Epidural SpaceAnesthesia, EpiduralNeedlesInjections, EpiduralDura MaterSpinal CanalLigamentum FlavumAnalgesia, EpiduralLumbosacral RegionEpidural NeoplasmsDepth PerceptionLipomatosisRadiculopathySpinal Nerve RootsCoccyxLumbar VertebraeAnalgesia, ObstetricalThoracic VertebraeMyelographySpinal DiseasesFiber Optic TechnologyTissue AdhesionsAnesthesia, ObstetricalMathematical ConceptsIntracranial HypotensionLaminectomySpinal CordIntervertebral Disc DisplacementSpinal Cord CompressionFluoroscopyBlood Patch, EpiduralAnesthetics, LocalInjections, SpinalEpidural AbscessSpinal NeoplasmsAnesthesia, CaudalAnatomy, Cross-SectionalCatheterizationFentanylCervical VertebraeBupivacaineTomography, X-Ray ComputedEndoscopySpinal Cord DiseasesMagnetic Resonance ImagingSpinal StenosisLidocaineLow Back PainSteroidsPregnancy Trimester, ThirdNerve Block