summary Ankylosing spondylitis (AS) is a chronic seronegative autoimmune spondyloarthropathy characterized by the formation of bridging spinal osteophytes, enthesitis, sacroiliitis, and uveitis Diagnosis is based on the presence of HLA-B27 antigens, bilateral sacroiliitis, and an ocular examination to assess for uveitis Treatment for mild symptoms consists of observation, NSAIDs, and physical therapy. Surgical management is indicated for unstable spinal fractures, progressive deformity, and neurologic deficits Epidemiology Incidence ~0.2% of the Caucasian population Demographics 4:1 male:female ratio usually presents in the third decade of life juvenile form (presents in patients <16 y/o) includes enthesitis <10% of HLA-B27-positive patients have symptoms of AS Etiology Pathoanatomy exact mechanism is unknown but is most likely related to an autoimmune reaction to an environmental pathogen in a genetically susceptible individual theories regarding the relationship to HLA-B27 include HLA-B27 aggregates with peptides in the joint, leading to a degenerative cascade cytotoxic T-cell autoimmune reaction against HLA-B27 enthesitis inflammation of the entheses leads to bony erosion, surrounding soft-tissue ossification, and eventually joint ankylosis inflammation preferentially targets the sacroiliac joints, spinal apophyseal joints, and pubic symphysis distinguishes AS from rheumatoid arthritis, which is a synovial process disc space involvement inflammation of the annulus leads to bridging osteophyte formation (syndesmophytes) Genetics there is a genetic predisposition, but the mode of inheritance is unknown HLA-B27 allele is located on sixth chromosome, B locus Diagnostic criteria bilateral sacroiliitis +/- uveitis HLA-B27 positive (present in ~90% of patients) Systemic manifestations acute anterior uveitis and iritis heart disease (cardiac conduction abnormalities) pulmonary fibrosis renal amyloidosis ascending aortic conditions (aortitis, stenosis, and regurgitation) Klebsiella pneumoniae synovitis HLA-B27-positive individuals are more susceptible Orthopaedic manifestations bilateral sacroiliitis progressive spinal kyphotic deformity cervical spine fractures large-joint arthritis (hip and shoulder) Anatomy Enthesis (the insertion of a tendon, ligament, or muscle into bone) Presentation Symptoms lumbosacral pain and stiffness present in most patients worse in the morning insidious onset in the third decade of life neck and upper thoracic pain occurs later in life acute neck pain should raise suspicion for fracture sciatica likely results from sciatic nerve involvement in the pelvis (possible caused by piriformis spasm) loss of horizontal gaze shortness of breath caused by costovertebral joint involvement leading to reduced chest expansion Physical exam limitation of chest wall expansion <2 cm of chest wall expansion is more specific than HLA-B27 positivity for making diagnosis decreased spinal motion Schober test login to view 1 more bullet kyphotic spine deformity chin-on-chest (flexion) deformity of the spine caused by multiple microfractures that occur over time chin-brow-to-vertical angle (CBVA) login to view 3 more bullets hip flexion contracture examining the patient in both supine and sitting positions helps determine whether sagittal-plane imbalance is caused by hip flexion contractures or a kyphotic spinal deformity sacroiliac provocative tests flexion, abduction, and external rotation (FABER) test login to view 1 more bullet Imaging Radiographs spine recommended views login to view 1 more bullet findings login to view 3 more bullets measurements login to view 3 more bullets pelvis and lower extremity recommended views login to view 3 more bullets findings login to view 4 more bullets CT will show bony changes but not active inflammation most sensitive test for diagnosing cervical fractures in patients with AS entire spinal axis should be imaged in AS patients who present after trivial trauma MRI will detect inflammation, making it the best modality for early detection of AS in young patients obtain in AS patients with cervical fractures to evaluate for epidural hemorrhage Bone scan will show inflammation in the sacroiliac joints, but lacks specificity Studies Labs little diagnostic value nonspecific elevations in ESR and CRP are often seen RF negative (seronegative) Diagnostic injections SI joint injection local anesthetic is injected into the SI joint under fluoroscopic guidance is often the most sensitive diagnostic test Differentials DISH vs. Ankylosing Spondylitis DISH Ankylosing Spondylitis Syndesmophytes Nonmarginal Marginal Radiographs "Flowing candle wax" "Bamboo spine" Squaring of vertebral bodies "Shiny corners" at the attachment of the annulus fibrosus (Romanus lesions) Disc space Preservation of the disc space AS in the cervical spine may show ossification of the disc space Osteopenia No osteopenia (rather, there may be increased radiodensity) Osteopenia present HLA No evidence of an association with HLA-B27 Associated with HLA-B8 (common in patients who have both DISH and diabetes) Strong association with HLA-B27 Age group Older patients (middle-aged) Younger patients SI joint involvement No involvement (SI joint abnormality generally excludes a diagnosis of DISH) Bilateral sacroiliitis Diabetes Yes No Treatment - General Nonoperative NSAIDs, COX-2 inhibitors, and physical therapy indications login to view 1 more bullet oral steroids are not recommended techniques login to view 1 more bullet TNF-⍺-blocking agents indications login to view 1 more bullet techniques login to view 1 more bullet outcomes login to view 1 more bullet Spine Trauma Introduction epidemiology fractures most often occur in the midcervical spine and at the cervicothoracic junction some fractures occur at the thoracolumbar junction pathoanatomy often an extension-type fracture affecting all three spinal columns prognosis high mortality rate secondary to epidural hemorrhage login to view 1 more bullet Presentation symptoms usually present with pain after a low-energy fall physical exam neurologic deficits often present late; therefore, patients should be admitted and observed Imaging radiographs fracture may be occult CT if a fracture is suspected, obtain a CT scan (best modality for making the diagnosis) MRI obtain due to high mortality rate associated with epidural hemorrhage Treatment nonoperative immobilize in the existing kyphotic position, admit for observation, and obtain advanced imaging login to view 3 more bullets operative spinal decompression with instrumented fusion login to view 19 more bullets Spinal Deformity Introduction usually a kyphotic deformity of the upper spine be sure to exclude hip contractures as the cause of the deformity Treatment lumbar osteotomy indications login to view 1 more bullet goals login to view 1 more bullet techniques login to view 14 more bullets outcomes and complications login to view 1 more bullet C7-T1 cervicothoracic osteotomy indications login to view 1 more bullet goals login to view 1 more bullet technique login to view 7 more bullets postoperative login to view 1 more bullet outcomes and complications login to view 1 more bullet Large-Joint Arthritis Introduction asymmetric involvement of large joints shoulders and hips are most commonly involved Treatment total hip arthroplasty indications login to view 1 more bullet technique login to view 1 more bullet bilateral total hip arthroplasty indications login to view 1 more bullet outcomes and complications login to view 1 more bullet