Cоnversiоn оf units: How mаny nаnoseconds does it tаke for a computer to perform one calculation if it performs calculations per second?
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Ankylоsing Spоndylitis (AS) Bаckgrоund A chronic seronegаtive spondyloаrthropathy primarily affecting the axial skeleton. Strongly associated with HLA-B27. Onset usually in young men (late teens to 30s). Part of the spondyloarthritis family (includes psoriatic arthritis, reactive arthritis, IBD-associated arthritis). Symptoms Chronic low back pain and stiffness with insidious onset. Symptoms worse in the morning and with rest, improve with activity. May also have peripheral arthritis (hips, shoulders). Extra-articular manifestations: anterior uveitis, aortic regurgitation, restrictive lung disease (due to decreased chest wall expansion). Physical Exam Findings Reduced spinal mobility and loss of lumbar lordosis. Decreased chest expansion. Positive Schober test (reduced lumbar flexion). Tenderness over sacroiliac joints. Making the Diagnosis X-ray of sacroiliac joints: sacroiliitis with erosions and sclerosis. Spine imaging: “bamboo spine” due to syndesmophyte formation. Labs: ESR/CRP elevated; RF and anti-CCP negative. Diagnosis is clinical + imaging. Management First-line: NSAIDs (indomethacin often used). Physical therapy/exercise to maintain posture and mobility. Biologic therapy (TNF inhibitors, IL-17 inhibitors) for refractory disease or axial disease not controlled with NSAIDs. Surgery (hip replacement, spinal osteotomy) for severe deformity. Monitor and treat extra-articular complications (uveitis, cardiac, pulmonary). Question A 26-year-old man presents with progressive low back pain and stiffness for the past 18 months. His symptoms are worst in the morning and improve after exercise. On exam, he has tenderness over both sacroiliac joints and limited forward flexion of the lumbar spine. Radiographs show bilateral sacroiliitis. Which of the following additional findings is most likely to be seen in this patient?
Osteоmyelitis Bаckgrоund Osteоmyelitis is аn infection involving bone, most often cаused by Staphylococcus aureus but may be polymicrobial. Pathogenesis can occur through: Hematogenous spread (more common in children; vertebral osteomyelitis most common in adults). Contiguous spread from adjacent soft tissue/joint infections. Direct inoculation from trauma, bite wounds, or surgery. Risk factors include orthopedic hardware, diabetes mellitus, peripheral vascular disease, IV drug use, and sickle cell disease. Symptoms Gradual onset of localized bone pain over several days. Associated swelling, erythema, warmth, and tenderness at the affected site. Fever, chills, or constitutional symptoms may be present. Chronic osteomyelitis may present with draining sinus tracts and intermittent symptoms. In children: irritability, decreased appetite or activity, refusal to bear weight or walk. Physical Exam Findings Localized tenderness and swelling over the affected bone. Warmth and erythema of overlying skin. Limited function or limp in children. Vertebral osteomyelitis: focal spinal tenderness to percussion, sometimes neurologic deficits if advanced. Making the Diagnosis Labs: CBC, ESR, CRP, and blood cultures. Imaging: X-ray: may appear normal in first 2 weeks; later shows bony destruction. MRI: most sensitive for early detection, especially for vertebral or diabetic foot cases. Bone scan may be useful if MRI contraindicated. Definitive diagnosis: positive bone biopsy culture and histopathology. Management Antibiotics: Empiric IV coverage for S. aureus and gram-negative organisms (e.g., Vancomycin + ceftriaxone/ceftazidime/cefepime). Tailor based on culture results. Surgical debridement: indicated for nonhematogenous cases, presence of abscesses, hardware involvement, or failure to improve after 48–72 hrs of antibiotics. Duration: Typically 6–8 weeks of antibiotics. Pediatric osteomyelitis: often requires IV antibiotics (e.g., cefazolin, clindamycin, or vancomycin) with possible surgical drainage if abscess present. QUESTION A 10-year-old boy presents with 4 days of progressive left leg pain and refusal to bear weight. He has swelling, erythema, and warmth over the mid-tibia. His temperature is 38.5°C (101.3°F). Laboratory studies show elevated ESR and CRP. Plain radiographs of the tibia are normal. Which of the following is the most appropriate next diagnostic step?