Osteomyelitis

Background

Osteomyelitis is an infection of the bone. Bacterial causes are the most common and may arise from a variety of sources. There are many conditions, such as a fracture, which may lead to this disease. In addition, depending upon the duration, there are both subacute and chronic forms of the disease.

DISEASE ASSOCIATIONS CHARACTERIZATION

Sickle cell disease Salmonella is a common accompanying infection

Fractures Usually <20 years of age of patient
Usually lower extremity in 75% of cases

Hematogenous

PATHOGENESIS CHARACTERIZATION

Bacteria 70-90% due to coagulase positve staphylococci

Additional organisms include:
Klebsiella
Aerobacter
Proteus
Pseudomonas
Streptococcus
Pneumococcus
Gonococcus
Meningococcus
Brucella
Salmonella

Sequence Dependent upon the age of the patient, bone, and virulence of organism

<1 year of age Permanent epiphyseal damage and joint infection may result in little damage to the metaphysis or diaphysis

Children > 1 year Cortical metaphyseal involvement is extensive but permanent damage to cartilage and joints is rare

Infection speads from the center of the metaphysis through the cortex via vessels of Volkmann's canals and spreads along the medullary canal to the rest of the bone

Pus may accumulate beneath periosteum leading to perforation

Sequestrum Dead bone

Involucrum New bone laid down by the cambium layer of the periosteum

LABORATORY/RADIOLOGY CHARACTERIZATION

Acute hematogenous osteomyelitis of children: assessment of skeletal scintigraphy-based diagnosis in the era of MRI.

Connolly LP, Connolly SA, Drubach LA, Jaramillo D, Treves ST.

Department of Radiology, Children's Hospital, Boston, Massachusetts 02115, USA.
J Nucl Med 2002 Oct;43(10):1310-6 Abstract quote
The emergence of MRI has challenged the long-standing primacy of skeletal scintigraphy in pediatric cases of suspected acute hematogenous osteomyelitis (AHO) with nondiagnostic radiographs. This study evaluated a strategy in which skeletal scintigraphy is the primary and MRI a supplemental test.

METHODS: We reviewed the records of 213 children (age range, 8 mo-18 y; mean age, 67 mo) with musculoskeletal symptoms and nondiagnostic radiographs who were referred for skeletal scintigraphy because of the possibility of AHO. MRI was performed when diagnostic uncertainty persisted after skeletal scintigraphy or when abscess was suspected.

RESULTS: Diagnosis was made using skeletal scintigraphy without referral for MRI in 179 (84%) of the children, including 79 (92%) of 86 with a final diagnosis of AHO. In no instance was the diagnosis of AHO indicated only by MRI. Treatment and diagnosis were accomplished without referral for MRI in 146 (69%) of all cases and 46 (53%) of the AHO cases. Abscesses that required drainage were found in 3 (6%) of 48 cases of major-long-bone AHO. Each of these 3 had exhibited a slow therapeutic response before MRI. Drainable abscesses were found in 5 (20%) of 25 cases affecting the pelvis, which was the other preponderant location of AHO. These were found with pelvic foci both when MRI was performed at diagnosis and when MRI was performed during treatment.

CONCLUSION: An imaging strategy in which skeletal scintigraphy is the first test used when AHO is suspected but radiographs are negative remains highly effective. This approach can be most strongly advocated when symptoms are poorly localized or are localized to major long bones. MRI should be performed after skeletal scintigraphy shows major-long-bone AHO if treatment response is slow. Skeletal scintigraphy is also an appropriate first test for suspected radiographically occult pelvic AHO. Because of the association of abscesses with pelvic AHO, however, the use of MRI should be strongly considered after pelvic AHO is detected, and MRI might be substituted diagnostically for skeletal scintigraphy when symptoms are well localized to the pelvis.

GROSS APPEARANCE/CLINICAL VARIANTS CHARACTERIZATION

General

Chronic osteomyelitis Persists as long as infected dead bone persists, surrounded by granulation tissue

VARIANTS

CHRONIC RECURRENT MULTIFOCAL OSTEOMYELITIS

Chronic recurrent multifocal osteomyelitis in children: diagnostic value of histopathology and microbial testing.

Girschick HJ, Huppertz HI, Harmsen D, Krauspe R, Muller-Hermelink HK, Papadopoulos T.

Universitats-Kinderklinik und Poliklinik, the Institut fur Hygiene und Mikrobiologie, Universitat Wurzburg, Germany.

Hum Pathol 1999 Jan;30(1):59-65 Abstract quote

Chronic recurrent, unifocal or multifocal osteomyelitis (CRMO), an inflammatory disorder of unknown origin, involves different osseous sites and may be associated with palmoplantar pustulosis. Bacterial cultures of affected tissue were reported negative in nearly all cases. Radiological and magnetic resonance imaging features of CRMO have been described, but differential diagnosis remains difficult, including rheumatic diseases, bacterial osteomyelitis, and malignancy.

Although definite diagnosis relies on histopathologic confirmation by biopsy, histopathologic criteria have not been defined. Because CRMO may be treated with nonsteroidal antiinflammatory drugs, but not antibiotics, distinguishing CRMO from bacterial osteomyelitis is of major importance.

Histopathologic analysis of 12 patients with CRMO indicated a wide variation of reparative changes of bone, but chronic inflammation could not be found at all sites in the same biopsy. The inflammatory infiltrate was mostly scattered, consisting mainly of lymphocytes, plasma cells, histiocytes, and also few neutrophil granulocytes. Immunohistochemistry showed a predominance of CD3(+), CD45RO(+) T-cells, which were mainly CD8(+). In addition, CD20(+) B cells and CD68(+) macrophages were abundant in each biopsy specimen. Mild lymphocytic and granulocytic infiltrates were also detected in three synovial biopsy specimens obtained from adjacent joints. All bacterial and fungal cultures from native biopsy tissues were negative. Amplification of partial-length 16S ribosomal DNA by polymerase chain reaction (PCR) using broad-range eubacterial primers was below the detection limit in all patients.

Because histopathologic features alone may not provide conclusive evidence, CRMO should be included in the differential diagnosis of chronic inflammatory bone lesions in children, and the definite diagnosis should be made by the clinical picture, x-ray studies, bone scan, bacterial culture, and histopathologic analysis in a multidisciplinary approach.

Garre's osteomyelitis (Sclerosing osteomyelitis, periostitis ossificans) Extensive regenerative bony changes, common in the jawbone

Osteomyelitic sinuses
May be lined by epithelium extending deeply into the bone and continuous with the skin surface

These may develop into squamous cell carcinomas with onset of pain and discharge

HISTOLOGICAL TYPES CHARACTERIZATION

General Fibrosis, bone necrosis, and new bone formation surrounded by an admixture of inflammatory cells

VARIANTS

Plasma cell osteomyelitis Predominance of plasma cells

Xanthogranulomatous Abundant foamy macrophages

Tuberculous Usually hematogenous infection in young adults and children

Fungal

Tertiary syphilis

Malakoplakia

N Engl J Med 1980;300:360-370
Am J Surg Pathol 1985;9:531-537

Commonly Used Terms

Bone and Joints

Last Updated 11/21/2001

DISEASE ASSOCIATIONS	CHARACTERIZATION
Sickle cell disease	Salmonella is a common accompanying infection
Fractures	Usually <20 years of age of patient Usually lower extremity in 75% of cases
Hematogenous

PATHOGENESIS	CHARACTERIZATION
Bacteria	70-90% due to coagulase positve staphylococci
	Additional organisms include: Klebsiella Aerobacter Proteus Pseudomonas Streptococcus Pneumococcus Gonococcus Meningococcus Brucella Salmonella
Sequence	Dependent upon the age of the patient, bone, and virulence of organism
<1 year of age	Permanent epiphyseal damage and joint infection may result in little damage to the metaphysis or diaphysis
Children > 1 year	Cortical metaphyseal involvement is extensive but permanent damage to cartilage and joints is rare
	Infection speads from the center of the metaphysis through the cortex via vessels of Volkmann's canals and spreads along the medullary canal to the rest of the bone Pus may accumulate beneath periosteum leading to perforation
Sequestrum	Dead bone
Involucrum	New bone laid down by the cambium layer of the periosteum

GROSS APPEARANCE/CLINICAL VARIANTS	CHARACTERIZATION
General
Chronic osteomyelitis	Persists as long as infected dead bone persists, surrounded by granulation tissue
VARIANTS
CHRONIC RECURRENT MULTIFOCAL OSTEOMYELITIS
Chronic recurrent multifocal osteomyelitis in children: diagnostic value of histopathology and microbial testing. Girschick HJ, Huppertz HI, Harmsen D, Krauspe R, Muller-Hermelink HK, Papadopoulos T. Universitats-Kinderklinik und Poliklinik, the Institut fur Hygiene und Mikrobiologie, Universitat Wurzburg, Germany.	Hum Pathol 1999 Jan;30(1):59-65 Abstract quote Chronic recurrent, unifocal or multifocal osteomyelitis (CRMO), an inflammatory disorder of unknown origin, involves different osseous sites and may be associated with palmoplantar pustulosis. Bacterial cultures of affected tissue were reported negative in nearly all cases. Radiological and magnetic resonance imaging features of CRMO have been described, but differential diagnosis remains difficult, including rheumatic diseases, bacterial osteomyelitis, and malignancy. Although definite diagnosis relies on histopathologic confirmation by biopsy, histopathologic criteria have not been defined. Because CRMO may be treated with nonsteroidal antiinflammatory drugs, but not antibiotics, distinguishing CRMO from bacterial osteomyelitis is of major importance. Histopathologic analysis of 12 patients with CRMO indicated a wide variation of reparative changes of bone, but chronic inflammation could not be found at all sites in the same biopsy. The inflammatory infiltrate was mostly scattered, consisting mainly of lymphocytes, plasma cells, histiocytes, and also few neutrophil granulocytes. Immunohistochemistry showed a predominance of CD3(+), CD45RO(+) T-cells, which were mainly CD8(+). In addition, CD20(+) B cells and CD68(+) macrophages were abundant in each biopsy specimen. Mild lymphocytic and granulocytic infiltrates were also detected in three synovial biopsy specimens obtained from adjacent joints. All bacterial and fungal cultures from native biopsy tissues were negative. Amplification of partial-length 16S ribosomal DNA by polymerase chain reaction (PCR) using broad-range eubacterial primers was below the detection limit in all patients. Because histopathologic features alone may not provide conclusive evidence, CRMO should be included in the differential diagnosis of chronic inflammatory bone lesions in children, and the definite diagnosis should be made by the clinical picture, x-ray studies, bone scan, bacterial culture, and histopathologic analysis in a multidisciplinary approach.
Garre's osteomyelitis (Sclerosing osteomyelitis, periostitis ossificans)	Extensive regenerative bony changes, common in the jawbone
Osteomyelitic sinuses	May be lined by epithelium extending deeply into the bone and continuous with the skin surface These may develop into squamous cell carcinomas with onset of pain and discharge

HISTOLOGICAL TYPES	CHARACTERIZATION
General	Fibrosis, bone necrosis, and new bone formation surrounded by an admixture of inflammatory cells
VARIANTS
Plasma cell osteomyelitis	Predominance of plasma cells
Xanthogranulomatous	Abundant foamy macrophages
Tuberculous	Usually hematogenous infection in young adults and children
Fungal
Tertiary syphilis
Malakoplakia