Introducer systems for bone access

Described herein are various implementations of systems and methods for accessing and modulating tissue (for example, systems and methods for accessing and ablating nerves or other tissue within or surrounding a vertebral body to treat chronic lower back pain). Assessment of vertebral endplate degeneration or defects (e.g., pre-Modic changes) to facilitate identification of treatment sites and protocols are also provided in several embodiments. Several embodiments comprise the use of biomarkers to confirm or otherwise assess ablation, pain relief, efficacy of treatment, etc. Some embodiments include robotic elements for, as an example, facilitating robotically controlled access, navigation, imaging, and/or treatment.