An infected implant is not only a failure of surgical goal but also results in increased morbidity, prolongs the treatment and can affect the outcomes of treatment. It is deemed as most devastating complication of surgery.
Any implant can get infected and when it does, the infection is quite stubborn to go. The main reasons of persistent infection is biofilm, a kind of microcolony or cell cluster. The bacteriae in the biofilm are resistant to the treatment because they are irreversibly attached to each other and bathe in an extracellular matrix. This gives them extra protection from host.
Moreover, traditional investigations may not be able to grow the bacteriae and thus detect the infection because biofilms do not grow on agar plate when recovered by scrapping.
Antibiotic therapy can control the acute episodes but cannot the biofilms per se.
An infected implant is a challenge to recognize, investigate and treat.
It is also important to recognize early subtle signs of infected implant so that early measures can be taken.
Presentation of an Infected Implant
The presentation of infected implant is also misleading as bacteriae in biofilm produce less inflammatory response and usually constitutional symptoms are absent.
The presentation is variable. The surgeon needs to be watchful with high index of suspicion.
Fever after third day onwards should raise the suspicion.
There could be three types of presentation
- Early – Within 8 weeks
- Delayed – Between 8 weeks to one year
- Late – After one year
The complaint may be a disproportionate pain or pain at previously painless site.
Local examination may reveal signs of infection depending upon the severity and stage at which patient has presented himself
- Serosanguineous or purulent discharge
- Cut through of stitches
- Wound gaping
- Chronic discharging sinus
If there is a prosthesis it might present as pain in the region, implant loosening, joint stiffness or swelling in the region.
many a cases have recurrent infections.
- Complete blood count
- Plain xrays of the region
- Aspiration of fluid and culture
Blood investigations provide little information. Plain xrays may show osteomylitis, bone resorption or localized ossteoporosis.
Culture may miss bacteriae in biofilm.
Bone scan, ultrasound, MRI and sinogram may be helpful in localization and extent of the infection.
Advanced methods like Polymerase chain reaction (PCR), Fluorescin In Situ Hybridization (FISH), Enzyme linked Immunno Sorbent Assay (ELISA) may help to detect the infection.
Following variables would affect the management strategies
- Time when infection occurs
- Stability of the implant
- Severity of the infection
For acute postoperative infections
– Intravenous antibiotics after culture and sensitivity.
– Rest to the part
– Removal of stitches to drain collection if present
In case the above measures fail to contain the infection, opening of the wound and copious irrigation is required.
Mild to moderate infections can be controlled by these measures.
If infection is very severe and not controlled by conservative means following measures might be needed
– Removal of implant and application of external fixator
– Delivering local antibiotics across fracture site
– Refixation at later date after infection is controlled
In case of late infections, the fracture union plays an important role. Mild and moderate infections can be controlled with conservative methods.
– For For severe late infections without union of the fracture which cannot be controlled with conservative methods an approach similar to early severe infections i.e. removal of implant, external fixation and resurgery at later date is required.
– For infections with united fractures, removal of implant is removed.
Infected prosthesis is a separate issue in itself and needs in detail discussion.
However, grossly speaking, the line of management remains the same. If conservative measures fail to control the infection, removal of prosthesis and revision of prosthesis at a later date.
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