KEY FACTS Imaging Erosions of dens, uncovertebral joints, facet joints Atlantoaxial instability in 20-86% patients with RA Atlantoaxial subluxation in 5% of cervical RA Cranial settling occurs in 5-8% of RA patients Lower cervical spine: Facet and uncovertebral joint erosions, instability Neutral, flexion, and extension lateral radiographs performed for evaluation of instability Normal = 2 mm between inner margin anterior ring of C1 and dens If…

KEY FACTS Terminology Defects in pars interarticularis (PI) thought to result from repetitive stress injury Pars is junction of pedicle, lamina, and facet Imaging Most common at L5: 80-90% Discontinuity in neck of “Scotty dog” on oblique plain films Elongation of spinal canal at level of pars defects on axial imaging Incomplete-ring sign on axial imaging Top Differential Diagnoses Acute traumatic fracture of posterior elements Facet…

KEY FACTS Terminology Anterolisthesis: Anterior displacement of vertebral body relative to 1 below Retrolisthesis: Posterior displacement of vertebral body relative to 1 below Imaging Lateral flexion and extension to evaluate for instability Napoleon's-hat sign on AP plain film Instability uncommon in degenerative listhesis – 90% of normal volunteers show 1-3-mm translation on flexion-extension radiographs Spondylolysis may be difficult to identify on MR T1-weighted sagittal images critical…

KEY FACTS Terminology Ossification of posterior longitudinal ligament (OPLL) Imaging Flowing multilevel ossification posterior to vertebral bodies Relatively minimal degenerative disc disease, absent facet ankylosis Midcervical (C3-C5) > midthoracic (T4-T7) PLL ossification narrows AP spinal canal dimension → spinal stenosis, cord compression Characteristic “upside-down T” or “bowtie” PLL configuration on axial images CT with sagittal reformats to confirm MR diagnosis, clarify extent of ossification for surgical…

KEY FACTS Terminology Diffuse idiopathic skeletal hyperostosis (DISH) Forestier disease, senile ankylosing hyperostosis, asymmetrical skeletal hyperostosis Imaging Flowing anterior vertebral ossification with minimal degenerative disc disease, facet arthropathy, absent facet ankylosis Thoracic spine (100%) > cervical (65-80%), lumbar spine (68-90%); R > L Lateral radiography inexpensive, reliable Reserve MR to evaluate for coexistent OPLL or spondylosis-related cord compression Top Differential Diagnoses Spondylosis Ankylosing spondylitis Psoriatic or…

KEY FACTS Terminology Spinal canal and neural foraminal narrowing in cervical spine secondary to multifactorial degenerative changes Imaging Completely effaced cerebral spinal fluid in cervical spine at disc levels Cervical spine, ventral epidural, centered at disc levels Sagittal diameter of cervical canal < 13 mm Disc osteophyte complex protruding into canal and compressing thecal sac and cord Completely effaced subarachnoid space at disc levels in cervical…

KEY FACTS Terminology Reduced AP canal diameter secondary to short, squat pedicles and laterally directed laminae Imaging Central canal diameter is smaller than normal Cervical spine: Absolute AP diameter < 14 mm Spinal stenosis present if AP canal diameter at L1 < 20 mm, L2 < 19 mm, L3 < 19 mm, L4 < 17 mm, L5 < 16 mm, S1 < 16 mm – Lumbar…

KEY FACTS Terminology Spinal canal narrowing in lumbar spine Secondary to multifactorial degenerative changes, being progressive and dynamic process Imaging Trefoil appearance of lumbar spinal canal on axial imaging Sagittal diameter of bony lumbar canal < 10 mm Top Differential Diagnoses Disc herniation Metastatic disease Paget disease Epidural hemorrhage Clinical Issues Chronic low back pain Neurogenic claudication Leg pain (80%) Bilateral lower extremity pain, paresthesia, and…

KEY FACTS Terminology Juvenile kyphosis, Scheuermann kyphosis Kyphosis secondary to multiple Schmorl nodes → vertebral body wedging Imaging Wedged-shaped thoracic vertebrae with irregular endplates ≥ 3 contiguous vertebrae, each showing ≥ 5° of kyphosis Undulation of endplates secondary to extensive disc invaginations Disc spaces narrowed, with greatest narrowing anteriorly Well-defined Schmorl nodes often present Top Differential Diagnoses Postural kyphosis Wedge compression fractures Congenital kyphosis Tuberculosis Osteogenesis…

KEY FACTS Terminology Definition: Node within vertebral body due to vertical disc extension (intravertebral disc herniation) through vertebral endplate Any level, although thoracic, thoracolumbar > cervical Imaging Focal invagination of endplate by disc material surrounded by sclerotic (old) or edematous (acute) bone Plain films Contour defect within endplate, extending from disc space into vertebral body spongiosa with well-corticated margins CT Island of low density surrounded by…

KEY FACTS Terminology Facet arthrosis, degenerative facet disease, degenerative joint disease, facet hypertrophy Osteoarthritis of synovially lined lumbar apophyseal joints Imaging Osseous overgrowth impinging on foramina in conjunction with articular joint space narrowing Mushroom cap facet appearance Joint space narrowing with sclerosis/bone eburnation, ligamentum flavum hypertrophy Intraarticular gas, effusion Spondylolisthesis not uncommon CT more sensitive than plain films for detecting presence and degree of arthrosis Facet…

KEY FACTS Terminology Facet arthrosis, degenerative facet disease, degenerative joint disease Imaging Osseous facet overgrowth impinging on neural foramina in conjunction with articular joint space narrowing Facet joint osteophytes producing foraminal narrowing Mushroom-cap facet appearance Joint space narrowing with sclerosis and bone eburnation Intraarticular gas (“vacuum phenomenon”) Enhancing inflammatory soft tissue changes surrounding facet joint are common Joint space narrowing, thinning of articular cartilage Facet effusions…

KEY FACTS Terminology Extruded disc material within neural foramen Far lateral is disc material lateral to neural foramen Imaging Obliterated perineural fat in neural foramen on sagittal images Soft tissue mass contiguous with parent disc T1WI isointense to parent disc T2WI iso-, hypo-, or hyperintense to parent disc May enhance peripherally Often missed on myelography Top Differential Diagnoses Schwannoma Spinal nerve root diverticulum Large facet osteophyte…

KEY FACTS Terminology Localized (< 25% of disc circumference) displacement of disc material beyond confines of disc space Protrusion Herniated disc with broad base at parent disc Extrusion Herniated disc with narrow or no base at parent disc Sequestered: Free fragment Imaging Anterior extradural mass contiguous with disc space extending into spinal canal Axial: Central, subarticular (lateral recess), foraminal, or extraforaminal (far lateral) Sagittal: Disc level,…

KEY FACTS Imaging Small mass in spinal canal contiguous with intervertebral disc Ventral epidural Rare in upper thoracic spine (T1-T3) May enhance peripherally after intravenous contrast material due to granulation tissue or dilated epidural plexus Peripheral enhancement may give “lifted band” or “tent” configuration Top Differential Diagnoses Osteophyte Sharp margins not arising directly from intervertebral disc level Tumor Homogeneous enhancement Hemorrhage Elongated within epidural space, tends…

KEY FACTS Terminology Protruded disc, extruded disc, free fragment, sequestered disc Localized (< 50% of disc circumference) displacement of disc material beyond edges of vertebral ring apophyses Imaging Small mass in ventral spinal canal, contiguous with intervertebral disc Protrusion is herniated disc with broad base at parent disc Extrusion is herniated disc with narrow or no base at parent disc Sequestered or free fragment: Extruded disc…

KEY FACTS Terminology Anular bulge Generalized extension of disc beyond edges of vertebral ring apophyses Imaging Circumferential disc “expansion” beyond confines of vertebral endplates Short radius of extension: ≤ 3 mm > 25% of disc circumference If morphologic abnormality is < 25% of disc circumference, then it is herniation and not bulge Smooth ventral extradural defect in contrast column, with indentation on anterior thecal sac Central…