The Relationship Between Concave Angle of Vertebral Endplate and Lumbar Intervertebral Disc Degeneration

Study Design. A retrospective study of magnetic resonance imaging of the lower lumbar spine. Objective. To describe the characteristics of the concave angle of vertebral endplate (CAVE) and study the association between CAVE and lumbar intervertebral disc degeneration (IVDD). Summary of Background Data. The vertebral endplate is responsible for transferring stress between disc and vertebral body, and its concavity is important in dispersing compression stress. However, the characteristics of CAVE and the relationship between CAVE and IVDD have not been investigated. Methods. Magnetic resonance images of the lower lumbar spine in 511 patients with low back pain were examined by 2 experienced spine surgeons. The grades of IVDD and lumbar disc herniation (LDH) were evaluated, several parameters including CAVE, height, and the sagittal diameter of vertebral body were measured, and the association between IVDD or LDH and CAVE was analyzed. Results. At L3-L4, L4-L5, and L5-S1, CAVE was smaller in the upper endplate (i.e., the inferior endplate of the superior vertebra) than in the lower endplate (i.e., the superior endplate of the inferior vertebra). There was no male/female difference in the size of CAVE in any of the segments. According to partial correlation analysis, CAVE was moderately related to IVDD, but no association between CAVE and LDH was found. Conclusion. When lumbar IVDD occurs, the CAVE increases and the endplate tends to flatten. The degree of flattening is related to the severity of the degeneration.