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THE KURSK STATE MEDICAL UNIVERSITY
DEPARTMENT OF SURGICAL DISEASES № 1
OSTEOMYELITIS
Information for self-training of English-speaking students
The chair of surgical diseases N 1 (Chair-head - prof. S.V.Ivanov)
BY ASS. PROFESSOR I.S. IVANOV
KURSK-2010
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INTRODUCTION
Osteomyelitis is a difficult-to-treat infection of bone and bone marrow. It is progressive
and results in inflammatory destruction of the bone, bone necrosis, and new bone
formation. Bacterial osteomyelitis causes substantial morbidity worldwide, despite
continued progress toward understanding its pathophysiology and optimal management.
The approach to osteomyelitis depends upon the route by which bacteria gained access to
bone, bacterial virulence, local and systemic host immune factors, and patient age. While
imaging studies and nonspecific blood tests may suggest the diagnosis, an invasive
technique is generally required to identify the causative pathogens. Antibacterial regimen
selection has been largely guided by knowledge of the relative activities and
pharmacokinetics of individual drugs, supported by data from animal models.
Definitive therapy often requires a combined medical and surgical approach. Newer
microvascular and distraction osteogenesis techniques and the use of laser Doppler allow
more complete surgical resection of infected material while maintaining function. Despite
recent advances, aggressive medical and surgical therapy fails in many patients with
osteomyelitis. More accurate diagnostic methods, better ways to assess and monitor the
effectiveness of therapy, and novel approaches to eradicate sequestered bacteria are
needed.
History of the Procedure: Osteomyelitis has been well known since antiquity.
Problem: Osteomyelitis results in inflammatory destruction of the bone, bone necrosis,
and new bone formation. Three major categories of osteomyelitis exist, based upon
pathogenic mechanisms of infection, as follows:
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Osteomyelitis following hematogenous spread of infection
Osteomyelitis secondary to a contiguous focus of infection
Osteomyelitis associated with vascular insufficiency
Three different subtypes of osteomyelitis are known: acute osteomyelitis, subacute
osteomyelitis, and chronic osteomyelitis.
Frequency: The overall prevalence of acute osteomyelitis is 2 cases per 10,000 children.
Neonatal prevalence is approximately 1 case per 1000 children. The annual incidence in
patients with sickle cell anemia is approximately 0.36%.
The prevalence of osteomyelitis after foot puncture may be as high as 16% (30-40% in
patients with diabetes).
Excluding the axial skeleton, lower extremity osteomyelitis accounts for 90% of
osteomyelitis cases and is much more common than upper extremity osteomyelitis, which
accounts for 10% of extremity cases.
The most common bones involved in osteomyelitis in descending order are as follows:
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Tibia (50%) Femur (30%) Fibula
Radius (2%)
(12%) Humerus (3%) Ulna (3%)
The prevalence of chronic osteomyelitis is 2 cases per 10,000 people.
Most studies support the idea that incidence is similar in developed countries. In
developing countries, incidence is higher due to higher incidence of puncture wounds,
contaminated injuries, and less wound care.
Epidemiology of vertebral osteomyelitis
It is primarily a disease of adults; most patients are older than 50 years. Generally, the
incidence increases progressively with each successive decade of life. Men are affected
approximately twice as often as women in most case series. The reason for this male
predominance is not clearly understood.
Reliable information regarding the overall incidence of vertebral osteomyelitis is difficult
to obtain. However, most authorities believe that the overall incidence of vertebral
osteomyelitis has steadily increased in recent years for 3 primary reasons: increasing rates
of nosocomial bacteremia due to intravascular devices and other forms of instrumentation,
increasing age of the population, and increasing injection drug use.
Etiology: While normal bone is resistant to infection, a number of conditions can
predispose one to development of osteomyelitis, including the following:
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Large inoculation of an organism
Trauma leading to bone damage or infarction
Presence of a foreign body
Illnesses compromising host defense
A single pathogenic organism is almost always recovered from the bone. The most
common bone isolates are Staphylococcus species, the most common gram-negative
organism is Pseudomonas aeruginosa, and the most common anaerobes are
Peptostreptococcus species. However, in immunocompromised patients, other organisms,
including fungi and mycobacteria, also must be considered.
Commonly isolated organisms in osteomyelitis can be summarized as follows:

Hematogenous osteomyelitis (monomicrobial infection)
o Infants (<1 y)
 Group B Streptococcus
 Staphylococcus aureus
 Escherichia coli
o Children (aged 1-16 y)
 S aureus
 Streptococcus pyogenes
 Haemophilus influenzae
o Adults (>16 y)
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S aureus
 Coagulase-negative Staphylococcus species
 Gram-negative bacilli
 P aeruginosa
 Serratia marcescens
 E coli
Contiguous focus osteomyelitis (polymicrobial infection)
o S aureus
o Coagulase-negative Staphylococcus species
o S pyogenes
o Enterococcus species
o Gram-negative bacilli
o Anaerobes
Diabetic foot osteomyelitis (polymicrobial Infection)
o S aureus
o Streptococcus species
o Enterococcus species
o Proteus mirabilis
o P aeruginosa
o Anaerobes
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Pathophysiology: The pathogenesis of osteomyelitis is multifactorial and poorly
understood. Some important factors include the following:
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Virulence determinants of the organisms
Underlying disease and the immune status of the host
Type and location of the bone
It is clear that bacterial cells adhere to nucleated cells, platelets, and a variety of
components of the extracellular bone matrix collagen and noncollagenous proteins.
Cellular and molecular pathogenesis
Cellular and molecular techniques provide new methods for determining the relative
importance of the many potential virulence factors by facilitating study of the interaction
between the host immune response and potential bacterial virulence factors. As an
example, S aureus, which is an important cause of both hematogenous and contiguous
focus osteomyelitis, produces a large number of extracellular and cell-associated factors
that may contribute to virulence, including the following:

Bacterial adherence: Bacteria adhere to bone by expressing receptors for the
components of bone matrix including fibronectin, laminin, collagen, and bone
sialoglycoprotein. Adherence appears to play a central role in the early stages of S
aureus–induced osteomyelitis or arthritis. Expression of adhesins permits attachment
of the pathogen to cartilage and synovial membrane. Strains positive for collagen
adhesin are also associated with the production of high levels of immunoglobulin G
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(IgG) and interleukin (IL)–6. Bone
infection has been speculated to be
possibly prevented by an adhesin-derived vaccine.
Proteolytic activity: Potential proteolytic activity present in normal joints is inhibited
in the absence of infection. However, this protective effect may be lost with
infection. In an in vitro model of adult chondrocytes inoculated with S aureus, for
example, overall protein synthesis was reduced by 84%, with an increase in the
release of collagenase and gelatinase.
Resistance to host defense mechanisms: The ability of microorganisms to resist host
defense mechanisms at both the cellular and matrix levels presents difficulties in the
treatment of osteomyelitis. S aureus can survive intracellularly in cultured
osteoblasts. Furthermore, the presence of arachidonic acid metabolites such as
prostaglandin E2, which is a strong osteoclast agonist, decreases the bacterial
inoculum needed to produce infection. Once the microorganisms adhere to bone,
they express phenotypic changes that make them resistant to antimicrobial treatment.
o S aureus organisms express a 42-kd protein, protein A, which is bound
covalently to the outer peptidoglycan layer of their cell walls. Protein A binds
to the Fc portion of IgG on polymorphonuclear leukocytes, interfering with
opsonization and phagocytosis of S aureus. This interference has been
demonstrated in vitro and in animal models of subcutaneous abscess and
peritonitis.
o S aureus also secretes 2 toxins: exotoxin and toxic shock syndrome toxin
(TSST)–1, which exert a profound effect on the immune system when
administered parenterally. The toxins act as superantigens and suppress
plasma cell differentiation. They also stimulate production of cytokines, such
as IL-1, interferon-gamma, and tumor necrosis factor-alpha. Animals infected
with strains of S aureus isogenic for TSST-1 developed frequent and severe
arthritis. Staphylococcal enterotoxin and TSST-1 subvert the cellular and
humoral immune system, which may determine whether a local infection is
eliminated or develops into osteomyelitis or septic arthritis.
Nitric oxide: The increased turnover of bone in osteomyelitis suggests that the
balance between bone formation and resorption is altered, an effect that may be
mediated by nitric oxide. Greatly increased levels of nitric oxide and bone resorption
have been recorded in the septic skeleton. This response may be driven by the
increased levels of cytokines, enterotoxin, and TSST-1, which may stimulate nitric
oxide production by endothelial, macrophage, and mesenchymal cells such as
osteoblasts. Thus, while low concentrations of nitric oxide are typically thought to
inhibit osteoclastic bone resorption, this response may be lost when cytokine and
nitric oxide levels increase greatly in skeletal inflammatory disease. Adjunctive local
treatment of osteomyelitis with nitric oxide synthetase inhibitors could be beneficial.
Routes of infection
As noted above, osteomyelitis develops via 3 major routes: hematogenous, contiguous
focus spread, and vascular insufficiency.
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Hematogenous
osteomyelitis:
Hematogenous
osteomyelitis
is
predominantly encountered in children; 85% of patients with hematogenous
osteomyelitis are younger than 17 years, accounting for 20% percent of the total
cases of osteomyelitis. In one study of 659 cases of S aureus osteomyelitis occurring
in Denmark from 1959-1988, the number of hematogenous osteomyelitis cases
declined, especially in children, and cases of vertebral osteomyelitis, more common
in adults, increased. In children, the bone infection usually affects the long bones,
while in adults, the lesion is usually located in the thoracic or lumbar vertebrae.
Contiguous focus osteomyelitis without generalized vascular insufficiency:
Osteomyelitis secondary to contiguous foci of infection accounts for at least one half
of all cases and has increased in incidence. The organisms may be directly
inoculated into the bone at the time of trauma, spread by nosocomial contamination
during perioperative or intraoperative procedures, or extend from an adjacent soft
tissue infection.
Contiguous focus osteomyelitis with generalized vascular insufficiency: The primary
cause of vascular insufficiency in patients with osteomyelitis is diabetes mellitus.
The small bones of the feet, talus, calcaneus and distal fibula, and tibia are
commonly involved. The patients in this group are aged 35-70 years. The infection
frequently is initiated by a portal of entry for organisms, such as infected nail beds,
cellulitis, or atrophic skin ulceration.
Diminished arterial blood supply has traditionally been considered to be the major
predisposing factor for contiguous focus osteomyelitis with generalized vascular
insufficiency in patients with diabetic foot. However, neuropathy now appears to be an
equally important factor. Identifiable neuropathy as a complication of diabetes mellitus is
present in approximately 80% of patients with foot disease. Neuropathy can cause foot
ulceration through 3 main mechanisms, as follows:
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Decreased sensation leads to mechanical or thermal injuries in the unaware patient
that can develop into skin ulcerations.
Motor neuropathy affecting the intrinsic muscles of the foot predisposes affected
persons to gait disturbances and foot deformities, such as hammertoe, clawtoe
deformity, and Charcot foot. These anatomic alterations can lead to a maldistribution
of weight and elevated focal pressure over the bony prominences. Subsequently, the
increase in pressure where the foot contacts the ground or rubs against shoes can
lead to skin ulceration.
Autonomic neuropathy interferes with sweating; the resultant dry, cracked skin
allows entry of microorganisms into the soft tissue.
A higher rate of nasal and skin colonization with S aureus, defects in host immunity, and
impaired wound healing are all important factors in diabetic foot infection. Superficial
fungal skin infections, which are common in patients with diabetes, also can facilitate
bacterial entry through macerated or broken skin.
Pathological differences based on age
Basic differences exist in the pathology of osteomyelitis in infants, children, and adults.
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In infants, small capillaries cross the epiphyseal growth plate and permit
extension of infection into the epiphysis and joint space. This is a newly well-understood
condition referred to as septic osteomyelitis in infants. The cortical bone of neonates and
infants is thin and loose, consisting predominantly of woven bone, which permits escape of
the pressure caused by infection but promotes rapid spread of the infection directly into the
subperiosteal region. A large sequestrum is not produced because extensive infarction of
the cortex does not occur; however, a large subperiosteal abscess can form.
In children older than 1 year, infection presumably starts in the metaphyseal sinusoidal
veins and is contained by the growth plate. The joint is spared unless the metaphysis is
intracapsular. The infection spreads laterally where it breaks through the cortex and lifts
the loose periosteum to form a subperiosteal abscess.
In adults, the growth plate has resorbed, and the infection may again extend to the joint
spaces, as in infants. In addition, the periosteum is firmly attached to the underlying bone;
as a result, subperiosteal abscess formation and intense periosteal proliferation are
observed less frequently. The infection can erode through the periosteum, forming a
draining sinus tract.
Clinical: The clinical presentation and location of osteomyelitis differ in infants, children,
and adults. In infants, medullary infection may spread to the epiphysis and joint surfaces
through capillaries that cross the growth plate. In contrast, in children older than 1 year, the
growth plate is avascular and infection is confined to the metaphysis and diaphysis. The
joint is spared unless the metaphysis is intracapsular. Thus, cortical perforation at the
proximal radius, humerus, or femur enables the infection to migrate to the elbow, shoulder,
or hip joint, respectively, regardless of the age of the patient.
Hematogenous osteomyelitis
In hematogenous osteomyelitis, local symptoms referable to bones are more frequently
absent in neonates than in children. In adults, soft tissue findings may be more prominent
than bony involvement.
In infants, local findings that may lead the clinician to suspect osteomyelitis are usually
absent in neonates. When they develop, local findings can include decreased motion of a
limb and edema (pseudoparalysis) and joint effusion adjacent to the bone infection (present
in 60-70% of cases).
Systemic symptoms are frequently present in S aureus osteomyelitis but may be absent
when other pathogens are involved.
Children with hematogenous osteomyelitis, in contrast with neonates, typically have the
following systemic symptoms:
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Abrupt fever
Irritability
Lethargy
Refusal to use the affected limb
Local signs of inflammation present for 3 weeks or less
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While this is the classic presentation, signs of systemic toxicity other than minimal
temperature elevation are absent in 50% of children with osteomyelitis.
In adults, acute clinical presentations of fever, chills, swelling, and erythema over the
involved bones are usually seen in acute hematogenous osteomyelitis.
Vertebral osteomyelitis is usually hematogenous in origin but may be secondary to trauma.
A preceding history of urinary tract infection or injection drug use often is present. Other
sources of infection include skin and soft tissue, respiratory tract, infected intravascular
device site, endocarditis, dental infection, or unknown sources.
The patient usually presents with vague symptoms and signs consisting of dull, constant
back pain and spasm of the paravertebral muscles. Localized pain and tenderness of the
involved bone segments is present in at least 90% of cases. The pain is usually insidious
and slowly progresses over 3 weeks to 3 months.
Contiguous focus osteomyelitis without vascular compromise
Common predisposing factors for contiguous focus osteomyelitis include surgical
reduction and internal fixation of a fracture, open fractures, and chronic soft tissue
infections. This form of osteomyelitis is biphasic in its age distribution. The infection
occurs in younger persons secondary to trauma and related surgery and in older adults from
decubitus ulcers.
The infection usually manifests within 1 month after inoculation of the organisms from
trauma, surgery, or a soft tissue infection. Affected patients typically present with lowgrade fever, pain, and drainage. Loss of bone stability, bone necrosis, and soft tissue
damage frequently occur, making this form of osteomyelitis difficult to treat.
Contiguous focus osteomyelitis with vascular compromise
Osteomyelitis in patients with vascular compromise, who are often diabetic, can be
difficult to diagnose. Patients can present with an apparently localized process including an
ingrown toenail, a perforating foot ulcer, cellulitis, or a deep space infection. Concurrent
peripheral neuropathy often alters the patient's perception of pain. Fever and systemic
toxicity are frequently absent.
Physical examination commonly reveals diminished dorsal pedis and posterior tibia pulses,
poor capillary refill, and decreased sensation.
Chronic osteomyelitis
No exact criteria exist for defining when acute osteomyelitis becomes chronic. Clinically,
the first bone infection is considered acute, and relapse of bone infection is labeled chronic.
However, this simplistic classification is clearly inadequate. The hallmark of chronic
osteomyelitis is the presence of dead bone (the sequestrum). Involucrum (reactive bony
encasement of the sequestrum), local bone loss, persistent drainage, and/or sinus tracts are
other common features of chronic disease.
The patient with chronic osteomyelitis commonly presents with chronic pain and sinus
formation with purulent drainage. Fever is usually low grade or absent. The chronic
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infection usually does not progress or does so slowly. If a sinus tract becomes
obstructed, the patient can present with a localized abscess, soft tissue infection, or both.
Prospects of halting the infection are reduced when the integrity of surrounding soft tissue
is poor or the bone is unstable due to an infected nonunion or an adjacent septic joint.
Squamous cell carcinoma at the site of tissue drainage and amyloidosis are rare
complications of chronic osteomyelitis.
Host factors
Systemic host factors affecting immune surveillance, metabolism, and vascularity include
the following:
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Diabetes mellitus
Renal, hepatic failure
Malnutrition
Chronic hypoxia
Immunosuppression
Immunodeficiency
Malignancy
Immune disease
Extremes of age
Local host factors affecting immune surveillance, metabolism, and vascularity include the
following:
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Major vessel compromise
Small and medium vessel disease
Extensive scarring
Arteritis
Radiation fibrosis
Chronic lymphedema
Tobacco abuse (>2 packs per day)
Neuropathy
Venous stasis
INDICATIONS
Successful management of osteomyelitis requires aggressive pursuit of the diagnosis and
early antimicrobial and surgical therapy. If acute osteomyelitis is not treated optimally, the
risk is high of developing chronic osteomyelitis, which is significantly less amenable to
treatment.
Staging and classification systems may be used in determining appropriate treatment for
osteomyelitis.
Surgical intervention is indicated in the following situations:
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The patient has not responded to
specific antimicrobial therapy within
48 hours.
Evidence exists of a persistent soft tissue abscess.
Concomitant joint infection is suspected or diagnosed.
In adults with hematogenous osteomyelitis, a thorough intramedullary reaming and
unroofing is usually performed with or without bone grafting. Soft tissues are
reapproximated, and the limb is protected by external means (brace or cast) until the
structural integrity of the bone is reestablished by normal remodeling
RELEVANT ANATOMY AND CONTRAINDICATIONS
Relevant Anatomy: In long bones such as the tibia and femur, the metaphysis is most
frequently involved, probably due to the anatomy of this region. The organization of blood
vessels feeding the metaphyseal region leads to a slowing of blood flow in this area, which
presumably allows bacteria to settle and initiate an inflammatory response. The nutrient
artery ends in the metaphyses as marrow capillaries that make sharp loops near the growth
plate and enter a system of large venous sinusoids where the blood flow becomes slow and
turbulent. These capillary loops are essentially the end-artery branches of the nutrient
artery.
The histology of the region may also contribute to the localization of infection. The
metaphyseal capillaries lack phagocytic lining cells, and the sinusoidal veins contain
functionally inactive phagocytic cells, both of which allow growth of microorganisms. In
addition, any form of end-capillary obstruction could produce an area of avascular
necrosis. Minor trauma probably predisposes the infant or child to infection by producing a
small hematoma, vascular obstruction, and subsequent bone necrosis, which leaves the
region susceptible to inoculation from a transient bacteremia.
Acute infection initially produces a local cellulitis, which results in a breakdown of
leukocytes, increased bone pressure, reduced pH, and decreased oxygen tension. The
cumulative effects of these physiologic factors further compromise the medullary
circulation and enhance the spread of infection. Infection may proceed laterally through the
haversian and Volkmann canal system, perforate the bony cortex, and lift the periosteum
from the surface of the bone. When this occurs in the presence of medullary extension, the
periosteal and endosteal circulations are compromised, capillaries are lost, and large
segments of cortical and cancellous (trabecular) bone die.
In infants, medullary infection may spread to the epiphysis and joint surfaces through
capillaries that cross the growth plate. In contrast, in children older than 1 year, the growth
plate is avascular and infection is confined to the metaphysis and diaphysis. The joint is
spared unless the metaphysis is intracapsular. Thus, cortical perforation at the proximal
radius, humerus, or femur enables the infection to migrate to the elbow, shoulder, or hip
joint, respectively, regardless of the age of the patient.
Contraindications: Contraindications to debridement of infected bone are limited and
include the following:
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In acute osteomyelitis in infants, the
infection usually responds well to
medical therapy alone. Surgery should be reserved for nonresponsive cases.
Suspicion of malignancy or presence of secondary bone infection with malignancy
should not be treated with debridement alone. Tumor workup and biopsy should be
performed first. If infection cannot be eradicated or tumor is not resectable,
amputation is indicated.
Massive debridement is not recommended in the presence of sickle cell disease;
usually a mixture of infection and avascular necrosis is present that may improve
after good reperfusion. Massive debridement may produce very large defects that
may not be easily amenable to reconstruction surgeries.
The use of a tourniquet is not recommended by many authors due to the acute
bacteremic phase after the tourniquet is released and toxemia.
Local anesthesia is generally ineffective and should be avoided due to the change in
the local Ph of the tissue that prevents the metabolism of the local anesthetics to the
active ingredients.
The general condition of the patient should not be considered a contraindication to urgent
surgery. Delaying surgery may lead to further deterioration.
WORKUP
Lab Studies:
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Routine laboratory test findings are usually nonspecific. These include CBC count,
erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), renal and hepatic
profile, and bone profile.
o
Complete blood count: Leukocytosis is common in acute osteomyelitis but not
in chronic osteomyelitis.
o
Erythrocyte sedimentation rate
 The ESR is usually elevated but may be in the reference range. In a
patient with a high ESR initially, monitoring the ESR may be useful in
detecting a relapse. In patients with a foot ulcer and diabetes mellitus,
an ESR greater than 100 mm/h is highly specific but insensitive for a
diagnosis of osteomyelitis.
 Although ESR is associated with low sensitivity and specificity, it is
widely employed. In the patient without a prior history of osteomyelitis,
the ESR is most helpful when infection is unlikely. For example, in
patients with low-back pain but without historical clues to suggest
vertebral osteomyelitis (eg, recent urinary tract infection), a normal
ESR is a reassuring finding. Conversely, an elevated ESR suggests the
need for further evaluation.
C-reactive protein
 CRP, like ESR, is an acute-phase reactant. Although said to be more
specific for infection than ESR, it is also relatively insensitive and
nonspecific.
o
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o
The primary difference
between these tests is
that the CRP has a shorter half-life than the ESR. Measuring in vitro
clumping of venous leukocytes (leukergy) may more closely correlate
with severity of infection than the ESR.
Renal and hepatic profile: Whether leukergy, which reflects altered surface
expression of leukocyte adhesion molecules, will be useful for managing
osteomyelitis is not known. This test is not routinely available.
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Efforts have been made to develop serologic assays to diagnose osteomyelitis caused
by S aureus. Patients with osteomyelitis mount a vigorous antibody response, but the
utility of detecting antibodies to cell wall components such as peptidoglycan or
teichoic acid has been limited by the presence of such antibodies in uninfected,
healthy persons. In a preliminary study, serum antibodies to S aureus exoproteins
differentiated 3 cases of S aureus osteomyelitis from 4 cases caused by other
organisms. Another limitation of serology is that it is unlikely to be developed for
nonstaphylococcal disease. However, highly specific assays for staphylococcal
osteomyelitis would be very useful. At present, serology cannot be recommended
clinically, and such tests are available only for research purposes.
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Blood culture results are positive in 50% percent of cases of acute osteomyelitis. A
positive blood culture result in a patient with radiological findings consistent with
osteomyelitis obviates the need for biopsy to obtain the specific microbiologic
diagnosis.
Imaging Studies:

Plain films: Plain radiographs are relatively inexpensive, may be used to make the
diagnosis, help in interpreting and choosing other studies, and allow one to exclude
other conditions (eg, gas in the soft tissues). In uncomplicated acute infection, the
triad of soft tissue swelling, bone destruction, and periosteal reaction is fairly
specific for osteomyelitis and is sufficient to warrant a course of therapy (empiric
until the microbiologic diagnosis has been established).
o
Plain films are generally insensitive for the diagnosis of acute osteomyelitis.
This is in part due to the 2-3 weeks required for bone changes to be evident on
plain films, although changes may be seen at this time on the other imaging
modalities. Furthermore, in complicated situations, bone changes may not be
distinguishable from those due to another process, such as a Charcot joint,
fractures, or cancer. Thus, the diagnosis of acute osteomyelitis cannot be
excluded if the plain film findings are negative. Further testing should be
performed because early therapy is essential to reduce the formation of
necrotic bone and the development of chronic osteomyelitis.
o
The primary findings are different in chronic osteomyelitis, which is
characterized by bone sclerosis, periosteal new bone formation, and sequestra.
It is difficult to distinguish active from inactive infection.
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CT scan: This modality is used to
evaluate an area in which focal
findings are present on examination and plain films findings are negative. The CT
scan (with and without contrast) is very accurate for detecting cortical destruction,
intraosseous gas, periosteal reaction, and soft tissue extension.
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MRI: This study is an alternative to CT scan and is especially useful in evaluating a
patient for osteomyelitis in the vertebrae and in the infected foot. In vertebral
osteomyelitis, findings on T1-weighted images include decreased signal intensity in
the disk and adjacent vertebral bodies and loss of endplate definition. Findings on
T2-weighted images include increased signal intensity in the disk and adjacent
vertebral bodies. With gadolinium, there is enhancement of the disk, adjacent
vertebral bodies, and involved paraspinal and epidural soft tissue.
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o
MRI provides useful anatomic detail in planning for surgical debridement,
since it may show abscesses that need drainage, and can reduce the risk of
operating on bland cellulitis. MRI can also be used to delineate soft
tissue/epidural involvement and spinal cord impingement that cannot be seen
on nuclear medicine images.
o
When evaluating the foot for osteomyelitis, MRI is as specific or more
specific and more sensitive than technetium bone scan. In one series in which
bone biopsy was used as the criterion standard, the sensitivity was 72% for
MRI, 68% for bone scan, and 45% for indium white blood cell scan.
o
MRI cannot be used in patients with certain metal implants. In addition, falsepositive results can occur with bone infarct or fracture or in healed
osteomyelitis. Differentiating cancer from osteomyelitis may be difficult with
MRI.
o
MRI for diabetic foot ulcers
 The diagnosis of osteomyelitis in diabetic foot ulcers is often missed
because of 2 major factors: most cases occur in ulcers not exposing
bone and most have no evidence of inflammation on physical
examination. In comparison, osteomyelitis was present in all patients in
whom bone was exposed in one series.
 MRI is the imaging procedure of choice for osteomyelitis in diabetic
foot ulcers, being more accurate than the other modalities (95% vs 5070% for plain films, bone scan, and indium scan in one series). Two
clinical factors also may be useful in these patients, probing the ulcer
and ulcer size).
Ultrasonography: Ultrasound findings consistent with osteomyelitis include fluid
collection adjacent to the bone without intervening soft tissue, elevation of the
periosteum by more than 2 mm, and thickening of the periosteum. Ultrasound may
also improve the yield from fine-needle biopsies.
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Scintigraphy:
Multiple
different
nuclear medicine imaging procedures
are available to evaluate for osteomyelitis, including bone scan, indium-labeled
leukocyte scan, and bone marrow scan.
o
Three-phase bone scan
 The 3-phase bone scan uses technetium Tc 99m bound to phosphorus as
the tracer, which accumulates in areas of increased osteoblast activity
(reactive new bone formation and increased blood flow). The images
obtained are immediate (flow), 15 minute (blood pooling), and 4 hour
(bone imaging). The scan findings are different in cellulitis and
osteomyelitis. Cellulitis results in increased activity in the first 2 phases
and normal or diffusely increased activity in the third phase. In
comparison, osteomyelitis results in intense uptake in all 3 phases.
 The 3-phase technetium bone scan is the test of choice in evaluating for
acute osteomyelitis if the plain film findings are normal. In this
situation, it has an estimated sensitivity and specificity of almost 95%
and findings generally are positive in 2-3 days of infection. However,
any process that results in increased bone turnover appears as a hot spot
that is indistinguishable from osteomyelitis. These false-positive
findings can occur with posttraumatic injury, following surgery,
diabetic feet, septic arthritis, noninfectious inflammatory bone disease,
cancer, healed osteomyelitis, and Paget disease.
o
Indium-labeled leukocyte scan: Indium-labeled leukocyte scanning uses white
blood cells labeled with radioactive indium as the tracer. It accumulates at
sites of inflammation or infection and in the bone marrow. It is not specific for
bone. Since it accumulates in marrow, it is less sensitive for imaging those
areas with red marrow (eg, the axial skeleton). The indium scan can also be
used for the diagnosis of osteomyelitis at sites of fracture nonunion. Two
prospective studies found a sensitivity and specificity of 91% and 97%,
respectively, in this setting. Indium scans have better sensitivity and
specificity than bone scans in diabetic feet, but the specificity is poor,
especially in the hindfoot.
o
Bone marrow scan: The bone marrow scan uses technetium Tc 99m–labeled
sulfur colloid as the tracer. It is taken up by the reticuloendothelial system,
including the bone marrow, spleen, and liver. It allows one to image the
marrow instead of the bone. Its main use is in conjunction with the indiumtagged white blood cell scan to evaluate for suspected osteomyelitis in the
axial skeleton, where the presence of marrow decreases the accuracy of the
indium scan.
o
Gallium citrate scanning: Gallium citrate scanning uses radioactive gallium
citrate as the tracer. It acts as an analog of calcium and iron and attaches to
transferrin to accumulate at sites of inflammation. Gallium imaging is the
most sensitive and specific radionuclide scanning technique for vertebral
15
osteomyelitis.
A
typical
positive test result reveals
intense uptake in 2 adjacent vertebrae with loss of the intervening disk space.
In one study of 41 patients with suspected vertebral osteomyelitis, increased
gallium uptake was detected in all of the 39 patients with biopsy-proven
osteomyelitis.
o
Dual tracer scans: Dual tracer examinations combine an inflammation
imaging tracer (indium or gallium) with an "anatomic" tracer (either
technetium bone scan or technetium sulfur colloid marrow scan), with images
being collected either sequentially or simultaneously. Sequential studies
combine the sensitivity of the bone scan (if findings are negative, no further
imaging is done) with the specificity of the indium scan. Simultaneous studies
combine the sensitivity and specificity of the indium scan and the bone scan to
provide the anatomic detail needed to localize the infection to bone or soft
tissue.
o
Other: Radiolabeled antigranulocyte antibodies are being investigated in an
attempt to find a more accurate tracer for localizing infection.
Other Tests:

Extended field of view ultrasound in musculoskeletal disorders: With the advent of
high-resolution linear array transducers (7.5 MHz and 10 MHz), interest in
musculoskeletal ultrasonography has continued to develop. Ultrasonography has
been applied in the evaluation of infectious processes such as osteomyelitis,
cellulitis, and subcutaneous abscesses. Extended field of view ultrasonography
combines the convenience of a real-time scanner with the spatial advantages of a
static B-mode scanner. Detailed examination of surfaces of cortical bone and
cartilage has application in the evaluation of rheumatologic diseases for periarticular
erosions, trauma for radiographically occult fractures, congenital hip dysplasia, and
early osteomyelitis.
Diagnostic Procedures:

Bone biopsy: The criterion standard for the diagnosis of osteomyelitis is open bone
biopsy with histopathologic examination and cultures. Histopathologic features
indicating osteomyelitis include necrotic bone with extensive resorption adjacent to
an inflammatory exudate. Needle biopsy is commonly used to obtain bone for
histopathologic analysis. However, the incidence of sampling error is not negligible,
with the sensitivity and specificity of this technique being 87% and 93%,
respectively. Sensitivity of needle biopsy is particularly low in the postoperative or
post-trauma patient.
o
If the clinical suspicion is strong and blood culture results and the needle
biopsy findings are negative, the needle biopsy should be repeated or an open
biopsy should be performed. In patients with compromised vasculature, a
16
bone sample can be obtained at
histopathologic diagnosis of osteomyelitis.
o

debridement
for
the
Accurate cultures can be obtained only if the bone biopsy is performed
through uninvolved tissue. In addition, cultures of the sinus tract are useful if
S aureus and possibly Salmonella species are cultured. The presence of other
common organisms does not predict those that will be found on bone biopsy.
Probing a diabetic foot ulcer
o
In a recent report, the detection of bone when a diabetic foot ulcer was probed
with a sterile probe was highly accurate in ruling in osteomyelitis. Seventyfive patients with 76 ulcers were studied, with the criterion standard for the
diagnosis of osteomyelitis being histopathologic examination of bone resected
at debridement. Contiguous osteomyelitis was present in 50 of the 76 ulcers.
Of these, bone was palpable by probe in 33. The sensitivity and specificity
were 66% and 85%, respectively, giving a positive predictive value of 89%
and a negative predictive value of 56% in this population. These patients had a
very high rate of osteomyelitis (61%); thus, the high positive predictive value
is not likely to be applicable to ulcers with a lower risk of complicating
osteomyelitis.
o
The size of a diabetic foot ulcer also may be helpful. In one series,
osteomyelitis was present in 94% of ulcers greater than 2 cm2 in area. Thus, in
a diabetic patient with a foot ulcer, either probing of bone or ulcer area above
2 cm2 is associated with about a 90% probability of having underlying
osteomyelitis. Further noninvasive testing is unlikely to improve the accuracy
of diagnosis.
Histologic Findings: Acute osteomyelitis presents as a suppurative infection with acute
inflammatory cells, accompanied by edema, vascular congestion, and small vessel
thrombosis. In early acute disease, the vascular supply to the bone is compromised by
infection extending into the surrounding soft tissue. When both the medullary and
periosteal blood supplies are compromised, large areas of dead bone (sequestra) may be
formed. Within this necrotic and ischemic tissue, the bacteria can be difficult to eradicate
even after an intense host response, antibiotic therapy, or both.
Pathologic features of chronic osteomyelitis include necrotic bone, the formation of new
bone, and polymorphonuclear leukocyte exudation joined by large numbers of
lymphocytes, histiocytes, and occasional plasma cells.
Host defense and mesenchymal cells, mainly the polymorphonuclear leukocytes,
macrophages, and the osteoclasts, release proteolytic enzymes that break down organic
elements in the dead bone. Because of lost blood supply, dead bone appears whiter than
living bone. Cancellous bone is absorbed rapidly and may be completely sequestrated or
destroyed in 2-3 weeks, but necrotic cortex may require 2 weeks to 6 months for
17
separation. After complete separation, the dead bone is slowly eroded by granulation
tissue and absorbed.
New bone formation is another characteristic feature of osteomyelitis. New bone forms
from the surviving fragments of periosteum, endosteum, and the cortex in the region of the
infection and is produced by a vascular reaction to the infection. New bone may be formed
along the intact periosteal and endosteal surfaces and may arise when the periosteum forms
an encasing sheath of live bone (involucrum) surrounding the dead bone. Involucrum is
irregular and is often perforated by openings through which pus may track into the
surrounding soft tissues and eventually to the skin surfaces through a sinus tract. The
involucrum can gradually increase in density and thickness to form part or all of a new
shaft.
New bone increases in amount and density for weeks or months according to the size of the
bone and the extent and duration of infection. Endosteal new bone may proliferate and
obstruct the medullary canal. After host defense, removal or surgical removal of the
sequestrum, the body, especially in children, may fill the remaining cavity with new bone.
However, in adults, the cavity may persist or the space may be filled with fibrous tissue.
The surviving bone in the osteomyelitis field usually becomes osteoporotic during the
active period of infection. Osteoporosis is the result of the inflammatory reaction and
disuse atrophy. After the infection subsides, bone density increases partially from reuse. It
may be difficult to distinguish between the old living bone and the newly formed bone as
time passes. All traces of osteomyelitis can disappear in children and, to a lesser extent, in
adults.
Staging:
Waldvogel classification
In 1970, Waldvogel described the first long bone osteomyelitis staging system. He
described 3 categories of osteomyelitis, as follows: hematogenous, contiguous focus, and
osteomyelitis associated with vascular insufficiency.


Hematogenous osteomyelitis is predominantly encountered in the pediatric
population; 85% of patients are younger than 17 years. This form of osteomyelitis is
more common in males at any age. The bone infection usually affects the long bones
in children, while in adults, the lesion is usually located in the thoracic or lumbar
vertebrae.
Osteomyelitis secondary to a contiguous focus of infection can derive from a direct
infection of bone, from a source outside the body (eg, soft tissue trauma, open
fracture, surgery), or from the spread of infection from an adjacent focus (eg, soft
tissue infection, dental abscess, decubitus ulcer). Contiguous focus osteomyelitis has
a biphasic age distribution: the infection occurs in younger individuals secondary to
trauma and related surgery and in older adults secondary to decubitus ulcers and
infected total joint arthroplasties.
18

Osteomyelitis
associated
with
vascular insufficiency is usually seen
in individuals with diabetes mellitus. Of the 31 patients in Waldvogel's study with
this form of osteomyelitis, 25 had diabetes, 5 had severe atherosclerosis not related
to diabetes, and one had vasculitis secondary to rheumatoid arthritis. All of the
infections affected the toes, metatarsals, tarsals, or hindfoot. Most patients in this
group were aged 40-70 years.
Waldvogel's remains the primary osteomyelitis classification system. However, it is an
etiologic classification system that does not readily lend itself to guiding surgical or
antibiotic therapy. As a result, other classification systems have been developed to
emphasize different clinical aspects of osteomyelitis.
Kelly classification
The Kelly classification system divides osteomyelitis in adults into 4 categories, as
follows:




Hematogenous osteomyelitis
Osteomyelitis in a united fracture (fracture with union)
Osteomyelitis in a nonunion (fracture with nonunion)
Postoperative osteomyelitis without fracture
This classification system emphasizes the etiology of the infection and its relationship to
fracture healing.
Weiland classification
Weiland defined chronic osteomyelitis as a wound with exposed bone, positive bone
culture results, and drainage for more than 6 months. A similar wound with drainage for
less than 6 months was not considered to be a site of chronic osteomyelitis. The infection
was further divided on the basis of soft tissue and the location of bone involved, as follows:



Type I osteomyelitis is defined as open exposed bone without evidence of osseous
infection but with evidence of soft tissue infection.
Type II osteomyelitis consists of circumferential, cortical, and endosteal infection.
Radiographs demonstrate a diffuse inflammatory response, increased bone density,
and spindle-shaped sclerotic thickening of the cortex. Other radiographic findings
included areas of bony resorption and often a sequestrum with a surrounding
involucrum.
Type III osteomyelitis consists of cortical and endosteal infection associated with a
segmental bone defect.
Ger classification
19
The Ger classification system addresses the physiology of the wound as it relates to
osteomyelitis. The categories include simple sinus, chronic superficial ulcer, multiple
sinuses, and multiple skin-lined sinuses. If the wound is not appropriately treated, the bone
infection cannot be arrested. Early coverage of open tibial fractures with soft tissue
prevents the later development of osteomyelitis, ulceration, and, perhaps, nonunion.
May classification
The May classification system focuses on the status of the tibia after soft tissue and skeletal
debridement (May, 1989). This system is useful in determining the length of rehabilitation
that will be needed, under ideal conditions, before the patient will be able to ambulate
without upper extremity aids.





Type I osteomyelitis is defined as an intact tibia and fibula capable of withstanding
functional loads (rehabilitation time, 6-12 wk).
Type II osteomyelitis consists of an intact tibia with bone graft only needed for
structural support (rehabilitation time, 3-6 mo).
Type III osteomyelitis demonstrates a tibial defect of 6 cm or less with an intact
fibula (rehabilitation time, 6-12 mo).
Type IV consists of a tibial defect greater than 6 cm and an intact fibula
(rehabilitation time, 12-18 mo).
Type V osteomyelitis consists of a tibial defect greater than 6 cm long with no
usable intact fibula (rehabilitation time, 18 mo or more).
May's classification system with the estimated time for rehabilitation assists the decisionmaking process in patients with post-traumatic tibial osteomyelitis. However, many
factors, including age, metabolic status, the mobility of the patient's foot and ankle,
neurovascular integrity, and the patient's motivation, can greatly affect the time necessary
for rehabilitation.
Gordon classification
The Gordon system classifies infected tibial nonunions and segmental defects based on the
osseous defects (Gordon, 1988):



Type A includes tibial defects and nonunions without significant segmental loss.
Type B includes tibial defects greater than 3 cm with an intact fibula.
Type C includes tibial defects of greater than 3 cm in patients without an intact
fibula.
The Gordon classification system correlates with the prognosis for successful free muscle
transportation (ie, the microvascular movement of a muscle flap). Once the wound and
infection have been successfully treated with staged microvascular muscle transplantation,
the nature of the underlying osseous problem will dictate the clinical results.
20
Cierny-Mader classification
The Cierny-Mader system is a good model for the diagnosis and treatment of long bone
osteomyelitis, since it permits stratification of infection and the development of
comprehensive treatment guidelines for each stage.
The Cierny-Mader classification is based upon the anatomy of the bone infection and the
physiology of the host. The stages are dynamic and may be altered by therapy outcome or
change in host status. The classification is determined by the condition of the disease
process itself, regardless of its etiology, region, or chronicity. The anatomic types of
osteomyelitis are medullary, superficial, localized, and diffuse.




Stage 1, or medullary osteomyelitis, denotes infection confined to the intramedullary
surfaces of the bone. Hematogenous osteomyelitis and infected intramedullary rods
are examples of this anatomic type.
Stage 2, or superficial osteomyelitis, is a true contiguous focus infection of bone; it
occurs when an exposed infected necrotic surface of bone lies at the base of a soft
tissue wound.
Stage 3, or localized osteomyelitis, is usually characterized by a full-thickness
cortical sequestration that can be removed surgically without compromising bony
stability.
Stage 4 or diffuse osteomyelitis is a through-and-through process that usually
requires an intercalary resection of the bone to arrest the disease process. Diffuse
osteomyelitis includes those infections with a loss of bony stability either before or
after debridement surgery.
The patient is classified as an A, B, or C host.



An A host is a patient with normal physiologic, metabolic, and immunologic
capabilities.
A B host has systemic compromise, local compromise, or both.
The C host is a patient in whom the morbidity of treatment is worse than that of the
disease itself.
The terms acute osteomyelitis and chronic osteomyelitis are not used in this staging
system, since areas of macronecrosis must be removed regardless of the duration of an
uncontrolled infection. This classification system aids in the understanding, diagnosis, and
treatment of bone infections in children and adults. It is used mainly to stratify the
infection in research protocols but is also being built into many new research protocols.
TREATMENT
Medical therapy: A single pathogenic organism is almost always recovered from the
bone. The most common bone isolates are staphylococci, the most common gram-negative
21
organism is P aeruginosa, and the most common anaerobe is Peptostreptococcus
species. However, in immunocompromised patients, other organisms must also be
considered, including fungi and mycobacteria.
Hematogenous osteomyelitis in children can usually be treated with antibiotic therapy
alone. However, it is vital to identify a pathogen in order to select the optimal antibiotic
therapy. Mismanagement with inappropriate antibiotic(s) encourages disease extension,
necrosis, and sequestra formation. A bone biopsy for culture is necessary unless the patient
has positive blood cultures along with radiographic findings consistent with osteomyelitis.
After cultures are obtained, empiric antibiotics should be selected to cover the most
probable pathogens.
Once the etiologic organism is identified, the antibiotic regimen should be modified, if
needed, based upon susceptibility patterns. The patient should be treated for 4-6 weeks
with appropriate antimicrobial therapy, dating from the initiation of therapy or following
the last major debridement surgery. If the initial medical management fails and the patient
is clinically compromised by a recurrent infection, medullary and/or soft tissue
debridement is necessary in conjunction with another 4- to 6-week course of antibiotics.
Oral antibiotics can be used in pediatric hematogenous osteomyelitis. However, the child
should receive 7-14 days of IV antibiotics or continue to receive IV antibiotics until
systemic improvement occurs prior to changing to an oral regimen. The latest reports
suggest the use of IV antibiotics for 3-4 days; this usually is enough for the systemic
manifestations to improve. In order to undergo oral therapy, the patient must be compliant
and have close outpatient follow-up care. Absorption and activity of the orally
administered antibiotic should be monitored using serum cidal levels. High doses of the
quinolone class of antibiotics can cause articular cartilage damage in young animals,
generating some concern about the long-term use of these agents in infants and children.
Thus, under most circumstances, children with osteomyelitis should not be treated with a
quinolone.
Table 1. Antibiotic Therapy in Osteomyelitis
Organism
First-Choice Antibiotics
S aureus
Nafcillin
or
cloxacillin Cefazolin
100-200 mg/kg/d q6h
sensitive)
S
aureus
Vancomycin 1 g q12h
(methicillin resistant)
Coagulase-negative
organisms
Group
A
or
Alternative Antibiotics
(methicillin
Trimethoprimsulfamethoxazole
or minocycline
rifampin
plus
Vancomycin 1 g q12h or
Cefazolin, clindamycin
nafcillin 2 g q6h (if sensitive)
B Clindamycin 900 mg q8h
Benzylpenicillin,
22
streptococci
cefazolin
Ampicillin 50-100 mg/kg/d
q6h
Vancomycin
+ gentamicin 5 mg/kg/d q8h
Enterococci
E
P mirabilis
coli,
Ampicillin 2 g q6h
Cefazolin, gentamicin,
levofloxacin
Surgical therapy: Surgical management of contiguous focus osteomyelitis can be very
challenging. The principles of treating any infection are equally applicable to the treatment
of infection in bone. These include adequate drainage, extensive debridement of all
necrotic tissue, obliteration of dead spaces, stabilization, adequate soft tissue coverage, and
restoration of an effective blood supply.
The number and nature of the required surgical procedures increases with the severity of
the infection, which can be divided into 4 categories, as follows:




Category 1 - Removal of necrotic tissue by extensive debridement
Category 2 - Dead space obliteration with flaps, antibiotic beads, and bone grafts
Category 3 - Provision of soft tissue coverage of the bone
Category 4 - Stabilization of bone by external or open reduction and internal fixation
Category 1
Debridement surgery is the foundation of osteomyelitis treatment. It is the most commonly
performed procedure and may need to be repeated multiple times. The goal of debridement
is to reach healthy, viable tissue, but even when all necrotic tissue has been adequately
debrided, the remaining bed of tissue must be considered contaminated with the
responsible organism. Debridement should be direct, atraumatic and executed with
reconstruction in mind. All dead or ischemic hard and soft tissue is excised unless a
noncurative procedure has been chosen. Surgical excision of bone is carried down to
uniform haversian or cancellous bleeding, known as the paprika sign.
Category 2
Adequate debridement may leave a large bony defect (dead space). Appropriate
management of dead space created by debridement surgery is mandatory in order to arrest
the disease and to maintain the integrity of the skeletal part. The goal of dead space
management is to replace dead bone and scar tissue with durable vascularized tissue. Local
tissue flaps or free flaps may be used to fill dead space. An alternative technique is to place
cancellous bone grafts beneath local or transferred tissues where structural augmentation is
necessary. Careful preoperative planning is critical for conservation of the patient's limited
cancellous bone reserves. Open cancellous grafts without soft tissue coverage are useful
when a free tissue transfer is not a treatment option and local tissue flaps are inadequate.
23
Complete primary or delayed primary wound closure should be performed
whenever possible. Suction irrigation systems are not recommended because of the high
incidence of associated nosocomial infections and the unreliability of the apparatus.
Healing by secondary intent is also discouraged since the scar tissue that fills the defect
may later become avascular. Antibiotic-impregnated acrylic beads can be used to sterilize
and temporarily maintain dead space. The beads are usually removed within 2-4 weeks and
replaced with a cancellous bone graft. The most commonly used antibiotics in beads are
vancomycin, tobramycin, and gentamicin. Local delivery of antibiotics (amikacin,
clindamycin) into dead space can also be achieved with an implantable pump.
Category 3
Adequate coverage of the bone by soft tissue is necessary to arrest osteomyelitis. Most soft
tissue defects are closed primarily, but small soft tissue defects may be covered with a split
thickness skin graft. In the presence of a large soft tissue defect or an inadequate soft tissue
envelope, local muscle flaps and free vascularized muscle flaps may be placed in a 1- or 2stage procedure.
Local and free muscle flaps, when combined with antibiotics and surgical debridement of
all nonviable osseous and soft tissue for chronic osteomyelitis, have a success rate ranging
from 65-100%. Local muscle flaps and free vascularized muscle transfers improve the
local environment by supplying blood vessels (which are critical for host defense)
antibiotic delivery, and osseous and soft tissue healing.
Category 4
If movement is present at the site of infection, measures must be taken to achieve
permanent stability of the skeletal unit. Stability can be achieved with plates, screws, rods,
and/or an external fixator. One type of external fixation allows bone reconstruction of
segmental defects and difficult infected nonunions. The Ilizarov external fixation method
uses the theory of distraction histogenesis, in which bone is fractured in the metaphyseal
region and slowly lengthened. The growth of new bone in the metaphyseal region pushes a
segment of healthy bone into the defect left by surgery. The Ilizarov technique is used for
difficult cases of osteomyelitis when stabilization and bone lengthening are necessary. It
also can be used to compress nonunions and correct malunions and in a small group of
patients for reconstruction of difficult deformities that result from osteomyelitis.
However, this technique is labor intensive and requires an extended period of treatment,
averaging 9 months in the device. The Ilizarov pins usually become infected, and the
device is painful. Infected pseudoarthrosis with segmental osseous defects can be treated
by debridement and microvascular bone transfers. Vascularized bone transfer is also useful
for the treatment of infected segmental osseous defects of long bones that are more than 3
cm in length. Vascularized bone transfers can be placed after 1 month without clinical
evidence of infection.
Loss of bone stability, bone necrosis, and soft tissue damage frequently occur in
contiguous focus osteomyelitis. Surgical debridement of infected bone and soft tissue
24
provides specimens for culture and hastens eradication of the infection. Other steps in
the surgical management of contiguous focus osteomyelitis should be tailored to the
specific anatomy of the bone infection. When osteomyelitis is characterized by a full
thickness cortical sequestration, patients usually can be treated with removal of the dead
infected bone (bone saucerization). Bone grafting may be necessary to augment structural
support. These patients may require external fixation for structural support while the bone
graft incorporates. Complex reconstruction of both bone and soft tissue is frequently
necessary.
In some cases, osteomyelitis progresses to an infection involving the entire diameter of the
bone. These patients often require an intercalary resection of the bone in order to arrest the
disease process. Since this advanced stage of osteomyelitis involves an entire through-andthrough section of bone, a loss of bony stability occurs either before or after debridement
surgery. As a result, treatment often must be directed toward establishing structural
stability and obliterating debridement gaps by means of cancellous bone grafts or the
Ilizarov technique. Vascularized bone grafting is the other possible treatment modality.
Preoperative details: In addition to routine preoperative preparations, supportive therapy
is needed; infants and children must be well hydrated and fever must be controlled before
the patient undergoes general anesthesia. Patients who are medically compromised should
be stabilized and supported. Diabetes should be controlled as much as possible, but this
should not delay drainage because the presence of infection makes the blood sugar level
refractory and difficult to control. Most of the systemic manifestations of osteomyelitis
improve dramatically after drainage and debridement.
Intraoperative details: Position the patient in the most accessible position to drain the
infected areas. Prepare all containers and swabs, and prepare the requests before scrubbing.
Prepare containers for tissue cultures. Prepare for Gram stain, aerobic culture and
sensitivity, anaerobic culture and sensitivity, and fungal culture and sensitivity. (Acid-fast
bacillus [AFB] stain and culture and sensitivity are recommended.) Incision should be
generous for ease of access to the infected bone. Decompression may release
intramedullary or subperiosteal pus. All necrotic soft tissue, bone, and devitalized tissue
must be removed. Infected loculations must be broken, and thorough washing with as
much as 2-4 L of isotonic sodium chloride solution is essential.
Complete debridement of all the devitalized bone and soft tissue, regardless of the size of
the wound created, is essential for cure. Immobilization of the bone by cast or external
fixations is a must.
Revascularization procedures are the best means of fighting recurrent infection; those
involving local pedicle muscle flaps and myocutaneous flaps are now the ones most
frequently used to fill the space created by surgery. Local muscle flaps are limited by the
availability of adjacent muscle but are very useful because the vascular supply is kept
intact. Myocutaneous flaps have the advantage of providing vascular supply to both the
muscle and the overlying skin. Increasingly, microsurgically transplanted muscle flaps (ie,
free-flaps) are being used in areas such as the distal tibia where no appropriate muscle
exists.
25
Complex orthopedic techniques are necessary to repair very large bone defects
that would otherwise be considered untreatable except by amputation. In the Ilizarov
technique, the resection of diseased tissue and bone creates a gap partially filled by a wellvascularized bone segment. Transfer of the bone graft leads to progressive local generation
of new bone.
Postoperative details: Dramatic improvement is the usual course after debridement, but
patients require attention to prevent complications related to their original medical
conditions, such as diabetes and heart failure. IV fluids, IV antibiotics, and suitable
analgesics are required for the first few days after surgery. ICU admission for respiratory
support and blood gases and renal function monitoring should be considered for patients
who have septicemia.
The wound should be dressed daily, and early sitting and mobilization (affected limb must
be immobilized) should be encouraged.
If no improvement occurs within 48 hours, a second look debridement and dressing under
general anesthesia is indicated.
Follow-up care: The patient must be compliant with care and have close outpatient
follow-up. The first visit is usually a week after discharge and consists of a general
examination for evaluation of improvement. Local examination and documentation of pain,
wound condition, tenderness, swelling, and discharges from wounds should be made in all
visits. Repeat CBC count, CRP, ESR, and plain radiographs to evaluate the progression
and behavior of the infection.
The cast should be removed when infection is eradicated, which is usually determined by
good reduction in the level of CRP, ESR, or both. The shoulder, elbow, and wrist should
not be immobilized more than 3, 4, and 5 weeks, respectively.
Physiotherapy is an essential part of follow-up care; isometric exercises should be started
early, and once the cast is removed, active and passive range of motion exercises are
suggested.
COMPLICATIONS
Recurrence of osteomyelitis has been reported in 3-40% of patients. Chronic osteomyelitis
is very serious and more difficult to treat than acute osteomyelitis.
In some cases, osteomyelitis progresses to an infection involving the entire diameter of the
bone. These patients often require an intercalary resection of the bone in order to arrest the
disease process. Since this advanced stage of osteomyelitis involves an entire through-andthrough section of bone, a loss of bony stability occurs either before or after debridement
surgery. As a result, treatment often must be directed toward establishing structural
stability and obliterating debridement gaps with cancellous bone grafts or the Ilizarov
technique. Vascularized bone grafting is the other possible treatment modality.
26
The most serious complication of vertebral osteomyelitis is neurologic impairment
secondary to either abscess formation or bony collapse. Most patients have gradual
alleviation of pain after therapy is begun. In most patients, the pain disappears after a bony
fusion occurs. However, back pain occasionally persists.
Major bone loss hinders limb length and results in permanent disability.
The patient with extensive osteomyelitis and poor tissue oxygen perfusion usually requires
some type of ablative surgery. Digital and ray resections (toe and corresponding
metatarsal), transmetatarsal amputations, midfoot disarticulations, and Syme amputations
(amputation of the foot with retention of the heel pad) permit the patient to ambulate
without a prosthesis. The amputation level is determined by the vascularity of the tissues
proximal to the site of infection and the requirements of a thorough debridement. The
patient should be given 4 weeks of antibiotics when infected bone is surgically transected.
Two weeks of antibiotics are prescribed when the infected bone is completely excised, but
some residual soft tissue infection remains. However, when the amputation is performed
proximal to the bone and soft tissue infection, the patient is only prescribed a 1- to 3-day
antibiotic regimen.
OUTCOME AND PROGNOSIS
Acute osteomyelitis
With new diagnostic methods and better treatment, those with ready access to health care
can be anticipated to have only rare sequelae of hematogenous osteomyelitis. Infection
control strategies and prophylactic antibiotics will further decrease the rate of postoperative
infection. However, the increase in reconstructive orthopedic procedures with prosthetic
materials will increase the overall number of infections, and whether any preventive
measures can reduce the rate of infection to below 0.5% is doubtful.
Osteopenia and osteoporosis
After the infection subsides and use of the part is increased, bone density returns to
baseline, and bone may undergo extensive transformation to meet the lines of the stress and
strain. In time, distinguishing the old living bone from the newly formed bone may be
difficult.
Chronic osteomyelitis
Chronic osteomyelitis entails a major financial burden and has a substantial impact on
quality of life. Collaboration between patient and physician is essential in the treatment of
this disease. A clear understanding of the risks, costs, and chances of success of treatment
options should form the basis of an open dialogue between the physician and the patient
with chronic osteomyelitis.
Vertebral osteomyelitis
27
Treatment results for patients vary. The outcome appears to be equivalent for
patients who ambulate with stabilization from a cast, a corset, or a brace and those treated
with bedrest alone. Recurrence of osteomyelitis has been reported in 3-40% of patients.
However, the rate of chronic cases of vertebral osteomyelitis (patients demonstrating
symptoms after 2 y) has been reduced and now ranges from 0-6%. The mortality rate from
this disease in the antibiotic era has been less than 5%. Residual neurologic deficits among
survivors should be less than 7%. Generally, the best way to reduce the morbidity and
mortality associated with vertebral osteomyelitis is to limit the amount of time between the
onset of symptoms and the initiation of appropriate therapy.
FUTURE AND CONTROVERSIES
Hyperbaric oxygen therapy
In situations in which osteomyelitis is associated with decreased systemic blood flow (eg,
in diabetes, vasculitis) or segmental blood flow (eg, in trauma), hyperbaric oxygen therapy
may be used as adjunctive therapy. Reduced oxygen tensions in infected bone have been
shown to interfere with normal polymorphonuclear leukocyte activity. Hyperbaric oxygen
therapy has been shown to increase the oxygen tensions within infected bone, thereby
augmenting polymorphonuclear leukocyte and macrophage activity.
Wound healing is a dynamic process that requires an adequate oxygen tension to proceed.
In the ischemic or infected wound, hyperbaric oxygen therapy provides oxygen to promote
collagen production, angiogenesis, and ultimately wound healing. Referral for hyperbaric
oxygen is made whenever refractory osteomyelitis occurs or a soft tissue infection
develops that is not amenable to a local or microvascular flap.
Microvascular surgery
Recent experience with the microvascular transfer of fibular grafts and composite
osteocutaneous iliac flaps into infected areas of bone has shown that massive autogenous
bone grafting with an intact vascular pedicle decreases the time needed for bone union and
shortens the period of immobilization. Reconstruction of large bony and soft tissue defects
has been facilitated by microvascular and distraction osteogenesis (Ilizarov) techniques. A
large piece of bone, soft tissue, or both can be introduced immediately or gradually into a
previously infected wound while maintaining its protective blood supply. This allows more
radical bone excision, increasing the chance of cure.
Local antibiotic delivery
Systems for local delivery of antibiotics into tissues have been used to overcome limited
penetration of systemic agents into poorly vascularized bone, to avoid toxicity, and to
minimize the need for long-term parenteral antibiotics. Such systems include closed
suction-irrigation, plaster pellets, fibrin, collagen, and porous calcium hydroxyapatite. The
greatest experience has been with antibiotic-loaded polymethyl methacrylate (PMMA)
bone cement. Antibiotic-loaded cement is used for prosthetic joint fixation to maintain and
sterilize dead space with antibiotic-impregnated beads during surgery for chronic
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osteomyelitis and to maintain extremity length during 2-stage revision arthroplasty
for infection.
Aminoglycosides, penicillins, cephalosporins, and clindamycin elute most effectively,
whereas vancomycin elutes much less well. Even for drugs that elute most effectively, only
a fraction of antibiotic is released. Approximately 10% of gentamicin added to PMMA
may be recovered from the urine 2 months following hip arthroplasty. However, extremely
high local concentrations are achieved as measured in surgical drains. To avoid systemic
toxicity in adults, it is suggested that no more than 17.5 g of aminoglycoside be added to
PMMA beads.