Introduction: Reports about the usefulness of FDG-PET in detecting infections were few in the last years but are greatly increasing in number in the recent years. The interest for this method is related to the demonstration that FDG uptake is increased in cells with elevated glycolitic activity as neoplastic cells, neutrophils, activated macrophages, probably bacteria. As far as a neoplasm is excluded, FDG uptake is increased in inflammatory sites. This study was done to test the possible use of this method in painful total hip-replacement diagnosis.

Materials and methods: A prospective study on 24 patients (33 hip arthroplasties) affected by painful total hip replacement was conducted. All patient has blood test, X-ray examinations of hips and chest, Ultrasound scan, cultures from sinus tract or hip aspiration, Tc^99m MDC bone scan (SPECT), FDG-PET. Areas of uptake were evaluated and compared. Fifteen patients were operated on (9 two-stage revisions, debridements), during operation cultures were repeated and bone biopsy were done at the sites of icreased PET uptake. Bone and soft tissue debridement was specifically performed on site of PET uptake with maximal preservation of bone stock.

Results: Infected hips were 20. Infection was demonstrated by positive culture and positive biopsy in all cases. Sensibility and specificity of PET were respectively 100% and 92%. The study of tracers uptake showed that these are complementary and give different information. All patients who were operated on were reviewed with a mean follow up of 7 months (range 3 months-15 months ). The nine patients who had revision were free of infection at follow-up.

Discussion: from our experience PET is easy to perform, has an excellent sensibility and good specificity and can be placed at the end point of the flow-chart for diagnosis of total hip replacement infection (preceeded in any case by standard X-Rays and bone scan). Moreover PET scan could be useful in pre-operative planning of revision surgery as it has better anatomical definition than traditional scans and may allows surgeon to localize on three planes infected bone and soft tissues. Therefore at the moment this tool has high costs so should be used in selected cases. Its real usefulness in revision surgery has to be confirmed by a longer follow-up of treated cases.

A prospective study on 24 patients (33 hip arthroplasties) affected by painful total hip replacement was conducted. All patient had a blood test, X-rays, ultrasound scan, cultures, Tc ^99m bone scan (SPECT), and F¹⁸FDG-PET. Fifteen patients were operated on (nine two-stage revisions, six débridements). During operation, cultures were repeated and bone biopsy was performed at the sites of increased PET uptake. Bone and soft tissue débridement was specifically performed at the site of PET uptake with maximal preservation of bone stock.

There were 20 infected prostheses. Infection was demonstrated by positive culture in all cases and positive biopsy in operated cases. Sensibility and specificity of PET were 100% and 92%, respectively. All patients who were operated on were reviewed with a mean follow-up of 7 months. The nine patients who had revision were free of infection at follow-up.

In our experience PET is easy to perform, has an excellent sensitivity and good specificity and can be placed at the end point of the flow-chart for diagnosis of total hip replacement infection. Moreover, PET scan could be useful in pre-operative planning of revision surgery as it has better anatomical definition than traditional scans. Presently, it involves high costs and should only be used in selected cases. Its real usefulness in revision surgery has to be confirmed by a longer follow-up of treated cases.

Bone loss, either due to a septic process or to surgical débridements, is frequently associated with bone infections. Bone loss may be present in septic non-unions, osteomyelitis or septic joint prosthesis. In each of these conditions the use of bone or bone substitutes may be indicated. However, the risk of septic recurrence makes the choice of the right implant in these patients particularly difficult.

Clinical cases are presented to show the different choices available. Attention is focussed on: (1) when, in the presence of bone loss, a bone graft can be avoided and with which suitable procedures good results can be obtained; (2) when and how autologous bone grafts should be used; (3) when homologous bone grafts or bone substitutes are indicated; (4) how bone grafts should be protected against bacterial adesion and proliferation; and (5) the role of new technologies, such as bone growth factors. In this regard the clinical results are presented of the use of platelet-rich plasma (PRP) added to autologous or homologous bone after bone débridement in six patients treated with two-stage non-cemented revision of septic hip prosthesis and in two patients with septic non-union of the femur. At a minimum follow-up of 6 months (max. 1 year), we did not observe any infection recurrence, while bone remodelling and clinical outcome were favourable.

The use of bone growth factors such as PRP possibly added to autologous or homologous bone appears to be a promising technique to achieve bone reconstruction in débrided bone infections. However, with the limited numbers of patients and the short-term follow-up conclusions cannot be drawn and the use of growth factors with this indication should be limited to selected cases: patients with wide bone loss and with no signs of active infections.

No international guidelines are available concerning bone reconstruction in infections. Clinical experience shows that different surgical procedures are effective and the choice should take into considerations the type and site of bone defect, the host type and the pathogenesis of the bone loss. Growth factors may be a useful tool in these conditions and further studies are indicated.