Physician Use of Multiple Criteria to Diagnose Periprosthetic Joint Infection May Be Less Accurate Than the Use of an Individual Test

Introduction

Multiple-criterion scoring systems for periprosthetic joint infection (PJI) can be algorithmically implemented in research, diagnostically outperforming individual tests. This improved performance may be lost in the practice setting, where clinicians rarely utilize strict algorithms. The ability of physicians to interpret multiple criteria for PJI and confront the complexity of combining them into a final diagnosis has never been studied. This study assessed the diagnostic characteristics of physicians using multiple criteria to diagnose PJI and compared the physicians’ diagnostic accuracy to that of individual tests.

Methods

A total of 12 physicians, including academic arthroplasty surgeons (N=4), community arthroplasty surgeons (N=4), and infectious disease (ID) specialists (N=4) were asked to use their routine clinical diagnostic practice to assign a diagnosis to 277 clinical vignettes using multiple preoperative laboratory criteria for PJI. The undecided rate, interobserver agreement, and accuracy of physicians were characterized relative to the 2013 Musculoskeletal Infection Society (MSIS) gold standard and compared to the accuracy of each individual laboratory test for PJI.

Results

Physicians interpreting multiple criteria for PJI demonstrated high undecided diagnosis rates (mean=23.5%), poor interobserver agreement (kappa range=0.49-0.63), and mean accuracy of 90.8% (range:85.8%-97.4%) compared to the 2013 MSIS gold standard. The group of academic arthroplasty surgeons had a lower rate of undecided diagnoses than community arthroplasty surgeons (16.2% vs. 29.1%; p<0.0001) or ID specialists (16.2% vs. 25.1%; p<0.0001). Academic arthroplasty surgeons also exhibited a higher interobserver agreement than community arthroplasty surgeons (kappa = 0.63 (95%CI:0.59-0.68) vs. 0.49 (95%CI:0.44-0.54)).

Mean physician accuracy (90.8%) was inferior to the alpha-defensin laboratory test (96.0%;p=0.0034) and the alpha-defensin lateral-flow test (94.6%;p=0.036), comparable to synovial fluid white blood cells (SF-WBC) (93.3%;p=0.17) and synovial fluid polymorphonuclear cell % (SF-PMN%) (94.0%;p=0.11), and superior to the erythrocyte sedimentation rate (ESR) (86.2%;p<0.0001) and C-reactive protein (CRP) (84.6%;p<0.0001). Only two academic arthroplasty surgeons in this study were able to outperform every individual test for PJI by combining multiple criteria to make a diagnosis.

Conclusion

Although multiple-criterion scoring systems may outperform individual tests for diagnosing PJI in the research setting, it appears that the complexity of using multiple tests to diagnose PJI causes indecision and variability among physicians. Physician use of multiple preoperative criteria to diagnose PJI is less accurate than the strict algorithmic calculation of the diagnosis as achieved in research. In fact, most physicians in this study would have improved their diagnostic accuracy for PJI by simply utilizing a single good test to make the diagnosis, instead of trying to combine multiple tests into a decision. We propose that less complex diagnostic criteria should be explored for routine clinical utilization.

Should an Age Cutoff Be Considered for Elective Total Knee Arthroplasty Patients? An Analysis of Operative Success Based on Patient-Reported Outcomes

Total knee arthroplasty (TKA) is increasing in the elderly population; however, some patients, family members, and surgeons raise age-related concerns over expected improvement and risks. This study aimed to (1) evaluate the relationship between age and change in patient-reported outcome measures (PROMs); (2) model how many patients would be denied improvements in PROMs if hypothetical age cutoffs were implemented; and (3) assess length of stay (LOS), readmission, reoperation, and mortality per age group. A prospective cohort of 4,396 primary TKAs (August 2015-August 2018) was analyzed. One-year PROMs were evaluated via Knee injury and Osteoarthritis Outcome Score (KOOS)-pain, -physical function short form (-PS), and -quality of life (-QOL), as well as Veterans Rand-12 (VR-12) physical (-PCS) and mental component (-MCS) scores. Positive predictive values (PPVs) of the number of postoperative "failures" (i.e., unattained minimal clinically important difference in PROMs) relative to number of hypothetically denied "successes" from a theoretical age-group restriction was estimated. KOOS-PS and QOL median score improvements were equivalent among all age groups (p = 0.946 and p = 0.467, respectively). KOOS-pain improvement was equivalent for ≥80 and 60-69-year groups (44.4 [27.8-55.6]). Median VR-12 PCS improvements diminished as age increased (15.9, 14.8, and 13.4 for the 60-69, 70-79, and ≥80 groups, respectively; p = 0.002) while improvement in VR-12 MCS was similar among age groups (p = 0.440). PPV for failure was highest in the ≥80 group, yet remained <34% for all KOOS measures. Overall mortality was highest in the ≥80 group (2.14%, n = 9). LOS >2, non-home discharge, and 90-day readmission were highest in the ≥80 group (8.11% [n = 24], p < 0.001; 33.7% [n = 109], p < 0.001; and 34.4% [n = 111], p = 0.001, respectively). Elderly patients exhibited similar improvement in PROMs to younger counterparts despite higher LOS, non-home discharge, and 90-day readmission. Therefore, special care pathways should be implemented for those age groups.

Aspirin Is an Effective Prophylaxis for Venous Thromboembolism in Ambulatory Patients with Femoral Neck Fracture Undergoing Hip Arthroplasty

BACKGROUND

Although aspirin has been adopted as an effective and safe prophylaxis against venous thromboembolism (VTE) by the arthroplasty community, the role of aspirin in the prevention of VTE in the setting of arthroplasty for trauma remains insufficiently known. Therefore, the present multicenter study investigated the efficacy of aspirin as VTE prophylaxis for patients with femoral neck fracture undergoing total hip arthroplasty or hemiarthroplasty.

METHODS

We reviewed the medical records of 1,141 patients with femoral neck fracture who underwent total hip arthroplasty or hemiarthroplasty from 2008 to 2018 at 3 different institutions. Data on patient demographic characteristics, body mass index, history of VTE, and comorbidities were obtained from an electronic chart query and were confirmed by reviewing the medical records manually. Patients were allocated to cohorts based on the type of prophylaxis administered: aspirin (n = 454) and other anticoagulants (n = 687). Patients were then propensity score-matched on the basis of the risk score calculated using a previously validated tool and the remaining confounding variables. The primary outcome was the development of symptomatic VTE, namely deep vein thrombosis (DVT) or pulmonary embolism (PE) confirmed by appropriate imaging, within 90 days after the surgical procedure. A bivariable analysis was performed.

RESULTS

The overall VTE rate was 1.98% for patients who received aspirin compared with 6.7% for patients who received other anticoagulants (p < 0.001). After propensity score matching and regression modeling, aspirin was found to be noninferior to more potent anticoagulation in preventing VTE after both total hip arthroplasty and hemiarthroplasty.

CONCLUSIONS

Aspirin is an effective option for VTE prophylaxis in patients with femoral neck fracture who undergo hip arthroplasty. Based on the patient management benefits of aspirin for elective arthroplasty and the present study, we suggest its use in standard-risk ambulatory patients.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Interim Spacer Exchange for Treatment of Periprosthetic Joint Infection: Almost Half the Patients Subsequently Fail

BACKGROUND

Interim spacer exchange may be performed in patients undergoing 2-stage exchange for periprosthetic joint infection. Several studies have demonstrated that interim spacer exchange is associated with poor outcomes. This study investigated the survivorship and risk factors for failure in patients with an interim spacer exchange.

METHODS

Two institutional databases identified 182 patients who underwent spacer exchange from 2000 to 2017. Primary outcomes included progression to reimplantation, treatment success, and mortality. Bivariate analysis was performed to evaluate risk factors associated with failure. Kaplan-Meier curves using host and local grades were generated to evaluate for primary outcomes and differences in survivorship.

RESULTS

The overall failure rate was 49% in patients with a spacer exchange. Most patients (60%) failed before 2 years. Higher comorbidity scores, elevated erythrocyte sedimentation rate, and non-White race were more prevalent in patients who failed. Negative cultures at the time of exchange were more prevalent in patients who did not fail. Failure rate was higher in immunocompromised conditions, and those who had revision prior to exchange. After considering clinically relevant variables, advanced host grade C was the single factor associated with treatment failure. Although survivorship curves were not significantly different between extremity local grades, higher host grades were associated with treatment failure.

CONCLUSION

Almost 1 out of 2 patients with spacer exchange were found to fail the intended 2-stage revision arthroplasty. Benefits of delivering additional antibiotic load with a new spacer should be balanced against poor outcomes in patients with the aforementioned risk factors.

When Total Joint Arthroplasty After Septic Arthritis Can Be Safely Performed

Background:

Patients undergoing total joint arthroplasty (TJA) following septic arthritis are at higher risk for developing periprosthetic joint infection (PJI). Minimal literature is available to guide surgeons on the optimal timing of TJA after completing treatment for prior native joint septic arthritis. This multicenter study aimed to determine the optimal timing of TJA after prior septic arthritis and to examine the role of preoperative serology in predicting patients at risk for developing PJI.

Methods:

A total of 207 TJAs were performed after prior septic arthritis from 2000 to 2017 at 5 institutions. Laboratory values, prior treatment, time from the initial infection, and other variables were recorded. Bivariate analyses were performed to identify the association between the time from septic arthritis to TJA and the risk of developing subsequent PJI. A subanalysis was performed between patients who underwent TJA in 1 setting (n = 97) compared with those who underwent 2-stage arthroplasties (n = 110). Receiver operating characteristic (ROC) curve analysis was performed for serum markers prior to TJA in predicting the risk of a subsequent PJI.

Results:

The overall PJI rate was 12.1%. Increasing time from septic arthritis treatment to TJA was not associated with a reduction of PJI, whether considering time as a continuous or categorical variable, for both surgical treatment cohorts (all p > 0.05). Although the ROC curve analysis found that the optimal threshold for timing of TJA from the initial treatment was 5.9 months, there was no difference in the PJI rate when the overall cohort was dichotomized by this threshold and when stratified by 1-stage compared with 2-stage TJA. There was no significant difference in erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level prior to conversion TJA between patients who subsequently developed PJI and those who did not.

Conclusions:

Serum markers have limited value in predicting subsequent PJI in patients who undergo TJA after prior septic arthritis. There was no optimal interim period between septic arthritis treatment and subsequent TJA; thus, delaying a surgical procedure does not appear to reduce the risk of PJI.

Level of Evidence:

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Results of preoperative screening for COVID-19 correlate with the incidence of infection in the general population -a tertiary care experience

Objectives: Many hospitals have recently instituted policies mandating preoperative COVID-19 testing. However, it is uncertain whether institutions can dictate such policies based on infection rates found in the general population. Therefore, the main aims of the study were to determine (1) what proportion of preoperative patients tested positive, (2) what percentage was asymptomatic, and (3) whether variations throughout time in numbers of positive patients reflected changes observed in our state.Methods: All COVID-19 preoperative screening tests (nasopharyngeal-swab RT-PCR testing) performed in our hospital between 04/13/2020 and 08/27/2020 were retrospectively reviewed. The unit of analysis was number of patients who tested negative/positive. Medical records of positive patients were reviewed to determine the presence of COVID-19 symptoms. A curve was created showing our number of positive patients per week and another one presenting the number of positive patients per day in Florida, both figures were compared.Results: A total of 7,213 patients from all specialties were preoperatively tested, out of which 85 were positive for an overall infection rate of 1.2%. In 18% (15/85) of positive patients, it was not possible to determine symptomatology. Among remaining patients, 49% (34/70) were asymptomatic while 51% (36/70) were symptomatic for COVID-19. Peak of positive cases occurred in mid-July in both curves, and the upward and downward tendencies in positive numbers mirrored each other.Conclusion: COVID-19 infection rate among our preoperative patients was very low. Nearly 50% of positive patients were asymptomatic. Our data suggest that a tertiary hospital can promulgate COVID-19 preoperative screening policies based on infection trends observed in the general population. However, in addition to the test, patients should be encouraged to self-quarantine for 14 days before surgery.

Total Knee Arthroplasty among Medicare Beneficiaries with Hemophilia A and B Is Associated with Increased Complications and Higher Costs

Operations on patients with hemophilia A and B are complex. Studies evaluating postoperative outcomes and costs following total knee arthroplasty (TKA) in patients with hemophilia are limited. A retrospective review of the entire Medicare dataset from 2005 to 2014 was performed. International Classification of Disease 9th revision codes were used to identify patients with hemophilia A and B and they were matched to controls using a 1:1 random matching process based on age, gender, Charlson Comorbidity Index (CCI), and select comorbidity burden. The 90-day preoperative period was evaluated for comorbidities and the 90-day postoperative period was analyzed for outcomes and reimbursements. Logistic regression models were generated to compare outcomes between cases and controls. A total of 4,034 patients with hemophilia were identified as having undergone TKA. About 44.8% were between the ages of 65 and 74 and 62.4% were female. Although the CCI was identical in both cohorts, individual comorbidities not controlled for varied significantly. Medical complications were more frequent among the patients with hemophilia: postoperative bleeding (odds ratio [OR]: 1.7; 95% confidence interval [CI]: 1.2-2.3), deep venous thrombosis (OR: 2.3; 95% CI: 1.8-2.8), pulmonary embolism (OR: 2.9; 95% CI: 2.1-3.9), and blood transfusions (OR: 1.8; 95% CI: 1.6-1.9). Hemophilia was associated with higher odds of periprosthetic infection (1.78 vs. 0.98%, OR: 1.8 95% CI: 1.2-2.7). The 90-day reimbursements were higher for patients with hemophilia (mean: $22,249 vs. $13,017, p < 0.001). Medicare beneficiaries with a diagnosis of hemophilia experience more frequent postoperative complications and incur greater 90-day costs than matched controls following TKA. Surgeons should consider this when optimizing patients for TKA and payors should consider this for risk-adjusting payment models.

Validation of the Alpha Defensin Lateral Flow Test for Periprosthetic Joint Infection

BACKGROUND

The synovial fluid test for alpha defensin has been reported to have an excellent performance in diagnosing periprosthetic joint infection (PJI). The purpose of this study was to evaluate the performance of the lateral flow test for synovial fluid alpha defensin by using the methods of a formal diagnostic accuracy study and to compare its performance with that of the laboratory-based alpha defensin test for PJI.

METHODS

We conducted a diagnostic accuracy study of the index lateral flow immunoassay for synovial fluid alpha defensin relative to the reference 2013 Musculoskeletal Infection Society (MSIS) multicriteria definition of PJI. The study included a prospective multicenter cohort of outpatients with a failed hip or knee arthroplasty and a supplemental control cohort of fresh synovial fluid specimens submitted by physicians for diagnostic PJI testing.

RESULTS

Among 57 patients with PJI and 248 patients without PJI in the overall prospective patient cohort, the sensitivity and specificity of the alpha defensin lateral flow test were 89.5% (95% confidence interval [CI]: 78.5% to 96.0%) and 94.8% (95% CI: 91.2% to 97.2%), respectively. The sensitivity increased to 94.3% (95% CI: 84.3% to 98.8%) after exclusion of 17 patients with grossly bloody aspirates (>1 million red blood cells/µL). Among the supplemental control cohort of fresh synovial fluid samples, including 65 samples from patients with PJI and 397 from patients without PJI, the sensitivity and specificity of the alpha defensin lateral flow test were 98.5% (95% CI: 91.7% to 100.0%) and 98.2% (95% CI: 96.4% to 99.3%), respectively. A comparison of the sensitivity and specificity of the alpha defensin lateral flow test with those of the alpha defensin enzyme-linked immunosorbent assay (ELISA) in the combined cohort did not demonstrate a significant difference in sensitivity (94.3% [95% CI: 88.5% to 97.7%] compared with 93.0% [95% CI: 87.1% to 96.7%]) or specificity (96.9% [95% CI: 95.3% to 98.1%] compared with 97.8% [95% CI: 96.4% to 98.8%]) (both p > 0.05).

CONCLUSIONS

The results of this study demonstrate the solid diagnostic performance of the alpha defensin test and have resulted in the U.S. Food and Drug Administration (FDA) authorization of the lateral-flow test with an intended use as an aid in the clinical diagnosis of PJI.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Hypovitaminosis D in lower extremity Joint Arthroplasty: A systematic review and meta-analysis

The purpose of the current systematic review was to identify the prevalence of hypovitaminosis-D in LE-TJA patients; and outline the association between pre-operative hypovitaminosis and post-operative outcomes. A search of PubMed-Medline and the Cochrane-Library databases was performed for literature published before November 27th, 2019. The eighteen studies analyzed had a pooled prevalence for vitamin D insufficiency (20 - <30 ng/mL) and deficiency (<20 ng/mL) of 53.4% and 39.4%, respectively. Hypovitaminosis-D was associated with higher complication rates (p = 0.043), and a greater prevalence among septic versus aseptic revisions (p = 0.016). Therefore, pre-operative screening for hypovitaminosis-D can be beneficial in patients undergoing LE-TJA.

LEVEL OF EVIDENCE

Systematic Review (Level III).

Development and Validation of an Evidence-Based Algorithm for Diagnosing Periprosthetic Joint Infection

BACKGROUND

The guidelines for diagnosis of periprosthetic joint infection (PJI) introduced by the American Academy of Orthopaedic Surgeons served the orthopedic community well. However, they have never been validated and do not account for newer diagnostic modalities. Our aim was to update current guidelines and develop an evidence-based and validated diagnostic algorithm.

METHODS

This multi-institutional study examined total joint arthroplasty patients from 3 institutions. Patients fulfilling major criteria for infection as defined by Musculoskeletal Infection Society were considered infected (n = 684). Patients undergoing aseptic revision for a noninfective indication and did not show evidence of PJI or undergo reoperation within 2 years served as a noninfected control group (n = 820). The algorithm was validated on a separate cohort of 422 cases.

RESULTS

The first step in evaluating PJI should include a physical examination, followed by serum C-reactive protein, erythrocyte sedimentation rate, and D-dimer. If at least one of these tests are elevated, or if high clinical suspicion exists, joint aspiration should be performed, sending the fluid for a white blood cell count, leukocyte esterase, polymorphonuclear percentage, and culture. Alpha defensin did not show added benefit as a routine diagnostic test. In inconclusive cases, intraoperative findings including gross purulence, histology, and next-generation sequencing or a single positive culture can aid in making the diagnosis. The proposed algorithm demonstrated a high sensitivity (96.9%) and specificity (99.5%).

CONCLUSION

This validated, evidence-based algorithm for diagnosing PJI should guide clinicians in the workup of patients undergoing revision arthroplasty and improve clinical practice. It also has the potential to reduce cost.

Polymyxin and Bacitracin in the Irrigation Solution Provide No Benefit for Bacterial Killing in Vitro

BACKGROUND

Many surgeons add topical antibiotics to irrigation solutions assuming that this has a local effect and eliminates bacteria. However, prior studies have suggested that the addition of antibiotics to irrigation solution confers little benefit, adds cost, may potentiate anaphylactic reactions, and may contribute to antimicrobial resistance. We sought to compare the antimicrobial efficacy and cytotoxicity of an irrigation solution containing polymyxin-bacitracin with other commonly used irrigation solutions.

METHODS

Staphylococcus aureus and Escherichia coli were exposed to irrigation solutions containing topical antibiotics (500,000-U/L polymyxin and 50,000-U/L bacitracin; 1-g/L vancomycin; or 80-mg/L gentamicin), as well as commonly used irrigation solutions (saline solution 0.9%; povidone-iodine 0.3%; chlorhexidine 0.05%; Castile soap 0.45%; and sodium hypochlorite 0.125%). Following 1 and 3 minutes of exposure, surviving bacteria were manually counted. Failure to eradicate all bacteria in any of the 3 replicates was considered not effective for that respective solution. Cytotoxicity analysis in human fibroblasts, osteoblasts, and chondrocytes exposed to the irrigation solutions was performed by visualization of cell structure and was quantified by lactate dehydrogenase (LDH) activity. Efficacy and cytotoxicity were assessed in triplicate experiments, with generalized linear mixed models.

RESULTS

Polymyxin-bacitracin, saline solution, and Castile soap at both exposure times were not effective at eradicating S. aureus or E. coli. In contrast, povidone-iodine, chlorhexidine, and sodium hypochlorite irrigation were effective against both S. aureus and E. coli (p < 0.001). Vancomycin irrigation was effective against S. aureus but not against E. coli, whereas gentamicin irrigation showed partial efficacy against E. coli but none against S. aureus. Within fibroblasts, the greatest cytotoxicity was seen with chlorhexidine (mean [and standard error], 49.38% ± 0.80%; p < 0.0001), followed by Castile soap (33.57% ± 2.17%; p < 0.0001) and polymyxin-bacitracin (8.90% ± 1.40%). Povidone-iodine showed the least cytotoxicity of the efficacious solutions (5.00% ± 0.86%). Similar trends were seen at both exposure times and across fibroblasts, osteoblasts, and chondrocytes.

CONCLUSIONS

Irrigation with polymyxin-bacitracin was ineffective at bacterial eradication, and statistically inferior to povidone-iodine. Chlorhexidine lavage conferred the greatest in vitro cytotoxicity.

CLINICAL RELEVANCE

These data suggest that the addition of polymyxin-bacitracin to saline solution irrigation has little value. Given the cost and antimicrobial resistance implications, our findings, combined with prior clinical literature, provide adequate reason to avoid widespread use of antibiotics in irrigation solutions. Povidone-iodine may be a more effective and safer option.

Potent Anticoagulation Does Not Reduce Venous Thromboembolism in High-Risk Patients

BACKGROUND

Based on current guidelines from the American Academy of Orthopaedic Surgeons (AAOS), a number of prophylactic modalities for the prevention of venous thromboembolism in total joint arthroplasty may be used. It is common practice that more potent prophylactic agents are used for patients at higher risk of venous thromboembolism. However, we are aware of no studies that have investigated the efficacy of potent anticoagulation in higher-risk individuals. Therefore, the purpose of our study was to test the hypothesis that low-molecular-weight heparin and warfarin result in a reduction in venous thromboembolism events in high-risk patients.

METHODS

A retrospective, multi-institutional study of 60,467 primary and revision total joint arthroplasties from 2000 to 2015 was performed. Identified medications were classified as aspirin, low-molecular-weight heparin, or warfarin. Patients with unavailable venous thromboembolism prophylaxis information or those not receiving the aforementioned prophylaxis were excluded. Information pertinent to the objective of this study was collected and a venous thromboembolism risk score was calculated based on 26 variables. Treatment outcomes assessed included 90-day rate of symptomatic venous thromboembolism and periprosthetic joint infection. Propensity score matching was performed (1:1), as well as logistic regression analysis on the total sample.

RESULTS

Aspirin prophylaxis demonstrated a lower rate of deep vein thrombosis, pulmonary embolism, and venous thromboembolism than warfarin and low-molecular-weight heparin alone throughout all risk scores. In the matched propensity score analysis, low-molecular-weight heparin and warfarin demonstrated increased odds of venous thromboembolism for both standard-risk and high-risk patients undergoing total knee arthroplasties compared with aspirin. For primary total hip arthroplasty, warfarin demonstrated an increased risk for high-risk patients and low-molecular-weight heparin demonstrated an increased risk for standard-risk patients. The prevalence of periprosthetic joint infection was higher in patients receiving warfarin (p < 0.001 for both comparisons of warfarin with aspirin and low-molecular-weight heparin).

CONCLUSIONS

The results of this multi-institutional study demonstrate that the use of warfarin and low-molecular-weight heparin in higher-risk patients does not necessarily result in a reduction in symptomatic venous thromboembolism. Aspirin administered to higher-risk patients seems to be as effective as potent anticoagulation and more effective than warfarin.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Diagnosing Periprosthetic Joint Infection in Inflammatory Arthritis: Assumption Is the Enemy of True Understanding

BACKGROUND

Despite concern over the interpretation of serum and synovial fluid tests to screen and diagnose periprosthetic joint infection (PJI) in patients with inflammatory arthritis, only a single study has investigated this area. We aimed to assess accuracy of clinical and laboratory markers for PJI diagnosis in the context of underlying inflammatory arthritis.

METHODS

This multicenter study was conducted on total joint arthroplasty patients at 3 different centers between 2001 and 2016. PJI was defined based on Musculoskeletal Infection Society criteria. Acute PJI cases were excluded. Patients operated for a diagnosis other than infection, who did not subsequently fail at 1-year follow-up, were considered aseptic revisions. Serum C-reactive protein and erythrocyte sedimentation rate, synovial white blood cell and differential, as well as alpha-defensin and results of frozen section were documented.

RESULTS

In total, 1220 patients undergoing revision total joint arthroplasty (567 PJI, 653 aseptic) were included. Fifty-five septic patients and 61 in the aseptic group had inflammatory arthritis. Although mean levels of serum C-reactive protein and synovial white blood cell in inflammatory arthritis patients were significantly higher compared to patients without inflammatory arthritis, there were no significant differences in PJI patients. The thresholds associated with increased risk for PJI in patients with and without inflammatory arthritis were similar and closely resembled traditional cut-points.

CONCLUSION

We demonstrate higher baseline immune upregulation in aseptic revision cases with inflammatory arthritis, but no significant differences are seen for PJI. Conventional PJI thresholds for serum and synovial diagnostic markers should be adhered to. Assumptions about inflammatory arthritis patients needing differential diagnostic protocols should be avoided.

The 2018 Definition of Periprosthetic Hip and Knee Infection: An Evidence-Based and Validated Criteria

BACKGROUND

The introduction of the Musculoskeletal Infection Society (MSIS) criteria for periprosthetic joint infection (PJI) in 2011 resulted in improvements in diagnostic confidence and research collaboration. The emergence of new diagnostic tests and the lessons we have learned from the past 7 years using the MSIS definition, prompted us to develop an evidence-based and validated updated version of the criteria.

METHODS

This multi-institutional study of patients undergoing revision total joint arthroplasty was conducted at 3 academic centers. For the development of the new diagnostic criteria, PJI and aseptic patient cohorts were stringently defined: PJI cases were defined using only major criteria from the MSIS definition (n = 684) and aseptic cases underwent one-stage revision for a noninfective indication and did not fail within 2 years (n = 820). Serum C-reactive protein (CRP), D-dimer, erythrocyte sedimentation rate were investigated, as well as synovial white blood cell count, polymorphonuclear percentage, leukocyte esterase, alpha-defensin, and synovial CRP. Intraoperative findings included frozen section, presence of purulence, and isolation of a pathogen by culture. A stepwise approach using random forest analysis and multivariate regression was used to generate relative weights for each diagnostic marker. Preoperative and intraoperative definitions were created based on beta coefficients. The new definition was then validated on an external cohort of 222 patients with PJI who subsequently failed with reinfection and 200 aseptic patients. The performance of the new criteria was compared to the established MSIS and the prior International Consensus Meeting definitions.

RESULTS

Two positive cultures or the presence of a sinus tract were considered as major criteria and diagnostic of PJI. The calculated weights of an elevated serum CRP (>1 mg/dL), D-dimer (>860 ng/mL), and erythrocyte sedimentation rate (>30 mm/h) were 2, 2, and 1 points, respectively. Furthermore, elevated synovial fluid white blood cell count (>3000 cells/μL), alpha-defensin (signal-to-cutoff ratio >1), leukocyte esterase (++), polymorphonuclear percentage (>80%), and synovial CRP (>6.9 mg/L) received 3, 3, 3, 2, and 1 points, respectively. Patients with an aggregate score of greater than or equal to 6 were considered infected, while a score between 2 and 5 required the inclusion of intraoperative findings for confirming or refuting the diagnosis. Intraoperative findings of positive histology, purulence, and single positive culture were assigned 3, 3, and 2 points, respectively. Combined with the preoperative score, a total of greater than or equal to 6 was considered infected, a score between 4 and 5 was inconclusive, and a score of 3 or less was not infected. The new criteria demonstrated a higher sensitivity of 97.7% compared to the MSIS (79.3%) and International Consensus Meeting definition (86.9%), with a similar specificity of 99.5%.

CONCLUSION

This study offers an evidence-based definition for diagnosing hip and knee PJI, which has shown excellent performance on formal external validation.

Venous thromboembolic prophylaxis after simultaneous bilateral total knee arthroplasty: aspirin versus warfarin

Aims

The aims of this study were to compare the efficacy of two agents, aspirin and warfarin, for the prevention of venous thromboembolism (VTE) after simultaneous bilateral total knee arthroplasty (SBTKA), and to elucidate the risk of VTE conferred by this procedure compared with unilateral TKA (UTKA).

Patients and Methods

A retrospective, multi-institutional study was conducted on 18 951 patients, 3685 who underwent SBTKA and 15 266 who underwent UTKA, using aspirin or warfarin as VTE prophylaxis. Each patient was assigned an individualised baseline VTE risk score based on a system using the Nationwide Inpatient Sample. Symptomatic VTE, including pulmonary embolism (PE) and deep vein thrombosis (DVT), were identified in the first 90 days post-operatively. Statistical analyses were performed with logistic regression accounting for baseline VTE risk.

Results

The adjusted incidence of PE following SBTKA was 1.0% (95% confidence interval (CI) 0.86 to 1.2) with aspirin and 2.2% (95% CI 2.0 to 2.4) with warfarin. Similarly, the adjusted incidence of VTE following SBTKA was 1.6% (95% CI 1.1 to 2.3) with aspirin and 2.5% (95% CI 1.9 to 3.3) with warfarin. The risk of PE and VTE were reduced by 66% (odds ratio (OR) 0.44, 95% CI 0.25 to 0.78) and 38% (OR 0.62, 95% CI 0.38 to 1.0), respectively, using aspirin. In addition, the risk of PE was 204% higher for patients undergoing SBTKA relative to those undergoing UTKA. For each ten-point increase in baseline VTE risk, the risk of PE increased by 25.5% for patients undergoing SBTKA compared with 10.5% for those undergoing UTKA. Patients with a history of myocardial infarction or peripheral vascular disease had the greatest increase in risk from undergoing SBTKA instead of UTKA.

Conclusion

Aspirin is more effective than warfarin for the prevention of VTE following SBTKA, and serves as the more appropriate agent for VTE prophylaxis for patients in all risk categories. Furthermore, patients undergoing SBTKA are at a substantially increased risk of VTE, even more so for those with significant underlying risk factors. Patients should be informed about the risks associated with undergoing SBTKA.

Cite this article: Bone Joint J 2018;100-B(1 Supple A):68–75.

Temporal Relations of Unplanned Readmissions Following Total Knee Arthroplasty: A Study of Large State Inpatient Databases

BACKGROUND

Centers for Medicare & Medicaid Services stipulate a 90-day global period for hospitals for unplanned readmissions after primary total knee arthroplasty (TKA). However, not all readmissions are directly attributable to index surgery, and reasons for readmissions vary during this time period. This study identifies causes and temporal relations of readmissions using large state inpatient databases.

METHODS

State inpatient databases of New York and California were queried for all primary TKAs performed from 2005 to 2011 and frequencies of all causes of unplanned readmission were identified from 0 to 90 days after index surgery using the International Classification of Diseases, Ninth Revision, codes. Temporal differences in proportions of readmission diagnoses were tested using the Pearson chi-square test.

RESULTS

The query identified 419,805 cases of primary TKA from 2005 to 2011. There were 26,924 readmissions during the 90-day recovery period, with 15,547 (57.7%) at 0-30 days, 6593 (24.5%) at 31-60 days, and 4784 (17.8%) at 61-90 days. Primary diagnoses at readmission that were identified to be directly attributable to surgery comprised 38.3% readmissions at 0-30 days, 24.0% at 31-60 days, and 16.3% at 60-90 days. Proportion of readmissions directly attributable to surgery decreased over the 90-day period after index surgery.

CONCLUSION

From this analysis of 2 large state inpatient databases, primary diagnoses at readmission vary with time, and majority of these may not be directly attributable to index surgery or postoperative state up to 90 days. These findings suggest that the current 90-day global period policy for this procedure should be reformed to better reflect the profile of unplanned readmissions after TKA.

Periprosthetic Joint Infections Caused by Enterococci Have Poor Outcomes

BACKGROUND

The definitive treatment and outcome of periprosthetic joint infection (PJI) caused by Enterococcus species is unknown. We performed a multi-institutional study to analyze the characteristics and treatment outcomes of patients with enterococcal PJI and to define an effective treatment protocol.

METHODS

We retrospectively reviewed all PJIs at 3 institutions between 1999 and 2014 using an electronic query followed by manual chart review. We included patients who met the Musculoskeletal Infection Society's criteria for PJI and had at least 1 positive intraoperative culture for any Enterococcus species. We identified 87 patients who had 12-month follow-up or treatment failure (mean, 4.03 years). Treatment failure was based on Delphi consensus criteria described previously. Kaplan-Meier survivorship analyses were performed. We assumed an alpha level of 0.05 for statistical significance.

RESULTS

The overall incidence of enterococcal PJI was 4.2%. The overall treatment success rate was 51.7% (45 of 87 patients). Thirteen cases (14.9%) that failed treatment had adverse outcomes including salvage procedures and PJI-related mortality. Treatment success rates stratified by procedure were 62.8%, 39.4%, and 45.5% for 2-stage exchange arthroplasty, irrigation and debridement, and 1-stage exchange arthroplasty, respectively (P = .037). Antibiotic treatment was heterogeneous; although combination antibiotics demonstrated a trend toward higher treatment success, it was not statistically different from monotherapy regimens (P = .174).

CONCLUSION

Enterococcal PJI has a high rate of treatment failure. Surgeons and patients should be aware of the difficulty in managing this condition and its dismal treatment outcomes. Although antibiotic treatment was heterogeneous, there was a trend toward higher success rates when combination antibiotic therapy was used.

The Alpha-defensin Test for Periprosthetic Joint Infections Is Not Affected by Prior Antibiotic Administration

BACKGROUND

Previous studies have demonstrated that the administration of antibiotics to patients before performing diagnostic testing for periprosthetic joint infection (PJI) can interfere with the accuracy of test results. Although a single-institution study has suggested that alpha-defensin maintains its concentration and sensitivity even after antibiotic treatment, this has not yet been demonstrated in a larger multiinstitutional study.

QUESTIONS/PURPOSES

(1) For the evaluation of PJI, is prior antibiotic administration associated with decreased alpha-defensin levels? (2) When prior antibiotics are given, is alpha-defensin a better screening test for PJI than the traditional tests (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], fluid white blood cells, fluid polymorphonuclear cells [PMNs], and fluid culture)?

METHODS

This retrospective study included data from 106 hip and knee arthroplasties with Musculoskeletal Infection Society-defined PJI from four centers. Of the 106 patients in this study, 30 (28%) were treated with antibiotics for PJI before diagnostic workup (ABX group), and 76 (72%) were not treated before the diagnostic workup (NO-ABX group). There were no differences in age, sex, joint, culture-negative rate, or bacteriology between groups. The patients in the ABX group had antibiotics initiated by physicians who commenced care before assessment for PJI by the treating surgeon's service. We compared the alpha-defensin levels and sensitivity between the ABX and NO-ABX groups. Additionally, the sensitivity of the alpha-defensin test was compared to that of traditional tests for PJI among patients on antibiotics.

RESULTS

The administration of antibiotics before performing the alpha-defensin test for PJI was not associated with a decreased median alpha-defensin level (ABX group, median 4.2 [range, 1.79-12.8 S/CO] versus NO-ABX, median 4.9 [range, 0.5-16.8 S/CO], difference of medians: 0.68 S/CO [95% confidence interval {CI}, -0.98 to 1.26], p = 0.451). Furthermore, the alpha-defensin test had a higher sensitivity (100%; 95% CI, 88.4%-100.0%) in diagnosing PJI among patients on antibiotics when compared with the ESR (69.0% [95% CI, 49.17%-84.72%], p = 0.001), the CRP (79.3% [95% CI, 60.3%-92.0%], p = 0.009), the fluid PMN% (79.3% [95% CI, 60.3%-92.0%), p = 0.009), and fluid culture (70.0% [95% CI, 50.6%-85.3%], p = 0.001).

CONCLUSIONS

The alpha-defensin test maintains its concentration and sensitivity for PJI even in the setting of antibiotic administration. Furthermore, among patients with PJI on antibiotics, the alpha-defensin tests demonstrated a higher sensitivity in detecting PJI when compared with the ESR, CRP, fluid PMN%, and fluid culture. The high sensitivity of the alpha-defensin test, even in the setting of prior antibiotic treatment, provides excellent utility as a screening test for PJI.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Premature Therapeutic Antimicrobial Treatments Can Compromise the Diagnosis of Late Periprosthetic Joint Infection

BACKGROUND

In the absence of positive cultures and draining sinuses, the diagnosis of periprosthetic joint infection (PJI) relies on laboratory values. It is unknown if administration of antibiotics within 2 weeks before diagnostic evaluations can affect these tests in patients with PJI.

QUESTIONS/PURPOSES

The purpose of this study was to investigate the correlation of antibiotic administration with (1) fluctuations in the synovial fluid and serology laboratory values; and (2) sensitivity of the diagnostic tests in patients with late PJI (per Musculoskeletal Infection Society [MSIS] criteria).

METHODS

Synovial white blood cell (WBC) count, polymorphonuclear neutrophil (PMN) percentage, and serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as well as culture results were investigated in 161 patients undergoing total knee arthroplasty with late PJI diagnosed with the MSIS criteria. Depending on whether presampling antibiotics were used, patients were divided in two groups (53 [33%] patients were on antibiotics). The median laboratory values and the false-negative rates were compared between the two groups.

RESULTS

The median of all variables were lower in the antibiotic group compared with the other group: ESR (mm/hr): 70 versus 85, difference of medians (DOM) = 15 mm/hr, p = 0.018; CRP (mg/L): 72 versus 130, DOM = 58 mg/L, p = 0.038; synovial WBC (cells/μL): 29,170 versus 46,900, DOM = 17,730, p = 0.022; and synovial PMN%: 88.5% versus 92.5%, DOM = 4%, p = 0.012. Furthermore, using the MSIS cutoffs, the false-negative rates of several parameters were higher in the antibiotic group; ESR: 19.2% (nine of 47) versus 6.1% (six of 99) (relative risk, 3.1; 95% confidence interval [CI], 1.2-8.3; p = 0.020); CRP: 14.9% (seven of 47) versus 2.00% (two of 100) (relative risk, 7.4; 95% CI, 1.6-34.4); PMN%: 23.1% (12 of 52) versus 9.4% (10 of 106) (relative risk, 2.4; 95% CI, 1.1-5.2; p = 0.027). Patients in the antibiotic group also had higher rates of negative cultures: 26.4% (14 of 53) versus 12.9% (14 of 108) (relative risk, 2.0; 95% CI, 1.05-3.9; p = 0.046).

CONCLUSIONS

It appears that premature antibiotic treatments are associated with lower medians of diagnostic laboratory values. Thus, and in line with the guideline recommendations of the American Academy of Orthopaedic Surgeons, patients with suspected late-PJI should not receive antibiotics until the diagnosis is reached or refuted.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Prospective randomized evaluation of the need for blood transfusion during primary total hip arthroplasty with use of a bipolar sealer

BACKGROUND

Blood loss during total hip arthroplasty can be substantial and may lead to adverse patient outcomes and increased health-care costs. Many blood-management options are available for these procedures. The purpose of the present study was to test the hemostatic efficacy of a bipolar sealer used during total hip arthroplasty in order to determine whether its use results in significantly lower transfusion requirements and/or improved clinical, functional, and health-related quality-of-life outcomes in healthy patients.

METHODS

This prospective, single-center, randomized, double-blinded study was designed to enroll a total of 140 patients. Patients with a low preoperative hemoglobin level or a history of bleeding abnormalities and other medical conditions were excluded. Patients were randomized to either the treatment arm (radiofrequency energy with use of the Aquamantys 6.0 bipolar sealer) or control arm (standard Bovie electrocautery). The primary outcome measure was the transfusion requirement, and the secondary outcome measures were intraoperative estimated blood loss, postoperative hemoglobin levels, perioperative narcotic usage, length of hospital stay, postoperative pain scores, and postoperative function as measured with the Harris hip score and the Short Form-12 quality-of-life score.

RESULTS

Seventy-one patients were assigned to the treatment arm, and sixty-nine were assigned to the control arm. The mean number of units of blood transfused for all patients in the study and control arms were 0.38 and 0.44, respectively (p = 0.72). The transfusion requirements were similar in the two groups, with fifteen of seventy-one patients in the treatment arm and fourteen of sixty-nine patients in the control arm requiring a transfusion (p = 0.9). No significant differences were detected between the groups in terms of estimated blood loss, postoperative hemoglobin levels, perioperative narcotic usage, length of hospital stay, postoperative pain scores, Harris hip scores, or Short Form-12 scores.

CONCLUSIONS

In this patient population, there were no significant differences between the treatment and control groups in terms of the need for blood transfusions or overall blood loss. Given these findings, we have discontinued the use of this bipolar sealing device in uncomplicated primary total hip arthroplasty patients at our institution.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Plaque, caries level and oral hygiene habits in young patients receiving orthodontic treatment

OBJECTIVE

To assess plaque, caries, and oral hygiene habits amongst patients receiving fixed-orthodontic treatment at the Dental-Clinic, Universidad-El-Bosque, Bogotá, Colombia.

BASIC RESEARCH DESIGN

Test-group: 74 12-29-year-olds receiving fixed-orthodontic treatment; reference-group: 63 12-29-year-olds before they started the orthodontic treatment. Visual examinations (one examiner) recorded the following: Ortho-plaque-Index (OPI) expressed per patient as good, fair and poor-oral-hygiene. Caries was scored with the modified-ICDAS-II criteria as: 0-sound; 1B/1W-brown/white-opacity-after-air-drying; 2B/2W-brown/white-opacity-without-air-drying; 3-microcavity; 4-underlying-shadow; 5/6-distinct/extensive-cavity. Filled/missing surfaces due-to-caries and caries-lesions on buccal surfaces at three sites around the brackets were recorded. A 7-item self-administered oral-hygiene habits' questionnaire was used.

RESULTS

Chi-square test revealed that the oral-hygiene level was significantly better in the reference group compared to the test group (p < 0.05). The traditional mean DMF-S was 6.7 +/- 6.3 in the test- and 6.2 +/- 5.9 in the reference-group (p > 0.05). When adding modified-ICDAS-II lesions scores 1-4, the figure increased to 23.6 +/- 9.4 in the test- and to 13.6 +/- 10.3 in the reference-group (p < 0.001). A total of 96% had > or = 1 white-opacity in the test group versus 56% in the reference group (P < 0.001). In the test-group the buccal-surfaces accounted for most white-opacities and close to 1/3 of these lesions on the upper-anterior teeth were located around the brackets. The questionnaire disclosed that 58% in the test- vs. 44% in the reference-group did not accept having dental caries lesions during the orthodontic treatment.

CONCLUSIONS

The results showed a high prevalence of white-opacities related to orthodontic appliances and indicate the need to implement preventive programmes at the dental clinic.

A computer model of the position of the combined component in the prevention of impingement in total hip replacement

Dislocation remains a major concern after total hip replacement, and is often attributed to malposition of the components. The optimum position for placement of the components remains uncertain. We have attempted to identify a relatively safe zone in which movement of the hip will occur without impingement, even if one component is positioned incorrectly. A three-dimensional computer model was designed to simulate impingement and used to examine 125 combinations of positioning of the components in order to allow maximum movement without impingement. Increase in acetabular and/or femoral anteversion allowed greater internal rotation before impingement occurred, but decreases the amount of external rotation. A decrease in abduction of the acetabular components increased internal rotation while decreasing external rotation. Although some correction for malposition was allowable on the opposite side of the joint, extreme degrees could not be corrected because of bony impingement.

We introduce the concept of combined component position, in which anteversion and abduction of the acetabular component, along with femoral anteversion, are all defined as critical elements for stability.

Hip and Knee Arthroplasty in the Geriatric Population

Osteoarthritis is the leading cause of hip and knee pathology in the geriatric population. Hip and knee arthroplasty are the definitive interventions to alleviate pain and restore physical functioning. Complications related to these procedures do occur: the most com-mon of these are infection, thromboembolism, dislocations, and periprosthetic fractures. New improvements related to minimally invasive and computer-assisted navigation surgery techniques are promising and already have shown excellent outcomes in patients exposed to joint arthroplasty.