Osteomyelitis Overview

Osteomyelitis

• Osteomyelitis is an infection in the bone.
• It can be reached by two methods:
  • Indirectly via the bloodstream (hematogenous).
  • Directly from trauma or surgery (exogenous).
• Predisposing factors include:
  • Vascular insufficiency
  • IV drug use
  • Immunodeficiency/Immunosuppression
• The most common pathogen is Staphylococcus aureus.

Hematogenous Osteomyelitis

• Bacteria travel through the bloodstream to the bone.
• This leads to bone destruction and abscess formation.
• Purulent exudate (pus) is a result.
• Minimal swelling is often initial symptom.
• Exudate under the periosteum can cause necrosis of blood vessels.
• Sequestra are devascularized bone fragments.

Hematogenous Osteomyelitis - Clinical Features

• Infectious organisms enter through a nutrient blood vessel in the metaphysis.
• Bacteria cause bone destruction and abscess formation, spreading to the medullary cavity.
• Purulent exudate accumulates beneath the periosteum, leading to necrosis and the formation of sequestra (bone fragments).

Osteomyelitis - Manifestations

• Symptoms include pain, fever, loss of movement, tenderness, erythema (redness), and swelling at the infection site. These manifestations are accompanied by bacteremia.

Osteomyelitis - Diagnosis

• X-rays might show periosteal elevation.
• Bone scans, MRIs, blood cultures, and bone aspiration cultures are used to confirm the diagnosis.

Chronic Osteomyelitis

• Usually secondary to open wounds or delayed treatment of hematogenous osteomyelitis.
• It can last for years.
• Hallmark is the presence of a sequestrum (separated piece of bone) and an involucrum (new bone formation around dead bone).
• Initial infection leads to subperiosteal abscess formation.

Chronic Osteomyelitis - Diagnosis

• X-ray, bone scan, sinograms, and wound cultures and sensitivities aid in diagnosing chronic osteomyelitis.

Chronic Osteomyelitis - Treatment

• Antimicrobials, surgical removal of sequestra, and long-term antibiotics are common treatments.
• Immobilization is often necessary.

Direct Osteomyelitis - Trauma/Fracture

• Bacteria directly enter open fractures or wounds.
• Inflammation caused by trauma devitalizes bone tissue which creates an effective environment for bacteria to proliferate.

Direct Osteomyelitis - Manifestations

• Recurrent fever.
• Increased pain at the trauma/operative site.
• Poor incisional healing.
• Wound drainage.
• Wound separation.

Direct Osteomyelitis - Treatment

• Antibiotics (but may not be effective in all cases)
• Surgical management, including decompression, to relieve pressure and remove drainage.

Growing Bones - Review

• Osteoblasts form new bone tissue.
• Osteoclasts break down calcium and phosphorus through resorption.
• Osteocytes maintain bone as living tissue.
• Osteopenia is decreased bone density.

Osteoporosis

• Decreased bone mass leading to a chronic, progressive metabolic disease.
• Porous bones increase risk of fractures.
• There is an imbalance between bone resorption and bone formation.
• Conditions associated with osteoporosis include:
  • Estrogen deficiency (common in elderly women)
  • Senile osteoporosis (common in elderly)
  • Elevated cortisol (Cushing's syndrome)
  • Chronic diseases (like kidney failure).
  • Prolonged immobilization
  • Poor diet

Osteoporosis - Clinical Features

• Changes in the diaphysis and metaphysis of bones.
• Loss of trabeculae (thin, boney structures).
• Increased osteoclast activity.
• Thinned trabeculae lead to microfractures and vertebral collapse.
• Haversian systems enlarge.
• This leads to fractures.

Osteoporosis - Manifestations

• Compression of vertebrae.
• Fractures (often with no preceding symptoms).
• Development of kyphosis ("dowager's hump").
• Decrease in height and back pain.

Osteoporosis - Diagnosis

• Bone mass density (BMD) assessment (DEXA scan is a type).
• Screening is critical to diagnosis.
• BMD is determined by:
  • Genetic factors.
  • Sex.
  • Hormone levels.
  • Exercise.
  • Calcium intake.
  • Age.

Osteoporosis - Treatment

• Prevention is key:
  • Increased Vitamin D and Calcium intake.
  • Weight-bearing exercises.
• Medications can help:
  • Bi-phosphonates
  • Selective estrogen receptor modulators
  • Calcitonin
  • Recombinant PTH.

This quiz provides an in-depth look at osteomyelitis, focusing on its causes, specifically hematogenous osteomyelitis, and its clinical features. Learn about the pathways of infection, predisposing factors, and key characteristics associated with bone infections. Test your knowledge on this critical topic in infectious disease.