New insights on metal allergy in total joint arthroplasty.

Metal allergy is an uncommon and not completely understood cause of failure in total joint arthroplasty (TJA). However, either immunopathology neither histologic studies clarified the mechanisms through which the metal ions could lead to the complications related to them. The lack of evidence around this topic also reflects the difficulties to diagnose the MRP in TJA. In fact, the diagnosis is generally based on the exclusion of other causes. Currently, skin-patch testing and lymphocyte transformation test (LTT) are being commonly used to investigate about metal hypersensitivity and a delayed type-IV hypersensitivity is the immuno-histologic response to metals involved in TJA loosening. A review of the recent publications about this topic has been made focusing on immunology, histopathology, and clinics to better understand a still debated topic in orthopedic practice.

Two-stage reimplantation in periprosthetic knee infection.

OBJECTIVE: The increasing number of total knee arthroplasties performed yearly worldwide has resulted in a concomitant rise in bacterial infections. Two-stage reimplantation has been reported as the most successful method of treating periprosthetic knee infections. The purpose of this study was to describe all the phases of the two-stage reimplantation and to review the literature regarding the topic. MATERIALS AND METHODS: Most significant and recent papers about the management of periprosthetic knee infection through a two-stage reimplantation protocol were carefully analysed and reviewed. Our personal experience, previously published, with two-stage-reimplantation protocol was also briefly reported. RESULTS: Two-stage reimplantation has been reported as the most successful method of treating periprosthetic knee infections. The strategy of using an antibiotic-loaded cement spacer and intravenous antibiotics with delayed exchange arthroplasty is actually considered the state-of-the-art, with a reported success rate of 88-96%. The two-stage protocol has been reported as a viable option also for patients with a periprosthetic knee infection by multidrug-resistant organisms. On the other hand, open debridement with polyethylene exchange and single-stage reimplantation have been reported effective only in selective case series involving acute infections by low-virulence organisms. CONCLUSIONS: The strategy that involves the use of cement spacer, intravenous antibiotic therapy, and successive revision total knee implantation is nowadays considered the gold standard for the management of the periprosthetic knee infection. This treatment is actually considered the first choice not only for chronic but also for acute infections, especially in the presence of resistant bacteria.