Frozen sections of samples taken intraoperatively for diagnosis of infection in revision hip surgery

Can we rely on histopathological results for the diagnostic of prosthetic joint infection?

BACKGROUND

Histopathology is one of the diagnostic criteria for prosthetic joint infection (PJI) proposed by all academic societies. The aim of this study was to compare histopathological and microbiological results from samples taken intraoperatively at the same site in patients with suspected or proven PJI.

PATIENTS AND METHODS

We conducted a monocenter retrospective study including all patients having undergone surgery from 2007 to 2015 with suspected or proven PJI. During surgery, both histopathological and microbiological samples were taken. Patients with a history of antimicrobial treatment 2 weeks prior to surgery were excluded. We considered as major criteria and gold standard for PJI diagnosis the presence of a sinus tract communication and/or the same microorganism in at least two cultures.

RESULTS

Finally, 181 patients who underwent 309 surgeries were included. The median number of samples per surgery was 4 (interquartile range (IQR) = 3-5) for histopathology and 5 (IQR=4-6) for microbiology. Major criteria were observed in 177 patients (57.3%), while positive histology in at least one intraoperative sample was present in 119 (38.5%). The concordance was 74%. The sensitivity and specificity of histopathology were 61% and 92% respectively. Available "histopathology-culture" sample pairs numbered 1247. Among them, positive histopathology was found in 292 samples (23%) and culture in 563 (45%). Concordance was 64%. The highest correlation was observed for very early infection (< 1 month) (OR: 9.1, 95% CI: 3.6-23) and for virulent microorganisms, such as Staphylococcus aureus (OR: 7.8, 95% CI: 5.2-11.8), Streptococci (OR:7.8; 95% CI: 4-15.2) or Enterobacterales (OR: 7.4; 95% CI: 4.2-13.1).

CONCLUSION

Histopathologic examination is a valuable criterion for PJI diagnosis, but it may lack sensitivity for chronic infections or due to low-virulence pathogens.

Clinical validity of the intraoperative histology in the diagnosis of prosthetic joint infection

BACKGROUND AND AIM

Different authors have demonstrated the usefulness of the histological analysis in the diagnosis of prosthetic joint infection; however, its clinical validity is still controversial. The aim of this article is to describe and analyze the clinical validity of histological analysis in the diagnosis of prosthetic infection in patients undergoing hip or knee prosthetic replacement.

MATERIAL AND METHODS

We present a retrospective study including 133 hip and knee prosthetic replacements performed in our center between 2008 and 2020. A descriptive, bivariate statistical analysis was performed and the clinical validity of the histological analysis was determined.

OUTCOMES

The clinical validity of the intraoperative histology offered a sensitivity of 48%, a specificity of 91%, a positive predictive value of 55% and a negative predictive value of 88%.

CONCLUSIONS

The determination of the clinical validity of histological analysis shows a high specificity. This analysis is an appropriate diagnostic tool for detecting healthy patients, with no infection.

[Translated article] Clinical validity of the intraoperative histology in the diagnosis of prosthetic joint infection

BACKGROUND AND AIM

Different authors have demonstrated the usefulness of the histological analysis in the diagnosis of prosthetic joint infection; however, its clinical validity is still controversial. The aim of this article is to describe and analyse the clinical validity of histological analysis in the diagnosis of prosthetic infection in patients undergoing hip or knee prosthetic replacement.

MATERIAL AND METHODS

We present a retrospective study including 133 hip and knee prosthetic replacements performed in our centre between 2008 and 2020. A descriptive, bivariate statistical analysis was performed and the clinical validity of the histological analysis was determined.

OUTCOMES

The clinical validity of the intraoperative histology offered a sensitivity of 48%, a specificity of 91%, a positive predictive value of 55% and a negative predictive value of 88%.

CONCLUSIONS

The determination of the clinical validity of histological analysis shows a high specificity. This analysis is an appropriate diagnostic tool for detecting healthy patients, with no infection.

One-stage exchange should be avoided in periprosthetic joint infection cases with massive femoral bone loss or with history of any failed revision to treat periprosthetic joint infection

AIMS

There is a paucity of long-term studies analyzing risk factors for failure after single-stage revision for periprosthetic joint infection (PJI) following total hip arthroplasty (THA). We report the mid- to long-term septic and non-septic failure rate of single-stage revision for PJI after THA.

METHODS

We retrospectively reviewed 88 cases which met the Musculoskeletal Infection Society (MSIS) criteria for PJI. Mean follow-up was seven years (1 to 14). Septic failure was diagnosed with a Delphi-based consensus definition. Any reoperation for mechanical causes in the absence of evidence of infection was considered as non-septic failure. A competing risk regression model was used to evaluate factors associated with septic and non-septic failures. A Kaplan-Meier estimate was used to analyze mortality.

RESULTS

The cumulative incidence of septic failure was 8% (95% confidence interval (CI) 3.5 to 15) at one year, 13.8% (95% CI 7.6 to 22) at two years, and 19.7% (95% CI 12 to 28.6) at five and ten years of follow-up. A femoral bone defect worse than Paprosky IIIA (hazard ratio (HR) 13.58 (95% CI 4.86 to 37.93); p < 0.001) and obesity (BMI ≥ 30 kg/m²; HR 3.88 (95% CI 1.49 to 10.09); p = 0.005) were significantly associated with septic failure. Instability and periprosthetic fracture were the most common reasons for mechanical failure (5.7% and 4.5%, respectively). The cumulative incidence of aseptic failure was 2% (95% CI 0.4 to 7) at two years, 9% (95% CI 4 to 17) at five years, and 12% (95% CI 5 to 22) at ten years. A previous revision to treat PJI was significantly associated with non-septic failure (HR 9.93 (95% CI 1.77 to 55.46); p = 0.009). At the five-year timepoint, 93% of the patients were alive (95% CI 84% to 96%), which fell to 86% (95% CI 75% to 92%) at ten-year follow-up.

CONCLUSION

Massive femoral bone loss was associated with greater chances of developing a further septic failure. All septic failures occurred within the first five years following the one-stage exchange. Surgeons should be aware of instability and periprosthetic fracture being potential causes of further aseptic revision surgery. Cite this article: Bone Joint J 2021;103-B(7):1247-1253.

Patients with no recurrence of infection five years after two-stage revision hip arthroplasty may be classified as periprosthetic infection 'in remission'

AIMS

We aimed to report the mid- to long-term rates of septic and aseptic failure after two-stage revision surgery for periprosthetic joint infection (PJI) following total hip arthroplasty (THA).

METHODS

We retrospectively reviewed 96 cases which met the Musculoskeletal Infection Society criteria for PJI. The mean follow-up was 90 months (SD 32). Septic failure was assessed using a Delphi-based consensus definition. Any further surgery undertaken for aseptic mechanical causes was considered as aseptic failure. The cumulative incidence with competing risk analysis was used to predict the risk of septic failure. A regression model was used to evaluate factors associated with septic failure. The cumulative incidence of aseptic failure was also analyzed.

RESULTS

There were 23 septic failures at final follow-up, with a cumulative incidence of 14% (95% confidence interval (CI) 8% to 22%) at one year, 18% (95% CI 11% to 27%) at two years, 22% (95% CI 14% to 31%) at five years, and 23% (95% CI 15% to 33%) at ten years. Having at least one positive culture (hazard ratio (HR) 2.38 (interquartile range (IQR) 1.19 to 4.74); p = 0.013), or a positive intraoperative frozen section (HR 2.55 (IQR 1.06 to 6.15); p = 0.037) was significantly associated with septic failure after reimplantation. With dislocation being the most common cause of aseptic revision (5.2%), the cumulative incidence of aseptic failure was 1% (95% CI 0% to 5%) at one year, 6% (95% CI 1% to 8%) at five years, and 8% (95%CI 3% to 17%) at ten years.

CONCLUSION

If there is no recurrent infection in the five years following reimplantation, the chances of further infection thereafter are remote. While the results of a frozen section may be a reliable guide to the timing of reimplantation, intraoperative culture has, currently, only prognostic value. Surgeons should be aware that instability remains a potential indication for further revision surgery. Cite this article: Bone Joint J 2021;103-B(1):79-86.

The EBJIS definition of periprosthetic joint infection

Aims

The diagnosis of periprosthetic joint infection (PJI) can be difficult. All current diagnostic tests have problems with accuracy and interpretation of results. Many new tests have been proposed, but there is no consensus on the place of many of these in the diagnostic pathway. Previous attempts to develop a definition of PJI have not been universally accepted and there remains no reference standard definition.

Methods

This paper reports the outcome of a project developed by the European Bone and Joint Infection Society (EBJIS), and supported by the Musculoskeletal Infection Society (MSIS) and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Implant-Associated Infections (ESGIAI). It comprised a comprehensive review of the literature, open discussion with Society members and conference delegates, and an expert panel assessment of the results to produce the final guidance.

Results

This process evolved a three-level approach to the diagnostic continuum, resulting in a definition set and guidance, which has been fully endorsed by EBJIS, MSIS, and ESGIAI.

Conclusion

The definition presents a novel three-level approach to diagnosis, based on the most robust evidence, which will be useful to clinicians in daily practice.

Cite this article: Bone Joint J 2021;103-B(1):18–25.

The Quality of Diagnostic Studies in Periprosthetic Joint Infections: Can We Do Better?

BACKGROUND

The diagnosis of periprosthetic joint infections (PJIs) continues to be a subject of extensive debate. This is in part due to the lack of a single "gold standard" test, and the marked heterogeneity in the design of studies evaluating the accuracy of different diagnostic modalities. The goal of this review is to critically analyze the evidence cited by the proceedings of the 2013 International Consensus Meeting (ICM) on PJI with regards to the diagnosis of PJI.

METHODS

References from the Proceedings of the ICM on PJI related to PJI minor criteria were retrieved and manually reviewed. A total of 25 studies were analyzed using a Validated Quality Assessment of Diagnostic Accuracy Studies tool.

RESULTS

A large number of studies were determined to have a high risk of bias for flow and timing domains due to the large numbers of exclusions. Studies of synovial white blood cells count and polymorphonuclear neutrophils percentage suffered from threshold optimization and lack of internal validity. Furthermore, due to the lack of homogeneity across studies, index test and reference standard domains showed high risk of bias for white blood cell/polymorphonuclear neutrophil percentage and the utility histological analysis, respectively. Leukocyte esterase testing lacked standardization with regard to the strip reagent used, and the exclusion of bloody samples limited sample sizes.

CONCLUSION

The 2013 ICM minor criteria were based on studies with a low quality of evidence. As the committee continues to adjust these guidelines, they should encourage future studies with sound clinical design, patient selection, and testing procedures.

Impaction Bone Grafting or Uncemented Modular Stems for the Treatment of Type B3 Periprosthetic Femoral Fractures? A Complication Rate Analysis

BACKGROUND

Because the gold standard for the treatment of Vancouver type-B3 periprosthetic femoral fractures (PFFs) is yet to be defined, we sought to analyze the complication rate between the impaction bone grafting (IBG) technique with a cemented stem and reconstruction with an uncemented distally-fixed modular stem (DFMS).

METHODS

We retrospectively studied 54 B3 PFFs operated between 2000 and 2016, comparing the complication rate of 33 patients treated with the IBG technique (group A) with 21 patients treated with a DFMS (group B). Median follow-up of groups A and B were 75 months (interquartile range [IQR], 36-111 months) and 55 months (IQR, 32-73 months), respectively (P = .008). Median age of groups A and B were 78 years (IQR, 74-83 years) and 81 years (IQR, 74-86 years), respectively (P = .30). Median grade of Endo-Klink femoral bone defect was 3 (IQR, 3-3) for both groups (P = .11). We performed a multiple regression analysis to determine risk factors for complications including the following variables: age, initial diagnosis, and surgical technique.

RESULTS

As for infection outcomes, 2-stage revision surgery was more frequent in group A than in group B (4 vs 0, P = .003). Group A presented more implant failures than group B (5 vs 1, P = .195). We found 4 dislocations in group B and 2 in group A (P = .192). Multiple regression analysis showed a significant association between surgical technique and complication rate (P = .01). The IBG technique presented an odds risk for complications of 4.77 (P = .016; IQR, 1.33-17.21).

CONCLUSION

Femoral reconstruction with the IBG technique evidenced an ostensibly higher complication rate than that of DFMS for the treatment of B3 PFF.

What Strategies Can Be Implemented to Help Isolate the Causative Organism in Patients With Infection of the Foot and Ankle?

RECOMMENDATION

Transfer of synovial aspirate in blood culture bottles, obtaining deep biopsy of tissues and bone, obtaining multiple samples, increasing incubation period of cultures, and the use of molecular techniques for culture negative cases are some of the strategies that can help improve the ability to isolate the causative organism(s) in infections of foot and ankle.

LEVEL OF EVIDENCE

Moderate.

DELEGATE VOTE

Agree: 100%, Disagree: 0%, Abstain: 0% (Unanimous, Strongest Consensus).

Can leucocyte esterase replace frozen sections in the intraoperative diagnosis of prosthetic hip infection?

AIMS

Leucocyte esterase (LE) has been shown to be an accurate marker of prosthetic joint infection (PJI), and has been proposed as an alternative to frozen section (FS) histology for intraoperative diagnosis. In this study, the intraoperative assessment of LE was compared with FS histology for the diagnosis of prosthetic hip infection.

PATIENTS AND METHODS

A total of 119 patients undergoing revision total hip arthroplasty (THA) between June 2015 and December 2017 were included in the study. There were 56 men and 63 women with a mean age of 66.2 years (27 to 88). Synovial fluid was collected before arthrotomy for the assessment of LE using enzymatic colourimetric strips. Between five and six samples were stained with haematoxylin and eosin for FS histology, and considered suggestive of infection when at least five polymorphonuclear leucocytes were found in five high-power fields.

RESULTS

The sensitivity and specificity of the LE assay were 100% and 93.8%, respectively; the positive (PPV) and the negative (NPV) predictive values were 79.3% and 100%, respectively. The mean time between the collection of the sample and the result being known was 20.1 minutes (sd 4.4). The sensitivity and specificity of FS histology were 78.3% and 96.9%, respectively; the PPV and the NPV were 85.7% and 94.9%, respectively. The mean time between the collection of the sample and the result being known was 27.2 minutes (sd 6.9).

CONCLUSION

The sensitivity of LE assay was higher, with similar specificity and diagnostic accuracy, compared with FS histology. The faster turnaround time, its ease of use, and low costs make LE assay a valuable alternative to FS histology. We now use it routinely for the intraoperative diagnosis of PJI. Cite this article: Bone Joint J 2019;101-B:372-377.

Diagnostic Accuracy of Serum, Synovial, and Tissue Testing for Chronic Periprosthetic Joint Infection After Hip and Knee Replacements: A Systematic Review

BACKGROUND

Chronic periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint replacement. Patients with chronic PJI report a substantially lower quality of life and face a higher risk of short-term mortality. Establishing a diagnosis of chronic PJI is challenging because of conflicting guidelines, numerous tests, and limited evidence. Delays in diagnosing PJI are associated with poorer outcomes and morbid revision surgery. The purpose of this systematic review was to compare the diagnostic accuracy of serum, synovial, and tissue-based tests for chronic PJI.

METHODS

This review adheres to the Cochrane Collaboration's diagnostic test accuracy methods for evidence searching and syntheses. A detailed search of MEDLINE, Embase, the Cochrane Library, and the grey literature was performed to identify studies involving the diagnosis of chronic PJI in patients with hip or knee replacement. Eligible studies were assessed for quality and bias using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Meta-analyses were performed on tests with sufficient data points. Summary estimates and hierarchical summary receiver operating characteristic (HSROC) curves were obtained using a bivariate model.

RESULTS

A total of 12,616 citations were identified, and 203 studies met the inclusion criteria. Of these 203 studies, 170 had a high risk of bias. Eighty-three unique PJI diagnostic tests were identified, and 17 underwent meta-analyses. Laboratory-based synovial alpha-defensin tests and leukocyte esterase reagent (LER) strips (2+) had the best performance, followed by white blood-cell (WBC) count, measurement of synovial C-reactive protein (CRP) level, measurement of the polymorphonuclear neutrophil percentage (PMN%), and the alpha-defensin lateral flow test kit (Youden index ranging from 0.78 to 0.94). Tissue-based tests and 3 serum tests (measurement of interleukin-6 [IL-6] level, CRP level, and erythrocyte sedimentation rate [ESR]) had a Youden index between 0.61 to 0.75 but exhibited poorer performance compared with the synovial tests mentioned above.

CONCLUSIONS

The quality of the literature pertaining to chronic PJI diagnostic tests is heterogeneous, and the studies are at a high risk for bias. We believe that greater transparency and more complete reporting in studies of diagnostic test results should be mandated by peer-reviewed journals. The available literature suggests that several synovial fluid-based tests perform well for diagnosing chronic PJI and their use is recommended in the work-up of any suspected case of chronic PJI.

LEVEL OF EVIDENCE

Diagnostic 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.

Histopathology in Periprosthetic Joint Infection: When Will the Morphomolecular Diagnosis Be a Reality?

The presence of a polymorphonuclear neutrophil infiltrate in periprosthetic tissues has been shown to correlate closely with the diagnosis of septic implant failure. The histological criterion considered by the Musculoskeletal Infection Society to be diagnostic of periprosthetic joint infection is “greater than five neutrophils per high-power field in five high-power fields observed from histologic analysis of periprosthetic tissue at ×400 magnification.” Surgeons and pathologists should be aware of the qualifications introduced by different authors during the last years in the histological techniques, samples for histological study, cutoffs used for the diagnosis of infection, and types of patients studied. Recently, immunohistochemistry and histochemistry studies have appeared which suggest that the cutoff point of five polymorphonuclear neutrophils in five high-power fields is too high for the diagnosis of many periprosthetic joint infections. Therefore, morphomolecular techniques could help in the future to achieve a more reliable histological diagnosis of periprosthetic joint infection.

Microscale characterization of prostate biopsies tissues using optical coherence elastography and second harmonic generation imaging

Photonics, especially optical coherence elastography (OCE) and second harmonic generation (SHG) imaging are novel high-resolution imaging modalities for characterization of biological tissues. Following our preliminary experience, we hypothesized that OCE and SHG imaging would delineate the microstructure of prostate tissue and aid in distinguishing cancer from the normal benign prostatic tissue. Furthermore, these approaches may assist in characterization of the grade of cancer, as well. In this study, we confirmed a high diagnostic accuracy of OCE and SHG imaging in the detection and characterization of prostate cancer for a large set of biopsy tissues obtained from men suspected to have prostate cancer using transrectal ultrasound (TRUS). The two techniques and methods described here are complementary, one depicts the stiffness of tissues and the other illustrates the orientation of collagen structure around the cancerous lesions. The results showed that stiffness of cancer tissue was ~57.63% higher than that of benign tissue (Young's modulus of 698.43±125.29 kPa for cancerous tissue vs 443.07±88.95 kPa for benign tissue with OCE. Using histology as a reference standard and 600 kPa as a cut-off threshold, the data analysis showed sensitivity and specificity of 89.6 and 99.8%, respectively. Corresponding positive and negative predictive values were 99.5 and 94.6%, respectively. There was a significant difference noticed in terms of Young's modulus for different Gleason scores estimated by OCE (P-value<0.05). For SHG, distinct patterns of collagen distribution were seen for different Gleason grade disease with computed quantification employing a ratio of anisotropic to isotropic (A:I ratio) and this correlated with disease aggressiveness.

Prosthetic joint infection development of an evidence-based diagnostic algorithm

BACKGROUND

Increasing rates of prosthetic joint infection (PJI) have presented challenges for general practitioners, orthopedic surgeons and the health care system in the recent years. The diagnosis of PJI is complex; multiple diagnostic tools are used in the attempt to correctly diagnose PJI. Evidence-based algorithms can help to identify PJI using standardized diagnostic steps.

METHODS

We reviewed relevant publications between 1990 and 2015 using a systematic literature search in MEDLINE and PUBMED. The selected search results were then classified into levels of evidence. The keywords were prosthetic joint infection, biofilm, diagnosis, sonication, antibiotic treatment, implant-associated infection, Staph. aureus, rifampicin, implant retention, pcr, maldi-tof, serology, synovial fluid, c-reactive protein level, total hip arthroplasty (THA), total knee arthroplasty (TKA) and combinations of these terms.

RESULTS

From an initial 768 publications, 156 publications were stringently reviewed. Publications with class I-III recommendations (EAST) were considered. We developed an algorithm for the diagnostic approach to display the complex diagnosis of PJI in a clear and logically structured process according to ISO 5807.

CONCLUSIONS

The evidence-based standardized algorithm combines modern clinical requirements and evidence-based treatment principles. The algorithm provides a detailed transparent standard operating procedure (SOP) for diagnosing PJI. Thus, consistently high, examiner-independent process quality is assured to meet the demands of modern quality management in PJI diagnosis.

Implementation of an Algorithm for Prosthetic Joint Infection: Deviations and Problems

BACKGROUND

The outcome of revision surgery in arthroplasty is based on a precise diagnosis. In addition, the treatment varies based on whether the prosthetic failure is caused by aseptic or septic loosening. Algorithms can help to identify periprosthetic joint infections (PJI) and standardize diagnostic steps, however, algorithms tend to oversimplify the treatment of complex cases. We conducted a process analysis during the implementation of a PJI algorithm to determine problems and deviations associated with the implementation of this algorithm.

PATIENTS AND METHODS

Fifty patients who were treated after implementing a standardized algorithm were monitored retrospectively. Their treatment plans and diagnostic cascades were analyzed for deviations from the implemented algorithm. Each diagnostic procedure was recorded, compared with the algorithm, and evaluated statistically.

RESULTS

We detected 52 deviations while treating 50 patients. In 25 cases, no discrepancy was observed. Synovial fluid aspiration was not performed in 31.8% of patients (95% confidence interval [CI], 18.1%-45.6%), while white blood cell counts (WBCs) and neutrophil differentiation were assessed in 54.5% of patients (95% CI, 39.8%-69.3%). We also observed that the prolonged incubation of cultures was not requested in 13.6% of patients (95% CI, 3.5%-23.8%). In seven of 13 cases (63.6%; 95% CI, 35.2%-92.1%), arthroscopic biopsy was performed; 6 arthroscopies were performed in discordance with the algorithm (12%; 95% CI, 3%-21%).

CONCLUSION

Self-critical analysis of diagnostic processes and monitoring of deviations using algorithms are important and could increase the quality of treatment by revealing recurring faults.

The Rule of Histology in the Diagnosis of Periprosthetic Infection: Specific Granulocyte Counting Methods and New Immunohistologic Staining Techniques may Increase the Diagnostic Value

Objective:

The current study investigates the diagnostic accuracy of the criteria described for frozen sections and whether modern leukocyte specific staining techniques including leukocyte peroxidase and Naphtol-AS-D-chloroacetate-esterase will improve the accuracy of the intra-operative histology.

Method:

77 patients undergoing revision total hip and knee arthroplasty were included in this retrospective study. Patients were grouped into septic and aseptic based on intraoperative cultures. Tissue samples were analyzed utilizing the Mirra, Feldman, Lonner, Banit and Athanasou criteria.

Results:

An experienced pathologist had a high specificity (96%), but rather low sensitivity (57%) diagnosing infection. By using the Banit-, Mirra-, or Athanasou-criteria the sensitivity is increased to 0.90. The Feldman- and Lonner-criteria have a lower sensitivity (0.48 and 0.38), however, an increased specificity of 0.96 and 0.98, respectively. The Banit cut off has the highest accuracy (86%). MPOX and NACE staining increased the sensitivity and accuracy up to 100% and 92% respectively.

Conclusion:

Banit’s cut off is the most accurate histologic criteria to diagnose infection. Modern leukocyte specific staining techniques slightly improve the accuracy. The synovial fluid white blood cell count appears to be the most accurate intraoperative test.

Higher reliability of triple-phase bone scintigraphy in cementless total hip arthroplasty compared to cementless bipolar hemiarthroplasty

Purpose

Periprosthetic infection is one of the main reasons for revision surgery after hip arthroplasty. The purpose of the present study is to compare the reliability of triple-phase bone scintigraphy (TPBS) in the diagnosis of periprosthetic infection between cementless total hip arthroplasty (THA) and bipolar hemiarthroplasty (BHA).

Methods

In this retrospective study, 52 patients were analyzed; 33 of them were performed with THA and 19 of them were performed with BHA. The exclusion criteria were cementation in previous surgery, romatological joint disorders, periprosthetic fracture and malignancy history. C reactive protein (CRP) and erythrocyte sedimentation (ESR) rate results were recorded preoperatively. Tissue samples from the different areas periprosthetic tissue were obtained for histopathological examination and sample tissue culture.

Results

In the present study, the sensitivity, specificity and accuracy were 90.9%, 77.3% and 81.8%, respectively, for THA and 77.8%, 60.0% and 68.4%, respectively, for BHA. Positive predictive values for THA and BHA were 66.7% and 63.6%, and negative predictive values were 94.4% and 75.0%, respectively.

Conclusions

Due to the higher sensitivity, specificity and accuracy, TPBS has a more reliable diagnostic value for cementless THA in the diagnosis of periprosthetic infection compared to cementless BHA.

•

Triple-phase bone scintigraphy is effective in ruling out infection with its higher sensitivity.

•

Triple-phase bone scintigraphy has relatively low specificity compared to its high sensitivity.

Risk factors and the clinical and surgical features of fungal prosthetic joint infections: A retrospective analysis of eight cases

Fungal prosthetic joint infections (PJI) and reports of their clinical investigation are rare. In addition, there has been little evidence regarding the outcome of the two-stage exchange protocol for the treatment of fungal PJI. In order to investigate the risk factors and clinical, microbiological and pathological features of fungal PJIs, as well as the effects of the two-stage exchange protocol on their outcome, the present study analyzed eight retrospective fungal PJI cases, involving four cases affecting the hips and four affecting the knees, between May 2000 and March 2012. In all cases, a cemented spacer saturated with antimicrobials was used during the two-stage exchange protocol, and systematic antifungal agents were administrated during the interim period. The average follow-up duration was 4.4 years. Of the eight cases, six had undergone additional surgery on the infected joint prior to infection with the fungus. Following histological analyses, it was determined that the average number of polymorphonuclear cells in the three patients infected with a fungus was only <5/high power field (HPF; magnification, ×400), and that of the five patients with a hybrid infection was >5/HPF. The average Harris Hip scores or Hospital for Special Surgery knee scores were 43.6 preoperatively and 86 at the last follow-up. The two-stage exchange protocol was performed eight times in seven cases, with a failure rate of 12.5%. The remaining case was successfully treated by resection arthroplasty. The average duration of antifungal agent administration during the interim period in five of the eight cases was 1.5 months. For three of the patients, the duration of antifungal agent administration was prolonged until the c-reactive protein levels were decreased to normal. The average duration of spacer implantation into the joint was 4.3 months. The results of the present study suggested that undergoing surgery on a prosthetic joint may be a potential risk factor for the development of fungal PJI. In addition, infiltration of polymorphonuclear leukocytes into the site of the infection may not occur at the same rate as bacterial PJI. Therefore, a two-stage exchange protocol with implantation of a cement spacer saturated with antimicrobials may be considered an effective therapeutic strategy for the treatment of fungal PJI.

Utility of Fresh Frozen Section Analysis in Foot and Ankle Surgery: A Pilot Study

The use of intraoperative fresh frozen section (FFS) analysis to determine the presence of infection has been well reported in orthopedic studies. Specifically, the number of polymorphonuclear leukocytes per high-power field has been used to diagnose total joint arthroplasty-related infection. Less commonly, reconstructive surgeons have extended the use of FFS analysis for intraoperative evaluation when suspicion of deep infection with or without hardware is high. The purpose of the present study was to retrospectively review the data from 11 patients undergoing foot and ankle reconstruction in the setting of possible deep infection and determine the usefulness of FFS analysis. A retrospective review of the medical records of patients who had undergone reconstructive foot and ankle revision surgery with intraoperative FFS analysis and tissue/swab cultures available was performed. A positive FFS was defined as >5 polymorphonuclear leukocytes per high-power field. A positive frozen section was associated with a positive tissue culture 4 of 7 times (57%). The sensitivity and specificity of FFS analysis for infection was 80% and 50%, respectively. The positive and negative predictive value of the FFS result was 57.1% and 75%, respectively. In conclusion, FFS analysis and intraoperative cultures correlated only 57% of the time in the present series. This test had moderate sensitivity for detecting infection at 80%, but the specificity was poor (50%). More research is needed to further evaluate the role of FFS analysis in foot and ankle surgery.

Intraoperative synovial C-reactive protein is as useful as frozen section to detect periprosthetic hip infection

BACKGROUND

Synovial quantification of C-reactive protein (SCRP) has been recently published with high sensitivity and specificity in the diagnosis of periprosthetic joint infection. However, to our knowledge, no studies have compared the use of this test with intraoperative frozen section, which is considered by many to be the best intraoperative test now available.

QUESTIONS/PURPOSES

We asked whether intraoperative SCRP could lead to comparable sensitivity, specificity, and predictive values as intraoperative frozen section in revision total hip arthroplasty.

METHODS

A prospective study was performed including 76 patients who underwent hip revision for any cause. SCRP quantification (using 9.5 mg/L as denoting infection) and the analysis of frozen section of intraoperative samples (five or more polymorphonuclear leukocytes under high magnification in 10 fields) were performed in all the patients. The definitive diagnosis of an infection was determined according to the Musculoskeletal Infection Society (MSIS). In this group, 30% of the patients were diagnosed with infection using the MSIS criteria (23 of 76 patients).

RESULTS

With the numbers available, there were no differences between SCRP and frozen section in terms of their ability to diagnose infection. The sensitivity of SCRP was 90% (95% confidence interval [CI], 70.8%-98.6%), the specificity was 94% (95% CI, 84.5%-98.7%), the positive predictive value was 87% (95% CI, 66.3%-97%), and the negative predictive value was 96% (95% CI, 87%-99.4%); the sensitivity, specificity, positive predictive value, and negative predictive value were the same using frozen sections to diagnose infection. The positive likelihood ratio was 16.36 (95% CI, 5.4-49.5), indicating a low probability of an individual without the condition having a positive test, and the negative likelihood ratio was 0.10 (95% CI, 0.03-0.36), indicating low probability of an individual without the condition having a negative test.

CONCLUSIONS

We found that quantitative SCRP had similar diagnostic value as intraoperative frozen section with comparable sensitivity, specificity, and predictive value in a group of patients undergoing revision total hip arthroplasty. In our institution, SCRP is easier to obtain, less expensive, and less dependent on the technique of obtaining and interpreting a frozen section. If our findings are confirmed by other groups, we suggest that quantitative SCRP be considered as a viable alternative to frozen section.

LEVEL OF EVIDENCE

Level I, diagnostic study.

Diagnosis and Management of Periprosthetic Shoulder Infections

➤ The unique bacterial flora of the shoulder present diagnostic and treatment challenges that are distinct from those seen with failed hip and knee arthroplasties.➤ The presentation, diagnosis, and management of suppurative periprosthetic joint infections of the shoulder are similar to those of the hip and the knee.➤ Failed arthroplasties with positive cultures (FAPCs) are poorly performing shoulder reconstructions associated with low-virulence microorganisms that do not evoke a suppurative inflammatory response. Propionibacterium acnes is the predominant bacterium isolated from these cases.➤ With improved surgeon awareness and the addition of longer tissue-culture incubation times, detection of FAPCs has become more common. However, management is hampered by the lack of reliable, timely tests that can determine the presence of less virulent organisms in the preoperative or intraoperative settings.➤ The implications of positive culture results in FAPCs are unclear. Key test characteristics such as the false-positive rate and the prevalence of positive cultures in well-performing shoulders are unknown as there is no useful confirmatory test to validate the culture data and no reliable way to detect the presence of less virulent microorganisms without reoperation.➤ Soft-tissue and osseous deficits are frequently encountered when revising previously infected shoulders. The rate of complications in these scenarios is high, and the outcomes are the least favorable compared with revisions for any other indication.➤ The development of a consensus definition of a periprosthetic shoulder infection is critical to future investigations of these devastating complications.

Conventional and molecular diagnostic strategies for prosthetic joint infections

An accurate diagnosis of prosthetic joint infection (PJI) is the mainstay for an optimized clinical management. This review analyzes different diagnostic strategies of PJI, with special emphasis on molecular diagnostic tools and their current and future applications. Until now, the culture of periprosthetic tissues has been considered the gold standard for the diagnosis of PJI. However, sonication of the implant increases the sensitivity of those cultures and is being increasingly adopted by many centers. Molecular diagnostic methods compared with intraoperative tissue culture, especially if combined with sonication, have a higher sensitivity, a faster turnaround time and are not influenced by previous antimicrobial therapy. However, they still lack a system for detection of antimicrobial susceptibility, which is crucial for an optimized and less toxic therapy of PJI. More studies are needed to assess the clinical value of these methods and their cost-effectiveness.

[SECOT consensus on painful knee replacement]

The opinions of 21 experts in knee surgery were evaluated in this study, using a DELPHI questionnaire method in two successive rounds, on 64 controversial scenarios that covered both the diagnosis and possible treatment of painful knee replacements. The level of consensus was significantly unanimous in 42 items and of the design in 5, with no agreement in 17 of the questions presented. light of the published scientific evidence, the surgeons who took part showed to have a notable level of information on the most effective diagnostic tests, although, it should be pointed out that there was a lack of confidence in the possibility of ruling out an infection when the erythrocyte sedimentation rate and the C-reactive protein were within normal values, which have been demonstrated in the literature to have a high negative predictive value As regards the treatments to employ in the different situations, the responses of the expert panel were mainly in agreement with the data in the literature. The conclusions of this consensus may help other surgeons when they are faced with a painful knee prosthesis.

Usefulness of histology for predicting infection at the time of hip revision for the treatment of Vancouver B2 periprosthetic fractures

When facing a Vancouver B2 periprosthetic fracture, the most recommended treatment is the prosthesis replacement. Current tests do not provide enough reliability to identify whether the fracture has been produced on a septic or an aseptic loosened prosthesis. Our aim was to evaluate the usefulness of the histology for the diagnosis of infection in these cases. A total of 11 hip revision procedures were performed (mean age: 78.1 years, 8 women and 3 men). Sensitivity, specificity, positive predictive value and negative predictive value of the histology were 100%, 55.5%, 33.3% and 100% respectively. Of the six patients presenting with a positive histology, four of them had negative cultures (66.6% of false positives). Our results suggest that periprosthetic fractures are a cause of false-positive histology results for the diagnosis of infection during revision of a hip prosthesis for the treatment of Vancouver B2 periprosthetic fractures.

Ten versus five polymorphonuclear leukocytes as threshold in frozen section tests for periprosthetic infection: a meta-analysis

We objectively appraised available evidence regarding the threshold for the number of polymorphonuclear leukocytes required in frozen section tests used to diagnose periprosthetic infection. Pooled summary estimates for sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio (OR) were compared for ten and five polymorphonuclear leukocytes per high power field as the threshold. The total cohort included 1011 patients and the rate of infection was 19.2%. Although there was no difference in sensitivity or diagnostic OR, specificity was significantly higher for ten than for five polymorphonuclear leukocytes per high power field (p=0.007) In sum, a threshold of 10 polymorphonuclear leukocytes is better for diagnosing periprosthetic infections.

Utility of synovial fluid aspirations in failed metal-on-metal total hip arthroplasty

White blood cell (WBC) count and neutrophil percentage from preoperative synovial fluid aspirations are used to help determine the presence or absence of periprosthetic joint infection (PJI) in failed total hip arthroplasty (THA). The clinical levels indicative of infection have not been delineated in metal-on-metal (MoM) bearings. We identified 39 patients who received a preoperative synovial fluid aspiration prior to MoM revision. Thirty-five of 39 cases were culture negative and 4 of 39 were culture positive. WBC count >3000 cells/μL was 100% sensitive and 57.1% specific. Neutrophil percentage >80% was 100% sensitive and 97.1% specific. Both CRP and ESR >8.0mg/L and >22 mm/h, respectively were 75.0% sensitive and 67.6% specific. Our data suggest that synovial WBC count and serum ESR and CRP have poor predictive value in diagnosing PJI for failed MoM THA, whereas synovial neutrophil percentage is a highly accurate marker for diagnosing infection in this patient population.

Advances in the diagnosis of periprosthetic joint infection

INTRODUCTION

Identification of periprosthetic joint infection (PJI) is critical, as the treatment between infected and non-infected arthroplasties is fundamentally different and missing the diagnosis may lead to a delay in diagnosis and the potential for a decreased rate of treatment success. Yet in the absence of a true gold standard, the diagnosis of PJI can be elusive. Given the rising incidence of this PJI and the growing infection burden anticipated in coming years, much effort is being put toward improving diagnostic tests for PJI.

AREAS COVERED

The best current practice for diagnosis of PJI is to follow an algorithmic approach. Emerging technology such as advanced imaging modalities, increasing availability of serum markers, synovial fluid biomarker analysis and new point-of-care modalities offer the potential to greatly enhance our ability to identify PJI in the future.

EXPERT OPINION

As there has been more focus on the diagnosis of PJI in recent years, new tests have been developed. These new tests will need to be rigorously evaluated before being incorporated into the diagnostic algorithm. Synovial fluid biomarker analysis and greater access to point-of-care testing may allow the biggest improvements in the diagnosis of PJI in the near future.

The diagnostic protocol for evaluation of periprosthetic joint infection

Infection is becoming the most important as well as the most devastating mechanism of prosthetic joint failure. The incidence is increasing because the absolute number of patients operated is increasing and because more often very sick, debilitated and immunocompromised patients are operated. The trend reveals a further increase in the years to come. Diagnosis may be very easy in case of high grade processes, but also extremely difficult in some other instances. Misdiagnosing infection leads to repeated early failures that are distressing for patients as well as surgeons. To avoid failures related to misdiagnosed prosthetic joint infections a step-wise algorithm of action is proposed and the diagnostic strength of the steps discussed. The key point is to select potential candidates to define the probability of an ongoing infection and then to select the tools to strengthen the suspicion. Further procedures are based on the analysis of the pseudo-synovial fluid obtained by aspiration. Diagnostic conclusions form the basis for treatment decisions.

High failure rate with the GAP II ring and impacted allograft bone in severe acetabular defects

BACKGROUND

Reconstruction rings and bone allografts have been proposed to manage severe acetabular bone loss. However, a high early failure rate of the Graft Augmentation Prosthesis (GAP) II reinforcement ring (Stryker Orthopaedics, Mahwah, NJ, USA) has been reported in one small series.

QUESTIONS/PURPOSES

We therefore determined (1) the survival of this device in combination with impacted morselized allograft bone in patients with severe defects and (2) the complication rate.

METHODS

We retrospectively reviewed 24 patients (21 aseptic and three septic) with severe acetabular bone loss (10 hips with Type III defects and 14 with Type IV defects according to the American Academy of Orthopaedic Surgeons classification). We determined function and numbers of failures. The minimum followup was 24 months (mean, 34 months; range, 24-72 months).

RESULTS

At latest followup, the reconstruction had failed in nine of the 24 patients: six with aseptic loosening, three with infection. The average postoperative Merle d'Aubigné-Postel score of the patients whose reconstructions had not failed was 16.6 points; at latest followup, these patients had radiographic evidence of incorporation and consolidation of bone allografts. Seven of the nine patients whose reconstructions had failed underwent reoperation. Fatigue fracture of the ring at the plate-cup union occurred in five patients at an average of 45 months postoperatively. All patients with failed reconstructions who underwent reoperation were treated with Trabecular Metal(™) (Zimmer Inc, Warsaw, IN, USA) cups and were functioning well at latest followup.

CONCLUSIONS

We observed a high rate (37%) of early catastrophic failures of the GAP II reconstruction ring, particularly in patients with Type IV defects. Due to this high failure rate, we have abandoned its use.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

Feasibility and clinical utility of intraoperative consultation with frozen section in osseous lesions

Intraoperative consultation (IOC) with frozen section (FS) allows the surgeon to make therapy decisions during the operation. However, there is relatively little information on the use of IOC in skeletal lesions. We performed a retrospective study to examine the indications for IOC and compare the histological findings of FS and permanent paraffin section (PS) results to determine its clinical benefits. Ninety-seven consecutive cases evaluated between 2008 and 2011 were retrieved from IOC archives of our Pathology Department. In 79 % of the cases, there was no prior core needle biopsy (CNB), and IOC was performed to confirm the clinical or radiological diagnosis. In 5 (5 %) cases, no definitive result could be obtained with FS, and diagnosis was deferred. The reasons for a deferred diagnosis (DD) included poor section quality in two lipomatous lesions and the sample heterogeneity in the others. When adjusted for DD, FS and PS results showed 100 % concordance in terms of discriminating "benign vs. malignant" and defining diagnostic categories as "benign non-tumoral," "benign tumoral/tumor-like," "malignant primary tumor," "malignant metastatic tumor," or "hematopoietic malignancy." The presence of non-sclerotic osseous tissues does not have a significant adverse impact on the FS section quality and diagnosis made by FS. Thus, sections with diagnostic value can be obtained from bone lesions via FS. In this study, specific diagnoses were made in 88 % of the cases. We believe that IOC with FS can be safely performed in tertiary referral centers where there is a multidisciplinary team working in collaboration.

The use of femoral struts and impacted cancellous bone allograft in patients with severe femoral bone loss who undergo revision total hip replacement

We determined the midterm survival, incidence of peri-prosthetic fracture and the enhancement of the width of the femur when combining struts and impacted bone allografts in 24 patients (25 hips) with severe femoral bone loss who underwent revision hip surgery. The pre-operative diagnosis was aseptic loosening in 16 hips, second-stage reconstruction in seven, peri-prosthetic fracture in one and stem fracture in one hip. A total of 14 hips presented with an Endoklinik grade 4 defect and 11 hips a grade 3 defect. The mean pre-operative Merle D’Aubigné and Postel score was 5.5 points (1 to 8).

The survivorship was 96% (95% confidence interval 72 to 98) at a mean of 54.5 months (36 to 109). The mean functional score was 17.3 points (16 to 18). One patient in which the strut did not completely bypass the femoral defect was further revised using a long cemented stem due to peri-prosthetic fracture at six months post-operatively. The mean subsidence of the stem was 1.6 mm (1 to 3). There was no evidence of osteolysis, resorption or radiolucencies during follow-up in any hip. Femoral width was enhanced by a mean of 41% (19% to 82%). A total of 24 hips had partial or complete bridging of the strut allografts.

This combined biological method was associated with a favourable survivorship, a low incidence of peri-prosthetic fracture and enhancement of the width of the femur in revision total hip replacement in patients with severe proximal femoral bone loss.

The Role of the Pathologist in Diagnosing Periprosthetic Infection

Most patients who undergo total joint arthroplasty experience dramatic relief of pain and improved ambulation for many years, but some eventually develop pain, often accompanied by radiographic evidence of bone resorption around their implants. The most frequent cause of device failure is osteolysis, but infection is another important cause of pain and arthroplasty failure. The distinction between infection and aseptic loosening is important because the 2 conditions are treated very differently. The purpose of this article is to summarize the role of the anatomic and clinical pathologist in helping distinguish aseptic loosening from infection.

Incidence of deep infection in aseptic revision THA using vancomycin-impregnated impacted bone allograft

The addition of antibiotic to cement is a frequent practice in aseptic revision hip surgery There is concern about adding vancomycin to cement due to potential effects on mechanical properties and prolonged elution of subtherapeutic levels antibiotic. Bone allografts can store and provide high levels of vancomycin to surrounding tissues. We analyzed the incidence of infection after one-stage aseptic revision hip reconstruction utilizing acetabular and/or femoral vancomycin-impregnated impacted bone allograft and a THA fixed with cement containing no antibiotic. We hypothesized that the infection rate may be similar to that reported in the literature following traditional impaction grafting using antibiotic loaded cement. Seventy five consecutive patients (80 hips) with a preoperative Merle D'Aubigné and Postel functional score averaging 4.8 points were followed up for a mean of 36 months (range 24 - 59 months). The incidence of infection was 1.25% (CI 95%=96.26-100%). A deep infection (thought to be haematognous in origin) occurred in 1 patient 2 years after the index surgery. The average postoperative Merle D´Aubigne score was 16.2 points. The last radiographic evaluation demonstrated a less than 5 mm acetabular migration and a less than 5 mm femoral subsidence in all cases. Vancomycin-supplemented allografts restored bone stock and provided sound fixation with a low incidence of infection. This incidence of deep sepsis is similar to that reported with antibiotic-loaded PMMA but without the reported mechanical and pharmacological disadvantages.

Interface membrane is the best sample for histological study to diagnose prosthetic joint infection

The objective of our study was to study which is the most accurate specimen for histological diagnosis of prosthetic joint infections (pseudocapsule or interface membrane). This is a prospective study including hip revision arthroplasties performed from January 2007 to June 2009. Specimens from pseudocapsule and from interface membrane were obtained from each patient. The histology was considered positive for infection when ≥5 neutrophils per high-power field ( × 40) were found. Definitive diagnosis of infection was considered when ≥2 cultures were positive for the same microorganism. According to the definition of infection, patients were classified in two groups: (A) patients with aseptic loosening in whom cultures obtained during surgery were negative and (B) patients with prosthetic joint infection. A total of 69 revisions were included in the study; 57 were classified in group A and 12 in group B. In group B, the percentage of positive interface membrane histology was significantly higher than the percentage of positive pseudocapsule histology (83 vs 42%, P=0.04, Fisher's exact test). The results suggest that periprosthetic interface membrane is the best specimen for the histological diagnosis of prosthetic joint infection.

Combining C-reactive protein and interleukin-6 may be useful to detect periprosthetic hip infection

BACKGROUND

The sensitivity and specificity to detect periprosthetic infection of the different methods have been questioned, and no single laboratory test accurately detects infection before revision arthroplasty.

QUESTIONS/PURPOSES

We asked whether preoperative C-reactive protein (CRP) and interleukin-6 (IL-6) could lead to similar sensitivity, specificity, and predictive values as our previous results obtained with intraoperative frozen section (FS) in revision total hip arthroplasty (THA).

METHODS

We prospectively followed 69 patients who had undergone revision THA for failure of a primary THA. The definitive diagnosis of an infection was determined on the basis of positive histopathologic evidence of infection or growth of bacteria on culture.

RESULTS

Eleven of the 69 hips were infected. The combination of an elevated CRP and IL-6 was correlated with deep infection in all the cases and showed a sensitivity of 0.57 (0.13-1.00), a specificity of 1.00 (0.99-1.00), a positive predictive value of 1.00 (0.87-1.00), and a negative predictive value of 0.94 (0.87-1.00). FS showed a sensitivity of 0.81 (0.54-1.00), a specificity of 0.98 (0.94-1.00), a positive predictive value of 0.90 (0.66-1.00), and a negative predictive value of 0.96 (0.91-1.00). Combining CRP and IL-6 provided similar sensitivity, specificity, and positive predictive values as the FSs.

CONCLUSIONS

Our data suggest the combination of CRP and IL-6 would be a useful serologic tool to complement others when diagnosing periprosthetic infection.

Diagnosis of periprosthetic joint infections of the hip and knee

No preferred test for diagnosis of periprosthetic joint infection exists, and the algorithm for the workup of patients suspected of infection remains unclear. The work group evaluated the available literature to determine the role of each diagnostic modality and devise a practical algorithm that allows physicians to reach diagnosis of periprosthetic joint infection. Ten of the 15 recommendations have strong or moderate evidence in support. These include matters involving erythrocyte sedimentation rate and C-reactive protein level testing, knee and hip aspiration, and stopping the use of antibiotics prior to obtaining intra-articular cultures. The group recommends against the use of intraoperative Gram stain but does recommend the use of frozen sections of peri-implant tissues in reoperation patients in whom infection has not been established, as well as multiple cultures in reoperation patients being assessed for infection. The group recommends against initiating antibiotic treatment in patients with suspected infection until after joint cultures have been obtained, but recommends that prophylactic preoperative antibiotics not be withheld in patients at lower probability for infection.

Aseptic lymphocyte-dominated vasculitis-associated lesion: a clinicopathologic review of an underrecognized cause of prosthetic failure

It is estimated that 35% of total hip arthroplasties (THAs) involve a second-generation metal-on-metal (MOM) prosthesis. A novel complication has appeared in a subset of patients with MOM THAs that is described as an aseptic, lymphocyte-dominated vasculitis-associated lesion (ALVAL). The clinical features of ALVAL are nonspecific, but patients complain of pain and may develop "pseudotumors." It is hypothesized that metal ions are released from the prosthesis and form haptens with native proteins that elicit a type IV hypersensitivity response in the local soft tissues. Histopathologic descriptions of ALVAL are similar to those of failed arthroplasty in general, with the addition of a dense perivascular inflammatory infiltrate that is the hallmark of ALVAL. We report 3 cases of ALVAL with clinical, radiographic, and histologic findings. Accurate assessment is crucial because an intraoperative diagnosis of chronic inflammation suggestive of ALVAL will necessitate a replacement of the prosthetic component surfaces.

Perioperative testing for persistent sepsis following resection arthroplasty of the hip for periprosthetic infection

Eighty-seven hips with an infected total hip arthroplasty were treated with an antibiotic spacer and 6 weeks of antibiotics. The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) measurements were repeated before attempted reimplanation, and a synovial fluid white blood cell (WBC) count was obtained intraoperatively. Nine hips (10.1%) had persistent infections. The mean ESR, CRP, and synovial fluid WBC count and differential decreased significantly (P < .001) between stages; however, the ESR remained elevated (>30 mm/h) in 50 patients (62.5%) and the CRP remained elevated (>10 mg/L) in 22 patients (27.5%) in whom the infection had been eradicated. The synovial fluid WBC count was the best test for identifying persistent infection, with an optimum cutoff of 3528 WBCs/microL(sensitivity, 78%; specificity, 96%) and an area under the curve of 0.91. The ESR and CRP were not sufficiently rigorous to aid in diagnosis and frequently failed to normalize even in patients without persistent infection.

Proximal femoral reconstructions with bone impaction grafting and metal mesh

Extensive circumferential proximal cortical bone loss is considered by some a contraindication for impaction bone grafting in the femur. We asked whether reconstruction with a circumferential metal mesh, impacted bone allografts, and a cemented stem would lead to acceptable survival in these patients. We retrospectively reviewed 14 patients (15 hips) with severe proximal femoral bone defects (average, 12 cm long; 14 type IV and one type IIIB using the classification of Della Valle and Paprosky) reconstructed with this method. The minimum followup was 20 months (average, 43.2 months; range, 20-72 months). Preoperative Merle D'Aubigné and Postel score averaged 4.8 points. With revision of the stem as the end point, the survivorship of the implant was 100% at one year and 86.6% at 72 months. The mean functional score at last followup was 14.4 points. We observed two fractures of the metal mesh at 31 and 48 months in cases reconstructed with a stem that did not bypass the mesh. Dislocation (3 cases) and acute deep infection (3 cases) were the most frequent complications. Patients with complete absence of the proximal femur may be candidates for biological proximal femoral reconstructions using this salvage procedure. Bone impaction grafting must be a routine technique if this method is selected.

Clinical practice. Infection associated with prosthetic joints

A 62-year-old woman with osteoarthritis presents with a 7-month history of progressively worsening left hip pain radiating to the groin, 8 months after undergoing total left-hip arthroplasty. The pain has not responded to nonsteroidal antiinflammatory drugs. Physical examination reveals a sinus tract overlying her left hip. Her leukocyte count is 8000 per cubic millimeter, and the C-reactive protein (CRP) level is 15.5 mg per liter. A radiograph shows loosening of the prosthesis at the bone–cement interface. Synovial-fluid aspirate shows 15×10³ cells per cubic millimeter (89% neutrophils); cultures of an aspirate from the hip grow Staphylococcus epidermidis. How should her case be managed?

Neutrophils in frozen section and type of microorganism isolated at the time of resection arthroplasty for the treatment of infection

INTRODUCTION

The histology of periprosthetic tissue is a gold standard for the diagnosis of periprosthetic joint infection. However, the specificity and sensitivity of histology has never been 100%. In the present study we hypothesized that the type of microorganism could be related to the effectiveness of histology in the detection of infection.

MATERIAL AND METHODS

Frozen sections and cultures from periprosthetic tissue of 38 revision arthroplasties taken at the time of resection arthroplasty for the treatment of infection were retrospectively reviewed. Frozen sections were evaluated following Feldman's criteria. A culture was considered positive when the same microorganism was isolated in at least two samples or when pus was present around the prosthesis. The literature providing information on histology and microbiology of arthroplasty-associated infection was reviewed.

RESULTS

Coagulase-negative staphylococcus (CNS) was the etiology in 13 cases, Gram-negative bacilli in 8, Staphylococcus aureus in 7, Candida sp in 2, Peptococcus sp in 2, Enterococcus sp in 1 and S. pneumoniae in 1. No microorganism was isolated in four cases. Almost all the frozen sections in the 38 cases were positive except in 2 of the 13 that were caused by CNS (15.3%). The articles reviewed supported our findings.

CONCLUSION

Frozen section is a useful test to intraoperatively confirm an infection when preoperative septic loosening is suspected. However, histology has false-negative results when the infection is due to low-virulence microorganisms.