Assessment
Chronic osteomyelitis is a combined problem of infection, devitalised bone, dead space, soft-tissue compromise and host factors.
Define three things:
- anatomical extent of bone infection
- condition of the soft-tissue envelope
- physiological status of the host
History:
- previous open fracture or surgery
- organism and antibiotics
- recurrent drainage
- implants
- smoking and host factors
- previous reconstruction
Examine:
- sinus
- scars
- soft-tissue envelope
- deformity
- stability
- limb perfusion
A chronic sinus communicating with bone or implant is highly significant for infection.
Imaging
- radiographs: sclerosis, sequestrum, involucrum, deformity, implant failure
- CT: cortical sequestra and cavitation
- MRI: marrow and soft-tissue extent
- nuclear or metabolic imaging: selected difficult cases
Microbiology
Deep tissue and bone samples are preferred. Multiple samples are obtained during surgery with separate instruments when possible. Superficial sinus swabs are unreliable for identifying the organisms in deep bone infection.
Surgical principles
Successful treatment generally requires:
- excision of non-viable bone and scarred infected tissue
- reduction of bacterial burden
- stable skeletal reconstruction
- management of dead space
- durable vascularised soft-tissue coverage
- appropriately targeted antimicrobial therapy
Bone defect reconstruction
Options include:
- autologous bone grafting after infection control
- induced-membrane techniques
- bone transport/distraction osteogenesis
- vascularised grafts in selected large defects
Choice depends on defect size, location, stability, host status and local expertise.
Host factors
Smoking, vascular disease, diabetes, renal disease, malnutrition, immune suppression and poor soft tissues reduce the chance of uncomplicated eradication. Optimisation is part of treatment rather than an optional extra.
Treatment goal
The realistic goal may range from eradication with limb reconstruction to durable suppression or amputation. The treatment burden must be proportionate to the expected function.
Pathology
Chronic osteomyelitis is characterised by persistent infection often associated with:
- necrotic bone
- sinus formation
- biofilm
- poor vascularity
- scarred soft tissues
A sequestrum is devitalised bone separated from viable bone. Involucrum is reactive new bone formed around infected bone. A cloaca is an opening through which pus may drain.
Investigations
Use:
- plain radiographs
- CT for sequestra/cortical anatomy
- MRI for marrow and soft tissue where interpretable
- inflammatory markers as supportive rather than definitive tests
Superficial sinus swabs are unreliable for planning definitive therapy. Deep samples at surgery are preferred.
Treatment principles
Successful treatment usually requires:
- radical debridement
- removal of necrotic bone
- management of infected/unstable implants
- multiple deep cultures
- dead-space management
- stable reconstruction
- durable soft-tissue cover
- targeted antibiotics
Dead space and bone loss
After debridement there may be substantial cavities or segmental defects. Options include:
- local antibiotic carriers
- staged induced-membrane techniques
- bone transport
- vascularised graft
- cancellous grafting in appropriate settings
Selection depends on defect size, biology, stability and expertise.
Host optimisation
Address:
- smoking
- malnutrition
- diabetes
- vascular disease
- immunosuppression
A technically perfect reconstruction can fail in a profoundly compromised host.
Malignant change
Long-standing draining sinuses rarely undergo malignant transformation, classically to squamous-cell carcinoma. Change in a chronic sinus warrants investigation.
FRCS synthesis
Chronic osteomyelitis is a surgical disease supported by antibiotics. The central task is complete removal of non-viable infected tissue followed by stable biological reconstruction.