Economic Impact of Outpatient Medicare Total Knee Arthroplasty at a Tertiary Care Academic Medical Center.

BACKGROUND: In January 2018, the Center for Medicare and Medicaid Services (CMS) removed total knee arthroplasty (TKA) from the inpatient-only list. This impacted hospital reimbursement, Comprehensive Joint Replacement (CJR) bundle volumes, and bundle performance. We describe these impacts at an academic teaching hospital. METHODS: We reviewed CJR bundle data provided by CMS and internal databases to identify the shift in CJR TKA episode volume since January 2018, the impact on postacute care (PAC) utilization rates and readmissions, financial impact to the bundle, and impact on hospital reimbursement. We used data provided to CJR participants, internal hospital sources, and the Medicare Limited Data Set. RESULTS: Between 2017 and 2018, CJR TKA episodes decreased from 91 to 51 (44% reduction). Inpatient PAC utilization was significantly higher in 2018 (20% vs 8%). The 90-day readmission rates increased from 5.5% to 12.7%. Average variance to target dropped from 15% to 5%. Average CMS reimbursement for TKA at our institution in 2019 was $14,823 for inpatients and $9299 for outpatients. We experienced $930,463 in decreased reimbursement from January 2018 to September 2019 as a result of the shift from inpatient to outpatient. In addition, we expect $625,143 in decreased incentive payments as higher functioning and lower cost outpatient TKAs are excluded from CJR. CONCLUSION: Although CMS projected a minimal impact on CJR bundle participants, this has not been the case at our institution. We experienced reduced volumes, increased PAC utilization, and a substantial financial impact. We expect a similar outcome when CMS removes total hip arthroplasty from the inpatient-only list.

The Financial Implications of the Removal of Total Knee Arthroplasty From the Medicare Inpatient-Only List.

BACKGROUND: Centers for Medicare and Medicaid Services removed total knee arthroplasties (TKAs) from the Inpatient-Only list on January 1, 2018, which meant TKAs could be performed on a hospital outpatient basis. We sought to understand (1) what the financial implications have been for hospitals, (2) to what extent financial incentives have influenced the adoption of outpatient TKAs across hospitals, (3) whether adoption of outpatient TKAs has impacted the success of hospitals with managing post-acute care (PAC) spend, and (4) the financial implications to Medicare of the adoption of outpatient TKAs. METHODS: We used national patient-level Medicare fee-for-service Part A claims data (100% sample) from January 2018 through June 2019 to calculate the inpatient and outpatient TKA payment rate for each hospital, and the distribution in these payments across the country. We then ran case-level regressions to understand the factors associated with adoption of outpatient TKAs, and the drivers of PAC spend. Finally, we quantified the savings to Medicare. RESULTS: Hospitals on average received $3682 (30%) lower payment from Medicare for outpatient TKA cases, but this varied widely across hospitals. The difference in payment rates across hospitals was not statistically significantly related to their adoption rate of outpatient TKAs. PAC spend was higher for same-day discharges, but lower for cases that stayed at least 1 night. Based on the adoption rate of outpatient TKAs in Q2 2019, Medicare saved $355M on a run rate basis. CONCLUSION: Hospitals have adopted outpatient TKAs independent of the financial impact. Medicare has benefited from lower PAC spend and lower payments to hospitals.

Preoperative Anemia Is Associated With Failure of Open Debridement Polyethylene Exchange in Acute and Acute Hematogenous Prosthetic Joint Infection.

BACKGROUND: Acute and acute hematogenous prosthetic joint infections (PJIs) are often treated with open debridement and polyethylene exchange (ODPE) in an effort to save the prosthesis, decrease morbidity, and reduce costs. However, failure of ODPE may compromise a subsequent 2-stage treatment. The purpose of this study is to identify patient factors that impact the success of ODPE for acute and acute hematogenous PJIs. METHODS: A retrospective review examined comorbidities, preoperative laboratory values, and patient history for patients with successful and failed ODPE treatment for acute perioperative or acute hematogenous periprosthetic hip or knee joint infections. Successful treatment was defined as retaining a well-fixed implant without the need for additional surgery for a minimum of 6-month follow-up with or without lifelong oral maintenance antibiotics. RESULTS: Fifty-three of 72 patients (73.6%) underwent successful ODPE. Of the 19 failures, 14 completed 2-stage revision with one subsequent known failure for recurrent infection. Patients with a Staphylococcus aureus infection were more likely to fail ODPE (48.3% vs 11.6%, P = .0012, odds ratio 7.1, 95% confidence interval 2.3-25.3). Patients with a preoperative hematocrit ≤32.1 were also more likely to fail ODPE (55% vs 16%, P = .0013, odds ratio 6.7, 95% confidence interval 2.2-22.4). When neither risk factor was present, 97.1% of PJIs were successfully treated with ODPE. CONCLUSION: S aureus infection and preoperative hematocrit ≤32.1 are independent risk factors for ODPE failure. ODPE is a safe alternative to 2-stage revision in patients without preoperative anemia and without S aureus infection. Two-thirds of patients with a failed ODPE were successfully treated with a 2-stage reimplantation.

Antibiotic-tolerant Staphylococcus aureus Biofilm Persists on Arthroplasty Materials.

BACKGROUND: The continued presence of biofilm may be one cause of the high risk of failure observed with irrigation and débridement with component retention in acute periprosthetic joint infection (PJI). There is a poor understanding of the role of biofilm antibiotic tolerance in PJI. QUESTIONS/PURPOSES: (1) Do increasing doses of cefazolin result in decreased viable biofilm mass on arthroplasty materials? (2) Is cefazolin resistance phenotypic or genotypic? (3) Is biofilm viability a function of biofilm depth after treatment with cefazolin? (4) Is the toxin-antitoxin system, yoeB expression, associated with antibiotic stress? METHODS: Methicillin-sensitive Staphylococcus aureus biofilm was cultured on total knee arthroplasty (TKA) materials and exposed to increasing doses of cefazolin (control, 0.5, 1.0, 10.0, 100.0 µg/mL). Quantitative confocal microscopy and quantitative culture were used to measure viable biofilm cell density. To determine if cefazolin resistance was phenotypic or genotypic, we measured minimum inhibitory concentration (MIC) after exposure to different cefazolin concentrations; changes in MIC would suggest genotypic features, whereas unchanged MIC would suggest phenotypic behavior. Finally, quantitative reverse transcription-polymerase chain reaction was used to quantify expression of yoeB levels between biofilm and planktonic bacteria after exposure to 1 µg/mL cefazolin for 3 hours. RESULTS: Although live biofilm mass was reduced by exposure to cefazolin when compared with biofilm mass in controls (39.2 × 10(3) ± 26.4 × 10(3) pixels), where the level after 0.5 µg/mL exposure also showed reduced mass (20.3 × 10(3) ± 11.9 × 10(3) pixels), no further reduction was seen after higher doses (mass at 1.0 µg/mL: 5.0 × 10(3) pixels ± 1.1 × 10(3) pixels; at 10.0 µg/mL: 6.4 × 10(3) ± 9.6 × 10(3) pixels; at 100.0 µg/mL: 6.4 × 10(3) ± 3.9 × 10(3)). At the highest concentration tested (100 µg/mL), residual viable biofilm was present on all three materials, and there were no differences in percent biofilm survival among cobalt-chromium (18.5% ± 15.1%), polymethylmethacrylate (22.8% ± 20.2%), and polyethylene (14.7% ± 10.4%). We found that tolerance was a phenotypic phenomenon, because increasing cefazolin exposure did not result in changes in MIC as compared with controls (MIC in controls: 0.13 ± 0.02; at 0.5 µg/mL: 0.13 ± 0.001, p = 0.96; at 1.0 µg/m: 0.14 ± 0.04, p = 0.95; at 10.0 µg/m: 0.11 ± 0.016, p = 0.47; at 100.0 µg/m: 0.94 ± 0.047, p = 0.47). Expression of yoeB after 1 µg/mL cefazolin for 3 hours in biofilm cells was greater in biofilm but not in planktonic cells (biofilm: 62.3-fold change, planktonic cells: -78.8-fold change, p < 0.001). CONCLUSIONS: Antibiotics are inadequate at complete removal of the biofilm from the surface of TKA materials. Results suggest that bacterial persisters are responsible for this phenotypic behavior allowing biofilm high tolerance to antibiotics. CLINICAL RELEVANCE: Antibiotic-tolerant biofilm suggests a mechanism behind the poor results in irrigation and débridement for acute TKA PJI.

Body Mass Index More Than 45 kg/m(2) as a Cutoff Point Is Associated With Dramatically Increased Postoperative Complications in Total Knee Arthroplasty and Total Hip Arthroplasty.

BACKGROUND: Higher body mass index (BMI) has been associated with postoperative complications in total knee arthroplasty (TKA) and total hip arthroplasty (THA). However, the association of incremental increases of BMI and its effects on postoperative complications has not been well studied. We hypothesize that there is a BMI cutoff at which there is a significant increase of the risk of postoperative complications. METHODS: We studied the American College of Surgeons National Surgical Quality Improvement Program from 2006 to 2013. The final cohort included 77,785 primary TKA and 49,475 primary THA subjects, respectively. Patients were separated into 7 groups based on BMI (18.5-24.9 kg/m(2), 25.0-29.9 kg/m(2), 30.0-34.9 kg/m(2), 35.0-39.9 kg/m(2), 40.0-44.9 kg/m(2), 45.0-49.9 kg/m(2), and >50.0 kg/m(2)). We analyzed data on five 30-day composite complication variables, including any complication, major complication, wound infection, systemic infection, and cardiac and/or pulmonary complication. RESULTS: The odds ratio for 4 (any complication, major complication, wound infection, and systemic infection) of 5 composite complications started to increase exponentially once BMI reached 45.0 kg/m(2) or higher in TKA. Similarly, the odds ratio in 3 (any complication, systemic infection, and wound infection) of 5 composite complications showed similar trends in THA patients. These findings were further confirmed with propensity score matching and entropy balancing. CONCLUSIONS: Our study suggested that there was a positive correlation between BMI and incidences of 30-day postoperative complications in both TKA and THA. The odds of complications increased dramatically once BMI reached 45.0 kg/m(2).

Economic Impact of Orthopedic Adult Reconstruction Office Practice: The Implications of Hospital Employment Models on Local Economies.

The purpose of this study was to evaluate the economic attributes of private practice adult reconstruction (AR) offices. 458 AAHKS surgeons responded; 65% were in private practice (fee-for-service, non-salaried, non-employed AR surgeons). 54% had considered hospital employment in the past two years. The average group employs 13.4 orthopedic surgeons (3.4 AR), and 105 other employees. The average total budget is $12.5 million per year with $4 million in salaries, and $238,000 in tax revenue generated. Co-management joint ventures are a better model than hospital employment for aligning AR surgeons and hospitals and realizing the cost effectiveness and quality improvement goals of PPACA and AARA while preserving the economic impact of AR private practice.

Revision total hip and knee arthroplasty implant identification: implications for use of Unique Device Identification 2012 AAHKS member survey results.

FDA's Unique Device Identification (UDI) Rule will mandate manufacturers to assign unique identifiers to their marketed devices. UDI use is expected to improve implant documentation and identification. A 2012 American Association of Hip and Knee Surgeons membership survey explored revision total hip and knee arthroplasty implant identification processes. 87% of surgeons reported regularly using at least 3 methods to identify failed implants pre-operatively. Median surgeon identification time was 20 min; median staff time was 30 min. 10% of implants could not be identified pre-operatively. 2% could not be identified intra-operatively. UDI in TJA registry and UDI in EMR were indicated practices to best support implant identification and save time. FDA's UDI rule sets the foundation for UDI use in patient care settings as standard practice for implant documentation.

Pulse lavage is inadequate at removal of biofilm from the surface of total knee arthroplasty materials.

In acute periprosthetic infection, irrigation and debridement with component retention has a high failure rate in some studies. We hypothesize that pulse lavage irrigation is ineffective at removing biofilm from total knee arthroplasty (TKA) components. Staphylococcus aureus biofilm mass and location was directly visualized on arthroplasty materials with a photon collection camera and laser scanning confocal microscopy. There was a substantial reduction in biofilm signal intensity, but the reduction was less than a ten-fold decrease. This suggests that irrigation needs to be further improved for the removal of biofilm mass below the necessary bioburden level to prevent recurrence of acute infection in total knee arthroplasty.

Effect of ethnicity and insurance type on the outcome of open thoracic aortic aneurysm repair.

OBJECTIVES: Mortality and complication rates for open thoracic aortic aneurysm repair have declined but remain high. The purpose of this study is to determine the influence of ethnicity and insurance type on procedure selection and outcome after open thoracic aneurysm repair. METHODS: Using the Nationwide Inpatient Sample database, ethnicity and insurance type were evaluated against the outcome variables of mortality and major complications associated with open thoracic aneurysm repair. The potential cofounders of age, gender, urgency of operation, and Deyo index of comorbidities were controlled. RESULTS: Between 2001 and 2005, a total of 10,557 patients were identified who underwent elective open thoracic aneurysm repair, with a significantly greater proportion of white patients (n = 8524) compared with black patients (n = 819), Hispanic patients (n = 556), and patients categorized as other (n = 658). Most patients (67%) were male. Almost half (45%) of the procedures were performed for urgent/emergent indications. Overall mortality was 10.7% (n = 1126) and the rate of spinal cord ischemia was 0.4% (n = 43). Univariate analysis revealed significant differences among race with regard to surgery type, income, hospital region, hospital bed size, and insurance type (P < 0.0001). Differences between insurance coverage were significant for gender, surgery type, income, hospital region, and race (P < 0.0001). Bivariate analysis by race revealed differences for death (P < 0.0001), pneumonia (P < 0.0001), renal complications (P = 0.011), implant complications (P < 0.0001), temporary tracheostomy (P = 0.004), transfusion (P < 0.0001), and intubation (P < 0.0001). In terms of payer status, bivariate analysis by insurance coverage revealed differences in death (P < 0.0001), central nervous system complications (P = 0.008), pneumonia (P < 0.0001), myocardial infarction (P = 0.001), infection (P < 0.0001), renal complications (P < 0.0001), malnutrition (P < 0.0001), temporary tracheostomy (P < 0.0001), spinal cord ischemia (P = 0.001), transfusion (P < 0.0001), and intubation (P < 0.0001). CONCLUSIONS: A high percentage of open thoracic procedures (45%) are performed urgently or emergently in the United States, which is associated with increased morbidity and mortality. Both ethnicity and payer status were associated with significant differences in surgical outcomes, including mortality and frequency of complications after open thoracic aortic aneurysm repair.

Total knee arthroplasty in patients with a left ventricular assist device.

Many patients with severe cardiac disease can now live for a prolonged period with left ventricular assist devices (LVADs), and some patients will develop noncardiac medical issues that may benefit from surgical intervention. Previous studies have reported a low rate of complications in patients with LVADs undergoing noncardiac surgical procedures. We report the cases of 2 patients with LVADs who underwent total knee arthroplasties for osteoarthritis. Both patients had significant pain relief and improved function; however, management of anticoagulation and bleeding complications was challenging.

Outcomes of total hip and knee arthroplasty after cardiac transplantation.

The outcomes of 18 primary or revision total hip (THA) and knee arthroplasties (TKA) in 9 patients with cardiac transplants were reviewed. Primary total joint arthroplasties were performed for osteonecrosis (5 hips) or osteoarthritis (5 hips, 4 knees). There were no infections in any of these patients. Final Harris Hip Scores were 71.8 for patients with osteonecrosis and 88.6 for osteoarthritis. Eight of 10 hips were pain-free at final follow-up. Two of the 10 primary THAs required late revision at 7 and 10 years after the index arthroplasty. One patient (2 hips and 1 knee) had chronic bilateral lower extremity pain. Total knee arthroplasty range of motion averaged from 7.5° to 118°. Average final Knee Society function score was 79, and objective score was 88. One of 4 patients with primary TKA required a manipulation under anesthesia. No reoperations were required in this group. Overall, patients with heart transplantations on immunosuppression had generally good pain relief after THA and TKA. There were no infections in this small cohort; however, there were many complications.

Impending Trunnion Failure: An Uncommon Radiographic Presentation of Total Hip Arthroplasty Failure.

Trunnionosis is emerging as an early mode of failure in conventional metal-on-polyethylene total hip arthroplasty. It is defined as wear or corrosion at the trunnion, the taper at the femoral head-neck interface. Trunnion wear can result in a variety of negative sequelae and, in severe cases, necessitate revision arthroplasty. We describe a 64-year-old man with a metal-on-polyethylene total hip arthroplasty who presented with a sensation of clunking in the hip. Initial imaging and laboratory studies were inconclusive, and the decision was made to monitor. Two years later, trunnion wear was detected on radiographs, presenting as an abnormal alignment of the femoral neck relative to the femoral head. Several case reports and series describe catastrophic total hip arthroplasty failure due to trunnionosis. However, few describe the radiographic signs of wear at the trunnion before gross failure. This early presentation is important to recognize to minimize patient morbidity and aid surgical planning.

Effects of ethnicity and insurance status on outcomes after thoracic endoluminal aortic aneurysm repair (TEVAR).

BACKGROUND: Thoracic endoluminal aortic aneurysm repair (TEVAR) is associated with improved outcomes compared with open thoracic aortic aneurysm repair. This study was designed to better characterize TEVAR outcomes in a large population, and to determine if outcomes are independently influenced by patient ethnicity and insurance status. METHODS: Using the Nationwide Inpatient Sample (NIS) database, we selected patients who underwent TEVAR between 2001 and 2005. Ethnicity and insurance type were independently evaluated against the outcome variables of mortality and postoperative complications. Age, gender, hospital region, hospital location, hospital size, and comorbidities were controlled as cofounders. RESULTS: Between 2001 and 2005, 875 patients underwent TEVAR. There was a significantly greater proportion of Caucasians (n = 650) compared with African Americans (n = 104) or Hispanics (n = 49). Patients had a male preponderance, and most procedures were elective. The overall mortality was 13.3% (n = 117), and spinal cord ischemia was 0.8% (n = 7), with no differences between patients of varied ethnicity or payer status. Significant differences were noted among the races including gender (P = .003), income (P < .0001), hospital region (P < .001), hospital bed size (P = .013), and insurance type (P < .001). Significant variations in demographics characteristics were also present between patients with different insurance classifications including gender (P < .001), surgery type (P = .009), income (P = .003), race (P < .0001), and comorbidity index (P < .0001). After adjustment for cofounders and multiple comparisons, there were no differences in rates of complications among patients with varying race or insurance status. CONCLUSIONS: Mortality after TEVAR remains high in the US, although this may be associated with its early introduction during the study period. Nonetheless, the incidence of spinal cord ischemia is very low. Ethnicity and insurance type do not appear to influence TEVAR outcomes.

Venous thromboembolism: management by American Association of Hip and Knee Surgeons.

A 2008 survey of American Association of Hip and Knee Surgeons membership explored current venous thromboembolism (VTE) protocols for lower-extremity total joint surgery. Fifty-three percent reported a change in VTE-related practices in the last 5 years. More than 70% reported that their primary hospital now mandates VTE prophylaxis. Although 74% of their primary hospitals recognized the American College of Chest Physicians guidelines, 68% of surgeons felt the American Academy of Orthopaedic Surgeons guidelines were more relevant to their practice. Respondents believe low molecular weight heparin to be the most efficacious but aspirin to be the easiest to use and has the lowest risks of bleeding and wound drainage. Warfarin was the most used in hospital prophylaxis, and 90% of respondents targeted an international normalized ratio of 1.6 to 2.5. Practice patterns continue to evolve, and there remains no consensus on specific treatment protocols or preferences.

Impact of the economic downturn on adult reconstruction surgery: a survey of the American Association of Hip and Knee Surgeons.

To evaluate the effects of the economic downturn on adult reconstruction surgery in the United States, a survey of the American Association of Hip and Knee Surgeons (AAHKS) membership was conducted. The survey evaluated surgical and patient volume, practice type, hospital relationship, total joint arthroplasty cost control, employee staffing, potential impact of Medicare reimbursement decreases, attitudes toward health care reform options and retirement planning. A surgical volume decrease was reported by 30.4%. An outpatient visit decrease was reported by 29.3%. A mean loss of 29.9% of retirement savings was reported. The planned retirement age increased to 65.3 years from 64.05 years. If Medicare surgeon reimbursement were to decrease up to 20%, 49% to 57% of AAHKS surgeons would be unable to provide care for Medicare patients, resulting in an unmet need of 92,650 to 160,818 total joint arthroplasty procedures among AAHKS surgeons alone. Decreases in funding for surgeons and inadequate support for subspecialty training will likely impact access and quality for Americans seeking adult reconstruction surgery.

A Multidisciplinary Approach to Expedite Surgical Hip Fracture Care.

INTRODUCTION: In 2014, we implemented a geriatric hip fracture patient care pathway at our institution which was designed to improve outcomes and decrease time to surgery. MATERIALS AND METHODS: We analyzed retrospective data from 463 patients, aged greater than 50, who had surgical treatment for a closed hip fracture due to a low-energy injury between 2013 and 2016 at an academic institution. Objective outcome measures included time to surgery, mortality rate, and total hospital length of stay. Our primary goal was to decrease the time to surgery for definitive fracture fixation to within 24 hours of admission to the hospital for patients who were medically fit for surgery. RESULTS: We implemented a multidisciplinary, collaborative approach to address the needs of this specific patient population. Prior to implementing the pathway in 2013, our baseline time to surgery within 24 hours was 74.67%. After implementation, we had incremental yearly increases in the percentage of patients operated on within 24 hours, 82.31% in 2014 (P = .10) and 84.14% in 2015 (P = .04). During the study period, our overall time to surgery was reduced by 27% with an initial average of 20.22 hours in 2013, decreasing to 15.33 hours in 2014, and 14.63 hours in 2015. Our mortality rate at 1 year was 16% in 2013, 17% in 2014, and 15% in 2015. CONCLUSION: With implementation of the pathway, we were able to expedite surgical care for our patients and demonstrate a 10% improvement in the percentage of patients able to have surgery within 24 hours over a 3-year period. Our mortality and hospital length of stay, however, remained the same. Through this collaborative process and system standardization, we believe we have significantly improved not only direct patient care but their overall hospital experience. We continue to make improvements in our pathway.

Symptomatic ileofemoral DVT after onset of oral contraceptive use in women with previously undiagnosed May-Thurner Syndrome.

OBJECTIVE: May-Thurner syndrome is characterized by left common iliac obstruction secondary to compression of the left iliac vein by the right common iliac artery against the fifth-lumbar vertebra. This anatomic variant results in an increased incidence of left-sided deep venous thrombosis (DVT). Furthermore, while a preponderance of left-sided DVT has been demonstrated in women during pregnancy and oral contraceptive use, patients are not typically screened for this condition after developing a left-sided DVT. As anticoagulation alone is ineffective for DVT treatment in the setting of May-Thurner anatomy, more aggressive treatment is warranted. Failure to diagnosis this condition predisposes these women to the unnecessary risks of recurrent DVT and post-thrombotic syndrome. METHODS: We present the occurrence of 7 adolescent patients with previously undiagnosed May-Thurner syndrome who presented with DVT after the initiation of oral contraceptive steroids (OCP) use. All 7 patients elected to proceed with mechanical thrombolysis/catheter based thrombolysis followed by endovascular stenting and were postoperatively treated with 6 months of warfarin. RESULTS: Mean patient age was 18.3 +/- 3.3 years (range, 16-24 years). Mean time to presentation after initiation of OCP was 5 weeks (range, 2-10 weeks). Mean time to intervention was 16.8 days (range, 10-24 days). All patients were treated with mechanical thrombectomy. Our rate of intraoperative clot resolution was 100%. All 7 patients were treated with self expanding nitinol stents after angioplasty of the iliac vein stenosis with resolution of the stenotic segment. Primary stent patency is 100% (7/7). Mean follow-up time is 13 +/- 13.84 months (range, 6-42 months). There have been no long-term complications related to surgical treatment or anticoagulation. All 7 patients have experienced resolution of left leg swelling and pain and have no evidence of post-thrombotic syndrome or DVT recurrence to date. CONCLUSIONS: Women on OCPs presenting with left-sided iliofemoral DVT should be screened for hypercoagulable disorders and underlying May-Thurner anatomy. Treatment of May-Thurner syndrome should include thrombolysis/thrombectomy and anticoagulation for current DVT in addition to angioplasty and stenting of the underlying obstruction.

Septic Arthritis of the Hip and Enterocutaneous Fistula Formation After Hip Arthroscopy: A Case Report of Psoas Abscess Misdiagnosed as Labral Pathology.

CASE: We describe a case of septic hip arthritis and enterocutaneous fistula formation caused by the seeding of a hip joint during hip arthroscopy performed in the setting of a psoas abscess. Treatment consisted of multiple debridements and femoral head resection with subsequent total hip arthroplasty. CONCLUSIONS: This case highlights the importance of a thorough history, physical examination, and assessment of available imaging before proceeding to surgery, even when the procedure is one considered to have minimal risks, such as arthroscopy.

Viable bacteria persist on antibiotic spacers following two-stage revision for periprosthetic joint infection.

Treatment in periprosthetic joint infection (PJI) remains challenging. The failure rate of two-stage revision and irrigation and debridement with component retention in PJI suggests that biofilm cells have a high tolerance to antibiotic chemotherapy. Previous work has demonstrated that biofilm cells have high antibiotic tolerance in vitro, but there is little clinical evidence to support these observations. The aim of this study was to determine if retrieved antibiotic spacers from two-stage revision total knee arthroplasty for PJI have evidence of remaining viable bacteria. Antibiotic poly (methyl methacrylate) (PMMA) spacers from two-stage revision total knee arthroplasty for PJI were prospectively collected and analyzed for bacterial 16s rRNA using polymerase chain reaction (PCR), reverse transcription (RT)-PCR, quantitative RT-PCR (qRT-PCR), and single genome analysis (SGA). PCR and RT-PCR identified bacterial species on 53.8% (7/13) of these samples. When initial culture negative cases are excluded, 68% (6/9) samples were identified with bacterial species. A more rigorous qRT-PCR analysis showed a strong positive signal for bacterial contamination in 30.7% (4/13) of cases. These patients did not show any clinical evidence of PJI recurrence after 15 months of follow-up. Because the half-life of bacterial rRNA is approximately a few days, the identification of bacteria rRNA on antibiotic PMMA spacers suggests that viable bacteria were present after conclusion of antibiotic therapy. This study provides evidence for the high tolerance of biofilm cells to antibiotics in vivo and the important role of bacterial persisters in PJI. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:452-458, 2018.