Musculoskeletal Infection Society (MSIS) Update on Infection in Arthroplasty.

Periprosthetic joint infection (PJI) continues to be a devastating problem in the field of total joint arthroplasty, and recent literature can be used to make the preoperative diagnosis of PJI, guide nonsurgical and surgical treatment, and provide postoperative antimicrobial management of PJI patients. The diagnosis of PJI relies on traditional serum and synovial fluid tests, with newer biomarkers and molecular tests. Surgical treatment depends on the duration of infection, host qualities, and surgeon factors, and procedures include débridement, antibiotics, and implant retention, one-stage exchange arthroplasty, two-stage exchange arthroplasty, resection arthroplasty, fusion, or amputation. Appropriate management of PJI involves coordination with infectious disease consultants, internal medicine physicians, and orthopaedic surgeons. Antimicrobial management is guided by the organisms involved, whether it is a new or persistent infection, and antibiotic suppression should be administered on an individual case basis. The goals of this instructional course lecture are to review the most relevant recent literature and provide treating physicians and surgeons with the most up-to-date armamentarium to reduce the recurrence of PJI.

Prior Manipulation under Anesthesia is a Predictor of Contralateral Manipulation in Staged Bilateral Total Knee Arthroplasty.

BACKGROUND: There are many risk factors for arthrofibrosis and manipulation under anesthesia (MUA) following total knee arthroplasty (TKA). However, no study has elucidated whether a history of MUA increases the risk of contralateral MUA in patients undergoing staged bilateral TKA. METHODS: A retrospective review of an institutional database of TKAs was performed. All patients aged ≥18 years who underwent primary staged bilateral TKAs were screened for inclusion. Staged bilateral TKAs were viewed as 2 distinct events based on the temporal order in which they occurred: TKA#1 (occurred first) and TKA#2 (occurred second). Following TKA#1, patients were split into 2 groups: those who underwent MUA (Group MANIP) and those who did not (Group NO MANIP). The subsequent risk of undergoing MUA following TKA#2 was then assessed and compared between the 2 groups. Chi-squared tests were used for comparison. RESULTS: A total of 5,330 patients who underwent primary uncomplicated staged bilateral TKAs (10,660 knees) during the study period were identified. Overall, 2.1% of patients underwent MUA following TKA#1 and 1.9% of patients underwent MUA following TKA#2. In the MANIP group, 21.4% of patients underwent MUA following TKA#2, while only 1.5% underwent MUA in the NO MANIP group. This 14.3-fold increase in the risk of MUA in the MANIP group following TKA#2 was statistically significant (21.4% vs 1.5%, absolute risk reduction = 19.9%, relative risk reduction = 93.0%, P < .0001). CONCLUSION: Patients who undergo MUA during the first TKA of a staged bilateral TKA are 14.3 times more likely to undergo a subsequent MUA than those who did not undergo MUA following their first TKA.

False-Positive Automated Synovial Fluid White Blood Cell Counting Is a Concern for Both Hip and Knee Arthroplasty Aspirates.

BACKGROUND: Although false elevation of automated leukocyte (white blood cell [WBC]) counts has been described in the setting of hip corrosion, the more general correlation between manual and automated cell counts among synovial fluid aspirates from hip and knee arthroplasties has not been studied. METHODS: This retrospective review at one laboratory identified 8607 consecutive synovial fluid samples from arthroplasties and 812 from native knees, each with an automated WBC count > 3000 cells/µL and a corresponding paired reflex manual count. The correlation between automated and manual counts was evaluated, as was the rate of false-positive automated WBC counts. RESULTS: The correlation between automated WBC counts for native knees, total knee arthroplasties, and total hip arthroplasties was near-perfect, strong, and moderate, respectively. The false-positive rates for automated counts were 4.4%, 10.1%, and 34.3%, respectively (P < .0001). International Consensus Meeting scores and culture positivity demonstrated that manual counts, not automated counts, were correct. CONCLUSION: The presence of a hip or knee arthroplasty appears to substantially increase the risk of a false-positive automated synovial fluid WBC count. Clinicians evaluating an arthroplasty should exercise caution when interpreting positive automated WBC counts, and consider requesting a reflex manual count, to verify the accuracy of automated cell counting.

Adverse Local Tissue Reaction due to Mechanically Assisted Crevice Corrosion Presenting as Late Instability Following Metal-on-Polyethylene Total Hip Arthroplasty.

BACKGROUND: Mechanically assisted crevice corrosion (MACC) at modular junctions can cause a spectrum of adverse local tissue reactions (ALTRs) in patients who have undergone total hip arthroplasty (THA). The purpose of this study is to describe the presentation, treatments, and related complications of a cohort of patients presenting with late instability following metal-on-polyethylene THA due to underlying MACC and ALTR. METHODS: This multicenter retrospective case series presents 17 patients (12 women, mean age 62.6, range 42-73) presenting with late instability secondary to ALTR and MACC. All patients had a metal (Cobalt Chrome)-on-polyethylene bearing surface. Patients experienced a mean 2.7 dislocations (range 1-6) at mean 4.3 years (range 0.4-17.0) following their index surgery. Serum metal levels (n = 12) demonstrated a greater elevation of cobalt (mean 6.9, range 0.13-20.88 ng/mL) than chromium (mean 1.9, range 0.13-3.23 ng/mL). RESULTS: Patients were revised for instability at a mean of 6.8 years (range 2.1-19.4) following their index surgery. ALTR was encountered in every case and the modular head-neck junction demonstrated visible corrosion. An exchange of the CoCr head to a ceramic head with a titanium sleeve and placement of a constrained liner was performed for a majority of patients (n = 15, 88.2%). Five patients (29.4%) had complications postoperatively including peroneal palsy (n = 2), periprosthetic joint infection (n = 2), and ALTR recurrence (n = 1). CONCLUSION: Recurrent instability in the setting of otherwise well-positioned THA components and without another obvious cause should raise concern for ALTR as a potential underlying etiology.

Comparison of Quadriceps-Sparing and Medial Parapatellar Approaches in Total Knee Arthroplasty: A Meta-Analysis of Randomized Controlled Trials.

BACKGROUND: The quadriceps-sparing (QS) technique for total knee arthroplasty (TKA) was introduced to improve outcomes associated with the medial parapatellar (MP) approach. There is no clear consensus on what advantages, if any, QS provides. METHODS: We performed a meta-analysis of randomized controlled trials (RCTs) comparing the QS and MP techniques. PubMed, Ovid, and Scopus were assessed for relevant literature. Long-term (primary) outcomes and short-term (secondary) outcomes from 8 RCTs (579 TKAs) were analyzed using OpenMetaAnalyst (2016). RESULTS: The QS approach did not demonstrate clinically significant advantages, but was associated with statistically and clinically significant increases in the primary outcomes of femoral (odds ratio [OR] 4.92, P = .005), tibial (OR 4.34, P = .01), and mechanical axis outliers (OR 4.77, P = .004). Secondary outcome assessments demonstrated increased surgical (mean differences [MD] 19.54, P < .001) and tourniquet time (MD 23.30, P < .001) for QS. Although statistically significant advantages for QS were identified in Knee Society Function scores at 1.5-3 months (MD 2.31, P = .004) and 2 years (MD 1.86, P < .001), these were not clinically significant (fell below the 6-point minimal clinically important difference). CONCLUSION: The QS approach to TKA fails to demonstrate clinically significant advantages, but shows increased malalignment. This increased incidence of implant malalignment may predispose QS patients to early prosthesis failure. Because the QS approach may increases the risk of malalignment while providing no clear benefit compared to MP, we recommend against the routine use of the QS TKA approach.

The Leukocyte Esterase Test Strip Is a Poor Rule-Out Test for Periprosthetic Joint Infection.

BACKGROUND: The urinary leukocyte esterase (LE) test strip has been suggested as a good screening test for periprosthetic joint infection (PJI). The purpose of this study is to compare the diagnostic profile of LE assays from different manufacturers and determine whether the LE test strip is a good rule-out test. METHODS: Synovial fluid samples (N = 344), sent to 1 laboratory for PJI testing, were used in this prospective study. Four different tests for synovial fluid LE were simultaneously evaluated for their performance in detecting white blood cell (WBC) positive samples (>3000 cells/µL). RESULTS: Both neutrophil elastase immunoassays demonstrated greater sensitivity than urinary LE test strips (92.0% and 90.8% vs 72.4% and 80.3%; all P < 0.011). Fifty-three percent of false-negative urinary LE test strip results clearly missed the presence of elevated levels of synovial fluid LE. Invalid urinary LE test strip results were 4-fold more likely among WBC (+) compared with WBC (-) samples (27.0% vs 6.8%; P < 0.0001). The combined failure to detect an elevated WBC count, because of either false-negative or invalid results, was 47.1% and 41.4% for the Roche and Siemens test strips, respectively. CONCLUSIONS: This study agrees with the existing literature demonstrating that the LE test strips are among the lowest sensitivity tests for PJI. The urinary LE tests strips should not be used to rule-out PJI, as they often fail to detect abundant levels of LE in synovial fluid. Instead, it is more appropriate to use the (++) LE test strip result as a secondary confirmatory rule-in test for PJI because of its high specificity.

Utility of Synovial White Blood Cell Count and Differential Before Reimplantation Surgery.

BACKGROUND: Determining optimal timing of reimplantation during 2-stage exchange for periprosthetic joint infection (PJI) remains elusive. Joint aspiration for synovial white blood cell (WBC) count and neutrophil percentage (PMN%) before reimplantation is widely performed; yet, the implications are rarely understood. Therefore, this study investigates (1) the diagnostic yield of synovial WBC count and differential analysis and (2) the calculated thresholds for persistent infection. METHODS: Institutional PJI databases identified 129 patients undergoing 2-stage exchange arthroplasty who had joint aspiration before reimplantation between February 2005 and May 2014. Persistent infection was defined as a positive aspirate culture, positive intraoperative cultures, or persistent symptoms of PJI-including subsequent PJI-related surgery. Receiver-operating characteristic curve was used to calculate thresholds maximizing sensitivity and specificity. RESULTS: Thirty-three cases (33 of 129; 25.6%) were classified with persistent PJI. Compared with infection-free patients, these patients had significantly elevated PMN% (62.2% vs 48.9%; P = .03) and WBC count (1804 vs 954 cells/µL; P = .04). The receiver-operating characteristic curve provided thresholds of 62% and 640 cells/µL for synovial PMN% and WBC count, respectively. These thresholds provided sensitivity of 63% and 54.5% and specificity of 62% and 60.0%, respectively. The risk of persistent PJI for patients with PMN% >90% was 46.7% (7 of 15). CONCLUSION: Synovial fluid analysis before reimplantation has unclear utility. Although statistically significant elevations in synovial WBC count and PMN% are observed for patients with persistent PJI, this did not translate into useful thresholds with clinical importance. However, with little other guidance regarding the timing of reimplantation, severely elevated WBC count and differential analysis may be of use.

A Current Procedural Terminology Code for "Knee Conversion" Is Needed to Account for the Additional Surgical Time Required Compared to Total Knee Arthroplasty.

BACKGROUND: Previous knee injury requiring surgical intervention increases the rate of future arthroplasty. Coding modifiers for removal of previous hardware or increased complexity offer inconsistent results. A Current Procedural Terminology code for knee conversion does not currently exist as it does for conversion hip arthroplasty. We investigate the extra time associated with conversion knee arthroplasty. METHODS: Sixty-three total knee arthroplasty (TKA) cases in the setting of previous knee hardware were identified from our institution between 2008 and 2015. Knee conversions were matched to primary TKA by age, gender, body mass index, Charlson Comorbidity Index, and surgeon, in a 3:1 ratio. Patients who underwent knee conversions were compared to matched TKA with regard to operative time, length of stay, discharge destination, readmission, and repeat procedures within 90 days from index procedure. RESULTS: The mean operating room time for primary TKA was 71.7 minutes (range 36-138). The mean operating room time for knee conversion was significantly greater by an additional 31 minutes; mean 102.1 minutes (range 56-256 minutes, P < .0001). Rates of readmission, 0.5% vs 3.2%, and repeat procedures, 5.3% vs 12.7%, within 90 days were greater for knee conversions. There was no difference in length of stay or discharge destination. CONCLUSION: Total knee conversion results in a 43% increase in operative time and more than twice the rate of readmission and repeat procedures within 90 days compared to TKA. This suggests the need for an additional Current Procedural Terminology code for knee conversion arthroplasty to compensate surgeons for the extra time required for conversions.

The C-Reactive Protein May Not Detect Infections Caused by Less-Virulent Organisms.

BACKGROUND: The aim of the present study was to evaluate the influence of organism type on the performance of the synovial fluid C-reactive protein (CRP) test. METHODS: We retrospectively reviewed the results of 21,422 synovial fluid samples sent to one common laboratory for the purpose of diagnostic testing for periprosthetic joint infection. Both a synovial fluid CRP result and a positive culture were present for 1789 submitted samples. The cultured organisms were grouped by species, virulence, and gram type; and the median CRP level was determined for each group. RESULTS: The median synovial fluid CRP level was significantly lower for less-virulent organisms, when compared to those organisms classified as virulent (15.10 mg/L vs 32.70 mg/L; P < .0001). Some less-virulent species such as yeast and Staphylococcus epidermidis were associated with a 4-10 times lower CRP response than those of virulent organisms such as Streptococcus agalactiae and Staphylococcus aureus (P < .0001). Bacterial gram type had no influence on the median CRP result. The rate of false-negative CRP values was 50.9% for yeast, 29.4% for S. epidermidis, 28.5% for all less-virulent organisms, and 11.6% for all virulent organisms. CONCLUSION: The CRP response appears to be highly dependent on the infecting organism and is more likely to provide false-negative results in the setting of less-virulent organisms. Although the use of a CRP level is an important part of the workup for periprosthetic joint infection, surgeons must be aware that this protein may yield a false-negative result in the setting of less-virulent organisms.

Prospective Evaluation of Sleep Disturbances After Total Knee Arthroplasty.

Sleep disturbance after total knee arthroplasty (TKA) has not been studied 6 months after surgery. A prospective study was conducted on 34 primary, unilateral TKA patients preoperatively until 6 months postoperatively. Sleep quality was measured using the Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale. Pain was measured on a visual analog scale. Sleep quality worsened from baseline during the first 6 weeks postoperatively (P = .03), but improved at 3 and 6 months (P = .003). Pain scores decreased from baseline over all time points, and there was no correlation between sleep quality and pain. The Epworth Sleepiness Scale did not change over time. This study can be used to counsel TKA patients to expect initial sleep disturbances that improve by 3 months.

Medicare fails to compensate additional surgical time and effort associated with revision arthroplasty.

In comparison to primary total knee arthroplasty, surgical time was 1.8 times greater for all knee revisions and 2.4 times greater for complex knee revisions. Knee revisions had an 8.5% higher rate of 90-day repeat procedures. In comparison to primary total hip arthroplasty, surgical time was 1.8 greater for all hip revisions and 2.6 fold greater for complex hip revisions. Hip revisions had a 3.4% higher rate of 90-day repeat procedures. Practices based on revisions or complex revisions alone would see a 32% and 50% decrease in reimbursement respectively compared to the ones based on primary arthroplasty. The projected future increase in primary arthroplasties and the relative incentive to perform primary arthroplasty may soon put patient access to physicians willing to perform revision arthroplasty at risk.

Clostridium difficile is common in patients with postoperative diarrhea after hip and knee arthroplasty.

Clostridium difficile is an antibiotic-associated gastrointestinal infection that has detrimental consequences. We sought to determine the incidence of C. difficile in TJA patients with postoperative diarrhea, to determine risk factors for C. difficile infection, and to establish the incidence of C. difficile-related complications. Our institutional protocol includes screening for C. difficile in all patients with diarrhea after TJA. We identified 121 such patients over four years with twenty-eight (23%) testing positive for C. difficile. Revision arthroplasty and prolonged postoperative antibiotic use were risk factors for C. difficile infection. With our protocol of screening and immediate treatment of C. difficile positive patients, we found no C. difficile-associated complications.

Staphylococcus aureus colonization among arthroplasty patients previously treated by a decolonization protocol: a pilot study.

BACKGROUND: Although testing and treatment for Staphylococcus aureus colonization before total joint arthroplasty (TJA) are well described and understood, the durability of decolonization has not been studied extensively. QUESTIONS/PURPOSES: The purpose of this pilot study is to determine the percentage of arthroplasty patients with S. aureus colonization despite previous decolonization at the time of TJA. METHODS: Over a 2-year period, all patients having TJA by one surgeon were screened and treated for nasal S. aureus. Of 634 patients, 139 had methicillin-sensitive S. aureus (15%) or methicillin-resistant S. aureus (6.6%) colonization before TJA. Fifty-eight of these 139 patients (42%) were retested at 3 to 30 months for persistent colonization by nasal culture. Data collection included age at time of TJA, type of TJA, and time from TJA to repeat testing. We performed no clonal analysis for strains. RESULTS: Thirty-nine of the 58 patients (67%) decolonized before surgery were negative on retesting and 19 (33%) were again positive for S. aureus colonization. Of the 19 patients who retested positive for colonization, 17 (89%) were colonized by bacteria with unchanged antibiotic sensitivity. CONCLUSIONS: We demonstrate that 33% (19 of 58) of postoperative arthroplasty patients test positive for S. aureus colonization at 3 to 30 months after surgery despite preoperative decolonization. Arthroplasty surgeons must be aware that a decolonization treatment does not guarantee that a patient will remain decolonized in the future. Although unchanged antibiotic sensitivity in 89% of these patients suggests a substantial role for persistence as opposed to eradication and repeat colonization, we were unable to retrospectively perform clonal analysis to confirm this conclusion. This group of patients demonstrating continued colonization with S. aureus after arthroplasty deserves further study, because it remains unclear whether there is a higher risk of late infection in this population. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The routine use of atypical cultures in presumed aseptic revisions is unnecessary.

BACKGROUND: In presumed aseptic hip and knee revisions, it is common practice to send intraoperative cultures to screen for occult infection. Currently no guidelines exist for the routine use of acid-fast bacillus (AFB) and fungal cultures in this setting. QUESTIONS/PURPOSES: We established (1) the rate of positive fungal and AFB cultures in aseptic hip and knee revision arthroplasties, (2) factors associated with positive fungal and AFB cultures, (3) the likelihood that positive cultures represent true-positive results, and (4) the hospital charges of sending fungal and AFB cultures routinely. METHODS: We retrospectively evaluated all 1717 presumed aseptic hip and knee revisions performed from January 2006 to November 2011: 1139 patients had at least one intraoperative fungal culture and 1133 patients had at least one intraoperative AFB culture, with 923 and 920, respectively, achieving 1-year followup. The Musculoskeletal Infection Society criteria were used to classify subsequent infections. We attempted to identify risk factors for positive cultures. RESULTS: We observed six (0.5%) patients with positive AFB cultures and 19 (1.7%) with positive fungal cultures. Patients undergoing reimplantation procedures were more likely to have a positive fungal culture. The true-positive rate was 0% and 0.1% for AFB and fungal cultures, respectively. The total hospital charges for these cultures over the time frame of our study were USD 1,315,533. CONCLUSIONS: Given the extremely low rate of true-positive AFB and fungal cultures in presumed aseptic revision joint arthroplasty and the charges associated with maintaining these cultures, we believe their routine use is unwarranted. LEVEL OF EVIDENCE: Level III, prognostic study. See the Instructions for Authors for a complete description of evidence.

Clostridium septicum growth from a total knee arthroplasty associated with intestinal malignancy: a case report.

BACKGROUND: Previous reports of infection with Clostridium septicum have identified an unexpected association with concurrent malignancy. The reported rate of associated malignancy has been found to be as high as 81 percent. The purpose of this case report was to present a case of a total knee arthroplasty infected with C. septicum and the subsequent finding of an occult colonic malignancy. CASE PRESENTATION: A 74 year-old man underwent uneventful bilateral total knee arthroplasties. Two weeks post-operatively, he presented with acute swelling, redness and pain of the left knee. Aspiration of the knee was sent for cell count and culture. The cell count demonstrated 39,000 white blood cells per cubic millimeter with 71% of white blood cells identified as neutrophils. Synovial fluid cultures identified the presence of C. septicum, Enterobacter and coagulase negative Staphylococcus. After urgent irrigation and debridement and polyethylene exchange of the affected knee, the patient was placed on intravenous Penicillin G for a period of six weeks. Two weeks into his course of antibiotics, the patient developed hematochezia and was found to have an obstructive colonic malignancy. The patient underwent hemi-colectomy and has since made a complete recovery of both his malignancy and total knee arthroplasty infection. CONCLUSION: Recognition of the association between C. septicum and malignancy is especially important considering the large predicted increase in total joint arthroplasty procedures over the coming decades. In addition to the standard treatment for infection after total joint arthroplasty, identification of Clostridium septicum should initiate a search for associated occult malignancy.

The use of a tripolar articulation in revision total hip arthroplasty: a minimum of 24 months' follow-up.

A retrospective cohort study of 31 hips revised with a tripolar articular construct was performed. Patient demographics and preoperative and postoperative information were recorded. Indications for a tripolar construct were recurrent dislocation and the inability to attain intraoperative stability during hip revision. Nine patients (29%) were revised to the tripolar construct after failure of a constrained liner. Twenty patients (65%) had at least one episode of instability before the most recent revision. At a mean follow-up of 38 months, modified Postel scores improved from a mean of 5.28 to 9.64 (P < .01). Radiographic follow-up revealed no evidence of component loosening/migration, osteolysis, or polyethylene wear. Two patients (7%) required further revision surgery for recurrent instability. A tripolar construct was effective in eliminating or preventing instability in 93% of the complex cases treated. These early results support the use of a tripolar construct in treating recurrent instability or instability encountered at the time of revision hip arthroplasty.