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) Klebsilella pneumoniae synovitis HLA-B27 individuals are more susceptible to Klebsilella 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 pelvic (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 used to evaluate lumbar stiffness 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) measured from standing exam of standing lateral radiograph useful for preoperative planning correction of this angle correlates with improved surgical outcomes 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 flexion abduction external rotation of the ipsilateral hip causes pain Imaging Radiographs spine recommended views standing full-length AP and lateral of axial spine findings negative in 50% of cases with spine fractures squaring of vertebrae with vertical or marginal syndesmophytes late vertebral scalloping (bamboo spine) measurements chin-brow to vertical angle used to measure chin-on-chest deformity useful for preoperative planning for osteotomy pelvis & lower extremity recommended views Ferguson pelvic tilt view allows for improved visualization of anterior SI joint xray beam directed 10 to 15 degrees cephalad findings bilateral symmetric sacroiliac erosion earliest radiographic sign is erosion of iliac side of sacroiliac joint joint space narrowing ankylosis 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 first line of treatment for pain and stiffness oral steroids not recommended techniques physical therapy should focus on maintaining flexibility TNF-alpha-blocking agents indications second line of medical management techniques includes infliximab, etanercept, adalimumab outcomes clinical studies show significant improvement in severity of symptoms 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 75% neurologic involvement 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 indications stable spine fractures with no neurologic deficits technique low-weight traction may facilitate reduction operative spinal decompression with instrumented fusion indications progressive neurologic deficit epidural hematoma with neurologic compromise unstable fracture patterns technique decompression decision to go anterior or posterior depends on fracture level, presence and location of hematoma, and osteoporosis instrumentation need to obtain long fusion construct multiple points of fixation above and below the fracture are necessary because of osteoporosis long lever arms of the ankylosed spine do not make an effort to correct deformity outcomes & complications high rate of complications including progressive deformity nonunion hardware failure infection Spinal Deformity Introduction usually a kyphotic deformity of upper spine be sure to eliminate hip contractures as reason for deformity Treatment lumbar osteotomy indications thoracolumbar kyphotic deformity goals goal is to restore sagittal balance and horizontal gaze techniques closing wedge (pedicle subtracting) osteotomy transpedicular decancelization procedure with removal of posterior elements location of osteotomy determined by type of spine flexion deformity hinge located on anterior vertebral body considered procedure of choice due to greater deformity correction (30 t0 40 degrees per level) better fusion and stability due to direct bony apposition vertebral body resection entire vertebral body is removed and replaced with a cage single-level opening wedge osteotomy hinges on posterior edge of vertebral body requires rupture of ALL multi-segment opening osteotomy advantage of less bone loss and preservation of ALL by distributing correction over multiple levels outcomes & complications lumbar approach avoids complications of thoracic cage, spinal cord injury, and has potential for greater correction due to long lever arm C7-T1 cervicalthoracic osteotomy indications cervicothoracic kyphotic (chin-on-chest) deformity goals slight under-correction with final brow-to-chin angle of 10 degrees technique osteotomy advantage of C7-T1 osteotomy include vertebral artery is external to transverse foremen larger canal diameter requires wide decompression with removal of C7 lateral mass and portions of C7-T1 pedicles to prevent iatrogenic SCI instrumentation usually a combination of lateral mass screws, pedicle screws, and sublaminar hooks postoperative postoperative halo immobilization often required in patients with poor bone quality outcomes & complications increased risk of venous air embolus (VAE) in the sitting operative position Large-Joint Arthritis Introduction asymmetric involvement of large joints shoulder and hip most commonly involved Treatment total hip replacement indications in patients with severe arthritis of this hips secondary to AS technique patients have more vertical and anteverted acetabulum (may lead to anterior dislocations after total hip arthroplasty) bilateral total hip arthroplasty indications kyphotic deformity due to hip flexion contracture deformity outcomes & complications at risk for dislocation