Methods

In this study, 120 synovial fluid samples were included, aspirated from patients with clinical signs of PJI. For these samples microbiology data (obtained in the clinical microbiology lab using standard procedures) and next generation sequencing (NGS) data, were available. The samples were incubated in the SSF medium at different oxygen levels (21% O₂, 3% O₂ and 0% O₂) for 10 days. Every 24h, the presence of growth was checked. From positive samples, cultures were purified on Columbia blood agar and identified using MALDI-TOF. In parallel, heat produced by metabolically active microorganisms present in the samples was measured using ITC (calScreener, Symcel), (96h at 37°C, in SSF, BHI and thioglycolate). From the resulting thermograms the ‘time to activity’ could be derived. The accuracy and time to detection were compared between the different detection methods.

Method

This investigation was set up as a multicenter prospective cohort study. Synovial fluid was obtained by means of joint aspiration or intra-operative tissue biopsies. A presumptive PJI diagnosis was made according to criteria outlined by the Musculoskeletal Infection Society (MSIS), the Infectious Diseases Society of America (IDSA) and the European Bone and Joint Infection Society (EBJIS). The intention to treat by the surgeon was logged. Sensibility and specificity for the ADLF test was plotted for each aforementioned diagnostic algorithm. Spearman correlations between all scores were analyzed. Multiple logistic regression was used to determine the contribution of independent variables to the probability of PJI.

Method

The diagnosis of a PJI was defined according to major and minor criteria following revised International Consensus Symposium algorithm

The validated McPherson staging system was used in our university hospital from January 2015 until January 2019 in referred PJI patients. Standardised preoperative and postoperative survey documents were completed in order to register data from the patient's medical, social and surgical history. The complexity of the infected implant was taken into consideration, including quantity of preceding procedures, residual bone stock, type of fixation, magnitude of prosthetic components and presence or absence of reconstructive options. Further, preoperatively obtained bacteriological information by means of arthrocentesis or tissue/bone biopsies was categorized according to the mono- or polybacterial nature and to the qualification of virulence and difficulties to treat. Social and professional history, financial impediments and patient's functional outcome wishes were included in the joint decision making.

Method

After introduction of ‘a clean phase’ concept in our center, we developed a method of using new instrumentation sets and waterproof cover sheets as well as sets of gloves and aprons after thorough debridement followed by copious irrigation under a splash sheet, once the prosthetic components were removed during which several (6 to 8) tissue biopsies and cultures were harvested. ‘Clean phase’ tissue specimens ad random were again obtained and cultured and compared with ‘dirty phase’ cultures and sonication results. Our zero hypothesis was that we were not able to entirely eradicate bacterial colonization. We tested this hypothesis during a period of 18 months in a consecutive series of first stage revisions for PJI at our center after introduction of the clean phase concept.

Method

A retrospective monocentric study was conducted at the 40-bed orthopedics department of a tertiary centre. Medical files of patients with proven prosthetic knee or hip infection with PJACs from maximum 6 months prior to the first stage of a two-stage revision admitted between March 2010 and December 2014 were evaluated. A proven PJI was defined as at least two positive preoperative or intraoperative cultures, the presence of purulent synovial fluid or purulence at the implant site or surrounding the prosthesis without other identifiable causes, the presence of acute inflammation upon histopathological examination of the periprosthetic tissue at the time of surgery or the presence of a sinus tract communicating with the prosthesis. In order to identify the causative pathogen(s) per patient, a multidisciplinary team, consisting out of a microbiologist, a septic orthopedic surgeon, two infectious diseases specialists and two clinical pharmacists, assessed the relevance of pathogens cultured in the PJACs and intraoperative deep samples based on the current 2012 IDSA guidelines. Per patient, agreement of PJACs corresponding to the retained causative pathogen(s) was investigated in two ways: 1) on species level and 2) on Gram stain or fungi level.

Conclusion

In this study, the sonographic information only led to a modest gain in diagnostic confidence. Ultrasound was particularly helpful for surgeons in clarifying hips with limited abduction or signs of leg length difference.