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 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 on a standing lateral radiograph useful for preoperative planning correction of this angle correlates with improved surgical outcomes 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 flexion, abduction, and external rotation of the ipsilateral hip reproduces pain Imaging Radiographs spine recommended views standing full-length AP and lateral of the axial spine findings negative in 50% of cases with spinal fractures squaring of vertebrae with vertical/marginal syndesmophytes late vertebral scalloping (bamboo spine) measurements chin-brow to vertical angle used to measure chin-on-chest deformity useful for preoperative osteotomy planning pelvis and lower extremity recommended views Ferguson pelvic tilt view allows improved visualization of the anterior SI joint x-ray beam is directed 10-15° cephalad findings bilaterally symmetric sacroiliac erosions earliest radiographic sign is erosion of the iliac side of the sacroiliac joint joint space narrowing ankylosis 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 first-line treatment for pain and stiffness oral steroids are not recommended techniques physical therapy should focus on maintaining flexibility TNF-⍺-blocking agents indications second-line medical treatment techniques agents include infliximab, etanercept, and adalimumab outcomes clinical studies show a significant reduction in symptom severity 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 ~75% have neurologic involvement 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 indications stable spine fractures with no neurologic deficits low-weight traction may facilitate reduction operative spinal decompression with instrumented fusion indications progressive neurologic deficit epidural hematoma with neurologic compromise unstable fractures technique decompression decision to use an anterior or posterior approach depends on the fracture level, presence and location of a hematoma, and degree of osteoporosis instrumentation long fusion construct multiple points of fixation above and below the fracture are necessary because of osteoporosis long lever arms created by the ankylosed spine do not attempt to correct the deformity outcomes and complications high rate of complications, including progressive deformity nonunion hardware failure infection 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 thoracolumbar kyphotic deformity goals restore sagittal balance and horizontal gaze techniques closing wedge (pedicle subtraction) osteotomy transpedicular decancellization involving the removal of the posterior elements location of the osteotomy is determined by the type of spinal flexion deformity hinge is located in the anterior portion of the vertebral body considered the procedure of choice due to greater deformity correction (30-40° 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 the posterior edge of the vertebral body requires splitting of ALL multi-segment opening osteotomy offers the advantages of less bone loss and preservation of the ALL by distributing the correction over multiple levels outcomes and complications lumbar approach avoids complications associated with the thoracic cage, spinal cord injury, and has the potential for greater correction because of the long lever arm C7-T1 cervicothoracic osteotomy indications cervicothoracic kyphotic (chin-on-chest) deformity goals slight undercorrection, resulting in a final brow-to-chin angle of 10° technique osteotomy advantages of a C7-T1 osteotomy include vertebral artery lies outside the transverse foramen larger spinal canal diameter requires wide decompression, with removal of the C7 lateral mass and portions of the C7-T1 pedicles to prevent iatrogenic SCI instrumentation usually a combination of lateral mass screws, pedicle screws, and sublaminar hooks postoperative postoperative halo immobilization is often required in patients with poor bone quality outcomes and complications increased risk of venous air embolus (VAE) if the patient is in the sitting position during the operation Large-Joint Arthritis Introduction asymmetric involvement of large joints shoulders and hips are most commonly involved Treatment total hip arthroplasty indications patients with severe arthritis of the hips secondary to AS technique patients have more vertically oriented and anteverted acetabula (may lead to anterior dislocation after total hip arthroplasty) bilateral total hip arthroplasty indications kyphotic deformity caused by hip flexion contractures outcomes and complications risk of dislocation