Aims. The aim of this study was to determine the diagnostic accuracy of α defensin (AD) lateral flow assay (LFA) and enzyme-linked immunosorbent assay (ELISA) tests for periprosthetic joint infection (PJI) in comparison to conventional synovial white blood cell (WBC) count and polymorphonuclear neutrophil percentage (PMN%) analysis. Methods. Patients undergoing joint aspiration for evaluation of pain after total knee arthroplasty (TKA) or total hip arthroplasty (THA) were considered for inclusion. Synovial fluids from 99 patients (25 THA and 74 TKA) were analyzed by WBC count and PMN% analysis, AD LFA, and AD ELISA. WBC and PMN% cutoffs of ≥ 1,700 cells/mm. 3. and ≥ 65% for TKA and ≥ 3,000 cells/mm. 3. and ≥ 80% for THA were used, respectively. A panel of three physicians, all with expertise in orthopaedic infections and who were blinded to the results of AD tests, independently reviewed patient data to diagnose subjects as with or without PJI. Consensus PJI classification was used as the reference standard to evaluate test performances. Results were compared using McNemar’s test and area under the receiver operating characteristic curve (AUC) analysis. Results. Expert consensus classified 18 arthroplasies as having failed due to PJI and 81 due to aseptic failure. Using these classifications, the calculated sensitivity and specificity of AD LFA was 83.3% (95% confidence interval (CI) 58.6 to 96.4) and 93.8% (95% CI 86.2 to 98.0), respectively. Sensitivity and specificity of AD ELISA was 83.3% (95% CI 58.6 to 96.4) and 96.3% (95% CI 89.6 to 99.2), respectively. There was no statistically significant difference between sensitivity (p = 1.000) or specificity (p = 0.157) of the two AD assays. AUC for AD LFA was 0.891. In comparison, AUC for synovial WBC count, PMN%, and the combination of the two values was 0.821 (sensitivity p = 1.000, specificity p < 0.001), 0.886 (sensitivity p = 0.317, specificity p = 0.011), and 0.926 (sensitivity p = 0.317, specificity p = 0.317), respectively. Conclusion. The diagnostic accuracy of synovial AD for PJI diagnosis is comparable and not statistically superior to that of synovial WBC count plus PMN% combined. Cite this article: Bone Joint J 2021;103-B(6):1119–1126

Aims

Current guidelines consider analyses of joint aspirates, including leucocyte cell count (LC) and polymorphonuclear percentage (PMN%) as a diagnostic mainstay of periprosthetic joint infection (PJI). It is unclear if these parameters are subject to a certain degree of variability over time. Therefore, the aim of this study was to evaluate the variation of LC and PMN% in patients with aseptic revision total knee arthroplasty (TKA).

Aims. To investigate the optimal thresholds and diagnostic efficacy of commonly used serological and synovial fluid detection indexes for diagnosing periprosthetic joint infection (PJI) in patients who have rheumatoid arthritis (RA). Methods. The data from 348 patients who had RA or osteoarthritis (OA) and had previously undergone a total knee (TKA) and/or a total hip arthroplasty (THA) (including RA-PJI: 60 cases, RA-non-PJI: 80 cases; OA-PJI: 104 cases, OA-non-PJI: 104 cases) were retrospectively analyzed. A receiver operating characteristic curve was used to determine the optimal thresholds of the CRP, ESR, synovial fluid white blood cell count (WBC), and polymorphonuclear neutrophil percentage (PMN%) for diagnosing RA-PJI and OA-PJI. The diagnostic efficacy was evaluated by comparing the area under the curve (AUC) of each index and applying the results of the combined index diagnostic test. Results. For PJI prediction, the results of serological and synovial fluid indexes were different between the RA-PJI and OA-PJI groups. The optimal cutoff value of CRP for diagnosing RA-PJI was 12.5 mg/l, ESR was 39 mm/hour, synovial fluid WBC was 3,654/μl, and PMN% was 65.9%; and those of OA-PJI were 8.2 mg/l, 31 mm/hour, 2,673/μl, and 62.0%, respectively. In the RA-PJI group, the specificity (94.4%), positive predictive value (97.1%), and AUC (0.916) of synovial fluid WBC were higher than those of the other indexes. The optimal cutoff values of synovial fluid WBC and PMN% for diagnosing RA-PJI after THA were significantly higher than those of TKA. The specificity and positive predictive value of the combined index were 100%. Conclusion. Serum inflammatory and synovial fluid indexes can be used for diagnosing RA-PJI, for which synovial fluid WBC is the best detection index. Combining multiple detection indexes can provide a reference basis for the early and accurate diagnosis of RA-PJI. Cite this article: Bone Joint Res 2023;12(9):559–570

Aims. The diagnosis of periprosthetic joint infection (PJI) can be challenging as the symptoms are similar to other conditions, and the markers used for diagnosis have limited sensitivity and specificity. Recent research has suggested using blood cell ratios, such as platelet-to-volume ratio (PVR) and platelet-to-lymphocyte ratio (PLR), to improve diagnostic accuracy. The aim of the study was to further validate the effectiveness of PVR and PLR in diagnosing PJI. Methods. A retrospective review was conducted to assess the accuracy of different marker combinations for diagnosing chronic PJI. A total of 573 patients were included in the study, of which 124 knees and 122 hips had a diagnosis of chronic PJI. Complete blood count and synovial fluid analysis were collected. Recently published blood cell ratio cut-off points were applied to receiver operating characteristic curves for all markers and combinations. The area under the curve (AUC), sensitivity, specificity, and positive and negative predictive values were calculated. Results. The results of the analysis showed that the combination of ESR, CRP, synovial white blood cell count (Syn. WBC), and polymorphonuclear neutrophil percentage (PMN%) with PVR had the highest AUC of 0.99 for knees, with sensitivity of 97.73% and specificity of 100%. Similarly, for hips, this combination had an AUC of 0.98, sensitivity of 96.15%, and specificity of 100.00%. Conclusion. This study supports the use of PVR calculated from readily available complete blood counts, combined with established markers, to improve the accuracy in diagnosing chronic PJI in both total hip and knee arthroplasties. Cite this article: Bone Jt Open 2023;4(11):881–888

Introduction: Necrotic fatty marrow is yellow, thick, and turbid like pus and the fat cell is counted as white blood cell in automated cell counting. When necrotic fatty marrow leaks into the hip joint through a crack in the cartilage of the osteonecrotic femoral head, a misdiagnosis of pyogenic infection can be made. The authors report cases of osteonecrosis of the femoral head, in which a misdiagnosis of pyogenic infection was made during the operation. Materials and Methods: Between September 1997 and December 2001, pyogenic arthritis was suspected during the operation in seven patients who were operated on due to advanced osteonecrosis of the femoral head. The markers of infection including white blood cell count, erythrocyte sedimentation rate, and C reactive protein in preoperative laboratory examination were normal in all of the seven patients. Total hip arthroplasty was scheduled for all patients. When the hip joint capsule was incised, joint fluid gushed out in all patients. The appearance, white blood cell count in automated cell counting, microscopic findings, and the results of culture of the joint fluid were evaluated. Results: The joint fluid was yellow, thick and turbid like pus. A pyogenic arthritis was suspected and the joint fluid was sent to the laboratory for automated blood cell count, smear and culture. The count of white blood cells ranged from 5800 to 18000 in automated cell counting. No microorganism was identified on joint fluid smear. On microscopic cell counting using a hemocytometer, white blood cells were rarely seen and the majority of cells which were counted as white blood cells, were necrotic fat cell. Total hip arthroplasty was performed immediately after microscopic examination of the joint fluid. No microorganism was identified in cultures of the joint fluid. There was no evidence of infection after total hip arthroplasty at a minimum of two-year followup. Discussion: When necrotic fatty marrow leaks into the hip joint, the joint fluid looks like pus and white blood cell counts of the joint fluid is increased in automated cell counting because fat cells are counted as white blood cells. In this situation, microscopic examination of the joint fluid is necessary. If the white blood cell count is not increased in microscopic cell counting, replacement arthroplasty can be performed without risk of infection

Aims. Implant-related postoperative spondylodiscitis (IPOS) is a severe complication in spine surgery and is associated with high morbidity and mortality. With growing knowledge in the field of periprosthetic joint infection (PJI), equivalent investigations towards the management of implant-related infections of the spine are indispensable. To our knowledge, this study provides the largest description of cases of IPOS to date. Methods. Patients treated for IPOS from January 2006 to December 2020 were included. Patient demographics, parameters upon admission and discharge, radiological imaging, and microbiological results were retrieved from medical records. CT and MRI were analyzed for epidural, paravertebral, and intervertebral abscess formation, vertebral destruction, and endplate involvement. Pathogens were identified by CT-guided or intraoperative biopsy, intraoperative tissue sampling, or implant sonication. Results. A total of 32 cases of IPOS with a mean patient age of 68.7 years (37.6 to 84.1) were included. Diabetes, age > 60 years, and history of infection were identified as risk factors. Patient presentation upon admission included a mean body temperature of 36.7°C (36.1 to 38.0), back pain at rest (mean visual analogue scale (VAS) mean 5/10) and when mobile (mean VAS 6/10), as well as elevated levels of CRP (mean 76.8 mg/l (0.4 to 202.9)) and white blood cell count (mean 9.2 units/nl (2.6 to 32.8)). Pathogens were identified by CT-guided or conventional biopsy, intraoperative tissue sampling, or sonication, and Gram-positive cocci presented as the most common among them. Antibiotic therapy was established in all cases with pathogen-specific treatment in 23 (71.9%) subjects. Overall 27 (84.4%) patients received treatment by debridement, decompression, and fusion of the affected segment. Conclusion. Cases of IPOS are rare and share similarities with spontaneous spondylodiscitis. While procedures such as CT-guided biopsy and sonication are valuable tools in the diagnosis of IPOS, MRI and intraoperative tissue sampling remain the gold standard. Research on known principles of PJI such as implant retention versus implant exchange need to be expanded to the field of spine surgery. Cite this article: Bone Jt Open 2023;4(11):832–838

Aims. While preoperative bloodwork is routinely ordered, its value in determining which patients are at risk of postoperative readmission following total knee arthroplasty (TKA) and total hip arthroplasty (THA) is unclear. The objective of this study was to determine which routinely ordered preoperative blood markers have the strongest association with acute hospital readmission for patients undergoing elective TKA and THA. Methods. Two population-based retrospective cohorts were assembled for all adult primary elective TKA (n = 137,969) and THA (n = 78,532) patients between 2011 to 2018 across 678 North American hospitals using the American College of Surgeons National Quality Improvement Programme (ACS-NSQIP) registry. Six routinely ordered preoperative blood markers - albumin, haematocrit, platelet count, white blood cell count (WBC), estimated glomerular filtration rate (eGFR), and sodium level - were queried. The association between preoperative blood marker values and all-cause readmission within 30 days of surgery was compared using univariable analysis and multivariable logistic regression adjusted for relevant patient and treatment factors. Results. The mean TKA age was 66.6 years (SD 9.6) with 62% being females (n = 85,163/137,969), while in the THA cohort the mean age was 64.7 years (SD 11.4) with 54% being female (n = 42,637/78,532). In both cohorts, preoperative hypoalbuminemia (< 35 g/l) was associated with a 1.5- and 1.8-times increased odds of 30-day readmission following TKA and THA, respectively. In TKA patients, decreased eGFR demonstrated the strongest association with acute readmission with a standardized odds ratio of 0.75 per two standard deviations increase (p < 0.0001). Conclusion. In this population level cohort analysis of arthroplasty patients, low albumin demonstrated the strongest association with acute readmission in comparison to five other commonly ordered preoperative blood markers. Identification and optimization of preoperative hypoalbuminemia could help healthcare providers recognize and address at-risk patients undergoing TKA and THA. This is the most comprehensive and rigorous examination of the association between preoperative blood markers and readmission for TKA and THA patients to date. Cite this article: Bone Jt Open 2021;2(6):388–396

Aims. The aim of this study was to evaluate the diagnostic value of preoperative serum CRP, white blood cell count (WBC), percentage of neutrophils (%N), and neutrophil to lymphocyte ratio (NLR) when using the fracture-related infection (FRI) consensus definition. Methods. A cohort of 106 patients having surgery for suspected septic nonunion after failed fracture fixation were studied. Blood samples were collected preoperatively, and the concentration of serum CRP, WBC, and differential cell count were analyzed. The areas under the curve (AUCs) of diagnostic tests were compared using the z-test. Regression trees were constructed and internally cross-validated to derive a simple diagnostic decision tree. Results. Using the FRI consensus definition, 46 patients (43%) were identified as infected. Sensitivity, specificity, and AUC of CRP were 67% (95% confidence interval (CI) 52% to 80%), 61% (95% CI 47% to 74%), and 0.64 (95% CI 0.54 to 0.74); of WBC count were 17% (95% CI 9% to 31%), 95% (95% CI 86% to 99%), and 0.57 (95% CI 0.50 to 0.62); of %N 13% (95% CI 6% to 26%), 87% (95% CI 76% to 93%), and 0.50 (95% CI 0.43 to 0.56); and of NLR 28% (95% CI 17% to 43%), 80% (95% CI 68% to 88%), and 0.54 (95% CI 0.46 to 0.63), respectively. A better performance of serum CRP was shown in comparison to the leucocyte count (p = 0.006), %N (p < 0.001), and NLR (p = 0.001). A statistically lower serum CRP level was shown in patients with an infection caused by a low virulence microorganism in comparison to high virulence bacteria (p = 0.008). We found that a simple decision tree approach using only low serum neutrophils (< 3.615 × 10. 9. /l) and low CRP (< 2.45 mg/l) may allow better identification of aseptic cases. Conclusion. The evaluated serum inflammatory markers showed limited diagnostic value in the preoperative diagnosis of FRI when using the uniform FRI Consensus Definition. Therefore, they should remain as suggestive criteria in diagnosing FRI. Although CRP showed a higher performance in comparison to the other serum markers, it is insufficiently accurate to diagnose a septic nonunion, especially when caused by low virulence microorganisms. Cite this article: Bone Joint J 2020;102-B(7):904–911

High doses of intra-articular (IA) antibiotics has been shown to effectively achieve a minimal biofilm eradication concentration which could mitigate the need for removal of infected but well-ingrown cementless components of a total hip arthroplasty (THA). However, there are concerns that percutaneous catheters could lead to multi-resistance or multi-organism peri-prosthetic joint infections (PJI) following single stage THA revisions for PJI. Eighteen single-stage revision procedures were performed for acute (N=9) or chronic (N=9) PJI following a primary (N=12) or revision (N=6) cementless THA. Modular and loosened components were replaced. All well ingrown components were retained. Two Hickmann catheters were placed in the joint space. Along with intravenous antibiotics, IA antibiotics were injected twice a day for two weeks, followed by 3 months of oral antibiotics. Per-operative cultures demonstrated 4 multi-bacterial PJIs. None of the patients developed post-operatively an AB related renal or systemic dysfunction. At a mean follow-up of 38 months [range, 8–72] all patients had normal erythrocyte sedimentation rate and white blood cell count. Four had a slightly elevated C-reactive protein but were completely symptom free and did not show any sign of loosening at a mean of 27 months [range, 16–59]. Addition of high doses of IA antibiotics following single-stage revision for PJI in cementless THA, is an effective and safe treatment option that allows for retention of well-ingrown components. We found no evidence for residual implant infection or catheter induced multi-resistance. Total hip arthroplasty, revision surgery, Periprosthetic Joint Infection, Intra-articular antibiotics. Level 4 (Case series)

Aims. This multicentre, retrospective study aimed to improve our knowledge of primary pyogenic spinal infections in children by analyzing a large consecutive case series. Patients and Methods. The medical records of children with such an infection, treated at four tertiary institutions between 2004 and 2014, were analyzed retrospectively. Epidemiological, clinical, paraclinical, radiological, and microbiological data were evaluated. There were 103 children, of whom 79 (76.7%) were aged between six months and four years. Results. We confirmed a significant male predominance in the incidence of primary pyogenic spinal infections in children (65%). The lumbar spine was the most commonly affected region, and 27 infections (26.2%) occurred at L4/5. The white blood cell count was normal in 61 children (59%), and the CRP level was normal in 43 (42%). Blood cultures were performed in 95 children, and were positive in eight (8%). A total of 20 children underwent culture of biopsy or aspiration material, which was positive in eight (40%). Methicillin-sensitive Staphylococcus aureus (MSSA) and Kingella (K.) kingae were the most frequently isolated pathogens. Conclusion. MSSA remains the most frequently isolated pathogen in children with primary pyogenic infection of the spine, but K. kingae should be considered as an important pathogen in children aged between six months and four years. Therefore, an empirical protocol for antibiotic treatment should be used, with consideration being made for the triphasic age distribution and specific bacteriological aetiology. In the near future, the results of polymerase chain reaction assay on throat swabs may allow the indirect identification of K. kingae spondylodiscitis in young children and thus aid early treatment. However, these preliminary results require validation by other prospective multicentre studies. Cite this article: Bone Joint J 2018;100-B:542–8

Guidelines for the use of preoperative blood tests for elective surgery were established. However, there is less evidence and no guidelines regarding using these tests when a young, healthy patient undergoes minor orthopaedic trauma surgery. Bloodwork is often ordered routinely, regardless of medical history or the nature of the injury. We hypothesized that unnecessary blood work is requested for younger pre-operative patients, and their results will not change peri-operative management. This practice is not a judicious use of healthcare resources. This study aimed to evaluate the frequency, type, cost, and impact on clinical decisions if standard preoperative bloodwork was completed in healthy patients requiring surgical management of a minor fracture or dislocation. After the approval of our institutional ethics board, a retrospective chart review was conducted. Inclusion criteria were patients aged 18-60 years, who had an isolated minor orthopaedic trauma requiring outpatient surgery, who were American Society of Anesthesiologists (ASA) class 1. ASA class 1 is defined as “a normal healthy patient, without any clinically important comorbidity and without a clinically significant past/present medical history.” Data records from January 1, 2016, to December 31, 2018, were extracted from a provincial database (the Analytics Data Integration, Measurement and Reporting) for five hospitals. Data including demographics, surgical treatment, type and number of blood tests ordered, and ordering physician were collected. Any abnormal test results were checked to see whether they led to a change in patient management or related to a postoperative adverse event. Independent samples t-tests and Chi-square tests were used to compare the characteristics of patients who had preoperative bloodwork versus those who did not. The cost of preoperative blood work was estimated. During these two years, 627 patients met inclusion criteria, and 27% (n=168) of these patients had bloodwork completed pre-operatively, while only 34% (n=57) of these had one or more abnormal laboratory parameters. These abnormalities were minor and did not alter clinical management or result in repeated bloodwork peri-operatively. Patients who had bloodwork were significantly older (40.2 years) compared with patients without preoperative blood work (37.8 years; p=0.03), but there was no difference in sex between those who had bloodwork (53.4% male) and those who did not (51.4% male; p=0.63). The most common blood test ordered was a complete blood count, and the most commonly abnormal result was a mildly elevated white blood cell count (19%; n= 29). The most common patients to receive bloodwork were those with ankle (34%) and distal radius (34%) fractures. The bloodwork was primarily ordered by clinical associates (26%; n=46) and emergency department physicians (22%; n=38). Without considering lab personnel, consumables, and analysis time, the cost of this bloodwork was approximately $7685, an average of $45 per patient. Pre-operative bloodwork in young, healthy, asymptomatic patients requiring outpatient surgery for minor orthopaedic trauma had no clinical significance and did not change patient management. Rigorous prospective research is warranted to establish national guidelines for appropriate pre-operative bloodwork ordering to minimize unnecessary and costly investigations

Inflammatory markers such as the C-reactive protein (CRP), white blood cell count and body temperature are easy to measure and are used as indicators of infection. The way in which they change in the early post-operative period after instrumented spinal surgery has not been reported in any depth. We measured these markers pre-operatively and at one, four, seven and 14 days postoperatively in 143 patients who had undergone an instrumented posterior lumbar interbody fusion. The CRP proved to be the only sensitive marker and had returned to its normal level in 48% of patients after 14 days. The CRP on day 7 was never higher than that on day 4. Age, gender, body temperature, operating time and blood loss were not related to the CRP level. A high CRP does not in itself suggest infection, but any increase after four days may presage infection

Endoscopic spine surgery is a promising and minimally invasive technique for the treatment of disc herniation and spinal stenosis. However, the literature on the outcome of interlaminar endoscopic decompression (IED) versus conventional microsurgical technique (CMT) in patients with lumbar spinal stenosis is scarce. We analyzed 88 patients (IED: 36/88, 40.9%; CMT: 52/88, 59.1%) presenting with lumbar central spinal stenosis between 2018–2020. Surgery-related (operation time, complications, time to hospital release (THR), ASA score, C-reactive protein (CRP), white blood cell count (WBC), side (unilateral/bilateral), patient-reported (ODI, NRS (leg-, back pain), eQ5D, COMI), and radiological (preoperative dural sack cross-sectional area (DSCA), Shizas score (SC), left (LRH) and right (RRH) lateral recess heights, left (LFA) and right (RFA) facet angle) parameters were extracted. Complication (most often re-stenosis due to hematoma and/or residual sensorimotor deficits) rates were higher in the endoscopic (38.9%) than microsurgical (13.5%) treatment group (p<0.01). Age, THR, SC, CRP, and DSCA revealed significant correlations with 3 weeks and 1 year postoperatively evaluated ODI, COMI, eQ5D, NRS leg, or NRS back values in our cohort. We did not observe significant differences in the endoscopic versus microsurgical group for the patient-reported outcomes. Age, THR, SC, CRP, and DSCA revealed significant correlations with patient-centered outcomes and should be considered in future studies. Endoscopic treatment of lumbar spinal stenosis was similarly successful as the conventional microsurgical approach, although it was associated with higher complication rates in our single-center study experience. This was probably because of the surgeons' lack of experience with this method and the resulting different learning curve compared with the conventional technique

Introduction: The results of total hip arthroplasty are in general very good. One of the factors with a negative influence on the outcome is an infection of the prosthesis. The prevalence of an acute post-operative infection is in the Netherlands in the range of 0.5 up to 2.0%. Different types of treatment are advised in the literature. Methods and Material: In 1997 we started to treat all the acute infected THA according a protocol of open surgical debridement, pulsative irrigation, application of several gentamicin loaded sponges and starting directly post-operative an antibiotic combination therapy of flucloxacillin and rifampin. The antibiotic therapy was adjusted to the cultures taken during the operation and continued till 3 months after the debridement. From Mars 1997 till July 2003 we subsequent included 32 patients, 26 with a minimal follow-up of 2 years are presented in this study. We evaluated the results of the treatment prospectively. The inflammatory parameters; C-reactive protein, erythrocyte sedimentation rate and white blood cell count (before and after debridement) The Harris Hip Score and radiograms were monitored multiple times. Results: The mean onset of infection symptoms till surgical debridement was ldays (range 0–15). All had high-elevated infection parameters and in all cases we found positive tissue cultures. 15 Times a Staphylococcus aureus was found, 5 times a Enterobacter cloacae, twice a Streptococcus, once a Pseudomonas, once a Klebsiella and once a peptostreptococcus. The average follow-up was 46 months (range 24–74). In 23 patients the infection did not re-appear. The C-reactive protein normalised from a mean of 103 (2–320) to lower than 5 at 2 years, the erythrocyte sedimentation rate from 72 (14–120) to lower than 10. The white blood cell count was not elevated. In none of the cases radiological signs of loosening was found and the mean HHS was 88 (75–96) points. However in 3 patients the infection did re-occur: once after 2.5 months with the same bacterium as the first infection, a Streptococcus, again treated with a surgical debridement. At present she is clinical free of infection at a follow up of 2 years. The 2 other re-infections occurred respectively after 9 and 10 months, once after a surgical treatment of a jaw abscess and once after an episode of diverticulitis. The cultures derived other bacteria, a streptococcus and an E. coli, than the first infection, both a Staphylococcus aureus. In both cases a two-stage revision was the choice of treatment. Conclusion: Finally 24 of the 26 acute infected hip arthroplasties were free of infection at 2 years follow-up. Surgical debridement and three months of antibiotics gave a good clinical result and a very low recurrent rate of the infection

This prospective study evaluates the role of new laboratory markers in the diagnosis of deep implant infection in 78 patients (41 men and 37 women) with a revision total knee or hip replacement. The mean age at the time of operation was 64.0 years (19 to 90). Intra-operative cultures showed that 21 patients had a septic and 57 an aseptic total joint replacement. The white blood cell count, the erythrocyte sedimentation rate and levels of C-reactive protein, interleukin-6, procalcitonin and tumour necrosis factor (TNF)-α were measured in blood samples before operation. The diagnostic cut-off values were determined by Received Operating Characteristic curve analysis. C-reactive protein (> 3.2 md/dl) and interleukin-6 (> 12 pg/ml) have the highest sensitivity (0.95). Interleukin-6 is less specific than C-reactive protein (0.87 vs 0.96). Combining C-reactive protein and interleukin-6 identifies all patients with deep infection of the implant. Procalcitonin (> 0.3 ng/ml) and TNF-α (> 40 ng/ml) are very specific (0.98 vs 0.94) but have a low sensitivity (0.33 vs 0.43). The combination of C-reactive protein and interleukin-6 measurement provide excellent screening tests for infection of a deep implant. A highly specific marker such as procalcitonin and pre-operative aspiration of the joint might be useful in identifying patients with true positive C-reactive protein and/or interleukin-6 levels

Aim. The diagnosis of septic arthritis mostly relies on clinical examination, several blood parameters including white blood cell count, C-reactive protein, sedimentation, and the analysis of the joint aspiration. However, the diagnosis can be difficult when the symptoms are vague and the information obtained from laboratory might be insufficient for definitive diagnosis. This study aimed to evaluate several ratios obtained from routine blood tests for a possible use in the diagnosis of septic arthritis. Method. The adult patients who were operated in our clinic due to septic arthritis between 2014–2020 were identified and retrospectively evaluated. The patients with any blood disorders or missing file information were excluded. A total of 36 patients were found to be eligible for inclusion. The control group included 40 patients without any sign of infection who underwent total knee arthroplasty due to knee osteoarthritis. Preoperative blood tests of each patients were examined. In addition to CRP and sedimentation values, neutrophil-lymphocyte, monocyte-lymphocyte, platelet-lymphocyte, and platelet count-mean platelet volume were calculated and receiving operating characteristics (ROC) curve analysis was made to determine the sensitivity, specificity and area under curve (AUC) values of these parameters. Results. The distribution of affected joint in septic arthritis group was as follow; 22 knees, 6 hips, 4 shoulders, 2 elbows, 1 wrist and 1 ankle. The cultures of joint aspiration yielded positive result in 19 patients while the cultures were negative in 17 patients. All of the analyzed parameters were significantly different between the groups (p<0.001). ROC curve analysis results are given in detail, in Table 1 and Figure 1. The AUC value was 97.3 when only CRP and sedimentation values were used but increased to 98.6 when neutrophile/ lymphocyte ratio was added and increased to 100 when all analyzed parameters were included. Conclusions. The analyzed parameters were found to increase the overall sensitivity and specificity when used together with acute phase reactants. However, when evaluated separately, CRP and sedimentation were still found as the most valuable parameters in the diagnosis of septic arthritis. In the diagnosis of septic arthritis, 35 mm/hr cut-off value for sedimentation and 10 mg/L cut-off value for CRP were found more sensitive and specific compared to standard laboratory cut-off values of 20 mm/hr and 5 mg/L. For any tables or figures, please contact the authors directly

Aims. This study aimed to explore the diagnostic value of synovial fluid neutrophil extracellular traps (SF-NETs) in periprosthetic joint infection (PJI) diagnosis, and compare it with that of microbial culture, serum ESR and CRP, synovial white blood cell (WBC) count, and polymorphonuclear neutrophil percentage (PMN%). Methods. In a single health centre, patients with suspected PJI were enrolled from January 2013 to December 2021. The inclusion criteria were: 1) patients who were suspected to have PJI; 2) patients with complete medical records; and 3) patients from whom sufficient synovial fluid was obtained for microbial culture and NET test. Patients who received revision surgeries due to aseptic failure (AF) were selected as controls. Synovial fluid was collected for microbial culture and SF-WBC, SF-PNM%, and SF-NET detection. The receiver operating characteristic curve (ROC) of synovial NET, WBC, PMN%, and area under the curve (AUC) were obtained; the diagnostic efficacies of these diagnostic indexes were calculated and compared. Results. The levels of SF-NETs in the PJI group were significantly higher than those of the AF group. The AUC of SF-NET was 0.971 (95% confidence interval (CI) 0.903 to 0.996), the sensitivity was 93.48% (95% CI 82.10% to 98.63%), the specificity was 96.43% (95% CI 81.65% to 99.91%), the accuracy was 94.60% (95% CI 86.73% to 98.50%), the positive predictive value was 97.73%, and the negative predictive value was 90%. Further analysis showed that SF-NET could improve the diagnosis of culture-negative PJI, patients with PJI who received antibiotic treatment preoperatively, and fungal PJI. Conclusion. SF-NET is a novel and ideal synovial fluid biomarker for PJI diagnosis, which could improve PJI diagnosis greatly. Cite this article: Bone Joint Res 2023;12(2):113–120

Aims. It can be extremely challenging to determine whether to perform reimplantation in patients who have contradictory serum inflammatory markers and frozen section results. We investigated whether patients with a positive frozen section at reimplantation were at a higher risk of reinfection despite normal ESR and CRP. Methods. We retrospectively reviewed 163 consecutive patients with periprosthetic joint infections (PJIs) who had normal ESR and CRP results pre-reimplantation in our hospital from 2014 to 2018. Of these patients, 26 had positive frozen sections at reimplantation. The minimum follow-up time was two years unless reinfection occurred within this period. Univariable and multivariable logistic regression analyses were performed to identify the association between positive frozen sections and treatment failure. Results. Treatment failure occurred in eight (30.77%) of the 26 PJI patients with positive frozen sections at reimplantation, compared with 13 (9.49%) of 137 patients with negative results. In the multivariate analysis, positive frozen section increased the risk of failure (odds ratio 4.70; 95% confidence interval (CI) 1.64 to 13.45). The mean number of months to reinfection was lower in the positive frozen section group than in the control group (p = 0.041). While there were nine (34.62%) patients with positive frozen section and 25 (18.25%) patients with negative frozen section who had prolonged antibiotic use (p = 0.042), the mean duration of antibiotic use was comparable in two groups. Synovial white blood cell count (p = 0.137) and polymorphonuclear leucocyte percentage (p = 0.454) were not associated with treatment failure in logistic regression model. Conclusion. Positive frozen section at reimplantation was independently associated with subsequent failure and earlier reinfection, despite normal ESR and CRP levels pre-reimplantation. Surgeons should be aware of the risk of treatment failure in patients with positive frozen sections and carefully consider benefits of reimplantation. Cite this article: Bone Joint J 2021;103-B(5):916–922

Aim. Although established serum inflammatory biomarkers, such as serum C-reactive protein (CRP) and serum white blood cell count (WBC), showed low accuracies in the literature, they are still commonly used in diagnosing periprosthetic joint infections (PJI). For a sufficient preoperative diagnosis novel more accurate serum parameters are needed. The aim of our study was to evaluate the performances of the established and novel routinely available serum parameters in diagnosing periprosthetic joint infections when using the proposed European Bone and Joint Infection Society (pEBJIS) criteria. Method. In this retrospective study, 177 patients with an indicated revision surgery after a total joint replacement were included from 2015 to 2019. The easily accessible and routinely available serum parameters CRP, WBC, the percentage of neutrophils (%N), the neutrophils to lymphocytes ratio (NLR), fibrinogen and the platelet count to mean platelet volume ratio (PC/mPV) were evaluated preoperatively. The performances were examined via receiver operating characteristic (ROC) curve analysis (AUC). The curves were compared using the z-test. Seventy-five cases (42%) showed a PJI based on the pEBJIS-criteria. Results. The sensitivities of serum CRP (cut-off: ≥10mg/L), WBC (≥10×10^9 cells/L), %N (≥69.3%), NLR(≥ 3.82), fibrinogen (≥ 457 mg/dL), and PC/mPV (≥ 29.4) were calculated with 68% (95% CI: 57–78), 36% (26 – 47), 66% (54 – 76), 63% (51 – 73), 69% (57 – 78), and 43% (32 – 54), respectively. Specificities were 87% (79 – 93), 89% (81 – 94), 67% (57 76), 73% (63 – 81), 89% (80 – 93), and 81% (72 – 88), respectively. Serum CRP and fibrinogen showed better performances than the other evaluated serum parameters (p<0.0001). The median serum CRP (17.6 mg/L) in patients with PJI caused by a low virulence microorganism was lower compared with infections caused by high virulence organisms (49.2 mg/L; p=0.044). Synovial fluid leucocyte count and histology showed better accuracies than serum CRP, serum WBC, %N, NLR, serum fibrinogen, and PC/mPV (p<0.0001). Conclusions. Although serum CRP and fibrinogen showed the best performances among the evaluated serum inflammatory markers, their results should be interpreted with caution in clinical practice. Serum parameters may remain normal in chronic infections or may be elevated in patients with other inflammatory conditions. In addition, they also correlated poorly with synovial fluid leukocyte count and histology. Therefore, serum parameters are still insufficient to confirm or exclude a periprosthetic joint infection. Hence, they can only be recommended as suggestive criteria in diagnosing PJI

Aims. In patients with a “dry” aspiration during the investigation of prosthetic joint infection (PJI), saline lavage is commonly used to obtain a sample for analysis. The aim of this study was to investigate prospectively the impact of saline lavage on synovial fluid analysis in revision arthroplasty. Methods. Patients undergoing revision hip (THA) or knee arthroplasty (TKA) for any septic or aseptic indication were enrolled. Intraoperatively, prior to arthrotomy, the maximum amount of fluid possible was aspirated to simulate a dry tap (pre-lavage) followed by the injection with 20 ml of normal saline and re-aspiration (post-lavage). Pre- and post-lavage synovial white blood cell (WBC) count, percent polymorphonuclear cells (%PMN), and cultures were compared. Results. A total of 78 patients had data available for analysis; 17 underwent revision THA and 61 underwent revision TKA. A total of 16 patients met modified Musculoskeletal Infection Society (MSIS) criteria for PJI. Pre- and post-lavage %PMNs were similar in septic patients (87% vs 85%) and aseptic patients (35% vs 39%). Pre- and post-lavage synovial fluid WBC count were far more disparate in septic (53,553 vs 8,275 WBCs) and aseptic (1,103 vs 268 WBCs) cohorts. At a cutoff of 80% PMN, the post-lavage aspirate had a sensitivity of 75% and specificity of 95%. At a cutoff of 3,000 WBCs, the post-lavage aspirate had a sensitivity of 63% and specificity of 98%. As the post-lavage synovial WBC count increased, the difference between pre- and post-lavage %PMN decreased (mean difference of 5% PMN in WBC < 3,000 vs mean difference 2% PMN in WBC > 3,000, p = 0.013). Of ten positive pre-lavage fluid cultures, only six remained positive post-lavage. Conclusion. While saline lavage aspiration significantly lowered the synovial WBC count, the %PMN remained similar, particularly at WBC counts of > 3,000. These findings suggest that in patients with a dry-tap, the %PMN of a saline lavage aspiration has reasonable sensitivity (75%) for the detection of PJI. Cite this article: Bone Joint J 2020;102-B(6 Supple A):138–144