Long-term stability of total hip arthroplasty (THA) depends on the integration between osseous tissue and the biomaterial implant. Integrity of the osseous tissue requires the contribution of mesenchymal stem cells and their continuous differentiation into an osteoblastic phenotype.

Some studies, like Wang ML et al., show that chronic exposure to titanium and zirconium oxide wear debris may contribute to decreased bone formation at the bone/implant interface by reducing the population of viable human mesenchymal stem cells (hMSCs) and compromising their differentiation into functional osteoblasts.

On the basis of our good experience in the use of Exeter technique in revision surgery of THA, two years ago we started to utilize bone grafts mixed with growth factors in order to improve grafts incorporation and implant fixation. At the moment we are studying the use of hMSCs during hip revision surgery, employing polyethylene cup to reduce the possible titanium and zirconium oxide debris. hMSCs are obtained with MarrowsStim Concentration Kit (Biomet Biologics Europe) by 60 ml of patient’s bone marrow.

Clinical outcomes and quality of life are evaluated on the basis of Harris Hip Score, Womac score and SF-36 score, while bone graft incorporation features are assessed with post operative computed tomography (CT) examination and further CT controls at two, four and eight months after surgery.

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.