PANCE Blueprint Musculoskeletal (8%)

Infectious Diseases (PEARLS)

The NCCPA™ Musculoskeletal Content Blueprint infectious diseases (PEARLS) 

Acute and chronic osteomyelitis (ReelDx)

ReelDx Virtual Rounds (Osteomyelitis)
Patient will present as → a 12-year-old girl brought to the clinic by her parents concerning a persistent, dull pain in her left leg that worsens with movement. She also has had a fever for the past three days. Her parents note that she had a puncture wound on the same leg about two weeks ago while playing near a construction site. On examination, the child is irritable, the left leg is swollen, and there is tenderness over the tibia. The overlying skin is warm and erythematous. Laboratory results reveal an elevated white blood cell count, and ESR and CRP levels are also high. An MRI of the leg demonstrates demineralization, periosteal thickening, and bone destruction. Blood cultures are taken, and empirical intravenous antibiotic therapy is initiated.

Osteomyelitis is an acute or chronic infection and inflammation of bone and bone marrow – it can occur as a result of hematogenous seeding, the contiguous spread of infection, or direct inoculation into intact bone (trauma/surgery)

  • Fever, restriction of movement of the involved extremity, or refusal to bear weight

Acute osteomyelitis is most commonly seen in children with S. aureus as the most common organism

  • Sickle cell disease - Salmonella is pathognomonic

Chronic osteomyelitis is most common in adults secondary to open injury of bone and surrounding soft tissue

  • S. aureus is the most common organism (80%)
  • Staph epidermidis in prosthetic joints
  • Gram-negative pseudomonas in IVDU
  • Pasteurella is seen in cases caused by cat/dog bites
  • Mycobacterium TB is seen in vertebral involvement (Potts DZ)

DX: bone aspiration = gold standard

  • X-ray triad: demineralization, periosteal reaction, bone destruction (lags behind symptoms 7-10 days); MRI shows changes before X-ray
  • Labs: CRP elevated for 4-6 weeks, WBC and ESR high in most cases
  • Definitive diagnosis = blood culture or by needle aspiration/bone biopsy

TX: Treat initially with a broad-spectrum antibiotic regimen. Base treatment on the results of cultured bone tissue to obtain the best outcome.

  • Duration of therapy: 4–6 weeks for acute osteomyelitis and generally >8 weeks for chronic osteomyelitis or MRSA infection
  • Newborn (<4 months) - Group B Strep - nafcillin or oxacillin + 3rd gen cephalosporin
  • > 4 months - S. aureus - MSSA - Nafcillin + Ancef. MRSA - Vancomycin or Linezolid
  • Sickle cell - Salmonella - 3rd gen cephalosporin or FQ (Cipro)
  • Puncture wound - Pseudomonas - Cipro or levofloxacin

Osteomyelitis of the 1st toe

ReferencesMerck Manual · UpToDate

Septic arthritis (ReelDx)

ReelDx Virtual Rounds (Septic arthritis)
Patient will present as → a 24-year-old male presents with abrupt onset of swelling, pain, redness, and increased warmth in his right knee. He denies any injury or previous joint issues. The symptoms began yesterday, along with generally not feeling well and possibly a low-grade fever. His past medical history is unremarkable. He takes no medications and has no known drug allergies. He denies tobacco use, consumes alcohol socially with no recent episodes of heavy drinking, and follows a vegetarian diet. He is sexually active with a recent new partner. On physical examination, T: 100°F, right knee is edematous and erythematous with increased warmth, and ROM decreased by pain. The left knee has no change in skin color or temperature with full pain-free ROM in flexion and extension. The examination of the hip and ankle joints is unremarkable. Right knee synovial fluid analysis reveals increased leukocytes and the absence of crystals.

Septic arthritis is a direct bacterial invasion of joint space - a most dangerous form of acute arthritis. It is a medical emergency!

  • A single, swollen, warm, painful joint that is tender to palpation + constitutional symptoms (fever, sweats, myalgia, malaise, pain)
  • MC = knee and hip
  • Caused by: hematogenous spread, direct inoculation, contiguous spread
  • S. aureus is most common (40-50%); N. gonorrhea in sexually active young adults, streptococci; pseudomonas in IVDU

DX: Diagnose with arthrocentesis: joint fluid aspirate for definitive diagnosis (WBC > 50,000 primarily PMNs)

  • WBC > 1000 is positive in pt with prosthetic joints

TX: Treatment is based on gram stain- 2-4 week course of antibiotics  + arthrotomy with joint drainage

  • Staph aureus = Vanco/nafcillin (Vanco or Clindamycin if PCN allergic)
  • Gonorrhea = ceftriaxone
  • IVDU = Cipro/Levaquin

Image: 'Sternoclavicular joint septic arthritis with chest wall abscess in a healthy adult: a case report' by Tanaka Y, Kato H, Shirai K, Nakajima Y, Yamada N, Okada H, Yoshida T, Toyoda I, Ogura S. License: CC BY 4.0

ReferencesMerck Manual · UpToDate

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