Advances in the management of bone infection
24 April 2012
Miss Deepa Bose
Consultant Orthopaedic Surgeon
Queen Elizabeth Hospital Birmingham
Miss Bose gave a superb insight into the many challenges faced when dealing with bone infections, including the problems posed by specific microbes and by complex anatomical issues.
She explained that the difficulty of attacking and killing microbes was underpinned by a number of factors, including being able to isolate the infection for analysis, the role of biofilms in protecting microbes and the inherent inaccessibility of bone infections when trying to deliver antibiotics.
However, she set out several effective techniques for isolating and obtaining of high quality tissue samples of infected sites.
In particular, she stressed the need to reduce the amount of handling of a sample and the length of time before it is plated for culturing in the laboratory.
She described some of the newer laboratory tests which can improve sampling accuracy and speed, including polymerase chain reaction (PCR) and DNA sequence recognition
Biofilms form on surfaces such as bone and implants in the presence of microbes. This film harbours microbes, can promote their propagation and is stubbornly resistant to antibiotics.
Bone infections also present difficulties in accessing and removing infected bone tissue, as well as preventing the recurrence of the infection.
When dead space is created in bone by a surgeon removing infected tissue, that space does not collapse and fill itself like soft tissue. This can mean the space fills with blood, which is an excellent medium for the development of infection.
In many such cases, Miss Bose uses porous calcium sulphate pellets, impregnated with antibiotics, to fill the space and deliver the antibiotics before they are dissolved by the body.
Bone infection is often associated with implants, such as screws or plates, and non-union of fractures. This presents a huge challenge to surgeons, as they must consider the stability of the fracture when making decisions on removing existing implants or carrying out new surgical repairs.
Miss Bose pointed out that surgeons and patients are faced with four choices in all such situations: do nothing; suppress the infection with antibiotics; limb salvage surgery; amputation.
She warned against “knee-jerk” removal of implants in such situations, and when necessary her preferred technique in many such situations is to remove existing implants and use a circular external frame to stabilise the fractures. This reduces the “footprint” of any implants in the bone to just the narrow pins and wires used to attached the frame to the bones.
Another anatomical challenge for bone infection is insufficiency soft tissue coverage, either because there is simply not enough soft tissue or because that tissue is useless.
Useless tissue does not enable blood flow, delivery of antibiotics or generation of mesenchymal stem cells.
In summing up a successful approach to managing bone infections she described three key elements:
- A co-operative multi-disciplinary approach
- Bespoke treatment for each patient
- Good decision making
However, she also stressed the importance of prevention to avoid infection through:
- good theatre discipline
- good tissue handling techniques
- minimal extra trauma to tissue
- use of laminar flow systems in theatre.