Thomas M. Randau

Interleukin-6 in serum and in synovial fluid enhances the differentiation between periprosthetic joint infection and aseptic loosening.

The preoperative differentiation between septic and aseptic loosening after total hip or knee arthroplasty is essential for successful therapy and relies in part on biomarkers. The objective of this study was to assess synovial and serum levels of inflammatory proteins as diagnostic tool for periprosthetic joint infection and compare their accuracy with standard tests. 120 patients presenting with a painful knee or hip endoprosthesis for surgical revision were included in this prospective trial. Blood samples and samples of intraoperatively acquired joint fluid aspirate were collected. White blood cell count, C-reactive protein, procalcitonin and interleukin-6 were determined. The joint aspirate was analyzed for total leukocyte count and IL-6. The definite diagnosis of PJI was determined on the basis of purulent synovial fluid, histopathology and microbiology. IL-6 in serum showed significantly higher values in the PJI group as compared to aseptic loosening and control, with specificity at 58.3% and a sensitivity of 79.5% at a cut-off value of 2.6 pg/ml. With a cut-off >6.6 pg/ml, the specificity increased to 88.3%. IL-6 in joint aspirate had, at a cut-off of >2100 pg/ml, a specificity of 85.7% and sensitivity of 59.4%. At levels >9000 pg/ml, specificity was almost at 100% with sensitivity just below 50%, so PJI could be considered proven with IL-6 levels above this threshold. Our data supports the published results on IL-6 as a biomarker in PJI. In our large prospective cohort of revision arthroplasty patients, the use of IL-6 in synovial fluid appears to be a more accurate marker than either the white blood cell count or the C-reactive protein level in serum for the detection of periprosthetic joint infection. On the basis of the results we recommend the use of the synovial fluid biomarker IL-6 for the diagnosis of periprosthetic joint infection following total hip and knee arthroplasty.

Comparison of clinical and radiological data in the treatment of patients with osteoporotic vertebral compression fractures using radiofrequency kyphoplasty or balloon kyphoplasty

PURPOSE Since the 1990s, balloon kyphoplasty has been proven as an effective method of treating patients with painful vertebral compression fractures (VCF). The radiofrequency kyphoplasty is an innovative procedure available since 2009, for which an ultra-high viscosity cement is used. For the statistical comparison of the two methods of augmentation, the clinical and radiological data of 2 larger patient groups were evaluated. MATERIALS AND METHODS As part of the surgical treatment of patients with conservative therapy-resistant osteoporotic vertebral fractures, a prospective study of radiofrequency kyphoplasty (RFK) was performed between 2009 and September 2010. The treatment was minimally invasive using the StabiliT® Vertebral Augmentation System by DFine for which the StabiliT® multiplex controller, the articulating VertecoR® Midline Osteotome, and the radiofrequency-sensitive StabiliT® ER2 bone cement were applied. From the clinical aspect, measurement parameters for efficacy and safety were the course of pain intensity using a visual analogue scale (VAS: 0 to 100 mm) and the Oswestry disability score (0-100%). For the radiological outcome the increase in the middle and anterior parts of the treated vertebra and also the reduction of kyphosis after surgery and after 6 months were evaluated. Furthermore, the extent of cement extrusion and the duration of operation time were compared. There were 2 groups of patients chosen with the same indication, and with the same average VAS prior to treatment. For the balloon kyphoplasty (BKP) the Kyphon® technology was used. For the BKP group the same parameters as in the first group were evaluated (matched pairs). To compare the data statistically, parametric and non-parametric tests were applied. RESULTS For the radiofrequency kyphoplasty group (RFK) 114 patients were recruited, and for the balloon kyphoplasty group (BKP) 114 appropriate patients were selected. In 48% of the RFK patients and in 44% of the BKP patients more than one vertebral body were treated (thoracic or lumbar). Prior to treatment 84 mm on the VAS were calculated in both groups. The decrease in VAS values (RFK vs. BKP) immediately after surgery was 58.8 vs. 54.7 mm (p = 0.02), and 73.0 vs. 58.9 mm after 6 months (p < 0.001). In both groups improvements in the Oswestry scores were registered after 6 months without a statistically significant difference. In both groups, the middle part of the vertebral bodies was increased by an average of 3.1 mm. RFK yielded a decrease in the average kyphosis angle of 4.4, the BKP resulted in about 3.8 degrees. Concerning cement leakage a key difference in favor of the radio frequency kyphoplasty was detected (6.1 % vs. 27.8%; p < 0.0001). For RFK a significant shorter duration of operation time was calculated (28.2 vs. 49.6 min; p < 0.001). CONCLUSIONS The RFK has proven to be a clinically very effective procedure that does somewhat better than BKP in long-lasting pain relief. No differences could be detected regarding improvement of functioning and the mean restoration of mid- and anterior vertebral height. As far as the safety aspect is concerned the RFK offers the advantage of a statistically significant lower proportion of cement extrusion.

Unyvero i60 implant and tissue infection (ITI) multiplex PCR system in diagnosing periprosthetic joint infection.

Periprosthetic joint infection (PJI) is one of the most challenging complications in orthopedic surgery. In cases of suspected periprosthetic joint infection several diagnostic methods are available. In this study we investigated the performance of the newly available Unyvero i60 implant and tissue infection (ITI) multiplex PCR System. 62 specimens from 31 patients with suspected PJI or aseptic loosening of a painful joint arthoplasty were included in this study. Besides the established diagnostic procedures we included a commercial multiplex PCR detection system for diagnosis of PJI. The PCR results obtained from analysis of sonication and synovial fluids (62 specimens) showed a sensitivity of 66.7%, a specificity of 100%, a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 68.4% when compared to cultural methods. Notably, cultures from sonication fluid displayed a sensitivity of 88.9%, a specificity of 61.5%, a PPV of 76.2% and a NPV of 80.0% when compared to tissue cultures. In conclusion, multiplex PCR is an additional - rapid - method for diagnosing PJI. Positive results with the PCR assay used in this study were always confirmed by subsequent matching culture positivity. However, apart from the time saved the nucleic acid amplification technique did not yield additional information than that obtained from microbiological cultures.

The Effect of Dexamethasone and Triiodothyronine on Terminal Differentiation of Primary Bovine Chondrocytes and Chondrogenically Differentiated Mesenchymal Stem Cells

The newly evolved field of regenerative medicine is offering solutions in the treatment of bone or cartilage loss and deficiency. Mesenchymal stem cells, as well as articular chondrocytes, are potential cells for the generation of bone or cartilage. The natural mechanism of bone formation is that of endochondral ossification, regulated, among other factors, through the hormones dexamethasone and triiodothyronine. We investigated the effects of these hormones on articular chondrocytes and chondrogenically differentiated mesenchymal stem cells, hypothesizing that these hormones would induce terminal differentiation, with chondrocytes and differentiated stem cells being similar in their response. Using a 3D-alginate cell culture model, bovine chondrocytes and chondrogenically differentiated stem cells were cultured in presence of triiodothyronine or dexamethasone, and cell proliferation and extracellular matrix production were investigated. Collagen mRNA expression was measured by real-time PCR. Col X mRNA and alkaline phosphatase were monitored as markers of terminal differentiation, a prerequisite of endochondral ossification. The alginate culture system worked well, both for the culture of chondrocytes and for the chondrogenic differentiation of mesenchymal stem cells. Dexamethasone led to an increase in glycosaminoglycan production. Triiodothyronine increased the total collagen production only in chondrocytes, where it also induced signs of terminal differentiation, increasing both collagen X mRNA and alkaline phosphatase activity. Dexamethasone induced terminal differentiation in the differentiated stem cells. The immature articular chondrocytes used in this study seem to be able to undergo terminal differentiation, pointing to their possible role in the onset of degenerative osteoarthritis, as well as their potential for a cell source in bone tissue engineering. When chondrocyte-like cells, after their differentiation, can indeed be moved on towards terminal differentiation, they can be used to generate a model of endochondral ossification, but this limitation must be kept in mind when using them in cartilage tissue engineering application.

Investigation of neutrophilic peptides in periprosthetic tissue by matrix-assisted laser desorption ionisation time-of-flight imaging mass spectrometry

PurposeThe accurate diagnosis of periprosthetic joint infection (PJI) relies on clinical investigation, laboratory parameters, radiological methods, sterile joint aspiration for synovial fluid leucocyte count and microbiological analysis and tissue sampling for histopathology. Due to the limits in specificity and sensitivity of these methods, molecular techniques and new biomarkers were introduced into the diagnostic procedure. Histological examination is related to the amount of neutrophils in the periprosthetic tissue in frozen sections and formalin-fixed paraffin embedded material (FFPE). However, the threshold of neutrophils per defined area of tissue among various studies is very inconsistent.MethodsWe have applied matrix-assisted laser desorption ionisation time-of-flight imaging mass spectrometry (MALDI IMS) to a total of 32 periprosthetic tissue samples of patients with PJI to detect peptides associated with areas of neutrophil infiltration.ResultsSpecific peaks associated with a high amount of neutrophils were detected. Of these m/z peaks, four could be assigned to predictive neutrophil molecules. These peptides include annexin A1, calgizzarin (S100A11), calgranulin C (S100A12) and histone H2A. By MALDI IMS, these peptides could be shown to be co-localised with the infiltration of neutrophils in the immediate vicinity of the periprosthetic interface, whereas more distant areas did not show neutrophil invasion or infection-related peptides.ConclusionsMALDI IMS is a new method allowing identification of neutrophil peptides in periprosthetic tissues and may be a surrogate for counting neutrophils as an objective parameter for PJI.

Comparison of bacterial growth in sonication fluid cultures with periprosthetic membranes and with cultures of biopsies for diagnosing periprosthetic joint infection

Total joint arthroplasty is a common operation worldwide with infection rates between 1% and 3%. In cases of suspected periprosthetic joint infection, it is very challenging to rule out the causative microorganisms. In this study, we compared the appearance of periprosthetic membranes with the microbiological results obtained from cultures of sonication fluid and the correlation between classical microbiological cultures and cultures of sonication fluid. The results confirmed a strong correlation of bacterial growth in sonication fluid cultures with bacterial growth in classical microbiological cultures. Most importantly, however, our study documented a highly significant correlation of periprosthetic membranes typical for periprosthetic joint infection (PJI) with bacterial growth in sonication fluid. Sonication fluid cultures yielded a better sensitivity than tissue cultures (72.34-60.87%). These 3 methods are useful tools in diagnosing PJIs, and even more, sonication fluid cultures should be included in the diagnostic path of PJI.

RANK-ligand and osteoprotegerin as biomarkers in the differentiation between periprosthetic joint infection and aseptic prosthesis loosening

AIM To assess serum levels of RANK-ligand (RANKL) and osteoprotegerin (OPG) as biomarkers for periprosthetic joint infection (PJI) and compare their accuracy with standard tests. METHODS One hundred and twenty patients presenting with a painful total knee or hip arthroplasty with indication for surgical revision were included in this prospective clinical trial. Based on standard diagnostics (joint aspirate, microbiological, and histological samples) and Musculoskeletal Infection Society consensus classification, patients were categorized into PJI, aseptic loosening, and control groups. Implant loosening was assessed radiographically and intraoperatively. Preoperative serum samples were collected and analyzed for RANKL, OPG, calcium, phosphate, alkaline phosphatase (AP), and the bone-specific subform of AP (bAP). Statistical analysis was carried out, testing for significant differences between the three groups and between stable and loose implants. RESULTS All three groups were identical in regards to age, gender, and joint distribution. No statistically significant differences in the serum concentration of RANKL (P = 0.16) and OPG (P = 0.45) were found between aseptic loosening and PJI, with a trend towards lower RANKL concentrations and higher OPG concentrations in the PJI group. The RANKL/OPG ratio was significant for the comparison between PJI and non-PJI (P = 0.005). A ratio > 60 ruled out PJI in all cases (specificity: 100%, 95%CI: 89, 11% to 100.0%) but only 30% of non-PJI patients crossed this threshold. The positive predictive value remained poor at any cut-off. In the differentiation between stable and loose implants, none of the parameters measured (calcium, phosphate, AP, and bAP) showed a significant difference, and only AP and bAP measurements showed a tendency towards higher values in the loosened group (with P = 0.09 for AP and P = 0.19 for bAP). CONCLUSION Lower RANKL and higher OPG concentrations could be detected in PJI, without statistical significance.

Two-stage knee arthrodesis with a modular intramedullary nail due to septic failure of revision total knee arthroplasty with extensor mechanism deficiency

BACKGROUND Periprosthetic joint infection is a serious complication and reconstruction after failed revision total knee arthroplasty with significant bone loss and compromised soft-tissues can be challenging. Objective of this study was to assess clinical and functional results, implant survival and infection recurrence rates in patients treated with two-stage arthrodesis after failed revision TKA with extensor mechanism deficiencies due to PJI, and to identify the factors that affect outcomes after surgery. METHODS Thirty seven patients with PJI treated within a two-stage exchange and reimplantation of an arthrodesis nail between 2008 and 2014 were included. Systemic and local risk factors were graded preoperatively according to McPherson et al. All patients were treated according to a structured treatment algorithm. Clinical and functional evaluation was performed using the Oxford Knee Score and the Visual Analogue Scale. RESULTS Thirty two of 37 patients (86.5%) were graded as free of infection. Five patients (13.5%) had recurrent infection after arthrodesis with the need of revision surgery. Mean leg-length discrepancy was 2.2cm. The mean VAS for pain was three, the mean Oxford Knee Score was 38±9. Total implant survival at a 74month follow-up was 74.3% (95% CI: 45.4 to 91.1%), as determined by Kaplan-Meier survival curves. Local McPherson Score, as well as number of revisions was found to be of significant influence to the survival rate. CONCLUSIONS Septic failure of revision knee arthroplasty can be effectively treated with two-stage arthrodesis using a modular intramedullary nail, providing a stable and painless limb with satisfactory functional results and acceptable infection eradication rates.

Single Molecule Microscopy Reveals an Increased Hyaluronan Diffusion Rate in Synovial Fluid from Knees Affected by Osteoarthritis.

Osteoarthritis is a common and progressive joint disorder. Despite its widespread, in clinical practice only late phases of osteoarthritis that are characterized by severe joint damage are routinely detected. Since osteoarthritis cannot be cured but relatively well managed, an early diagnosis and thereby early onset of disease management would lower the burden of osteoarthritis. Here we evaluated if biophysical parameters of small synovial fluid samples extracted by single molecule microscopy can be linked to joint damage. In healthy synovial fluid (ICRS-score < 1) hyaluronan showed a slower diffusion (2.2 μm2/s, N = 5) than in samples from patients with joint damage (ICRS-score > 2) (4.5 μm2/s, N = 16). More strikingly, the diffusion coefficient of hyaluronan in healthy synovial fluid was on average 30% slower than expected by sample viscosity. This effect was diminished or missing in samples from patients with joint damage. Since single molecule microscopy needs only microliters of synovial fluid to extract the viscosity and the specific diffusion coefficient of hyaluronan this method could be of use as diagnostic tool for osteoarthritis.

Detection of Pantoea agglomerans in hip prosthetic infection by sonication of the removed prosthesis: The first reported case

Pantoea agglomerans is a rare isolate in orthopaedic patients. We describe the first case of an acute hip prosthetic joint infection (PJI) caused by Pantoea agglomerans. The microorganism was detected after sonication of the removed hip endoprosthesis.