Ovid: 5-Minute Sports Medicine Consult, The

Alex B. Diamond
  • Inflammatory process of bone and its components secondary to infection by pyogenic organism
  • Categorized as acute, subacute, or chronic
  • Other classification systems have emerged:
    • Waldvogel: Hematogenous, contiguous, or chronic
    • Cierny-Mader: Based on dynamic status of disease process
  • Acute osteomyelitis develops within 2 wks of disease onset:
    • Predominantly in children
    • Typically the result of hematogenous dissemination
    • Metaphysis of long bones the most commonly involved location
  • Subacute osteomyelitis presents within 1 to several months of disease onset
    • Diagnosis difficult, as characteristic signs and symptoms of acute form absent
    • Brodie abscess most common type of subacute form:
      • Cavitary lesion in epiphysis or metaphysis characterized by small, localized lucency surrounded by reactive, dense-appearing bone
    • Subacute form represents favorable host-pathogen response, as dependent on balanced interplay between infecting bacteria and host immune mechanisms
    • Subacute form mimics various other conditions, which results in delayed diagnosis and treatment:
      • Most frequent incorrect diagnosis is that of tumor, either benign or malignant
  • Chronic osteomyelitis develops after few months of disease onset:
    • May be recurrent or intermittent in presentation
    • Direct contamination frequent cause of chronic form (open fracture, penetrating wound, surgical manipulation)
    • Simultaneous presence of microorganisms and necrotic bone (sequestra) is hallmark
  • Overall prevalence in children is 1 per 5,000
  • Overall incidence higher in developing countries
  • Most prevalent type is result of injury (associated with open fracture, surgical reconstruction of bone)
  • Males: Females = 2:1; no association with race
  • Special populations:
    • Annual incidence in sickle cell patients is 0.36%.
    • Prevalence after foot puncture in diabetic patients is 30–40%.
  • Incidence of subacute osteomyelitis has increased since use of antibiotics:
    • Most common form in East Africa
  • Long-term recurrence rate of chronic osteomyelitis is 20–30%.
  • Secondary hematogenous infections more common in adults:
    • Represent reactivation of quiescent focus of primary hematogenous osteomyelitis from childhood
  • Deep musculoskeletal infection incidence from open fracture as high as 23%
  • Spine becomes most common site of infection in patients >45 yrs old
  • Culture more likely positive if history of trauma, shorter duration of symptoms, higher WBC count and erythema, swelling or cellulitis overlying infected bone
  • Morbidity significant:
    • Pain, disability, amputation, extension of infection and sepsis
    • 10–15% with vertebral osteomyelitis develop neurologic symptoms or spinal cord compression
    • 30% of pediatric cases may develop deep vein thrombosis.
  • Mortality low unless associated sepsis
Risk Factors
  • Open or compound fracture
  • Surgical manipulation (orthopedic, colorectal, genitourinary procedures)
  • IV drug abuse
  • Immunosuppression (AIDS, chronic steroid use)
  • Peripheral vascular disease (diabetes mellitus)
  • Sickle cell disease
  • Genitourinary or biliary tract infection
  • Chronic joint disease
  • Presence of prosthetic orthopedic device
  • Low socioeconomic status
  • Infancy
  • Elderly
  • Alcoholism
  • History of tuberculosis (Pott disease)
General Prevention
  • Timely diagnosis and treatment of primary infections to avoid seeding of bone
  • Appropriate wound management and possible use of prophylactic antibiotics with injury or manipulative surgery
  • Normal bone highly resistant to infection unless result of very large inocula, trauma, or presence of foreign bodies
  • Microorganisms adhere to bone/devices; survive intracellularly in osteoblasts; express resistance to antimicrobial treatment (high failure rate of short courses of therapy); form inflammatory markers (potent osteolytic factors) and phagocytes (generate toxic oxygen radicals and release enzymes that lyse surrounding tissues); pus develops and spreads into vascular channels increasing intraosseous pressure and impairing blood flow; ischemic necrosis of bone
  • Infectious agents include bacteria, mycobacteria, and fungi.
  • Routes of infection include hematogenous, contiguous focus, and direct inoculation.
  • Primary hematogenous osteomyelitis occurs mainly in infants and children:
    • Sluggish circulation at highly vascular metaphyseal-physeal barrier predisposes vessels to thrombosis and bone to localized necrosis and bacterial seeding.
    • Metaphyseal arteries lack phagocytic lining cells and sinusoidal veins (in growth plate) contain functionally inactive phagocytic cells.
    • Usually monomicrobial
  • Manifestations more localized, but can involve multiple organisms when result of contiguous or direct inoculation
  • Subacute osteomyelitis occurs in much wider variety of bones:
    • Femur > tibia > remaining lower limb > upper limb
    • Metaphyseal-equivalent locations (pelvis, vertebrae, calcaneus, clavicle, talus)
  • Chronic osteomyelitis characterized by sequestrum of necrotic bone harboring bacteria
  • Capability to persist or recur, regardless of initial cause/mechanism and despite aggressive intervention
  • Pathogen isolated in 35–40% of cases
  • Fungal agent usually result of catheter-related complication, use of illicit drugs, or prolonged neutropenia
  • P.429

  • Bacterial agents:
    • Most common include Staphylococcus aureus, coag-negative staph and aerobic gram-negative bacilli; others include strep, enterococci, and anaerobes
    • Increasing MRSA
    • Age of patient and inoculation method important factor in species prevalence:
      • Hematogenous: Children and adolescents: S. aureus (80%), group A streptococcus species, H. influenzae. Adults: Staph, occasional Enterobacter or strep species
      • Direct or contiguous: Generally staph (75% of cultures), Enterobacter, pseudomonas
    • Puncture wound through sneaker typically staph, pseudomonas
    • Chronic osteomyelitis most likely S. epidermidis or S. aureus, pseudomonas, serratia, E. coli
    • Consider anaerobes if “fight bite” injury
    • Staph and salmonella predominate sickle cell disease
  • Children with acute hematogenous osteomyelitis may present with abrupt-onset high fever, chills, fatigue, irritability, lethargy, restricted motion and local pain, edema, erythema, and tenderness.
  • In a young child, inability to get to seated position, limp, and refusal to walk may be observed if the spine, pelvis, or lower extremity is involved; pseudoparalysis if upper extremity
  • 50% of children and most adults present with vague complaints, nonspecific pain of involved limb, and minimal if any temperature elevation or constitutional symptoms.
  • Limitation of joint motion usually present if primary lesions particularly close to joint spaces leading to sympathetic effusions
  • Osteomyelitis due to contiguous focus often presents with painful or unstable joint, little or no fever
  • Subacute osteomyelitis presents with mild pain, minimal fever, and few constitutional symptoms.
  • In chronic osteomyelitis, there is local bone loss, persistent drainage through fistulas or sinus tracts, nonhealing ulcers, recurrent pain, possibly low-grade fever, and mild systemic symptoms (ie, chronic fatigue).
  • An insidious onset with history of acute bacteremic episode, local tenderness, erythema, and edema is common in vertebral osteomyelitis.
Physical Exam
  • Fever (temperature >100.4°F), but not always present
  • Tenderness to palpation, swelling, erythema, warmth over involved area
  • Fluctuance
  • Decreased use of extremity, refusal to bear weight
  • Limited movement of adjacent joint
  • Other possible foci of infection
  • Sinus tract drainage
  • Passive range of motion tolerated, unlike septic arthritis
Diagnostic Tests & Interpretation
  • CBC may reveal elevated WBC or left shift, but frequently normal
  • C-reactive protein (CRP) and erythrocyte sedimentation rate almost always elevated, but nonspecific tests:
    • Changes in CRP detected sooner
  • Blood culture positive 50% of cases
  • Aspiration from affected site normal 25% of the time
  • Bone biopsy can be achieved by percutaneous needle, radiographic guided instruments, or open surgical procedure:
    • Send for Gram stain and culture (aerobic, anaerobic, mycobacterial, and fungal)
    • Obtain 2nd specimen for histopathology
  • In early disease, x-rays may be normal or show only soft tissue swelling.
  • Osseous changes usually appear 7–14 days after symptom onset; 90% with changes on x-ray by 28 days:
    • Include periosteal elevation and/or destruction of bone with radiolucency, fading cortical margins, and no surrounding reactive bone. Periosteal elevation followed by cortical or medullary lucencies.
  • In acute osteomyelitis in children, classic findings include deep, circumferential soft tissue swelling with obliteration of muscular planes.
  • In adults, plain radiographs are of less value because ∼50% of the bone matrix must be destroyed before lytic changes are visible.
  • Radioisotope bone scan (triple phase with technetium 99m) is highly sensitive and initial test of choice for early diagnosis of osteomyelitis, especially if x-ray studies are ambiguous (Termaat MF, et al. JBJS Am, 2005. LOE = III).
  • MRI effective in early detection and localization. Reported 90–100% sensitivity.
  • Consider MRI if bone scan is negative or when very minor destructive changes present. Spatial resolution of MRI makes it useful in differentiating between bone and soft tissue infection. Good for diagnosis and assessment of extension. IV contrast useful in differentiating vascularized and inflamed tissue from abscess.
  • CT scanning may play role in diagnosis and assisting the surgeon in operative planning. Most useful in evaluation of spinal vertebral lesions or other areas with complex anatomy (pelvis, sternum, calcaneous). May reveal small areas of osteolysis, gas, or foreign bodies.
  • US may show periosteal thickening and elevation, soft tissue abscess, or fluid collection. Provides direction for aspiration. May demonstrate changes earlier, but can't evaluate bone cortex.
Diagnostic Procedures/Surgery
Histopathologic and microbiologic exam of bone is gold standard:
  • Requires 2 of 4:
    • Purulent material on aspiration of affected bone
    • Positive findings of bone tissue or blood culture
    • Localized classic physical findings of bony tenderness, overlying soft tissue erythema, or edema
    • Positive radiological imaging study
Pathological Findings
  • Principal histiologic findings in acute osteomyelitis include microorganisms, infiltrations of neutrophils, and congested or thrombosed blood vessels
  • Distinguishing feature of chronic osteomyelitis is necrotic bone
Differential Diagnosis
  • Acute leukemia
  • Acute rheumatic fever
  • Rheumatoid arthritis (adult or juvenile)
  • Acute gout, pseudogout
  • Cellulitis
  • Malignant bone tumors (Ewing sarcoma, osteosarcoma)
  • Septic arthritis
  • Multiple myeloma (elderly)
  • Sepsis
  • Deep vein thrombosis, thrombophlebitis
  • Intervertebral disc disorders
  • Fracture
  • Aseptic bone infarction
  • Neuropathic joint disease
  • Transient synovitis



Ongoing Care
  • Protection of the joint with traction or splinting and starting protected motion early is a consideration.
  • Limitation of weight-bearing until x-ray evidence of defect's partial healing due to risk of collapse
  • Follow-up based on response to therapy and overall health of patient after completion of treatment regimen.
  • Should continue for at least 2 yrs in subacute cases:
    • Closely monitor at 1st for signs of response to treatment (clinical and laboratory).
    • Then ensure compliance with antibiotic therapy for 6 wks. Clinical response is usually within a few days of initiation of treatment.
    • For next 6 mos, monitor for signs of recurrence. Most recurrences occur within this time, but recurrence after up to 18 mos has been reported.
  • Radiologic healing is slower than clinical healing and usually occurs within 3–12 mos. Metaphyseal and epiphyseal cavities usually heal, leaving either a small area of sclerosis or a small, indistinct lucency in the cortex.
  • The purpose of follow-up after a year is for assessment of bone growth and alignment.
Variable, but markedly improved with timely diagnosis and aggressive treatment
  • 730.00 Acute osteomyelitis, site unspecified
  • 730.01 Acute osteomyelitis involving shoulder region
  • 730.02 Acute osteomyelitis involving upper arm

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