Chronic Osteomyelitis
 Osteomyelitis is an infection of bone and bone marrow and can be subdivided into
acute, subacute, and chronic stages.
 often a recurring condition because it is difficult to treat definitively
 may result from
1) inadequately treated acute osteomyelitis
2) a hematogenous type of osteomyelitis
 most common type in children
3) trauma
4) radiotherapy
5) iatrogenic causes such as joint replacements and the internal fixation of
fractures;
6) compound fractures;
7) infection with organisms, such as Mycobacterium tuberculosis and Treponema
species (syphilis)
8) contiguous spread from soft tissues, as in diabetic ulcers or ulcers in peripheral
vascular disease.
 ends of long bones are the most common locus of infection
Microbiology
1. Staphylococcus aureus is the most common infective organism involved in acute
OM
2. Staphylococcus epidermidis, S. aureus, Pseudomonas aeruginosa, Serratia
marcescens, Enterobacteriaceae, Enterococcus faecalis and Escherichia coli are
commonly isolated in chronic OM
3. Atypical – syphilis, TB
Classification (Cierny and Mader)
1. Type 1 - Endosteal or medullary lesion
2. Type 2 - Superficial osteomyelitis limited to the surface
3. Type 3 - Localized, well-marked legion with sequestration and cavity
formation
4. Type 4 - Diffuse osteomyelitis lesions
Pathogenesis
 Infection at the bone locus creates an increase of intramedullary pressure due to
inflammatory exudate
 strips the periosteum, leading to vascular thrombosis followed by bone necrosis
and the formation of sequestra
 haversian canals are blocked with scar tissue, and the bone is surrounded by
thickened periosteum and scarred muscle.
 Antibiotics cannot penetrate these relatively avascular tissues and are hence
ineffective in clearing the infection.
 New bone formation occurs at the same time (involucrum).
 Children younger than 2 years of have transphyseal vessels, which cross from
metaphysis to epiphysis. This causes the spread of infection into the joint. In
children older than 2 years, the transphyseal vessels are absent, and hence the
epiphyseal plate acts as a barrier to the spread of infection into the joint.
Types
1. Garrès sclerosing osteomyelitis - rare type of sclerotic nonpurulent form of
osteomyelitis
2. Brodie abscess is a form of chronic osteomyelitis without a preceding episode
of acute osteomyelitis. The lesion causes a localized abscess within the bone,
often close to metaphysis.
3. Tuberculous osteomyelitis of the bone is secondary spread from a primary source
in the lung or GI tract. It most commonly occurs in the vertebrae (body) and long
bones.
4. Congenital syphilis spreads transplacentally and commonly involves long bones 2 forms: periosteitis and metaphysitis.
a. In periosteitis, the periosteum is lifted of the diaphysis of long bone with
subperiosteal new-bone formation. This process gives the characteristic
appearance called sabre tibia.
b. In metaphysitis, the juxtaepiphyseal metaphysis is involved with increased
bone resorption. Absent osteoblastic activity results in separation of the
epiphyseal from the metaphysis.
Clinical
 Unlike acute osteomyelitis, chronic osteomyelitis causes no acute constitutional
symptoms
 long-standing, discharging sinus or chronic bone pain
Investigations
 bloods – raised WCC, ESR
 Radiology
o Aims:
1. to evaluate bone involvement (eg, the extent of active intramedullary
infection or abscess superimposed on areas of necrosis, sequestrum and
fibrosis)
2. to identify soft-tissue involvement (areas of cellulitis, abscess, and sinus
tracts).
o Xrays
1. acute OM = deep soft-tissue swelling, a periosteal reaction, cortical
irregularity, and demineralization
2. chronic OM = thick, irregular, sclerotic bone interspersed with
radiolucencies, an elevated periosteum, and chronic draining sinuses.
o CT
1. good for studying the entire articular surface of bone and periarticular soft
tissues; for delineating the extent of medullary and soft-tissue
involvement; and for demonstrating cavities, serpiginous tracts, sequestra,
or cloacae in osteomyelitis.
o Nuclear Medicine
1. Technetium-99m diphosphonate bone scanning

particularly valuable in looking for other sites of infection, such as
multifocal osteomyelitis.
 Increased focal activity may persist in sterile disease for up to 2 years
following successful therapy.
 sensitivity can be improved by using a 3-phase bone scan
2. Gallium-67 scanning
 Mechanisms of 67 Ga citrate uptake include the following: (1) direct
leukocyte and bacterial uptake, (2) lactoferrin and transferring
binding, (3) increased vascularity, and (4) increased bone turnover.
 Gallium scanning has a proven role in the monitoring of treatment.
o MRI
1. will show bone AND soft tissue involvement
2. MRI has sensitivity and specificity higher than those of plain
radiography and CT, and it is particularly good at depicting bone marrow
abnormalities.
3. changes secondary to the replacement of marrow fat with water secondary
to edema, exudate, hyperemia, and bone ischemia.
4. Findings include the following: decreased signal intensity in the involved
bone on T1-weighted images, increased signal intensity in the involved
bone on T2-weighted image, and increased signal intensity in the involved
bone on short-tau inversion recovery (STIR) images.
 Biopsy
o Mackowiak et al established bone specimen cultures as the gold standard
for microbiological diagnosis of COM in 1978
o Cultures of sinus tract samples are not reliable for identifying causative
organisms. In 50% of cases, the bacteria will be isolated in bone but not sinus
tract
o Biopsy
 Open
 Core
Complications of osteomyelitis include
1) septic arthritis
2) destruction of the adjacent soft tissues
3) malignant transformation (eg, Marjolin ulcer [squamous cell carcinoma],
epidermoid carcinoma of the sinus tract)
4) secondary amyloidoses
5) pathologic fractures.
Management
 Open biopsy
o Take at least 5 samples using 5 different bone nibblers
 Remove foreign bodies/implants
o organisms stick to the biomaterials and are covered by glycocalyx biofilm that
presents a barrier to the antibiotics
 Debridement and soft tissue reconstruction
o In most cases of chronic osteomyelitis, saucerization, not diaphysectomy, is
the preferred method.
 Antibiotics 4-6 weeks
o without adequate debridement, chronic osteomyelitis does not respond to
most antibiotic regimens, no matter what the duration of therapy is
 Antibiotic beads in cases where bony defect was present
o primary saucerization with implantation of antibiotic-impregnated
polymethylmethacrylate beads and secondary bone grafts.
o these beads provide local depot administration of antibiotic and maintain space
for subsequent bone graft;
o Infected pseudarthrosis with segmental osseous defects may also be treated by
debridement and microvascular bone transfers. Vascular bone transfers in
case of bone defects more than 3 cm in length can be placed after one month
of inactive sepsis.
o cement beads are usually removed within 2-4 weeks and replaced with a
cancellous bone graft in certain cases. Antibiotic-impregnated cement has also
proved effective for replacing infected prostheses. However, only heat-stable
antibiotics which are released slowly from cement surrounding the tissue can
be used because heat which is generated during the polymerization process
makes heat-unstable antibiotics ineffective. The most commonly used
antibiotics in beads are vancomyscin, tobramycin and gentamicin.
o as noted by Keating et al 1996, bead pouches help reduce the infection rate in
open tibia fractures from 16% to 4%;
o Debridement with the implantation of gentamicin-PMMA beads and
debridement followed by systemic antibiotics were significantly more
successful forms of treatment for chronic osteomyelitis than debridement
alone or debridement with the implantation of PMMA beads not impregnated
o with antibiotics.
 Hyperbaric therapy
o shown to increase the oxygen tensions within infected bone, thereby
augmenting the polymorphonuclear leucocyte and localized host immune
response.