Epidural SpaceAnesthesia, EpiduralNeedlesInjections, EpiduralDura MaterSpinal CanalLigamentum FlavumAnalgesia, EpiduralLumbosacral RegionEpidural NeoplasmsLipomatosisRadiculopathySpinal Nerve RootsLumbar VertebraeCoccyxAnalgesia, ObstetricalThoracic VertebraeSpinal DiseasesFiber Optic TechnologyMyelographyTissue AdhesionsAnesthesia, ObstetricalMathematical ConceptsIntracranial HypotensionSpinal CordLaminectomyIntervertebral Disc DisplacementFluoroscopySpinal Cord CompressionAnesthetics, LocalBlood Patch, EpiduralAnatomy, Cross-SectionalInjections, SpinalEpidural AbscessSpinal NeoplasmsAnesthesia, CaudalCatheterizationTomography, X-Ray ComputedFentanylMagnetic Resonance ImagingCervical VertebraeBupivacaineEndoscopySpinal Cord DiseasesSpinal StenosisLow Back PainLidocaineReproducibility of ResultsSteroidsPregnancy Trimester, ThirdNerve Block