Infections

Osteomyelitis is an infection the affects the bones; germs can colonize them through direct contact or through the blood in cases of systemic infections through hematogenic dissemination.

Generally, osteomyelitis is a consequence of direct post-traumatic (exposed fractures) or post-surgical contamination.

Acute osteomyelitis typically causes pain, heat, redness and bruising. In the most severe cases there can be systemic symptoms such as fever.

In chronic osteomyelitis in which there is no secretory fistula (ie, skin contact), the symptoms are often very light and sometimes the organism can keep the infection in a quiescent phase; the bacteria are basically “walled” within the bone and any reactivation would be caused by a decrease in immune defense or another condition that favors a fresh outbreak.

Treatment of osteomyelitis includes a pharmacological and a surgical approach; the removal of infected tissue is fundamental and it is necessary to be as radical as possible to avoid relapses. Often it is necessary to sacrifice soft and bone tissues and then proceed at a later time with plastic-reconstructive surgery.

This second surgical step must occur after the complete resolution of the infective process; often the injuries remain open and protected by advanced bandaging such as that with negative pressure or VAC-therapy.

This system, in addition to guaranteeing adequate protection with regards to external contamination, ensures the formation of granulation tissue, the first step towards healing the lesion.

When an infection is localized within a fracture and prevents healing, it is called septic pseudoarthrosis. Generally, it occurs when synthesis means become colonized with bacteria.

As opposed to aseptic pseudoarthrosis, the infection must be cured, or else all other attempts at curing the pseudoarthrosis will fail.

Therefore, a careful cleaning (debridement) of the site of the infection is required, including the removal of the synthesis means and/or non-vital tissue if necessary, and the stabilization of the fracture through the use of external fixtures that remove the need for inert material at the infection site.

Sometimes the septic locus is very large and the removal of a large portion of bone is necessary. In these cases the length of the segment of bone is recovered through various techniques:

1. Elevator with circular fixture (Ilizarov): a portion of bone tissue is removed and the segment is synthesized with an external circular fixture (Ilizarov). A second fracture is made at a proximal level and with daily adjustment of the screws on the external circular apparatus, the free diaphyseal portion is “moved” so that the upper part forms a new callus and the lower one gradually comes into contact with the distal portion until the healing of the pseudoarthrosis is complete.
   

2. Biological chamber (Masquelet): once the infected bone portion has been cut and removed, the gap in the bone is filled with a spacer made of antibiotic-loaded bone cement.  This spacer will be removed after some weeks and the membrane that has formed in the meantime will have distinct biological properties that favor the onset of bone transplants.
   

One of the most dangerous complications in prosthetic surgery is the infection of the implant. Currently it is not possible to eliminate the risk of peri-prosthetic infections; international literature puts this risk at approximately 1-2% in first implants and 4-5% in revisions.  As mentioned previously, the surface of the prosthesis is an optimal place for bacteria to grow. The majority of peri-prosthetic infections are caused by bacterial infection during the surgical intervention to implant the prosthesis. It is however possible for the infection to be caused by successive surgical interventions (in particular dental), or following general infections; in these cases the germs enter the bloodstream and can colonize the prosthesis. For this reason, it is fundamental to use adequate antibiotic protection every time the patient undergoes surgery, even in body parts far from the implant.

The symptoms of peri-prosthetic infections include localized pain, heat, skin redness, fever, possibly secreting fistula and progressive loss of mobility. The most severe aspect, however, is that the bacteria trigger a process that leads to the release of toxic substances that provoke the reabsorption of the bone around the prosthesis leading to its immobilization.

It is thus fundamental to recognize an infection as early as possible to preserve the bone tissue.

A correct diagnosis is fundamental to set-up an adequate treatment plan. The isolation of the germ that is causing the infection is not always easy, but it is a critical step in finding a targeted antibiotic therapy.

Peri-prosthetic infections can be acute or chronic.

In all cases, antibiotic therapy alone will not destroy the septic process due to the capability of the bacteria to produce their defenses within the first 48 hours.

Surgery is essential to physically remove the bacteria involved; if the infection is recognized and treated within the first 3 weeks from the time of contamination, there is a good chance of saving the prosthesis. After this time limit, international guidelines recommend a substitution of the prosthesis.

This process can occur in 2 different ways:

1. One-stage exchange: in which the prosthesis is removed and substituted in the same intervention after careful cleaning.
2. Two-stage exchange: the prosthesis is removed and substituted with an antibiotic-loaded spacer with the same shape as the prosthesis; after a period which varies from a few weeks to several months and, if possible, a targeted antibiotic therapy, after normalization of inflammation parameters, the spacer is removed and the prosthesis is replaced with a new one.
   

Septic arthritis refers to the infection of a joint by one or more germs that infiltrate it; the infection damages the joint, causing severe pain, heat, redness, bruising and progressive limited functionality.

The septic process, if not cured, can lead to the destruction of the cartilage and thus compromise joint function.

The most common location for septic arthritis is the knee, but also other joints can be affected (ankle, hip, wrist, elbow, shoulder, spinal column being the most frequent).

A complex diagnostic process allows for recognition of the pathology and often, for the identification of the germ involved.

The treatment includes, in this case as well, a targeted antibiotic therapy and often, in septic arthritis of the largest joints, surgical cleaning that normally is done arthroscopically.