Spondylitis, AnkylosingSpondylitisBone and BonesHLA-B27 AntigenBone RemodelingSacroiliac JointBone DensityBone ResorptionSpineBone MarrowSpondylarthritisBone NeoplasmsBone DevelopmentBone Marrow CellsAntirheumatic AgentsBone DiseasesSpondylarthropathiesBone RegenerationBone TransplantationArthritisBone MatrixBlood SedimentationTuberculosis, SpinalIritisSeverity of Illness IndexArthritis, ReactiveBone Marrow TransplantationArthritis, PsoriaticLumbar VertebraeRheumatic DiseasesBalneologyUveitis, AnteriorBone SubstitutesBone Diseases, MetabolicFractures, BoneKyphosisThoracic VertebraeOsteogenesisArthritis, RheumatoidBone Morphogenetic ProteinsOsteitisHLA AntigensTreatment OutcomeBone Morphogenetic Protein 2PseudarthrosisSpinal DiseasesImmunoglobulin GReceptors, Tumor Necrosis FactorCervical VertebraeAntibodies, MonoclonalAnti-Inflammatory Agents, Non-SteroidalBack PainSulfasalazineTemporal BoneOsteoporosisTumor Necrosis Factor-alphaSacroiliitisParietal BoneHyperostosisKlebsiellaPsoas Abscess