Chronic bone exposure is important for two reasons. First, it is the most common problem of neglected wounds or of wounds which present late; second, it may result from correct wound management, i.e. wound excision may inevitably leave bone cortex, fractures or joints exposed (case 3).
In wounds that present late there may be signs of spontaneous healing in the form of granulation tissue and re-epithelialization or callus formation. The wound becomes inflamed and discharges pus and small bone fragments. Large unattached bone fragments may become surrounded by new bone. Much later, there may be enough consolidation for the limb to be used, albeit with difficulty because of pain and malunion. In children the process is rapid and bone fragments are readily incorporated or sequestered.
A simple algorithmic approach, utilizing basic management principles, helps this common and difficult problem.
A severely infected limb wound may necessitate amputation as a life-saving measure when the wound severity renders it beyond wound excision. The patient is pyrexial, confused and anaemic. The wound is offensive. The level and requirement for amputation are difficult decisions for the surgeon.
Question 1: Is the limb threatening life?
Patients may present with old wounds which are not life-threatening but have rendered the limb useless and painful. Amputation must be considered. Local culture and prosthetic facilities may influence the surgeon's decision.
Question 2: Is the best possible result acceptable to the patient or better than a prosthesis?
The few cases that are not helped by surgery have a good limb, minimal symptoms, a small chronic sinus and good callus formation. This is an acceptable and likely outcome of treatment of chronic bone infection.
Question 3: Will the limb be helped by surgical treatment?
No: accept small chronic sinus.
A wound with no spontaneous healing requires careful and complete excision and subsequent management by the basic principles outlined in Chapter 2. This is increasingly difficult with time as the tissues become inflamed and oedematous.
Formal wound excision is impractical when there has been healing. The wound may need exploration to remove foreign material and dead bone. After some weeks, dead bone is soft, white and slightly dimpled. Curettage only removes small fragments not involved in the healing process. Every effort is made to extract large bone fragments from the depths of a sinus, even if surrounded by new bone. Exposed bone ends that have died are shiny, dry, brown or green in appearance and should be excised back to normal bone, using powerful bone nibblers for compact bone. The fractured anterior tibial border is commonly avascular, although in continuity with the rest of the bone; it is easily exposed by injury and is hard to excise.
After excision of dead bone, the cavity feels smooth to the finger (glove perforations are common in this operation) and is left open. Temporary insertion of gentamicin-impregnated beads may supplement correct surgery in a small number of cases.
Immaculate fracture reduction is rarely possible following surgery. Immobilization is achieved by skeletal traction, plaster-of-Paris or external fixation.
Question 4: Has there been any healing or callus formation?
Yes: explore the wound; excise dead bone (± gentamicin-impregnated beads).
No: excise soft tissue and bone fragments (difficult wound excision). Then reconsider questions 1 and 2 or continue.
Most wounds of bone will heal by secondary intention if wound excision is complete. Large defects granulate quickly and will accept a skin graft. Reconstruction achieves soft tissue cover more rapidly and facilitates bone union or bone grafting. It may be a necessary step in the preservation of limb function.
Question 5: Is soft tissue reconstruction necessary?
Yes: reconstruct to achieve soft tissue cover.
No: allow to heal by secondary intention ± skin graft. Then continue.
Most fractures will rapidly form callus with wound excision and soft tissue cover, whether by direct closure, reconstruction or healing by secondary intention. Segments of bone loss of 3 cm may be bridged with time. Bone grafting should only be undertaken in basic facilities when the possible benefits outweigh the chance of failure.
Question 6: Will adequate callus form?
Yes: immobilize the fracture.
No: bone graft and immobilization. Await the outcome. Consider re-entry to the algorithm at question 2.
This algorithm provides an approach to a difficult and common problem. It is not presented as a cure of chronically infected bone. It helps the problems of pain, pyrexia, purulent discharge and a useless limb in patients with exposed bone in war wounds. Dead bone excision is mandatory and is often the only surgical step necessary for wound healing. A minority require a soft tissue reconstruction and still fewer require a bone graft.
Joints are frequently exposed long after wounding and the algorithm still applies. Wounds involving joints may heal by secondary intention if cartilage is not left exposed; it may have to be scraped off periarticular bone. Cover by soft tissue reconstruction is preferable. An acceptable result is a painless joint which is stiff or fused in a functional position.
Antibiotic prophylaxis is an essential part of the management of fresh, potentially gangrenous wounds. In chronically exposed wounds and with no microbiological facilities the value of systemic antibiotics, particularly antistaphylococcal agents, is unclear. The best antibacterial measure in this situation is excision of the dead bone.