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Racial and socioeconomic disparities have been associated with complications and poorer patient-reported outcomes after THA and TKA, but little is known regarding the variation of postacute care resource utilization based on socioeconomic difference in the communities in which patients reside. Hip and knee arthroplasty are among the most common elective orthopaedic procedures. Therefore, understanding social factors provides insight into patients at risk for readmission and the way in which these patients use other postoperative resources. This knowledge can help surgeons better understand which patients are at risk for complications or preventable readmissions and how to anticipate when additional surveillance or intervention might reduce this risk.(1) Do patients from communities with a higher distress level experience higher rates of readmission after THA and TKA? (2) Do patients from distressed communities have increased postoperative resource utilization?Demographics, ZIP code of residence, and Charlson comorbidity index (CCI) were recorded for each patient undergoing TKA or THA between 2016 and 2019 at two high-volume hospitals. Patients were classified according to the Distressed Communities Index (DCI) score of their ZIP code of residence. The DCI combines seven metrics of socioeconomic well-being (high school graduation, poverty rate, unemployment, housing vacancy, household income, change in employment, and change in establishment) to create a single score. ZIP codes are then classified by scores into five categories based on national quintiles (prosperous, comfortable, mid-tier, at-risk, and distressed). The DCI was chosen because it provides a single composite measure of multiple important socioeconomic factors. Multivariate analysis with logistic, negative binomial regression, or Poisson was used to investigate the association of DCI category with postoperative resource utilization while controlling forage, gender, BMI, and comorbidities. The primary outcome was 90-day readmissions. Secondary outcomes included postoperative medication prescriptions from the orthopaedic team, patient telephone calls to the surgeon's office, physical therapy sessions attended, follow-up office visits, and emergency department visits. A total of 5077 patients who underwent TKA (mean age 66 ± 9 years, 59% [2983 of 5077] are women, and 69% [3519 of 5077] are White), and 5299 who underwent THA (mean age 63 ± 11 years, 50% [2654 of 5299] are women, and 74% [3903 of 5299] are White) were included.When adjusting for age, gender, race and CCI, readmission risk was higher in distressed communities compared with prosperous communities for patients undergoing TKA (odds ratio 1.6 [95% confidence interval 1.1 to 2.3]; p = 0.02) but not for THA. For secondary outcomes after TKA, at-risk communities had more postoperative prescriptions compared with prosperous communities, but no other differences were found. After THA, no major differences were found in the likelihood to utilize postoperative resources based on DCI category. Race was not associated with readmissions or resource utilization.We found that socioeconomic distress was associated with readmission after TKA, but, after controlling for relevant confounding variables, race had no association. Patients from these communities do not demonstrate an increased or decreased use of other resources after post-TKA discharge. Increased awareness of these disparities may allow for closer monitoring and improved patient education and communication, with the goal of reducing the frequency of complications and preventable readmissions.Level III, therapeutic study.

Given the current healthcare economic environment, substantial efforts have been made to help streamline the in-hospital care for total knee arthroplasty (TKA) patients. While potential cost-reducing factors have been identified in the literature, analyses specifically considering post-anesthesia care unit (PACU) lengths of stay (LOS) are lacking. Therefore, the purpose of this study was to identify factors associated with (1) longer PACU LOS as well as (2) longer Hospital LOS. Prospectively collected TKA data from seven participating hospitals within a large health system were evaluated for patient demographics, body mass indices, Charlson Comorbidity Indices (CCI), surgeon volumes/training, admission types, anesthesia types, PACU LOS, and overall hospital LOS. Complete data was available for 1,690 patients (1,082 females, mean age: 67 years). Univariate and multivariate analytical models were constructed to identify which factors were predictive of longer PACU and overall hospital LOS. Same-day admissions, higher volume surgeons (≥ 100 cases per year), fellowship-trained arthroplasty surgeons, and longer operative times were associated with longer PACU LOS (p 0.05). These data identify associative factors for PACU LOS, as well as the influence of time spent in the PACU on overall hospital LOS. Interestingly, this analysis revealed that patients of arthroplasty fellowship-trained and higher-volume surgeons had longer PACU LOS; however, this could be explained by the observation that these particular surgeons tend to perform more complex deformity cases. Also of importance, increased PACU LOS, meaning the patient spent more time in a high-monitored setting immediately after surgery, did not necessarily confer a longer overall hospital LOS. Based on these data, it may be more beneficial to identify alternate sources than time spent in the operating room or PACU to potentially help reduce overall hospital LOS. Level of Evidence II, prospective cohort

Chronic refractory pain after total joint replacement is debilitating and a source of dissatisfaction for patients. The management of pain following total joint replacement varies during the acute postoperative period compared to the 3 months postoperative at which point the pain is considered chronic pain. Acute postoperative pain relief programs have seen promising results with multimodal pain control through the use of combinations of opioids, acetaminophen, nonsteroidal anti-inflammatory drugs, gabapentinoids and ketamine. The addition of regional blocks to the multimodal regimen has improved acute postoperative pain control following total joint replacements. On the other hand, chronic pain can be successfully managed with options including genicular nerve radioablation therapy (GN-RFA), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and peripheral subcutaneous field stimulation (PSFS). While there is still minimal data on chronic pain relief regimens, meta-analyses and case reports have demonstrated the effectiveness and promising outcomes. This paper aims to evaluate the current medications and treatment options for managing refractory pain following TJA.

The aim of this study was to track the annual rates and trends of overall, deep, and superficial surgical site infections (SSIs) following total knee arthroplasty using the most recent results from a large and nationwide database. A total of 197,192 cases were performed between 2012 and 2016 from a nationwide database stratified into years and based on superficial and/or deep SSIs. Cohorts were analyzed individually and then combined to evaluate overall SSI rates. The infection incidence for each year was calculated. After a 6-year correlation and trends analysis, univariate analyses were performed to compare the most recent year, 2016, with each of the preceding 4 years. Overall, there was a downward trend in overall SSI rates over the study period (2012–2016, with the lowest rate occurring in the most recent year, 2016 [0.11%]). Additionally, there was a decreasing trend for superficial SSI, with the lowest superficial SSI incidence occurring in 2016 (0.47%) and the greatest incidence occurring in 2012 (0.53%). An overall trend of decreasing SSI rates was observed nationwide over the 5-year period evaluated. A similar decreasing trend was also noted specifically for deep SSI rates, which can be potentially more complicated to manage, and result in decreased implant survivorship. The down trending SSI rates observed give potential credence to the value for newer and developing SSI preventative therapies as well as improved medical and surgical patient management. Nevertheless, there is still room for improvement, and continued efforts are needed to further lower SSIs after total knee arthroplasty.

Background: The direct anterior approach (DAA) used for primary total hip arthroplasty has been shown to improve early postoperative outcomes, but prior studies have identified a marked learning curve for surgeons transitioning to this approach. However, these studies do not capture surgeons with postgraduate fellowship training in DAA. Therefore, the purpose of this study was to evaluate the learning curve by comparing perioperative outcomes for the first 100 to latter 100 cases and first 50 to final 50 cases. Methods: The first 200 consecutive primary total hip arthroplasties performed by a single surgeon were prospectively followed up for up to 2 years postoperatively. Data on demographic and perioperative factors, 90-day readmissions, and short- and long-term complications were collected. Radiographic outcomes included acetabular cup anteversion and abduction measurements. Logistic regressions were used to calculate odds ratios and confidence intervals for surgical time greater than 2 hours. Results: The first 100 and second 100 cases had significant differences in operative times (118.1 vs 110.4 minutes, P = .009), acetabular abduction (38.3 vs 35.5 degrees, P = .001) and anteversion (13.5 vs 15.1 degrees, P = .009), and incidence of neuropraxia (41 vs 9%, P < .001). Estimated blood loss, transfusions, discharge disposition, length of stay, readmission, and other complications had no statistical significance between the first and second 100 cases. The first 50 cases had higher odds of surgical time greater than 2 hours (odds ratio = 5.2, 95% confidence interval = 1.84-14.75, P = .002) than the final 50 cases. Conclusions: When compared with the existing literature, incorporation of DAA into fellowship training can lead to reduction in fractures and reoperation rates.

The Coronavirus Disease 2019 (COVID-19) pandemic has caused a substantial number of patients to have their elective arthroplasty surgeries rescheduled. While it is established that patients with COVID-19 who are undergoing surgery have a significantly higher risk of experiencing postoperative complications and mortality, it is not well-known at what time after testing positive the risk of postoperative complications or mortality returns to normal.PubMed (MEDLINE), Excerpta Medica dataBASE, and professional society websites were systematically reviewed on March 7, 2022 to identify studies and guidelines on the optimal timeframe to reschedule patients for elective surgery after preoperatively testing positive for COVID-19. Outcomes included postoperative complications such as mortality, pneumonia, acute respiratory distress syndrome, septic shock, and pulmonary embolism.A total of 14 studies and professional society guidelines met the inclusion criteria for this systematic review. Patients with asymptomatic COVID-19 should be rescheduled 4-8 weeks after testing positive (as long as they do not develop symptoms in the interim), patients with mild/moderate COVID-19 should be rescheduled 6-8 weeks after testing positive (with complete resolution of symptoms), and patients with severe/critical COVID-19 should be rescheduled at a minimum of 12 weeks after hospital discharge (with complete resolution of symptoms).Given the negative association between preoperative COVID-19 and postoperative complications, patients should have elective arthroplasty surgery rescheduled at differing timeframes based on their symptoms. In addition, a multidisciplinary and patient-centered approach to rescheduling patients is recommended. Further study is needed to examine the impact of novel COVID-19 variants and vaccination on timeframes for rescheduling surgery.

AIMS: Venous thromboembolism (VTE) has a 30-day mortality rate of between 10 and 30%. The Caprini score is a VTE risk assessment model, which assigns points to 20 past medical history and current health factors. We hypothesized that the Caprini score could predict VTE incidence and recommend prophylaxis following total joint arthroplasty. PATIENTS AND METHODS: We performed a retrospective review of prospectively collected institutional data identifying Caprini scores on 2155 primary hip (n = 840) and knee (n = 1315) arthroplasties. Surgeons were blinded to Caprini scores when prescribing VTE prophylaxis. Patients were separated into prophylaxis groups receiving Aspirin (81 mg BID or 325 mg BID) or other (Rivaroxaban, Warfarin, Enoxaparin, Apixaban, Dabigatran, Heparin). Univariate, multivariate, and Cohen's effect size analyses assessed the predictive power of the Caprini score on VTE incidence. RESULTS: The mean Caprini score was 9.49 (5–25). A majority, 83% (1792) of patients were in the Aspirin group, and 17% (363) in the other group. Other prophylaxis patients had statistically significantly higher Caprini scores (10 vs. 9, p 40 or Caprini scores ≥11 to predict VTE incidence in the Aspirin or other prophylaxis groups (p = 0.52 and p = 0.15 respectively). Cohen's effect size was small, comparing Caprini scores in patients who had and had not had a VTE in both Aspirin and other prophylaxis groups (Cohen's d = 0.25 and d = 0.16 respectively). CONCLUSION: Surgeons rely on stronger pharmacologic prophylaxis for a select high risk group of their primary lower extremity total joint arthroplasty patients. When controlling for prophylaxis, the Caprini score had a small effect size and did not have the predictive power necessary to guide treatment

Modular dual mobility cups have been developed to potentially address postoperative hip instability, which can occur in nearly 20% of all revision total hip arthroplasty (THA) patients. By having a prosthetic construct that contains two points of articulation between the femoral head and liner and between the liner and shell, joint stability can be increased. The purpose of this study was to report on dual mobility cup survivorships, patient satisfaction outcomes, complications, and radiographic outcomes at a minimum 7-year follow-up. A high-volume academic surgeon performed a total of 143 consecutive dual mobility primary THAs on patients who had a minimum follow-up of 7 years (range, 7–8.5 years). The study cohort consisted of 77 females (54%) and 66 males (46%) who had a mean age of 65 years (range, 34–90 years). Aseptic, septic, and all-cause survivorship was determined by Kaplan-Meier analysis. Harris Hip Scores (HHS), postoperative complications, and radiographs were also assessed. No cup failures were observed. Overall, septic survivorship was 99.3% (95% confidence interval [CI]: 0.98–1.0) and all-cause survivorship was 98.6% (95% CI: 0.97–1.0). Two patients (1.4%) required revision surgery unrelated to the use of a modular dual mobility cup. Of these, one patient experienced femoral stem loosening and the other developed a periprosthetic infection that was treated with a two-stage revision. The mean total HHS was above 95 points at the most recent follow-up. Three patients (2.3%) experienced medical complications, including two deep vein thromboses and one for nonfatal pulmonary embolism. Radiographic evidence revealed incomplete seating of the metallic liner in one patient. Dual mobility cups were developed in an attempt to decrease the rate of instability following THA. The results from this study indicate that excellent clinical and patient-reported outcomes can be achieved at 7-year follow-up in patients who undergo THA with a dual mobility cup. Therefore, dual mobility cups appear to be an appropriate treatment option for primary THA.

Catheterization for the prophylaxis against or treatment for urinary retention commonly occurs after total knee arthroplasty (TKA). Recent studies have questioned the use of the indwelling catheterization, especially in its potential role as a nidus for infection. We are still unsure of its downstream effects on periprosthetic joint infections (PJIs). Therefore, this study aimed to compare the risks of postoperative PJI following intermittent vs indwelling catheterization after TKA.Between 2017 and 2019, 15 hospitals in a large health system collected data on patients undergoing TKA. Patient treatments with indwelling catheter only, intermittent straight catheter only, and both indwelling and intermittent straight catheterizations were recorded. Patient demographics, comorbidities, body mass indices, and PJIs were collected from time of surgery to time of data collection at mean 14 months of follow-up. Univariate and multivariate analyses were performed with independent t-tests and multiple linear regression models to compare catheterization treatment types.A total of 9123 TKAs were performed, with patients receiving indwelling catheter only (62%, n = 734), intermittent straight catheter only (25%, n = 299), or both indwelling and intermittent catheterizations (13%, n = 160). Univariate analyses showed that PJIs occurred in 1.1% of no-catheter patients and 2.3% of patients treated with bladder catheterization (P = .002). Using multivariate analyses, indwelling catheter use (odds ratio [OR] 2.647, P.001), diabetes (OR 1.837, P = .005), and peripheral vascular disease (OR 2.372, P = .046) were found to have a statistically significant increased risk for PJIs. The use of intermittent straight catheterization (OR 1.249, P = .668) or both indwelling and intermittent (OR 1.171, P = .828) did not increase the risk for PJIs.Urinary bladder catheterization is commonly required for prophylaxis against or treatment for urinary retention following TKA. The use of a urinary catheter can provide a potential nidus for infection in these patients. This study found that indwelling catheterization, but not intermittent catheterization, was associated with an increased risk for PJI. Surgeons should therefore limit the duration of catheterization in an effort to decrease the risk for PJI.

Recent regulatory changes made by the Center for Medicare and Medicaid Services (CMS) will result in a 9% decrease in reimbursement for hip and knee replacements by the end of 2022. Combining this with CMS's recent removal of total knee and total hip arthroplasty from the inpatient-only list has begun to take effect on the bottom line for hospital systems, which now employ around 50% of the arthroplasty community. Employed joint replacement surgeons should continue to innovate and be leaders within their hospital systems in the outpatient and ambulatory surgery space to recoup lost value, increase autonomy, and should be compensated for this work. Employed arthroplasty surgeon leaders can better align goals with and control the narrative in the C-suite to redefine their value as the most consistent, dependable, and transparent department within a larger health system or corporate medical group.

Psoriasis is a dermatologic condition characterized by erythematous plaques that may increase wound complications and deep infections following total knee arthroplasty (TKA). There is a paucity of evidence concerning the association of this disease and complications after TKA. This study aimed to determine if patients who have psoriasis vs non-psoriatic patients have differences in demographics and various comorbidities as well as post-operative infections, specifically the following: (1) wound complications; (2) cellulitic episodes; and (3) deep surgical site infections (SSIs).We identified 10,727 patients undergoing primary TKA utilizing an institutional database between January 1, 2017 and April 1, 2019. A total of 133 patients who had psoriasis (1.2%) were identified using International Classification of Diseases, Tenth Revision codes and compared to non-psoriatic patients. The rate of wound complications, cellulitic episodes, and deep SSIs were determined. After controlling for age and various comorbidities, multivariate analyses were performed to identify the associated risks for post-operative infections.Psoriasis patients showed an increased associated risk of deep SSIs (3.8%) compared to non-psoriasis patients (1.2%, P = .023). Multivariate analyses demonstrated a significant associated risk of deep SSIs (odds ratio 7.04, 95% confidence interval 2.38-20.9, P.001) and wound complications (odds ratio 4.44, 95% confidence interval 1.02-19.2, P = .047).Psoriasis is an inflammatory dermatologic condition that warrants increased pre-operative counseling, shared decision-making, and infectious precautions in the TKA population given the increased risk of wound complications and deep SSIs. Increased vigilance is required given the coexistence of certain comorbidities with this population, including depression, substance use disorder, smoking history, gastroesophageal reflux disease, and inflammatory bowel disease.

Concerns regarding target price methodology and financial penalties have led to withdrawal from Medicare bundled payment programs for total hip (THA) and knee arthroplasty (TKA), despite its early successful results. The purpose of this study was to determine whether there was any difference in patient comorbidities and outcomes following our institution's exit from the Bundled Payments for Care Improvement - Advanced (BPCI-A).We reviewed consecutive 2,737 primary TKA and 2,009 primary THA patients following our withdraw from BPCI-A January 1, 2020-March 30, 2021 and compared them to 1,203 TKA and 1,088 THA patients from October 1, 2018-August 2, 2019 enrolled in BPCI-A. We compared patient demographics, comorbidities, discharge disposition, complications, and 90-day readmissions. Multivariate analysis was performed to identify if bundle participation was associated with complications or readmissions.Post-bundle TKA had shorter length of stay (1.4 vs 1.8 days, P.001). Both TKA and THA patients were significantly less likely to be discharged to a rehabilitation facility (5.6% vs 19.2%, P.001 and 6.0% vs 10.0%, P.001, respectively). Controlling for confounders, post-bundle TKA had lower complications (OR = 0.66, 95% CI 0.45-0.98, P = .037) but no difference in 90-day readmission (OR = 0.80, 95% CI 0.55-1.16, P = .224).Since leaving BPCI-A, we have maintained high quality THA care and improved TKA care with reduced complications and length of stay under a fee-for-service model. Furthermore, we have lowered rehabilitation discharge for both TKA and THA patients. CMS should consider partnering with high performing institutions to develop new models for risk sharing.

The purpose of this study was to compare the: 1) RVUs; 2) lengths-of-surgery; 3) RVU per minute between revision hip (THA) and knee (TKA) arthroplasties; and 4) perform an annualized surgeon cost analysis. Using the ACS-NSQIP from 2008 to 2015, 8081 revision TKAs, 7233 THAs were compared. Revision THA had greater mean RVUs (30.27 vs. 27.10 RVUs, p

Chronic pain after total joint replacement (TJA), specifically total knee replacement (TKA), is becoming more of a burden on patients, physicians, and the healthcare system as the number of joint replacements performed increases year after year. The management of this type of pain is critical, and therefore, understanding the various modalities physicians can use to help patients with refractory pain after TJA is essential. The modalities by which chronic pain can be successfully managed include genicular nerve radioablation therapy (GN-RFA), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and peripheral subcutaneous field stimulation (PSFS). Meta-analyses and case reports have demonstrated the effectiveness of these treatment options in improving pain and functional outcomes in patients with chronic pain after TKA. The purpose of this paper is to review and synthesize the current literature investigating the different ways that refractory pain is managed after TJA, with the goal being to provide treatment recommendations for providers treating these patients.

Orthopaedic surgeons have the highest prevalence of death by suicide among all surgical subspecialties, comprising 28.2% of surgeon suicides from 2003 to 2017. There is a continuum of burnout, depression, and other mental health illnesses likely contributing to these numbers in our profession. Stigmatization in terms of medical licensing and professional development are currently barriers to seeking mental health treatment. Education on the risk and treatment of burnout, depression, and suicidal ideations should begin early in a surgeon's career. This review documents the issue of physician burnout and depression and makes recommendations regarding necessary changes to counteract mental illness in orthopaedic surgeons.

BACKGROUND: Recent studies have shown that patients with opioid use disorder have impaired immunity. However, few studies with large patient populations have evaluated the risks of surgical site infection (SSI) and prosthetic joint infection (PJI) with opioid use disorder after total joint arthroplasty (TJA), and there is a lack of evidence for revision TJA in particular. QUESTIONS/PURPOSES: Are patients with opioid use disorder who undergo (1) primary THA, (2) primary TKA, (3) revision THA, or (4) revision TKA at a higher risk of experiencing SSIs 90 days after surgery or PJIs 2 years after surgery than those who do not have opioid use disorder? METHODS: All primary and revision TJAs performed between 2005 and 2014 were identified from the Medicare Analytical Files of the PearlDiver Supercomputer using ICD-9 codes. This database is one of the largest nationwide databases; it comprehensively and longitudinally tracks patients based on all insurance claims rather than particular hospital visits, and has a low error rate (estimated at 1.3%). Boolean command operators were used to form a study group of patients with a history of opioid use disorder before surgery. ICD-9 diagnosis codes 304.00 to 304.02 and 305.50 to 305.52 were used to identify patients with opioid use disorder. Study group patients were matched 1:1 to control participants without opioid use disorder undergoing TJA, according to age, sex, and comorbidity burden (Elixhauser comorbidity index [ECI]). The ECI is comprised of 31 different comorbidities and can be used for large administrative databases. The query yielded a study population of 54,332 patients: 14,944 undergoing primary THA (opioid use disorder: n = 7472), 23,680 undergoing primary TKA (opioid use disorder: n = 11,840), 8116 undergoing revision THA (opioid use disorder: n = 4058), and 7592 undergoing revision TKA (opioid use disorder: n = 3796). The primary outcomes analyzed were SSI at 90 days and PJI at 2 years postoperatively, which were identified with ICD-9 codes. Logistic regression analyses were performed to calculate the risk that an infection would develop in a patient with opioid use disorder compared with the matched control patients without opioid use disorder. RESULTS: Patients with opioid use disorder undergoing primary THA had an increased risk of SSI at 90 days (OR 1.85 [95% CI 1.51 to 2.25]; p < 0.001) and PJI at 2 years (OR 1.66 [95% CI 1.42 to 1.93]; p < 0.001). Compared with matched controls, opioid use disorder patients undergoing primary TKA had an increased risk of SSI at 90 days (OR 1.72 [95% CI 1.46 to 2.02]; p < 0.001) and PJI at 2 years (OR 1.31 [95% CI 1.16 to 1.47]; p < 0.001). Similarly, for revision THAs, there was an increase in 90-day SSIs (OR 1.89 [95% CI 1.53 to 2.32]; p < 0.001) and 2-year PJIs (OR 4.24 [95% CI 3.67 to 4.89]; p < 0.001). The same held for revision TKAs for 90-day SSIs (OR 1.88 [95% CI 1.53 to 2.29]; p < 0.001) and 2-year PJIs (OR 4.94 [95% CI 4.24 to 5.76]; p < 0.001). CONCLUSIONS: After accounting for age, sex, and comorbidity burden, these results revealed that patients with opioid use disorder undergoing TJA were at increased risk of having SSIs and PJIs. Based on these findings, healthcare systems and/or administrators should recognize the increased associated PJI and SSI risks in patients with opioid use disorder and enact clinical policies that reflect these associated risks. Additionally, these findings should encourage surgeons to pursue multidisciplinary approaches to help patients reduce their opioid consumption before their arthroplasty procedure. LEVEL OF EVIDENCE: Level III, therapeutic study.

BACKGROUND: Patients older than 80 years of age form an increasing proportion of the patient population undergoing total joint arthroplasty (TJA). With increasing life expectancy and the success of TJA, orthopaedic surgeons are more likely to operate on patients older than 80 years than ever before. Given that most other studies focus on younger populations, only evaluate primary TJA, or limit patient populations to institutional or regional data, we felt a large-database, nationwide analysis of this demographic cohort was warranted, and we wished to consider both primary and revision TJA. QUESTIONS/PURPOSES: In this study, we sought to investigate the risk factors for surgical site infections (SSIs) at 90 days and periprosthetic joint infections (PJIs) at 2 years after surgery in patients aged 80 years and older undergoing (1) primary and (2) revision lower extremity TJA. METHODS: All patients aged 80 years or older who underwent primary or revision TJA between 2005 and 2014 were identified using the Medicare Analytical Files of the PearlDiver Supercomputer using ICD-9 codes. This database is unique in that it is one of the largest nationwide databases, and so it provides a large enough sample size of patients 80 years or older. Additionally, this database provides comprehensive and longitudinal patient data tracking, and a low error rate. Our final cohort consisted of 503,241 patients (TKA: n = 275,717; THA: n = 162,489; revision TKA: n = 28,779; revision THA: n = 36,256). Multivariate logistic regression models were constructed to evaluate the association of risk factors on the incidences of 90-day SSI and 2-year PJI. Variables such as sex, diabetes, BMI, and congestive heart failure, were included in the multivariate regression models. Several high-risk comorbidities as identified by the Charlson and Elixhauser comorbidity indices were selected to construct the models. We performed a Bonferroni-adjusted correction to account for the fact that multiple statistical comparisons were made, with a p value < 0.002 being considered statistically significant. RESULTS: For primary TKA patients, an increased risk of 90-day SSIs was associated with male sex (OR 1.28 [95% CI 1.25 to 1.52]; p < 0.001), BMI greater than 25 k/m(2) (p < 0.001), and other comorbidities. For primary THA patients, an increased risk of 90-day SSIs was associated with patients with obesity (BMI 30-39 kg/m(2); OR 1.91 [95% CI 1.60 to 2.26]; p < 0.001) and those with morbid obesity (BMI 40-70 kg/m(2); OR 2.58 [95% CI 1.95 to 3.36]; p < 0.001). For revision TKA patients, an increased risk of SSI was associated with iron-deficiency anemia (OR 1.82 [95% CI 1.37 to 2.28]; p < 0.001). For revision THA patients, electrolyte imbalance (OR 1.48 [95% CI 1.23 to 1.79]; p < 0.001) and iron-deficiency anemia (OR 1.63 [95% CI 1.35 to 1.99]; p < 0.001) were associated with an increased risk of 90-day SSI. Similar associations were noted for PJI in each cohort. CONCLUSIONS: These findings show that in this population, male sex, obesity, hypertension, iron-deficiency anemia, among other high-risk comorbidities are associated with a higher risk of SSIs and PJIs. Based on these findings, orthopaedic surgeons should actively engage in comanagement strategies with internists and other specialists to address modifiable risk factors through practices such as weight management programs, blood pressure reduction, and electrolyte balancing. Furthermore, this data should encourage healthcare systems and policy makers to recognize that this patient demographic is at increased risks for PJI or SSI, and these risks must be considered when negotiating payment bundles. LEVEL OF EVIDENCE: Level III, therapeutic study.

Because of the early follow-up positive outcomes with cementless fixation, continued evaluations need to be performed to ensure longer-term efficacy. Additionally, although many studies report on the results of femoral and tibial component fixation, few studies report specifically on patellar outcomes. Therefore, the purpose of this study was to report on the: (1) implant survivorship; (2) complications; and (3) radiographic outcomes in a large cohort of patients who received cementless total knee arthroplasties (TKAs), with particular attention to the patellar component. A total of 261 patients who underwent cementless TKA by a single, high-volume academic surgeon were studied. Patients had a mean age of 66 years and were distributed between 192 women (74%) and 69 men. All patients received the same cementless tibial, femoral, and patellar components. Mean follow-up period was 4.5 years (range, 4–5 years). Primary outcomes evaluated included all postoperative complications, with particular emphasis on the patellar component. Only one patellar loosened leading to a patellar aseptic loosening rate of 0.3% (1 of 261). The one patellar loosening was the component being dislodged after a manipulation under anesthesia (MUA) at 6 weeks. This was revised to a cemented component and the patient is doing well 4 years later. A second patient experienced a patellar tendon rupture, later surgically repaired. Another patient sustained a patella fracture that was managed nonoperatively. The fracture healed by 1 year and the patient continued to have an otherwise successful outcome, now at 2 years follow-up. No progressive radiolucencies, subsidence, or changes in initial postoperative axial alignment were observed at final follow-up. The results from this study highlight a 98% success rate at mean 4.5 years follow-up in a large cohort of patients with a diverse spread of demographic details. Specific to the patella, only one patient experienced an adverse event, which was managed nonoperatively. Therefore, based on this data, patellar fixation in cementless TKA can be considered a safe technique.

The demographics of total knee arthroplasty (TKA) patients are changing. Individuals are more active, younger, and more obese. These changing demographics and a higher demand for longevity creates a new challenge for reliable and long-term implant fixation. Historically, cemented fixation has remained the gold standard, as cementless design and techniques from the 1980s and 1990s did not obtain long-term positive outcomes due to a failure of ingrowth onto the implants. Advances in the modern-day cementless TKA designs appear to have overcome their initial challenges, indicating the dependence of cementless TKA on implant design. However, there remains the perception that cementless total knee arthroplasty are inferior to cemented TKA. This review discusses the longer-term survivorship data for recent systems, which has shown the potential advantages of cementless fixation.

Rapid recovery protocols (RRP) in total hip arthroplasty (THA) aim to decrease patient length of stay (LOS), reduce postoperative pain, minimize complications, and improve patient satisfaction. RRP require attention to detail during preoperative, intraoperative, and postoperative care. Despite being referred to as the practice of medicine, most of the “practices,” including the physical, mental, and emotional energy, should occur before entering into the operating room. The operating room should be reserved for execution of a well-thought-out and prepared surgical plan (and backup plans) with efficiency.

Medical education has undergone an evolution from passive, lecture-based learning environments to curricula that accentuate an active and dynamic system. Stemming from technological innovation, a greater amount of responsibility has been placed on students during clerkships and residency. In addition, a shift in USMLE assessment focuses on interpretation and application as compared to the former memorization-heavy approach. Therefore, learning has been modified to prepare students for the future medical landscape. Through the use of Team-Based, Problem-Based, and/or Case-Based Learning, medical students are taught to understand content rather than memorize it. The authors elucidate the rationale behind active learning and present a guide for medical educators to adopt this style of learning in every part of the undergraduate medical school training process.

Urinary bladder catheters are potential sources of infection after total hip arthroplasty (THA). Therefore, the goal of this study was to determine if intermittent catheterization provides a decreased risk of postoperative urinary tract infections (UTIs) compared with indwelling catheterization in THA patients.Patients undergoing THA at 15 hospitals within a large health system were prospectively collected between 2017 and 2019 and then stratified based on catheterization technique: no-catheter; indwelling catheter-only; intermittent catheter-only; and both intermittent and indwelling catheter. Patient demographics, medical comorbidities, anesthesia types, and postoperative UTIs were assessed. Independent Student t-tests were used to perform univariate analyses for the catheterization groups. Multiple linear regression models were used to compare the different groups while controlling for confounding variables.There were a total of 7306 THA patients recorded with 5513 (75%) no-catheter, 1181 (16%) indwelling catheter-only, 285 (3.9%) intermittent catheter-only, and 327 (4.5%) indwelling and intermittent catheterization patients. A total of 580 patients experienced postoperative UTI. Urinary bladder catheterization increased the risk of postoperative UTIs (P.001) in univariate analyses. Multiple linear regression models showed that indwelling catheter-only (OR: 2.178, P.001), intermittent catheterization (OR: 1.975, P = .003), and both indwelling and intermittent (OR: 2.372, P = .002) were more likely to experience UTIs compared with no catheters.This study found that patients treated with indwelling catheterization, with or without preceding intermittent catheterization, were significantly more likely to experience UTIs. Therefore, in an effort to decrease the risk of UTIs, THA patients experiencing postoperative urinary retention should be treated with intermittent catheterization.

Substance abuse disorder (SUD), alcohol abuse disorder (AUD), and depression have been identified as independent risk factors for complications after total knee arthroplasty (TKA). However, these mental health disorders are highly co-associated, and their cumulative effect on postoperative complications have not been investigated. Therefore, this study aimed to determine if patients who have more than one mental health disorder (SUD, AUD, or depression) were at an increased risk for postoperative complications following TKA.A total of 11,403 TKA patients were identified from a prospectively collected institutional database between January 1, 2017 and April 1, 2019. Patients who had depression, SUD, and AUD were separated into 7 mental health subgroups including each of these diagnoses alone and their combined permeations. Patient demographics, body mass indices, medical comorbidities, and 15 postoperative complications were collected. Univariate analyses were performed using independent Student's t-tests. Multivariate analyses were then performed to identify odds ratios (ORs) for mental health disorders subgroups associated with complications.We found a total of 2073 (18%) patients diagnosed with either SUD (4%), AUD (0.6%), or depression (12%). Univariate analyses showed that depression was associated with mechanical failures (P.001). SUD was associated with periprosthetic joint infection (PJI) (P.001), wound complications (P = .022), and aseptic loosening (P = .007). AUD was associated with PJI (P.001) and deep vein thromboses (P = .003). Multivariate analyses found that AUD (OR: 19.419, P.001) and SUD (OR:3.693, P = .010) were independent risk factors for PJI. Compared with SUD alone, patients with depression plus SUD were found to have a 4-fold (OR: 13.639, P.001) and 2-fold (OR:4.401, P = .021) increased risk for PJI and cellulitis, respectively.Patients who had depression, SUD, or AUD were at increased risk for postoperative complications following primary TKA. When patients have more than one mental health diagnosis, their risk for complications was amplified. The results of this study can help identify those patients who are at greater risk of postoperative complications to enable improved preoperative optimization and patient education.

Although intermittent catheters are immediately removed, indwelling catheterization may lead to decreased ambulation and participation in physical therapy, critical components to post-total knee arthroplasty (TKA) management. Therefore, this study aimed to compare the effect of catheterization treatments on (1) postoperative ambulation distances, (2) deep vein thromboses (DVTs), and (3) pulmonary emboli (PEs) following TKA.A total of 9123 prospectively collected primary TKA patients were assessed based on postoperative catheter status. Patient demographics, Charlson Comorbidity Indices, body mass indices, DVT prophylaxes, first ambulation distances, DVTs, and PEs were collected at approximately mean 12 months of follow-up. Univariate and multivariate analyses were performed with independent t-tests and multiple linear regression models in order to compare catheterization techniques.There were 1193 patients who had urinary retention and treated with either indwelling only (62%, n = 734), both indwelling and intermittent catheterizations (13%, n = 160), or intermittent only (25%, n = 299). Multivariate analyses found that indwelling catheter-only use had an 11% decrease in ambulation distance (P.001). Additionally, the indwelling catheterization-only group was found to be at increased risk of DVTs (odds ratio 2.605, P.001), even after controlling for DVT prophylaxes (odds ratio 2.807, P.001).This study showed that the use of an indwelling catheter for treatment of urinary retention significantly decreased TKA patient ambulation distance and subsequently increased the risk for DVTs. This information is important as we would recommend the treatment with intermittent catheterization rather than indwelling catheters to decrease the risk of immobilization and postoperative DVTs.

Introduction:Robotic-arm assisted surgery allows for the execution of well-aligned knee arthroplasty regardless of pre-existing deformity. This case series is presented to show the utility of robotic-arm assisted TKA in achieving well-balanced, well-aligned results in a variety of challenging scenarios.Methods:We present seven challenging cases of robotic-arm assisted total knee arthroplasty. There were two conversion TKAs following a previous surgery. One case featured a previous tibial plateau fracture treated with a plate and screws construct while another featured a prior femoral nail with significant bony overgrowth. Five cases of severe deformity were also identified, with one tibial nonunion, two valgus knees and one patient with two varus knees due psoriatic arthritis treated with staged bilateral TKAs. Patient clinical history, physical examinations, intraoperative surgical techniques and postoperative courses were recorded.Results:All cases were able to utilize effective preoperative planning to obtain precise intraoperative bone cuts and component positioning. Each of the seven cases achieved well-balanced, well-aligned arthroplasties. There were no intraoperative or postoperative complications. At latest follow up, all patients showed significant improvements in pain and ambulation compared to preoperative exams.Discussion:Robotic-arm assisted surgery allows for the integration of preoperative CT scans to establish and execute a surgical plan with precision. Despite the complexity of these cases, excellent results were achieved without the need for revision-type components. These cases display the ability of robotic-arm assisted surgery to achieve consistent well-aligned results with minimal bone loss in challenging total knee arthroplasty cases.

Several recent intraoperative and wound management techniques have been developed and implemented in the United States over the past decade; however, it is unclear what the effects of these newer modalities have on reducing surgical site infection (SSI) rates. Therefore, the purpose of this study was to track the annual rate and trends of (1) overall, (2) deep, and (3) superficial SSIs following revision total knee arthroplasty (TKA). The National Surgical Quality Improvement Program database was queried for all revision TKA cases performed between 2011 and 2016, which yielded 9,887 cases. Cases with superficial and/or deep SSIs were analyzed separately and then combined to evaluate overall SSI rates. After an overall 6-year correlation and trends analysis, univariate analysis was performed to compare the most recent year, 2016, with the preceding 5 years. Correlation coefficients and chi-square tests were used to determine correlation and statistical significance. No significant correlations between combined, deep, and/or superficial SSI rates and year were noted (p > 0.05). The lowest overall SSI incidence was in 2012 (1.16%), while the greatest incidence was in 2014 (1.76%). The deep SSI incidence over the 6 years was 0.67% (66 out of 9,887 cases). Deep SSI rate decreased by 10% in 2016 compared with 2011 (0.50 vs. 0.56%, p > 0.05). In this 6-year period, 94 cases out of 9,887 were complicated by a superficial SSI, an incidence of 0.95%. The lowest superficial SSI incidence occurred in 2015 (n = 17, 0.77%). Overall, the incidence of SSIs in revision TKA has remained fairly low with some annual variance, indicating room for improvement. These variations likely as revision surgeries can be more complex and have several associated confounding factors influencing outcomes, when compared with primary cases. Further research is needed to identify revision-specific strategies to reduce the risk of surgical site infections.

BACKGROUND: Relative value units (RVUs) are a physician reimbursement model based on the effort required, or value, in providing a procedure or service for a patient. Procedures such as conversion total hip arthroplasties (THAs) can be compared to primary THAs, but many studies have revealed increased difficulties in conversion cases. Despite the increased time and effort for conversion THA, it is unknown if this is reflected in the RVU compensation model. Therefore, the purpose of this study was to compare the: (I) mean operative times; (II) mean RVUs; (III) RVU/minute for primary and conversion THAs; and (IV) perform an individualized idealized surgeon annual cost difference analysis. METHODS: A total of 103,702 primary THA patients were identified using CPT code 27130 and 2,986 conversion THA patients were identified using CPT code 27132 using the National Surgical Quality Improvement Program (NSQIP) database. The mean RVUs, operative times (minutes), and RVU/minute were calculated and compared. An annualize cost analysis of dollar amounts per case, day, and the year was also performed. RESULTS: The mean operative times for the primary and conversion THA cohorts were 94 vs. 146 minutes (P

The purpose of this study is to track the 30-day postoperative annual rates and trends of (1) overall, (2) deep, and (3) superficial surgical site infections (SSIs) following total hip arthroplasty (THA) using a large nationwide database.The National Surgical Quality Improvement Program database was queried for all THA cases performed between 2012 and 2016. After an overall 5-year correlation and trends analysis, univariate analysis was performed to compare the most recent year, 2016, with the preceding 4 years. Correlation coefficients and chi-squared tests were used to determine correlation and statistical significance.The lowest incidence of SSIs was in the most recent year, 2016 (0.81%), while the greatest incidence was in the earliest year, 2012 (1.12%), marking a 31% decrease (P.01). The lowest rate was in the most recent year, 2016 (0.23%), marking a 26% decrease from 2012. The lowest superficial SSI incidence occurred in the most recent year, 2016 (0.58%), while greatest incidence was in 2012 (0.83%), marking a 31% decrease over time (P.05). There was an inverse correlation among overall, deep, and superficial SSI rates with operative year.The findings from this study suggest a decreasing trend in SSIs within 30 days following THA. Furthermore, deep SSIs, which can pose substantial threats to implant survivorship, have also decreased throughout the years. These results highlight that potentially through improved medical and surgical techniques, we are winning the fight against short-term infections, but that more can still be done.

BACKGROUND: Revision total knee arthroplasty (TKA) is associated with increased rates of infections, readmissions, longer operative times, and lengths-of-stay (LOS) compared to primary TKA. Additionally, increasing operative times and prolonged postoperative LOS are independent risk factors for these postoperative complications in lower extremity total joint arthroplasty (TJA). This has led to an increased effort to reduce these risk factors in order to improve patient outcomes and reduce cost. However, the relationship between operative time and LOS has not been well assessed in revision arthroplasty. Therefore, the purpose of this study was to: (I) identify predictors of longer operative times; (II) identify predictors of longer LOS; and (III) evaluate the effects of operative time, treated as both a categorical variable and a continuous variable, on LOS after revision TKA. METHODS: The NSQIP database was queried for all revision TKA cases (CPT code 27487) between 2008 and 2016 which yielded 10,604 cases. Mean operative times were compared between patient demographics including age groups, sex, and body mass indexes (BMIs). To determine predictors of LOS, mean LOS were also compared between patient demographics in the same groups. To assess the correlation of operative time on LOS, the mean LOS for 30-minute operative time intervals were compared. Univariate analysis was performed with one-way analysis of variance (ANOVA) and t-tests. A multivariate analysis with a multiple linear regression model was performed to evaluate the association of LOS with operative times after adjusting for patient age, sex, and BMI. RESULTS: The mean LOS for revision TKA was 4 (±3) days. Further analysis showed that young age is associated with increased LOS (P

Owing to an extensive range of motion, the stability of the shoulder joint depends heavily on important ligament and muscular attachments. Overuse or acute injuries to any of these structures predisposes to the pathologic conditions of shoulder pain and instability. Isolation of anatomic structures through physical exam is crucial to develop a differential diagnosis and treatment plan.

The hip is a ball-and-socket joint with robust muscular attachments. Hip pain can originate from spinal, intra-articular, and systemic pathologic issues which often renders diagnosis difficult. Range of motion deficits, specific physical exam tests, and radiographic imaging are useful for developing a differential diagnosis.

The specific influence of operative times on lengths-of-stay (LOS) has not been well assessed and is therefore an important topic of evaluation for multiple reasons, including potential economic implication. The purpose of this study is to (1) identify predictors of longer operative times; (2) identify predictors of longer LOS; and (3) evaluate the effects of operative times on LOS in primary total knee arthroplasty (TKA).The National Surgical Quality Improvement Program database was queried for primary TKAs performed between 2008 and 2016, yielding 225,344 cases. Multivariate analysis was performed to determine the effect of operative times on LOS after adjusting for patient factors. Univariate analyses were performed with 1-way analysis of variance (ANOVA), linear regression, and independent sample t-tests where appropriate. Multivariate analysis was performed with a multiple linear regression model adjusted for patient age, sex, and body mass index (BMI).The mean operative time was 93 ± 35 minutes and the mean LOS was 3 ± 3 days. Young age, male sex, and obesity were predictors of longer operative times (P.001). Similarly, there were significant associations of age, sex, and BMI with LOS (P.001). Increasing 30-minute operative time intervals were associated with increasing LOS (P.001). Longer operative times had significant associations with longer LOS even after adjusting for patient factors (β = 0.076, SE0.001, P value.001). Out of all study covariates, operative times had the greatest effect on LOS.This study provides unique insight by directly correlating operative times to LOS in over 200,000 TKAs. The results from this study indicate that there is a strong correlation between operative times and LOS, so that operative time had a greater association than age, sex, and BMI with postoperative TKA LOS.

BACKGROUND: Elective total hip arthroplasties (THAs) entail a more extensive pre-operative planning process compared to non-elective THAs and this may contribute to a disparity in outcomes. However, the differences in peri- and post-operative outcomes between elective and non-elective THAs remain unclear. Therefore, the purpose of this study was to: (I) determine nationwide trends in operative times and (II) evaluate the association between surgery type, elective or non-elective with respect to (I) operative times; (II) hospital lengths-of-stay (LOS); (III) discharge disposition; (IV) 30-day post-operative complications; (V) reoperations; and (VI) readmissions. METHODS: The NSQIP database was queried for all primary THAs (CPT code 27130) performed between 2011 and 2016. This yielded 130,261 cases, which were then stratified into elective (n=125,293) and non-elective (n=4,968) cases. One-way analysis of variance (ANOVA) were used to evaluate the associations between operative times and surgery year. Univariate analyses of surgery type with the following outcomes of interest were also performed: operative times, LOS, and discharge disposition as well as 30-day complication, reoperation, and readmission rates. A multiple linear regression model was used to evaluate the relationships of operative times and LOS with surgery types after adjusting for surgery year and patient factors [age, sex, body mass index (BMI), and American Society of Anesthesiologists (ASA) score]. A log-transformed dependent variable was used to calculate the percentage difference in mean operative times and LOS. Multivariate logistic regression models adjusted for patient factors and year of surgery were used to evaluate associations of surgery type with complication, reoperation, and readmission rates. RESULTS: Over the 6-year period, mean operative times (93 vs. 103 minutes, P

BACKGROUND: Substantial efforts have been made to reduce the risk of infection after total hip arthroplasty (THA), including pre-operative patient optimization, skin preparation with alcohol-based solutions, perioperative antibiotics, and minimizing wound drainage with novel sutures and dressings. While these approaches have been effective in primary THA, their effects on revision THA to improve surgical site infection (SSI) rates are less clear. Therefore, the purpose of this study was to identify the annual rates and trends of: (I) overall; (II) deep; and (III) superficial SSIs following revision THA using the most recent results (2011 to 2016) from a large, nationwide database. METHODS: The National Surgical Quality Improvement Program (NSQIP) database was queried for all revision THA cases (CPT code 27134) between 2011 and 2016, yielding 8,562 cases. A steady increase in the total number of revision THA cases was observed from 2011 to 2016 (750 vs. 1,951, 260%). Cases with reported superficial and/or deep SSI were analyzed separately and then combined to evaluate overall SSI rates. The infection incidence for each year was calculated. After an overall 6-year correlation and trends analysis, univariate analysis was performed to compare the most recent year, 2016, with each of the preceding 5 years. Additionally, percent differences between 2016 and each previous year were calculated to evaluate rate changes. Pearson correlation coefficients and chi-squared tests were used to determine correlation and statistical significance which was maintained at a P value less than 0.05. RESULTS: There were 217 cases out of 8,562 (2.53% of all cases) complicated by any SSI. Overall, there was an inverse correlation between combined SSI rate and year, however, this was not statistically significant (P>0.05). The lowest incidence was in 2016 (n=41, 2.10%), while the highest incidence was in 2014 (n=45, 2.86%). The combined SSI rate in 2016 decreased by 22% when compared to 2015 (2.10% vs. 2.69%, P>0.05). A larger, 27% decrease in rate was found between 2016 and 2014 (2.10% vs. 2.86%, P>0.05). For deep SSI, there was an inverse correlation between rate and year of surgery, however, this was not statistically significant (P>0.05). The deep SSI incidence over the 5 years was 1.38% (118 out of 8,562 cases). There was a 35% decrease in deep SSI rate from 2016 to 2015 (0.92% vs. 1.43%, P>0.05). A larger, 53% decrease, was seen between 2016 and 2014 (0.92% vs. 1.04%, P0.05). In this 6-year period, 99 cases out of 8,562 were complicated by a superficial SSI; an incidence of 1.16%. The lowest incidence occurred in 2014 (n=14, 0.89%), while 2012 had the highest incidence (n=17, 1.61%). The rate in 2016 decreased by 6% when compared to 2015 (1.18% vs. 1.07%, P>0.05). A larger, 27% decrease in rate was observed between 2016 and 2012 (1.18% vs. 1.61%, P>0.05). CONCLUSIONS: Revision total hip arthroplasties exhibited a trend towards decreasing overall SSI nationwide between 2011 and 2016. Deep SSI rates had marked improvements, specifically between 2014 and 2016. This trend indicates some benefit from pre- and post-operative infection preventative strategies, but importantly, indicates continued room for improvement. Due to the potentially devastating complications associated with infection in revision THAs, further research is required to identify revision-specific strategies to lower the rates of SSIs.

The chemical composition and microstructure of reaction layers formed under the presence of lubricants with different wear and fatigue protection properties on cylindrical roller thrust bearings made of SAE 52100 (100Cr6) steel were analysed by transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the TEM investigations, thin cross-sections prepared by focused ion beam (FIB) techniques showed pores inside the reaction layers for the tribological systems lubricated with mineral oil. ToF-SIMS studies revealed that both the reaction and the tribomutation layers contain atomic incorporations of the oil additive formulations used. The nanomechanical properties of the different tribological layers were also analysed by static and dynamic nanoindentation. The results show that the nanomechanical properties vary strongly with the base oil and the specific additives and that these variations can also be correlated with the ToF-SIMS depth profile distributions. Our investigations reveal that wear protection not only relies on the lubricant-induced formation of a reaction layer, but even more on the properties of the combined protection layer system of a reaction layer and an underlying fine crystalline tribomutation layer. The properties of both parts of the tribological layer system are influenced by the lubricant additive formulation used.

PVD-Beschichtungen konnen die Eigenschaften trockenlaufender Hybridwalzlager verbessern. So kann der Verschleis, aber auch das Reibmoment mit ihrer Hilfe herabgesetzt werden. Um dies zu erreichen, wurden PVD-Schichten im Hinblick auf die auftretenden Belastungen weiterentwickelt. Untersuchungen mit Hilfe des standardisierten FE8-Walzlagerprufstands dienten zum Nachweis des Potentials der PVD-Beschichtungen fur den Trockenlauf. Die Ergebnisse dieser Untersuchung wiederum flossen in die Schichtentwicklung ein. PVD coatings for dry running hybrid roller bearings PVD coatings are able to improve the characteristics of dry running hybrid roller bearings. Wear and friction moment can be reduced by coatings. Therefore PVD coatings were adjusted for the appearing loads. Examinations with the help of the standardised FE8 test-rig were used to verify the potential of PVD coatings in dry running applications. The results of the tests were taken into account for further coating development.

In a tribological system consisting of roller thrust bearings and various lubricants, we investigated reaction layers formed in the presence of lubricants with low wear protection, high wear and fatigue protection as well as high wear but low fatigue protection. The bearings were tested under heavy-duty conditions in an FE-8 test rig in order to rapidly asses the efficiency of different reaction layer systems. Chemical composition and microstructure analysis of the layers was subsequently carried out by transmission electron microscopy on thin cross-sections prepared by the focused ion beam technique. The nanomechanical properties of the different tribological layers were analyzed by nanoindentation. The formation and structure of the layered system, and thus the ability to protect against wear and fatigue, depends on the lubricants and additives, respectively. Our results indicate that wear protection not only relies on the reaction layer itself but also on the properties of the combined system of the re...

The chemical composition and microstructure of reaction layers formed under the presence of lubricants with low wear protection, high wear and fatigue protection, and high wear but low fatigue protection on thrust cylindrical roller bearings made of 100Cr6 steel were analysed by transmission electron microscopy. Thin cross sections prepared by the focused ion beam technique were investigated. The nanomechanical properties of the different tribological layers were analysed by static and dynamic nanoindentation. Our results indicate that wear protection not only relies on the lubricant induced formation of a reaction layer, but also on the properties of the combined system of a reaction layer and an underlying tribomutation layer. The formation and structure of the layer system varies with the chemical nature of the basic oil. Our investigations show that its ability to protect against wear and fatigue strongly depends on the oil viscosity and the additives.

On the basis of cylindrical roller thrust bearings, it was systematically examined to what extent PVD coatings are able to take over the function of extreme pressure and anti-wear lubricant additives. The bearings were tested under heavy-duty conditions in order to quickly distinguish the efficiency of different coating substrate systems. Close regard is paid to the structure of the coatings. Two different (Crx,Al1−x)N coatings, one with a columnar structure and one with a fine-grained structure, are tested concerning wear protection and friction reduction. It is shown that PVD coatings are able to reduce friction enormously on the example of cylindrical roller thrust bearings. Friction coefficients measured on a pin on disc tester could not be correlated to the FE8 roller bearing test rig, where the values for friction were not distinguishable. The FE8 test rig tests roller bearings with a rolling and sliding motion in contrast to the pin on disc test where sliding friction is produced. So the friction in the roller bearing test is more complex and the sliding contact does not make a major contribution to the frictional torque. Nevertheless, the lower sliding friction of contacts, which can be tested in the pin on disc test, reduces shear stresses in the slippage zones of roller bearings. Here, sensitive columnar and fine-grained coatings with high-friction coefficients [(Crx,Al1−x)N] failed earlier than coatings with low friction values (ZrCg). Additionally, the wear protection of (Crx,Al1−x)N coatings could be increased by a fine-grained coating microstructure. This coating architecture is more able to withstand shear loads. The conclusions of these tests are the need of a coating with fine-grained structure and friction-reducing properties in the FE8 roller bearing test rig.

Zur Realisierung von umweltvertraglichen Tribosystemen werden im Sonderforschungsbereich SFB 442 PVD (Physical Vapour Deposition) -Schichtsysteme entwickelt, welche zusammen mit entfeinerten Schmierstoffen deren tribologische Eigenschaften verbessern. Bei Bewertung von Schicht-Substrat-Systemen fur den Einsatz in tribologischen System ist es von besonderer Bedeutung zu erfassen, welchen Beanspruchungen diese Systeme ausgesetzt sind und wie ihre Eigenschaften das Beanspruchungs-Kollektiv beeinflussen. Gegenstand der vorgestellten Untersuchungen ist eine Analyse der Parameter des Schicht-Substrat-Systems mit signifikanten Effekten der Oberflachenbeanspruchung. Dabei werden Unterschiede zu den bekannten Oberflachenbeanspruchungen der Massivwerkstoffe aufgezeigt und mathematische Modelle zur Beschreibung des Schicht-Substrat-Einflusses entwickelt. Ziel dieser Untersuchungen ist es, die im Tribosystem (z. B. Walzlager) auftretenden Belastungen mit denen in den Schicht-Prufverfahren (z. B. Rockwell-Haftklassenuntersuchung, Nanoindentermessung) aufgebrachten Belastungen in einen Zusammenhang zu stellen. Denn nur so ist es moglich, die in den Schicht-Prufverfahren gewonnenen Ergebnisse zur Bewertung eines Schicht-Substrat-Systems heranzuziehen. Entscheidendes Hilfsmittel ist hier die Simulation der mechanischen Oberflachenbeanspruchung mittels FEM (Finite Element Methode). Hiermit ist es moglich, den anisotropen und inhomogenen Werkstoffeigenschaften des Schicht-Substrat-Systems Rechnung zu tragen. Evaluation of Coating Substrate Compounds Strain Using Contact Stress Simulation For the realisation of environmental compatible tribosystem in collaborative research centre SFB 442 new PVD-coatings are developed. These improve combined with additive free lubricants the tribological characteristics of this tribosystem. To evaluate these coated compounds for the application in tribosystems, it is important to understand to which loading these systems are exposed to and how their properties affect their mechanical stress. The subject of the presented investigation is an analysis of which coated substrate systems parameter have significant effect on the system strains. The differences between known mechanical stress theories of bulk materials are pointed out and a mathematical model for the description of stresses are developed. The goal of this investigation is to find correlations between tribological loads (for example roller bearing) and coated substrate testing stresses (for example Rockwell test, Nanoindenter measurement). With these, it is possible to use the results of coated substrate tests to evaluate the coated substrate system. A crucial aid herein is the simulation of surface loading using FEM (Finite Element Method). With this method, it is possible to regard the anisotropic and inhomogeneous material characteristics of a coated substrate system.