summary Ankylosing Spondylitis is a chronic seronegative autoimmune spondyloarthropathy characterized by bridging spinal osteophyte formation, enthesitis, sacroiliitis, and uveitis. Diagnosis is made with the presence of HLA-B27 antigens, the presence of bilateral sacroiliitis, and ocular examination to assess for uveitis. Treatment is observation, NSAIDs, and physical therapy for mild symptoms. Surgical management is indicated for unstable spinal fractures, progressive deformity, and the presence of neurological deficits. Epidemiology Incidence affects ~0.2% of Caucasian population Demographics 4:1 male:female usually presents in 3rd decade of life juvenile form <16-years-old includes enthesitis fewer than 10% of HLA-B27 positive patients have symptoms of AS Etiology Pathoanatomy exact mechanism is unknown, but most likely due to an autoimmune reaction to an environmental pathogen in a genetically susceptible individual. theories of relation to HLA-B27 include HLA-B27 aggregates with peptides in the joint and leads to a degenerative cascade cytotoxic T-cell autoimmune reaction against HLA-B27 enthesitis entheses inflammation leads to bony erosion, surrounding soft-tissue ossification, and eventually joint ankylosis preferentially targets sacroiliac joints, spinal apophyseal joints, symphysis pubis this differentiates from RA, which is a synovial process disc space involvement inflammation of the annulus lead to bridging osteophyte formation (syndesmophytes) Genetics there is a genetic predisposition, but mode of inheritance is unknown HLA-B27 is located on sixth chromosome, B locus Diagnostic criteria bilateral sacroiliitis +/- uveitis HLA-B27 positive (90% positive) Systemic manifestations acute anterior uveitis & iritis heart disease (cardiac conduction abnormalities) pulmonary fibrosis renal amyloidosis ascending aortic conditions (aortitis, stenosis, regurgitation) Klebsiella pneumoniae synovitis HLA-B27 individuals are more susceptible to Klebsiella pneumoniae synovitis Orthopaedic manifestations bilateral sacroiliitis progressive spinal kyphotic deformity cervical spine fractures large-joint arthritis (hip and shoulder) Anatomy Enthesis defined as the insertion of tendon, ligaments, or muscle into bone Presentation Symptoms lumbosacral pain and stiffness present in most patients worse in morning insidious onset in 3rd decade of life neck and upper thoracic pain occurs later in life acute neck pain should raise suspicion for fracture sciatic likely originates from sciatic nerve involvement in the pelvis (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 < 2cm of expansion is more specific than HLA-B27 for making diagnosis decreased spine 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 patient in supine and sitting position helps differentiate sagittal plane imbalance due to hip flexion contractures or kyphotic spinal deformity sacroiliac provocative tests 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 & 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 CT is most sensitive test to diagnose cervical fractures in patients with AS entire spinal axis should be imaged in patients presenting with trivial trauma MRI will detect inflammation, making it the best modality for early detection of AS in young patients obtain with cervical fractures to look for epidural hemorrhage Bone scan will show inflammation in the sacroiliac joints, but lacks specificity Studies Labs little diagnostic value often see nonspecific elevations in ESR and CRP RF negative (seronegative) Diagnostic Injections SI joint injection local anesthetic injected into SI joint under fluoroscopic guidance often 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 annulus fibrosus (Romanus lesions) Disc space Preservation of disc space AS in cervical spine will show ossification of disc space Osteopenia No osteopenia (rather, there may be increased radiodensity) Osteopenia present HLA No evidence of association with HLA-B27 Associated with HLA-B8 (common in patients with 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 the diagnosis of DISH) Bilateral sacroiliitis Diabetes Yes No Treatment General Nonoperative NSAIDS, COX-2 inhibitors, and therapy indications login to view 2 more bullets techniques login to view 1 more bullet TNF-alpha-blocking agents indications login to view 1 more bullet techniques login to view 1 more bullet outcomes login to view 1 more bullet Operative see below Spine Trauma Introduction epidemiology most occur in midcervical and cervicothoracic junction (some occur at thoracolumbar junction) pathanatomy often extension-type fracture that involved all three columns prognosis high mortality rate secondary to epidural hemorrhage login to view 1 more bullet Presentation symptoms usually present with pain after low energy fall physical exam neurologic deficits often present late and therefore patients should be admitted and observed Imaging radiographs may be occult CT if suspicious consider CT scan (best modality to make diagnosis) MRI high mortality rate secondary to epidural hemorrhage Treatment nonoperative immobilize in existing kyphotic position, admit for observation and advanced imaging login to view 4 more bullets operative spinal decompression with instrumented fusion login to view 19 more bullets Spinal Deformity Introduction usually a kyphotic deformity of upper spine be sure to eliminate hip contractures as reason for 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 & complications login to view 1 more bullet C7-T1 cervicalthoracic 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 & complications login to view 1 more bullet Large-Joint Arthritis Introduction asymmetric involvement of large joints shoulder and hip most commonly involved Treatment total hip replacement 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 & complications login to view 1 more bullet