Ruling out an infection in one-stage knee and hip revisions for presumed aseptic failure by conventional tissue cultures takes up to 14 days. Multiplex polymerase chain reaction (PCR) is a quick test (4–5 hours) for detecting infections. The purpose of this study was to evaluate the negative predictive value of an automated multiplex PCR for the detection of microorganisms in synovial fluid obtained intraoperatively in unsuspected knee and hip revisions.

The NPV of the multiplex PCR U-ITI system of synovial fluid compared to tissue cultures of knee and hip revisions was 95.7% and 92.5%, respectively. Cultures required several days for growth whereas the automated mPCR U-ITI system provided results within five hours.

The multiplex PCR U-ITI system is a quick and reliable test in ruling out infection in presumed aseptic knee and hip revisions. With this test the number of unsuspected infected revisions can be lowered and antibiotic overtreatment as well as undertreatment after one-stage revision arthroplasty can be avoided. This directly results in a reduction in length of hospital stay, hospital costs and possible antibiotic resistance development.

Aim

Currently, despite a thorough diagnostic work up, around ten percent of the presumed aseptic revisions turn out to have unexpected positive cultures during the revision procedure. The purpose of this study was to evaluate the negative predictive value (ruling out) of the automated multiplex PCR Unyvero i60 implant and tissue infection (ITI) cartridge (U-ITI) system for the detection of microorganisms in synovial fluid obtained intraoperatively.

Prosthetic joint infections (PJI) caused by Streptococcus species are relatively common.

The aim of our study was to assess outcome after treatment for early and late PJI with Streptococcus species after a follow-up of two years.

For this study we retrospectively included all patients with primary or revision total knee arthroplasty (TKA) or total hip (THA) arthroplasty, a minimum of two periprosthetic tissue cultures positive for Streptococcus species and a minimum follow-up of one year. According to international guidelines patients were classified as having early or late PJI. All patients with an early PJI were treated according to a standard treatment protocol, i.e. debridement and retention of the prosthesis, followed by adequate antibiotic therapy. Patients with late PJI underwent a debridement followed by adequate antibiotic therapy or joint revision. Patients’ hospital records were reviewed and we evaluated the status of the original prosthesis after an infection.

Forty cases were included; 24 early and 16 late PJI. For early PJI, open debridement was performed in all patients, after a mean of 19 (range: 9 – 80) days. At final follow-up 21 prostheses (88%) were still in situ and without clinical signs of infection. Eight cases (41%) of late PJI were successfully treated with debridement and retention. Nine patients (59%) underwent a one- or two-stage revision. At final follow-up 16 patients (100%) with late PJI had a prosthesis in situ. Streptococcus dysgalactiae species accounted for more than 50% of the early infections, followed by Streptococcus agalactiae with 30%.

In case of PJI with Streptococcus species open debridement and retention of the prosthesis should be performed followed by adequate and long-term antibiotic treatment. As expected, the retention rate for early PJI is much higher than that for late PJI.

Background: ASPS is a rare, high grade sarcoma primarily affecting children and young adults. Its origin remains enigmatic and there has until recently been no diagnostic markers. Diagnostic problems particularly occur when presenting as metastasis before detection of the primary tumour and when there is morphologic overlap with other malignancies. Recently, identification ASPS/TFE3 fusion transcripts and immuno-detection of TFE3 have been reported as useful diagnostic tools.

Design: 17 ASPS were analysed in terms of clinicopatho-logic characteristics, treatment and follow up. Archival formalin-fixed and paraffin embedded tissues were used for TFE3 immuno-histochemistry and RNA extraction followed by RT-PCR analysis and sequencing. Novel primers to detect ASPS/TFE3 fusion transcripts, type 1 and 2, were designed.

Results: The patients, 9 females/8 males, ranged in age from 3 to 46 years (median 23 years); 16 involved the extremities (9 lower, 7 upper) and one the pelvis. All but one patient had primary, curative surgery; chemotherapy and radiotherapy was given for metastatic disease. Five had lung metastases at diagnosis and 3 developed lung and brain metastases later. Four patients died of disease (after 1–5 years), 4 are alive with metastases and 9 are alive and well (after 6 mos.-10 years). 15/15 ASPS showed ASPL/TFE3 fusion transcripts (8 type 1, 7 type 2) and TFE3 immuno-positivity. Of 26 control tumours, several of which with overlapping morphologic features, none had fusion transcripts, 4 showed immuno-positivity (all granular cell tumours).

Conclusions: Immuno-detection of TFE3 and RT-PCR based identification of ASPL/TFE3 fusion transcripts in formalin-fixed/paraffin embedded tissues are powerful tools in the diagnosis of ASPS.