Do one-stage indications predict success following two-stage arthroplasty for chronic periprosthetic joint infection?

Introduction: The 2018 International Consensus Meeting (ICM) proposed criteria for one-stage exchange arthroplasty in treating periprosthetic joint infection (PJI). Our study aimed to determine what proportion of PJI patients met the 2018 ICM criteria and how this affected infection-free survivorship for patients. Methods: All chronic PJI patients treated with two-stage exchange within our institution between 2017-2020 were retrospectively reviewed. Included cases met 2011 Musculoskeletal Infection Society (MSIS) criteria for PJI and had a 2-year minimum follow-up. Treatment success was defined as Tier 1A in the 2019 MSIS working group definition. ICM one-stage criteria included non-immunocompromised host, absence of sepsis, adequate soft tissue for closure, known preoperative pathogen, and susceptibility. Immunocompromised host was analyzed as two separate definitions. Kaplan-Meier survivorship, Cox regression, and univariate analyses were performed. Results: A total of 293 chronic PJI patients were included. Overall, treatment failure occurred in 64/293 (21.8 %) patients. Only 13 % (n=37) met ICM criteria definition no. 1 for one-stage exchange; 12 % (n=33) met definition no. 2. In both definitions, infection-free survivorship at 2 years did not differ between patients who met and did not meet criteria (p>0.05). Cox proportional hazard regression analyses demonstrated that the only variable predicting treatment failure was knee joint involvement (p=0.01). Conclusions: We found that a very limited number of chronic PJI patients were suitable for a one-stage exchange. Furthermore, the supposition that healthier hosts with known pathogens (the basis of the ICM criteria) yield better PJI treatment outcomes was not observed. These results justify the ongoing multicenter randomized control trial comparing one-stage versus two-stage treatment for chronic PJI.

Clinical and Biomechanical Evaluation of Mid-Level Constrained and Posterior-Stabilized Polyethylene Inserts in Primary Total Knee Arthroplasty: An Analysis of 12,674 Cases.

BACKGROUND: Mid-level constraint polyethylene designs provide additional stability in total knee arthroplasty (TKA). The purposes of this study were to (1) compare the survivorship and reason for revision between mid-level inserts and posterior-stabilized (PS) used in primary TKA and (2) evaluate the biomechanical constraint characteristics of mid-level inserts. METHODS: We reviewed all cases of primary TKA performed at our institution from 2016 to 2019 using either PS or mid-level constrained inserts from 1 of 6 manufacturers. Data elements included patient demographics, implants, reasons for revision, and whether a manipulation under anesthesia was performed. We performed finite element analyses to quantify the varus/valgus and axial-rotation constraint of each mid-level constrained insert. A one-to-one propensity score matching was conducted between the patients with mid-level and PS inserts to match for variables, which yielded 2 cohorts of 3,479 patients. RESULTS: For 9,163 PS and 3,511 mid-level TKAs, survivorship free from all-cause revision was estimated up to 5 years and was lower for mid-level than PS inserts (92.7 versus 94.1%, respectively, P = .004). When comparing each company's mid-level insert to the same manufacturer's PS insert, we found no differences in all-cause revision rates (P ≥ .91) or revisions for mechanical problems (P ≥ .97). Using propensity score matching between mid-level and PS groups, no significant differences were found in rates of manipulation under anesthesia (P = .72), all-cause revision (P = .12), revision for aseptic loosening (P = .07), and revision for instability (P = .45). Finite element modeling demonstrated a range in varus/valgus constraint from ±1.1 to >5°, and a range in axial-rotation constraint from ±1.5 to ±11.5° among mid-level inserts. CONCLUSIONS: Despite wide biomechanical variations in varus/valgus and axial-rotation constraint, we found minimal differences in early survivorship rates between PS and mid-level constrained knees.

Diagnostic Utility and Thresholds for Commonly Obtained Serum and Synovial Markers Prior to Reimplantation in Periprosthetic Joint Infection.

BACKGROUND: Accurate diagnosis of persistent periprosthetic joint infection (PJI) during 2-stage exchange remains a challenge. This study evaluated the diagnostic performance and thresholds of several commonly obtained serum and synovial markers to better guide reimplantation timing. METHODS: This was a retrospective review of 249 patients who underwent 2-stage exchange with antibiotic spacers for PJI. Serum and synovial markers analyzed included white blood cell (WBC) count, polymorphonuclear percentage (PMN%), neutrophil-to-lymphocyte ratio (NLR), and absolute neutrophil count (ANC). Serum markers analyzed were erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), as well as percentage change in ESR and CRP from initial diagnosis to reimplantation. Area under the curve (AUC) analyses were performed to determine diagnostic accuracy of detecting PJI. RESULTS: In TKAs, synovial ANC and WBC had the highest AUCs (0.76), with thresholds of 2,952 and 3,800 cells/µL, respectively. The next best marker was serum CRP (0.73) with a threshold of 5.2 mg/dL. In THAs, serum CRP had the highest AUC (0.84) with a threshold of 4.3 mg/dL, followed by synovial PMN% (0.80) with a threshold of 77%. Percentage change in serum ESR or CRP provided low diagnostic value overall. CONCLUSION: Regarding serum markers, CRP consistently performed well in detecting persistent PJI in patients with antibiotic spacers. Absolute values of serum CRP and ESR had better diagnostic value than trends for guiding reimplantation timing. Diagnostic performance differed with joint type; however, synovial markers outperformed serum counterparts. No marker alone can be utilized to diagnose residual PJI in these patients, and further work is needed in this domain.

The Influence of Dorr Type and Femoral Fixation on Outcomes Following Total Hip Arthroplasty for Acute Femoral Neck Fractures: A Multicenter Study.

BACKGROUND: The American Academy of Orthopaedic Surgeons guidelines report moderate evidence for cementing femoral stems for hip fractures, mainly derived from hemiarthroplasty literature. This is the first large, nonregistry study examining the influence of femoral fixation, implant type, patient characteristics, and radiographic factors on outcomes after total hip arthroplasty (THA) for acute femoral neck fractures. METHODS: A multicenter retrospective study was performed of 709 THA cases (199 cemented, 510 cementless) for femoral neck fractures from 2006 to 2020 at three large academic institutions. Demographics, perioperative characteristics, and radiographs were reviewed. Kaplan-Meier survivorship curves were generated for multiple outcomes. Univariate and multivariate analyses were performed with P ≤ .05 denoting significance. RESULTS: Cementless stems had a higher all-cause aseptic femoral revision rate (5.1 versus 0.5%, P = .002) and periprosthetic femoral fracture rate (4.3 versus 0%, P = .001). Each successive Dorr type had a higher fracture rate with cementless implants: 2.3%, 3.7%, and 15.9% in Dorr A, B, and C, respectively (P < .001). Logistic regression analyses confirmed that cementless stems (P = .02) and Dorr C bone (P = .001) are associated with periprosthetic fractures; collared implants and prophylactic cables did not protect against fractures. There was no difference in rates of dislocation, septic revision, or mortality between groups. CONCLUSION: Cementless stems during THA for femoral neck fractures have a higher aseptic femoral revision rate, specifically for periprosthetic fractures. Dorr C bone was particularly prone with an alarmingly high fracture rate. All fractures occurred in cementless cases, suggesting that cemented stems may minimize this complication. LEVEL OF EVIDENCE: III.

Synovial Fluid Absolute Neutrophil Count and Neutrophil-To-Lymphocyte Ratio are not Superior to Polymorphonuclear Percentage in Detecting Periprosthetic Joint Infection.

BACKGROUND: Serum and synovial biomarkers are currently used to diagnose periprosthetic joint infection (PJI). Serum neutrophil-to-lymphocyte ratio (NLR) has shown promise as an inexpensive test in diagnosing infection, but there are no reports of synovial NLR or absolute neutrophil count (ANC) for diagnosing chronic PJI. The purpose of this study was to investigate the diagnostic potential of both markers. METHODS: A retrospective review of 730 patients who underwent total joint arthroplasty and subsequent aspiration was conducted. Synovial white blood cell (WBC) count, synovial polymorphonuclear percentage (PMN%), synovial NLR, synovial ANC, serum erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), serum WBC, serum PMN%, serum NLR, and serum ANC had their utility in diagnosing PJI examined by area-under-the-curve analyses (AUC). Pairwise comparisons of AUCs were performed. RESULTS: The AUCs for synovial WBC, PMN%, NLR, and ANC were 0.84, 0.84, 0.83, and 0.85, respectively. Synovial fluid ANC was a superior marker to synovial NLR (P = .027) and synovial WBC (P = .003) but not PMN% (P = .365). Synovial NLR was inferior to PMN% (P = .006) but not different from synovial WBC (P > .05). The AUCs for serum ESR, CRP, WBC, PMN%, NLR, and ANC were 0.70, 0.79, 0.63, 0.72, 0.74, and 0.67, respectively. Serum CRP outperformed all other serum markers (P < .05) except for PMN% and NLR (P > .05). Serum PMN% and NLR were similar to serum ESR (P > .05). CONCLUSION: Synovial ANC had similar performance to PMN% in diagnosing chronic PJI, whereas synovial NLR was a worse diagnostic marker. The lack of superiority to synovial PMN% limits the utility of these tests compared to established criteria.

Synovial Fluid and Serum Neutrophil-to-Lymphocyte Ratio: Novel Biomarkers for the Diagnosis and Prognosis of Native Septic Arthritis in Adults.

BACKGROUND: Septic arthritis (SA) is a musculoskeletal emergency for which prompt diagnosis and treatment are critical. However, traditional diagnostic criteria of a synovial fluid (SF) white blood-cell count (WBC) of >50,000 cells/mm 3 or >90% polymorphonuclear leukocytes (%PMN) are not particularly sensitive or specific for the diagnosis of SA. Furthermore, prognostic markers are lacking. The purposes of this study were to assess the discriminative ability of the SF neutrophil-to-lymphocyte ratio (NLR) in the diagnosis of SA and of the serum NLR in the prognosis of SA. METHODS: A multi-institution, retrospective study of 598 patients with native shoulder, hip, or knee SA in 2000 to 2018 was conducted. SF-NLR was calculated from the arthrocentesis cell count with differential. Receiver operating characteristic curves were analyzed, and the optimal threshold of SF-NLR for SA diagnosis was determined using the Youden index. Results were compared with traditional SF diagnostic criteria. Similar analyses assessed the association of serum NLR with 90-day treatment failure and mortality for the subset of patients with confirmed hip or knee SA and with serum complete blood-cell counts with differentials (n = 235). Results were compared with traditional serum prognostic markers (WBC, C-reactive protein [CRP], and erythrocyte sedimentation rate [ESR]). RESULTS: The SF-NLR (area under the receiver operating characteristic curve [AUC], 0.85 [95% confidence interval (CI), 0.82 to 0.88]) was significantly more accurate for an SA diagnosis than SF-WBC (AUC, 0.80 [95% CI, 0.76 to 0.83]; p = 0.002) and SF-%PMN (AUC, 0.81 [95% CI, 0.77 to 0.84]; p = 0.01). The optimal threshold of SF-NLR was 25 (78% sensitivity and 81% specificity), compared with >50,000 cells/mm 3 for SF-WBC (56% sensitivity and 80% specificity) and >90% for SF-%PMN (65% sensitivity and 78% specificity). Elevated serum NLR was independently associated with 90-day treatment failure (odds ratio [OR], 7.04 [95% CI, 3.78 to 13.14]; p < 0.001) and mortality (OR, 7.33 [95% CI, 2.00 to 26.92]; p = 0.003); elevated serum WBC and CRP were also associated with treatment failure, and WBC, CRP, and ESR were not associated with mortality. CONCLUSIONS: This study provides compelling data on the superior diagnostic and prognostic ability of serum NLR and SF-NLR for SA compared with current clinical standards. Given that this biomarker requires no additional cost or time to return than current laboratory tests already being performed, pending validation, it can readily be used to aid clinicians in the diagnosis and prognostication of SA. LEVEL OF EVIDENCE: Diagnostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Diagnosis of Prostate Adenocarcinoma on Routine Pathology After a Primary Total Hip Arthroplasty.

We present a 67-year-old male patient who presented with insidious worsening of right hip pain over a 6-month period with clinical and radiographic evidence of severe osteoarthritis. The patient underwent a primary total hip arthroplasty where the femoral head specimen was sent to pathology as a routine specimen. Pathology results demonstrated metastatic adenocarcinoma of prostate origin. The present case emphasizes the importance of routine pathologic examination of femoral head specimens retrieved during total hip arthroplasty, particularly since this was a clinically unsuspected finding. Although cases like these are rare and the process of routine pathologic examination raises a concern for economic implications, a timely diagnosis of adenocarcinoma provides benefits for the patient, for which cost-benefit ratios are difficult to quantify.

Reduced Infection Rate After Aseptic Revision Total Knee Arthroplasty With Extended Oral Antibiotic Protocol.

BACKGROUND: The optimal postoperative antibiotic duration has not been determined for aseptic revision total knee arthroplasty (R-TKA) where the risk of periprosthetic joint infection (PJI) is 3%-7.5%. This study compared PJI rates in aseptic R-TKA performed with extended oral antibiotic prophylaxis (EOAP) to published rates. METHODS: Aseptic R-TKAs consecutively performed between 2013 and 2017 at a tertiary care referral center in the American Midwest were retrospectively reviewed. All patients were administered intravenous antibiotics while hospitalized and discharged on 7-day oral antibiotic prophylaxis. Infection rates and antibiotic-related complications were assessed. RESULTS: Sixty-seven percent of the 176 analysis patients were female, with an average age of 64 years and body mass index of 35 kg/m2. Instability and aseptic loosening comprised 86% of revision diagnoses. Overall, 87.5% of intraoperative cultures were negative, and the remainder were single positive cultures considered contaminants. PJI rates were 0% at 90 days, 1.8% (95% confidence interval 0.4%-5.3%) at 1 year, and 2.2% (95% confidence interval 0.6%-5.7%) at mean follow-up of approximately 3 years (range, 7-65 months). CONCLUSION: EOAP after aseptic R-TKA resulted in a PJI rate equivalent to primary TKA, representing a 2- to-4-fold decrease compared with published aseptic R-TKA infection rates. Further study on the benefits and costs of EOAP after aseptic R-TKA is encouraged.

External Validation Demonstrates Limited Clinical Utility of a Preoperative Prognostic Calculator for Periprosthetic Joint Infection.

BACKGROUND: Preoperative calculation of treatment failure risk in patients undergoing surgery for periprosthetic joint infection (PJI) is imperative to allow for medical optimization and targeted prevention. A preoperative prognostic model for PJI treatment failure was previously developed, and this study sought to externally validate the model. METHODS: A retrospective review was performed of 380 PJIs treated at two institutions. The model was used to calculate the risk of treatment failure, and receiver operating characteristic curves were generated to calculate the area under the curve (AUC) for each institution. RESULTS: When applying this model to institution 1, an AUC of 0.795 (95% confidence interval [CI]: 0.693-0.897) was found, whereas institution 2 had an AUC of 0.592 (95% CI: 0.502-0.683). Comparing all institutions in which the model had been applied to, we found institution 2 represented a significantly sicker population and different infection profile. CONCLUSION: In this cohort study, we externally validated the prior published model for institution 1. However, institution 2 had a decreased AUC using the prior model and represented a sicker and less homogenous cohort compared with institution 1. When matching for chronicity of the infection, the AUC of the model was not affected. This study highlights the impact of comorbidities and their distributions on PJI prognosis and brings to question the clinical utility of the algorithm which requires further external validation.

The AAHKS Clinical Research Award: Extended Oral Antibiotics Prevent Periprosthetic Joint Infection in High-Risk Cases: 3855 Patients With 1-Year Follow-Up.

BACKGROUND: Surgical and host factors predispose patients to periprosthetic joint infection (PJI) after primary total hip arthroplasty (THA) and total knee arthroplasty (TKA). While surgical factors are modifiable, host factors can be challenging, and there are limited data demonstrating that preoperative patient optimization decreases risk of PJI. The goal of this study was to evaluate whether extended oral antibiotic prophylaxis reduces the one-year infection rate in high-risk patients. METHODS: A total of 3855 consecutive primary THAs and TKAs performed between 2011 and 2019 at a suburban academic hospital with modern perioperative and infection-prevention protocols were retrospectively reviewed. Beginning in January 2015, a 7-day oral antibiotic prophylaxis protocol was implemented after discharge for patients at high risk for PJI. The percentage of high-risk patients diagnosed with PJI within 1 year was compared between groups that did and did not receive extended antibiotic prophylaxis. Univariate and logistic regression analyses were performed, with P ≤ .05 denoting statistical significance. RESULTS: Overall 1-year infection rates were 2.26% and 0.85% after THA and TKA, respectively. High-risk patients with extended antibiotic prophylaxis had a significantly lower rate of PJI than high-risk patients without extended antibiotic prophylaxis (0.89% vs 2.64%, respectively; P < .001). There was no difference in the infection rate between high-risk patients who received antibiotics and low-risk patients (0.89% vs 1.29%, respectively; P = .348) with numbers available. CONCLUSION: Extended postoperative oral antibiotic prophylaxis for 7 days led to a statistically significant and clinically meaningful reduction in 1-year infection rates of patients at high risk for infection. In fact, the PJI rate in high-risk patients who received antibiotics was less than the rate seen in low-risk patients. Thus, extended oral antibiotic prophylaxis may be a simple measure to effectively counteract poor host factors. Moreover, the findings of this study may mitigate the incentive to select healthier patients in outcome-based reimbursement models. Further study with a multicenter randomized control trial is needed to further validate this protocol. LEVEL OF EVIDENCE: Therapeutic level III.

The Fate of Unmatched Orthopaedic Applicants: Risk Factors and Outcomes.

INTRODUCTION: Orthopaedic surgery residency has become increasingly competitive for medical school applicants with at least one in five applicants not matching annually. For unmatched applicants, the new application cycle is a perplexing and disconcerting period, where unique decisions must be addressed by the applicant. We aimed to investigate the risk factors and outcomes of unmatched orthopaedic applicants. METHODS: This was a retrospective study using a survey-based questionnaire administered electronically to medical students annually from 2016 to 2019 immediately after match day. Applicant responses totaled 934 completed surveys, of which 81 identified themselves as unmatched from the previous year and reapplied for a subsequent cycle. Variables collected through the survey included demographics, United States Medical Licensing Examination scores, Electronic Residency Application Service application characteristics, and interim year pursuits. A univariate analysis was performed with an alpha level of 0.05 denoting statistical significance. RESULTS: Overall, 58.0% of unmatched applicants subsequently matched into an orthopaedic residency. Applicants who pursued a research year or surgical internship after initially not matching had a subsequent match rate of 52.1% and 64.0%, respectively (p = 0.46). Of those who matched, 19.1% were Alpha Omega Alpha (AOA) compared with 2.9% in the unmatched group (p = 0.04). When stratified by gender, 83.3% of women matched subsequently compared with 50.8% of men (p = 0.02). There were no differences in Step 1 scores (242.5 vs. 240.7, p = 0.60), Step 2 clinical knowledge (CK) scores (248.3 vs. 244.5, p = 0.60), or the number of publications (15.6 vs. 10.9, p = 0.25) between applicants who matched or did not match, respectively. DISCUSSION: Our findings demonstrate that most orthopaedic applicants matched during their subsequent attempt. Women and those with AOA status had a significantly higher match rate than their counterparts. There was no difference in outcomes between those who pursued a research year or surgical internship, Step 1 or 2CK scores, or the number of publications. Further study is warranted to properly analyze risk factors for not matching on a subsequent attempt. LEVEL OF EVIDENCE: Prognostic Level IV.

Do Antibiotic-Impregnated Intramedullary Dowels Assist in Eradicating Infection in Total Knee Arthroplasty?

Antibiotic-impregnated intramedullary dowels historically have been advocated and are frequently used to facilitate periprosthetic knee infection eradication. They are used for focused delivery of antibiotics into the femoral and tibial intramedullary canals during 2-stage resection utilizing an antibiotic cement spacer. However, the literature is limited on the use and efficacy of antibiotic-eluding intramedullary dowels in periprosthetic joint infection. We reviewed the available literature and have found that the data at this point are equivocal with respect to whether antibiotic-impregnated cement intramedullary dowels augment the intra-articular antibiotic cement spacer in eradicating infection in total knee arthroplasty. Thus, we believe that the decision to use dowels can be left up to the surgeon preference. However, further research is warranted to review operative room efficiency and healthcare costs, and to validate the clinical efficacy of antibiotic-impregnated dowels in periprosthetic joint infection.

Causes of in-hospital mortality after hip fractures in the elderly.

OBJECTIVES: Although there are numerous studies reporting early mortality after hip fracture, the incidence and aetiology of in-hospital mortality following hip fractures is largely unknown. This study aimed to determine the causes and the incidence of in-hospital mortality in patients with a hip fracture who received surgical treatment. METHODS: This was a multi-institutional retrospective study identifying 2464 consecutive patients >65 years of age who were treated for a hip fracture from 2000 to 2016 at 2 institutions. Revision surgeries were excluded. An electronic query followed by manual chart review was performed to collect patient demographics, Charlson comorbidity index (CCI), type of anaesthesia, and cause of death. RESULTS: The overall in-hospital mortality rate for patients undergoing surgical intervention for an acute hip fracture was 3.0% (75/2464). The most common causes of death in descending order were: respiratory failure (n = 26), cardiac failure (n = 13), multiorgan failure (n = 6), septic shock (n = 6), pulmonary embolism (n = 5), end stage renal disease (n = 5) and others (n = 14). In-hopsital mortality was associated with older age (p = 0.001) and higher CCI scores (p = 0.001). There was no association with gender (p = 0.165), type of anaesthesia (p = 0.497), extracapsular versus intracapsular fracture (p = 0.627), pathologic versus non-pathologic fracture (0.799), or body mass index (p = 0.781). CONCLUSION: This study demonstrated that hip fracture patients are at relatively high risk of in-hospital mortality following surgical intervention with a high proportion of patients succumbing to respiratory failure. The findings compel us to investigate strategies that can minimize mortality related to respiratory failure in this patient population such as minimising opioid use, early mobilisation, and implementing greater respiratory monitoring.

Surgical Treatment of Chronic Periprosthetic Joint Infection: Fate of Spacer Exchanges.

BACKGROUND: Patients with periprosthetic joint infection (PJI) undergoing 2-stage exchange arthroplasty may undergo an interim spacer exchange for a variety of reasons including mechanical failure of spacer or persistence of infection. The objective of this study is to understand the risk factors and outcomes of patients who undergo spacer exchange during the course of a planned 2-stage exchange arthroplasty. METHODS: Our institutional database was used to identify 533 patients who underwent a 2-stage exchange arthroplasty for PJI, including 90 patients with a spacer exchange, from 2000 to 2017. A retrospective review was performed to extract relevant clinical information. Treatment outcomes included (1) progression to reimplantation and (2) treatment success as defined by a Delphi-based criterion. Both univariate and multivariate Cox regression models were performed to investigate whether spacer exchange was associated with failure. Additionally, a propensity score analysis was performed based on a 1:2 match. RESULTS: A spacer exchange was required in 16.9%. Patients who underwent spacer exchanges had a higher body mass index (P < .001), rheumatoid arthritis (P = .018), and were more likely to have PJI caused by resistant (0.048) and polymicrobial organisms (P = .007). Patients undergoing a spacer exchange demonstrated lower survivorship and an increased risk of failure in the multivariate and propensity score matched analysis compared to patients who did not require a spacer exchange. DISCUSSION: Despite an additional load of local antibiotics and repeat debridement, patients who underwent a spacer exchange demonstrated poor outcomes, including failure to undergo reimplantation and twice the failure rate. The findings of this study may need to be borne in mind when managing patients who require spacer exchange.

Failure After 2-Stage Exchange Arthroplasty for Treatment of Periprosthetic Joint Infection: The Role of Antibiotics in the Cement Spacer.

BACKGROUND: Failure after a 2-stage exchange surgery for periprosthetic joint infection (PJI) is high. Previous studies demonstrated that positive cultures at reimplantation are associated with failure afterward. The aim of this multicenter study was to define the role of antibiotics in the cement spacer in relation to reimplantation cultures and subsequent failure. METHODS: We retrospectively evaluated 2-stage exchange procedures between 2000 and 2015. Culture-negative PJIs, cases in which no cultures were obtained during reimplantation, and cases without data on cement spacers were excluded. RESULTS: Three hundred forty-four cases were included. The rate of positive cultures during reimplantation was 9.5% for cement spacers containing a glycopeptide (27/284) (with or without an aminoglycoside) vs 21.7% for those containing monotherapy with an aminoglycoside (13/60) (P = .008), and was mostly attributed by a reduction in coagulase-negative staphylococci (CoNS) (17% vs 2%, P < .001). The failure rate was >2-fold higher at 40.0% (16/40) in cases with positive cultures at reimplantation compared to 15.8% (48/304) for those with negative cultures (P < .001). Overall, a glycopeptide in the cement spacer was not associated with a lower failure rate (18% vs 23%, P = .3), but was associated with lower failure due to CoNS (2.5% vs 13.3%, P < .001). CONCLUSIONS: In a 2-stage exchange procedure for PJI, adding a glycopeptide to the cement spacer reduces the rate of positive cultures during reimplantation and is associated with a lower failure rate due to CoNS afterward.

Routine Diagnostic Tests for Periprosthetic Joint Infection Demonstrate a High False-Negative Rate and Are Influenced by the Infecting Organism.

BACKGROUND: Current guidelines recommend serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as the first-line testing for evaluation of suspected periprosthetic joint infection, in addition to synovial white blood-cell (WBC) count and polymorphonuclear percentage. However, the sensitivity and other diagnostic measures of these tests using a standardized definition of periprosthetic joint infection and the influence of organisms on these inflammatory markers remain inadequately investigated. METHODS: A retrospective review of an institutional database of 549 periprosthetic joint infection cases and 653 aseptic total joint arthroplasty revisions was performed. Periprosthetic joint infection was defined using major criteria from the International Consensus Meeting (ICM) on Periprosthetic Joint Infection. The mean inflammatory marker levels were compared among organisms with Student t tests and the proportions of elevated laboratory levels were compared among organisms with chi-square analyses. Receiver operating characteristic curve analyses were performed to calculate new cutoffs, sensitivities, and specificities for each organism and overall for serum CRP and ESR and synovial WBC and polymorphonuclear percentage. RESULTS: The sensitivity of these markers for diagnosing chronic periprosthetic joint infection was 0.85 for ESR, 0.88 for CRP, 0.83 for WBC count, and 0.78 for polymorphonuclear percentage. For ESR, antibiotic-resistant organisms had higher mean values (84.3 mm/hr) than culture-negative cases (57.4 mm/hr), coagulase-negative Staphylococcus (68.3 mm/hr), and Streptococcus species (66.1 mm/hr); Staphylococcus aureus (81.0 mm/hr) was higher than culture-negative cases (57.4 mm/hr). For CRP, culture-negative cases had lower mean values (41.0 mg/L) than gram-negative organisms (87.4 mg/L), antibiotic-resistant organisms (86.0 mg/L), S. aureus (112.2 mg/L), and Streptococcus species (114.6 mg/L); S. aureus (112.2 mg/L) was higher than coagulase-negative Staphylococcus (66.0 mg/L). For WBC count, culture-negative cases had lower mean values (27,984.5 cells/mL) than S. aureus (116,250.0 cells/mL) and Streptococcus species (77,933.7 cells/mL). For polymorphonuclear percentage, there were no significant differences in mean values among all organisms. CONCLUSIONS: It appears that serological markers, namely ESR and CRP, have a higher false-negative rate than previously reported. Synovial markers similarly exhibit high false-negative rates. Furthermore, the sensitivity of these tests appears to be related to organism type. Surgeons should be aware of the high rate of false-negatives associated with low-virulence organisms and culture-negative cases. LEVEL OF EVIDENCE: Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Culture-Negative Periprosthetic Joint Infection: An Update on What to Expect.

BACKGROUND: Culture-negative periprosthetic joint infection (PJI) is a challenging condition to treat. The most appropriate management of culture-negative PJI is not known, and there is immense variability in the treatment outcome of this condition. The purpose of this study was to elucidate the characteristics, outcomes, and risk factors for failure of treatment of culture-negative PJI. METHODS: A retrospective review of 219 patients (138 hips and 81 knees) who had undergone surgery for the treatment of culture-negative PJI was performed utilizing a prospectively collected institutional PJI database. PJIs for which the results of culture were unavailable were excluded. An electronic query and manual review of the medical records were completed to obtain patient demographics, treatment, microbiology data, comorbidities, and other surgical characteristics. Treatment failure was assessed using the Delphi consensus criteria. RESULTS: The prevalence of suspected culture-negative PJI was 22.0% (219 of 996), and the prevalence of culture-negative PJI as defined by the Musculoskeletal Infection Society (MSIS) was 6.4% (44 of 688). Overall, the rate of treatment success was 69.2% (110 of 159) in patients with >1 year of follow-up. Of the 49 culture-negative PJIs for which treatment failed, 26 (53.1%) subsequently had positive cultures; of those 26, 10 (38.5%) were positive for methicillin-sensitive Staphylococcus aureus. The rate of treatment success was greater (p = 0.019) for patients who had 2-stage exchange than for those who underwent irrigation and debridement. CONCLUSIONS: The present study demonstrates that culture-negative PJI is a relatively frequent finding with unacceptable rates of treatment failure. Every effort should be made to isolate the infecting organism prior to surgical intervention, including extending the incubation period for cultures, withholding antibiotics prior to obtaining culture specimens, and possibly using newly introduced molecular techniques. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.