P < 0.05). ISA, ISH, and IFH showed significant postoperative increases across all fundamental types. Cage migration occurred in 8 segments, predominantly in degenerative-type intervertebral spaces. Logistic regression revealed that the degenerative type was associated with a 17-fold increased risk of cage migration (OR = 17.02). No significant association was found between fundamental type and migration. Fusion rates exceeded 98% across all groups. CONCLUSION: The novel classification of lumbar intervertebral spaces effectively predicts cage migration risk. The degenerative modified type is a strong risk factor for migration. Tailoring surgical strategies to intervertebral space morphology may improve stability and outcomes in lumbar interbody fusion procedures.