Static Versus Articulating Spacer: Does Infectious Pathogen Type Affect Treatment Success?

BACKGROUND: Treatment with a static or an articulating antibiotic-containing spacer is a common strategy for treating periprosthetic joint infection (PJI), yet many patients have persistent infections after spacer treatment. Although previous studies have compared the efficacy of a static and articulating spacer for treating PJI, few studies have assessed infection control from the time of spacer implantation, or they defined treatment failure as including reinfection, reoperation, or chronic suppressive therapy. Additionally, few studies have examined whether there is an interaction between spacer and pathogen type with respect to treatment success. QUESTIONS/PURPOSES: (1) Is there a difference in failure-free survival (defined as no reoperation, reinfection, or suppressive antibiotic therapy) between static and articulating spacers after spacer implantation for PJI? (2) Did the relationship between spacer type and failure-free survival differ by pathogen type (staphylococcal versus nonstaphylococcal and difficult-to-treat [including methicillin-resistant Staphylococcus aureus, methicillin-susceptible S. aureus, Corynebacterium, Mycobacterium, Enterococcus spp, and other gram-negative bacterium] versus not-difficult-to-treat organisms)? METHODS: Between January 2014 and January 2022, a convenience sample of 277 patients was identified as having knee PJIs treated with an articulating (75% [208 of 277]) or static (25% [69 of 277]) antibiotic spacer and potentially eligible for this study. During that time, providers at our institution generally used spacers for later-presenting or chronic infections. Spacer choice was determined by surgeon preference, with static spacers used more often in instances of higher bone loss and poor soft tissue coverage. Thirty-one patients (8 static and 23 articulating spacers) were considered lost to follow-up or had incomplete datasets and were excluded from the analysis, resulting in a final analysis cohort of 246 patients: 25% (61 of 246) received a static spacer and 75% (185 of 246) received an articulating spacer. The mean ± standard deviation age of patients was 66 ± 9.9 years, BMI was 33.3 ± 6.9 kg/m2, and Elixhauser score was 18.1 ± 16.9. Demographic and clinical characteristics were similar between the two groups. Pathogen type was collected and categorized as staphylococcal versus nonstaphylococcal, and difficult-to-treat (including methicillin-resistant Staphylococcus aureus, methicillin-susceptible S. aureus, Corynebacterium, Mycobacterium, Enterococcus spp, and other gram-negative bacterium) versus not-difficult-to-treat, as defined by an infectious disease physician. Other variables we collected included sex, age, American Society of Anesthesiologists classification, BMI, and Elixhauser score. The primary outcome of interest was failure-free survival, which was a composite time-to-event outcome, with failure defined as reoperation, reinfection, death owing to infection, or chronic antibiotic use at a minimum of 1 year after the completion of the patient's Stage 1 postoperative antibiotic course, whichever came first. Reinfection was determined by the treating physicians in accordance with the Musculoskeletal Infection Society guidelines and included an evaluation of infectious laboratory values, cultures, and clinical signs of infection. We compared static and articulating spacers using a Cox proportional hazards model, with spacer type as the primary predictor variable. We compared staphylococcal versus nonstaphylococcal and difficult-to-treat versus not-difficult-to-treat infections by running additional models with interaction terms between spacer type and pathogen type. RESULTS: No difference was observed in the cause-specific hazard ratio for static versus articulating (reference) spacers (HR 1.45 [95% confidence interval 0.94 to 2.22]; p = 0.09), after adjusting for covariates. Additionally, no difference in the association between spacer type and failure-free survival was found between pathogen types or treatment difficulty after evaluating interactions (staphylococcal HR 0.37 [95% CI 0.15 to 0.91], nonstaphylococcal HR 0.79 [95% CI 0.49 to 1.28]; p value for interaction = 0.14; difficult-to-treat HR 0.37 [95% CI 0.14 to 0.99], not-difficult-to-treat HR 0.75 [95% CI 0.47 to 1.20]; p value for interaction = 0.20). CONCLUSION: The lack of a difference in failure-free survival and insufficient evidence of a difference in the association between spacer type and treatment failure by pathogen type suggests that infectious organism may not be an important consideration in the decision about spacer treatment type. Further studies should aim to elucidate which patient factors are the most influential in surgeon decision-making when choosing a spacer type in patients with PJI of the knee.Level of Evidence Level III, therapeutic study.

What Are the Underlying Mental Health Constructs Associated With Level of Capability in People With Knee and Hip Osteoarthritis?

BACKGROUND: Mental health characteristics such as negative mood, fear avoidance, unhelpful thoughts regarding pain, and low self-efficacy are associated with symptom intensity and capability among patients with hip and knee osteoarthritis (OA). Knowledge gaps remain regarding the conceptual and statistical overlap of these constructs and which of these are most strongly associated with capability in people with OA. Further study of these underlying factors can inform us which mental health assessments to prioritize and how to incorporate them into whole-person, psychologically informed care. QUESTIONS/PURPOSES: (1) What are the distinct underlying factors that can be identified using statistical grouping of responses to a multidimensional mental health survey administered to patients with OA? (2) What are the associations between these distinct underlying factors and capability in knee OA (measured using the Knee Injury and Osteoarthritis Outcome Score, Joint Replacement [KOOS JR]) and hip OA (measured using Hip Disability and Osteoarthritis Outcome Score, Joint Replacement [HOOS JR]), accounting for sociodemographic and clinical factors? METHODS: We performed a retrospective cross-sectional analysis of adult patients who were referred to our program with a primary complaint of hip or knee pain secondary to OA between October 2017 and December 2020. Of the 2006 patients in the database, 38% (760) were excluded because they did not have a diagnosis of primary osteoarthritis, and 23% (292 of 1246) were excluded owing to missing data, leaving 954 patients available for analysis. Seventy-three percent (697) were women, with a mean age of 61 ± 10 years; 65% (623) of patients were White, and 52% (498) were insured under a commercial plan or via their employer. We analyzed demographic data, patient-reported outcome measures, and a multidimensional mental health survey (the 10-item Optimal Screening for Prediction of Referral and Outcome-Yellow Flag [OSPRO-YF] assessment tool), which are routinely collected for all patients at their baseline new-patient visit. To answer our first question about identifying underlying mental health factors, we performed an exploratory factor analysis of the OSPRO-YF score estimates. This technique helped identify statistically distinct underlying factors for the entire cohort based on extracting the maximum common variance among the variables of the OSPRO-YF. The exploratory factor analysis established how strongly different mental health characteristics were intercorrelated. A scree plot technique was then applied to reduce these factor groupings (based on Eigenvalues above 1.0) into a set of distinct factors. Predicted factor scores of these latent variables were generated and were subsequently used as explanatory variables in the multivariable analysis that identified variables associated with HOOS JR and KOOS JR scores. RESULTS: Two underlying mental health factors were identified using exploratory factor analysis and the scree plot; we labeled them "pain coping" and "mood." For patients with knee OA, after accounting for confounders, worse mood and worse pain coping were associated with greater levels of incapability (KOOS JR) in separate models but when analyzed in a combined model, pain coping (regression coefficient -4.3 [95% confidence interval -5.4 to -3.2], partial R 2 0.076; p < 0.001) had the strongest relationship, and mood was no longer associated. Similarly, for hip OA, pain coping (regression coefficient -5.4 [95% CI -7.8 to -3.1], partial R 2 0.10; p < 0.001) had the strongest relationship, and mood was no longer associated. CONCLUSION: This study simplifies the multitude of mental health assessments into two underlying factors: cognition (pain coping) and feelings (mood). When considered together, the association between capability and pain coping was dominant, signaling the importance of a mental health assessment in orthopaedic care to go beyond focusing on unhelpful feelings and mood (assessment of depression and anxiety) alone to include measures of pain coping, such as the Pain Catastrophizing Scale or Tampa Scale for Kinesiophobia, both of which have been used extensively in patients with musculoskeletal conditions. LEVEL OF EVIDENCE: Level III, prognostic study.

Does Medically Supervised Weight Loss Prior to Total Knee Arthroplasty Improve Patient-Reported Pain and Physical Function?

BACKGROUND: Weight loss is commonly recommended before total knee arthroplasty (TKA) despite inconsistent evidence for better outcomes. This study sought to examine the impacts of preoperative weight loss on patient-reported and adverse outcomes among TKA patients supervised by a medical weight management clinic. METHODS: This study retrospectively analyzed patients who underwent medical weight management supervision within 18 months before TKA comparing patients who did and did not have clinically relevant weight loss. Preoperative body mass indices, demographics, Patient-Reported Outcomes Measurement Information System physical function and pain interference scores, pain intensity scores, and adverse outcomes were extracted. Multivariable linear regressions were performed to determine if preoperative weight loss correlated with patient-reported outcomes after controlling for confounders. RESULTS: There were 90 patients, 75.6% women, who had a mean age of 65 years (range, 42-82) and were analyzed. There were 51 (56.7%) patients who underwent clinically relevant weight loss with a mean weight loss of 10.4% and experienced no difference in adverse outcomes. Preoperative weight loss predicted significantly improved 3-month postoperative physical function (ß = 15.2 [13.0-17.3], P < .001), but not pain interference (ß = -18.9 [-57.1-19.4], P = .215) or pain intensity (ß = -1.8 [-4.9-1.2], P = .222) scores. CONCLUSION: We found that medically supervised preoperative weight loss predicted improvement in physical function 3 months after TKA. This weight loss caused no major adverse effects. Further research is needed to understand the causal relationships between preoperative weight loss, medical supervision, and outcome after TKA and to elucidate potential longer-term benefits in a larger sample.

Continuation of Oral Antidiabetic Medications Was Associated With Better Early Postoperative Blood Glucose Control Compared to Sliding Scale Insulin After Total Knee Arthroplasty.

BACKGROUND: This study evaluated blood glucose (BG), creatinine levels, metabolic issues, length of stay (LOS), and early postoperative complications in diabetic primary total knee arthroplasty (TKA) patients. It examined those who continued home oral antidiabetic medications and those who switched to insulin postoperatively. The hypothesis was that continuing home medications would lead to lower BG levels without metabolic abnormalities. METHODS: Patients who had diabetes who underwent primary TKA from 2013 to 2022 were evaluated retrospectively. Diabetic patients who were not on home oral antidiabetic medications or who were not managed as an inpatient postoperatively were excluded. Patient demographics and laboratory tests collected preoperatively and postoperatively as well as 90-day emergency department visits and 90-day readmissions, were pulled from electronic records. Patients were grouped based on inpatient diabetes management: continuation of home medications versus new insulin coverage. Acute postoperative BG control, creatinine levels, metabolic abnormalities, LOS, and early postoperative complications were compared between groups. Multivariable regression analyses were performed to measure associations. RESULTS: A total of 867 primary TKAs were assessed; 703 (81.1%) patients continued their home oral antidiabetic medications. Continuing home antidiabetic medications demonstrated lower median maximum inpatient BG (180.0 mg/dL versus 250.0 mg/dL; P < .001) and median average inpatient BG (136.7 mg/dL versus 173.7 mg/dL; P < .001). Logistic regression analyses supported the presence of an association (odds ratio = 17.88 [8.66, 43.43]; P < .001). Proportions of acute kidney injury (13.5 versus 26.7%; P < .001) were also lower. There was no difference in relative proportions of metabolic acidosis (4.4 versus 3.7%; P = .831), LOS (2.0 versus 2.0 days; P = .259), or early postoperative complications. CONCLUSIONS: Continuing home oral antidiabetic medications after primary TKA was associated with lower BG levels without an associated worsening creatinine or increase in metabolic acidosis. LEVEL III EVIDENCE: Retrospective Cohort Study.

Inertial Sensor Gait Analysis of Trendelenburg Gait in Patients Who Have Hip Osteoarthritis.

BACKGROUND: Gait abnormalities such as Trendelenburg gait (TG) in patients who have hip osteoarthritis (OA) have traditionally been evaluated using clinicians' visual assessment. Recent advances in portable inertial gait sensors offer more sensitive, quantitative methods for gait assessment in clinical settings. This study sought to compare sensor-derived metrics in a cohort of hip OA patients when stratified by clinical TG severity. METHODS: There were 42 patients who had hip OA and were grouped by TG severity (mild, moderate, and severe) through visual assessment by a single arthroplasty surgeon who had > 30 years of experience. After informed consent, wireless inertial sensors placed at the midpoint of the intercristal line collected gait parameters including pelvic shift, support time, toe-off symmetry, impact, and cadence. Clinical data on hip strength, range of motion, and Kellgren-Lawrence grade were collected. RESULTS: Worsening TG severity had a higher mean Kellgren-Lawrence grade (2.5 versus 3.2 versus 3.4; P = .014) and reduced passive hip abduction (P = .004). Severe TG group demonstrated predominantly contralateral pelvic shift (n = 9 of 10, 90.0%), while ipsilateral shift was more frequently detected in moderate (n = 10 of 18, 55.6%) and mild groups (n = 9 of 14, 64.3%; P = .021). Contralateral single support time bias was greatest in severe TG (35.7% versus 50.0 versus 90.0%; P = .027). Asymmetric toe-off, impact, and support times were observed in all groups. CONCLUSIONS: Traditional understanding of TG is that truncal shift occurs to the ipsilateral side. Using sensor-based measurements, the present study demonstrates a shift of the weight-bearing axis toward the contralateral side with increasing TG severity, which has not been previously described. Inertial sensors are feasible, quantitative gait measuring tools, and may reveal subtle patterns not readily discernible by traditional methods.

Unsuspected Positive Intraoperative Cultures in Aseptic Revision Knee Arthroplasty: Prevalence, Management, and Infection-Free Survivorship.

BACKGROUND: The purpose of this study was to evaluate the management and outcomes of aseptic revision total knee arthroplasty (arTKA) with unsuspected positive cultures (UPCs) compared to those with sterile cultures. METHODS: The institutional database at a single tertiary center was retrospectively reviewed for arTKA from January 2013 to October 2023. Patients who met Musculoskeletal Infection Society (MSIS) criteria for periprosthetic infection (PJI) based on available preoperative infectious workup, received antibiotic spacers, or did not have at least 1 year of follow-up were excluded. Patients were stratified based on intraoperative cultures into 4 cohorts: sterile cultures, 1 UPC, ≥ 2 UPCs with different organisms, and ≥ 2 UPCs with the same organism. Univariable analyses were used to compare these groups. Kaplan-Meyer survivorship analysis assessed infection-free survival at 5 years, and Cox proportional hazards regressions were used to evaluate factors that influence infection-free survival. A total of 691 arTKAs at a mean follow-up of 4.2 years were included in the study. Of these, 49 (7.1%) had 1 UPC with a new organism, 10 (1.4%) had ≥ 2 UPCs of the same organism, and 2 (0.2%) had ≥ 2 UPCs with different organisms. RESULTS: Postoperative antibiotics were prescribed to 114 (16.5%) patients - 13 (26.5%) with 1 UPC, 6 (60.0%) with ≥ 2 UPCs of the same organism, and 0 (0.0%) of patients who had ≥ 2 UPCs of different organisms. There were no differences in infection-free survival at 5 years between patients who had sterile cultures and 1 UPC (96 versus 89%; P = 0.39) nor between sterile cultures and ≥ 2 UPCs of different organisms (96 versus 100%; P < 0.72). However, patients who had ≥ 2 UPCs of the same organism had significantly worse infection-free survival at 5 years compared to patients who had sterile cultures (58 versus 96%; P < 0.001). Cox proportional hazards regression suggested that when adjusting for covariates, an American Society of Anesthesiologists classification of ≥ 3 (hazard ratio [HR] = 3.1; P = 0.007), ≥ 2 UPCs of the same organism (HR = 11.0; P < 0.001), 1 UPC (HR = 4.2; P = 0.018), and arTKA with hinge constructs (HR = 4.1; P = 0.008) were associated with increased risk of re-revision for PJI. CONCLUSION: Patients who had 1 UPC or ≥ 2 UPCs with different organisms had similar infection-free survival at 5 years as patients who had sterile cultures. However, patients who had ≥ 2 UPCs of the same organism had significantly worse infection-free survival at five years. Overall, 1 UPC or ≥ 2 UPCs of the same organism at the time of arTKA may suggest the patient is at higher risk of re-revision for PJI. More studies are needed to determine what interventions can be implemented to mitigate this risk.

D-Dimer, Erythrocyte Sedimentation Rate, and C-Reactive Protein Sensitivities for Periprosthetic Joint Infection Diagnosis.

BACKGROUND: There is contradicting evidence on the diagnostic value of inflammatory biomarkers for periprosthetic joint infection (PJI). We sought to quantify the sensitivity of D-dimer for acute and chronic PJI diagnosis and evaluate D-dimer lab values in the 90-day postoperative window in a control cohort of primary joint arthroplasty patients for comparison. METHODS: An institutional database was queried for patients undergoing revision procedures for PJI after total hip arthroplasty (THA) and total knee arthroplasty (TKA) from 2014 to present. CRP, ESR, and D-dimer were collected within 90 days pre and postoperatively and sensitivities for the diagnosis of PJI were calculated. The control group included patients who underwent a negative diagnostic workup for deep venous thrombosis (DVT) or pulmonary embolus (PE) and had a D-dimer lab collected within 90 days postoperatively from primary total joint arthroplasty (TJA). RESULTS: A total of 604 PJI patients were identified, and 81 patients had D-dimer, ESR, and CRP collected. There were 50/81 acute PJI patients and 31/81 chronic PJI patients who had median D-dimer values of 2,136.5 ng/mL [interquartile range (IQR): 1,642-3,966.5] and 3,336 ng/mL [IQR: 1,976-5,594]. Only the chronic PJI group had significantly higher D-dimer values when compared to the control cohort (P = .009). The sensitivity of D-dimer was calculated to be 92% and 93.5% in the acute and chronic PJI groups, respectively. CONCLUSION: Serum D-dimer may not have high diagnostic utility for acute PJI, especially in the setting of recent surgery; however, it still may be useful for patients who have chronic PJI.

Does Preoperative Weight Loss Within 6 Months or 1 Year Change the Risk of Adverse Outcomes in Total Knee Arthroplasty by Initial Body Mass Index Classification?

BACKGROUND: High body mass index (BMI) is associated with adverse outcomes after total knee arthroplasty (TKA). Thus, many patients are advised to lose weight before TKA. This study examined how weight loss before TKA is associated with adverse outcomes depending on patients' initial BMI. METHODS: This was a retrospective study of 2,110 primary TKAs at a single academic center. Data on preoperative BMIs, demographics, comorbidities, and incidences of revision or prosthetic joint infection (PJI) were obtained. Multivariable logistic regressions segmented by patients' initial (1-year preoperative) BMI classifications were performed to determine if a > 5% BMI decrease from 1 year or 6 months preoperatively predicted PJI and revision controlling for patient age, race, sex, and Elixhauser comorbidity index. RESULTS: Preoperative weight loss did not predict adverse outcomes for patients who had Obesity Class II or III. 6-month weight loss had greater odds of adverse outcomes than 1-year weight loss and most significantly predicted the occurrence of 1-year PJI (adjusted odds ratio: 6.55, P < .001) for patients who had Obesity Class 1 or lower. CONCLUSION: This study does not show a statistically significant effect to patients who had Obesity Class II and III losing weight preoperatively with respect to PJI or revision. For patients who have Obesity Class I or lower pursuing TKA, future research should consider potential risks associated with weight loss. Further study is needed to determine if weight loss can be implemented as a safe and effective risk reduction strategy for specific BMI classes of TKA patients.

A Permanent Articulating Spacer Versus Two-Stage Exchange for Chronic Periprosthetic Joint Infection: A Propensity Score-Matched Study.

BACKGROUND: Although 2-stage revision has been proposed as gold standard for periprosthetic joint infection treatment, limited evidence exists for the role of articulating spacers as definitive management. The purpose of this study was to compare clinical outcomes and costs associated with articulating spacers (1.5-stage) and a matched 2-stage cohort. METHODS: A retrospective review was performed for patients who had chronic periprosthetic joint infections after total knee arthroplasty defined by Musculoskeletal Infection Society criteria and were matched via propensity score matching using cumulative Musculoskeletal Infection Society scores and a comorbidity index. Patients who maintained an articulating spacer (cemented cobalt-chrome femoral component and all-poly tibia) were included in the 1.5-stage cohort. Patients who underwent a 2-stage reimplantation procedure were included in the 2-stage cohort. Outcomes included visual analog scale pain scores, 90-day emergency department visits, 90-day readmission, unplanned reoperation, reinfection, as well as cost at 1 and 2-year intervals. A total of 116 patients were included for analyses. RESULTS: The 90-day pain scores were lower in the 1.5-stage cohort compared to the 2-stage cohort (2.9 versus 4.6, P = .0001). There were no significant differences between readmission and reoperation rates. Infection clearance was equivalent at 79.3% for both groups. Two-stage exchange demonstrated an increased cost difference of $26,346 compared to 1.5-stage through 2 years (P = .0001). Regression analyses found 2 culture-positive results with the same organism decreased the risk for reinfection [odds ratio: 0.2, 95% confidence interval 0.04-0.8, P = .03]. CONCLUSION: For high-risk candidates, articulating spacers can preserve knee function, reduce morbidity from second-stage surgery, and lower the costs with similar rates of infection clearance as 2-stage exchange. LEVEL OF EVIDENCE: Level III, therapeutic study.

A Validated Pre-operative Risk Prediction Tool for Extended Inpatient Length of Stay Following Primary Total Hip or Knee Arthroplasty.

BACKGROUND: As value-based reimbursement models mature, understanding the potential trade-off between inpatient lengths of stay and complications or need for costly postacute care becomes more pressing. Understanding and predicting a patient's expected baseline length of stay may help providers understand how best to decide optimal discharge timing for high-risk total joint arthroplasty (TJA) patients. METHODS: A retrospective review was conducted of 37,406 primary total hip (17,134, 46%) and knee (20,272, 54%) arthroplasties performed at two high-volume, geographically diverse, tertiary health systems during the study period. Patients were stratified by 3 binary outcomes for extended inpatient length of stay: 72 + hours (29%), 4 + days (11%), or 5 + days (5%). The predictive ability of over 50 sociodemographic/comorbidity variables was tested. Multivariable logistic regression models were created using institution #1 (derivation), with accuracy tested using the cohort from institution #2 (validation). RESULTS: During the study period, patients underwent an extended length of stay with a decreasing frequency over time, with privately insured patients having a significantly shorter length of stay relative to those with Medicare (1.9 versus 2.3 days, P < .0001). Extended stay patients also had significantly higher 90-day readmission rates (P < .0001), even when excluding those discharged to postacute care (P < .01). Multivariable logistic regression models created from the training cohort demonstrated excellent accuracy (area under the curve (AUC): 0.755, 0.783, 0.810) and performed well under external validation (AUC: 0.719, 0.743, 0.763). Many important variables were common to all 3 models, including age, sex, American Society of Anesthesiologists (ASA) score, body mass index, marital status, bilateral case, insurance type, and 13 comorbidities. DISCUSSION: An online, freely available, preoperative clinical decision tool accurately predicts risk of extended inpatient length of stay after TJA. Many risk factors are potentially modifiable, and these validated tools may help guide clinicians in preoperative patient counseling, medical optimization, and understanding optimal discharge timing.

Cutibacterium positive cultures in total joint arthroplasty: a comparison of the hip, knee, and shoulder.

PURPOSE: Cutibacterium spp. (formerly Propionibacterium) is a slow growing, Gram-positive, anaerobic bacteria and is an emerging clinical entity in prosthetic joint infection (PJI). This study compares the presentation, surgical management, and post-operative antibiotic therapy of patients with positive intraoperative cultures during revision total joint arthroplasty (TJA) of the hip, knee, and shoulder. METHODS: This was a retrospective cohort study of patients from 2014 to 2020 of 57 revision TJAs (27 total hip arthroplasty (THA), 17 total shoulder arthroplasty (TSA), and 13 total knee arthroplasty (TKA)) with intraoperative cultures positive for Cutibacterium at a tertiary academic centre. Patient demographics, pre-operative labs, radiographs, and aspirate results were collected. Intraoperative data was reviewed. Post-operative antibiotic therapy and repeat infections were recorded. Data was compared with univariate analyses. RESULTS: There was no significant difference in pre-operative lab values between the cohorts. All cohorts had > 58% radiographic lucency. Revision TSA patients had significantly fewer pre-operative aspirates. Six patients undergoing revision THA, three TKA and one TSA had a repeat infection requiring further surgery. Four in the THA cohort and one in the TKA cohort with repeat infections did not receive prolonged antibiotic therapy. CONCLUSION: Cutibacterium is an infectious agent that can present in an indolent fashion after TJA. It commonly causes progressive radiographic lucency. The workup and post-operative management differs in the hip, knee, and shoulder, which is likely due to existing literature guiding physician practice. In all joints, Cutibacterium is a virulent pathogen that can cause repeat infections requiring surgical treatment.

Cutibacterium Positive Cultures in Total Hip Arthroplasty: Contaminant or Pathogen?

BACKGROUND: Cutibacterium spp. is an emerging pathogen in total hip arthroplasty (THA) that is not well evaluated in the literature. This study reported on the presentation and management of THA complicated by positive intraoperative Cutibacterium cultures. METHODS: This is a retrospective review of 27 revision THAs with positive monomicrobial intraoperative Cutibacterium cultures from 2014 to 2020 at one academic center. These patients were divided into two cohorts based on meeting Musculoskeletal Infection Society (MSIS) criteria for prosthetic joint infections (PJI). Patient demographics, preoperative labs, and hip aspirate results were collected. Procedure performed, postoperative antibiotic regimens, and repeat infections were recorded. Data were compared with univariate analysis. RESULTS: Nine of the 27 patients preoperatively met MSIS criteria for PJI. Patients with positive MSIS criteria had significantly higher median synovial cell count (P = .048) and neutrophil percentage in a preoperative aspirate (P = .050). Eight patients with positive MSIS criteria received six weeks of postoperative antibiotics compared to two patients with negative criteria. Two patients with positive MSIS criteria had a postoperative infection that required further surgical intervention. Four patients with negative criteria who required further surgical intervention did not receive postoperative antibiotics after initial revision. CONCLUSION: While often categorized as a contaminant, Cutibacterium is an increasingly recognized pathogen in THA. Cutibacterium can often present with normal serology, which may result in misdiagnosis as aseptic THA failure. Without the administration of postoperative antibiotics after positive cultures, there is a risk for persistent infection requiring further surgical intervention.

Patterns and Predictors of Weight Change Before and After Total Hip Arthroplasty in Class 2 and 3 Obese Patients.

BACKGROUND: This study aimed to better understand body mass index (BMI) change patterns and factors associated with BMI change before and after total hip arthroplasty (THA) in Class 2 and 3 obese patients, and assess if preoperative or postoperative BMI change affects postoperative clinical outcomes. METHODS: We retrospectively reviewed World Health Organization Class 2 and 3 obese patients (BMI > 35.0 at surgery) who underwent THA at a tertiary medical center from 2010 to 2020. BMI was recorded at 1 year preoperatively (mean 11.6 months), and at most recent postoperative visit (mean 29.0 months). Baseline demographics and postoperative clinical outcomes were recorded. RESULTS: We reviewed 436 THAs with a mean age of 59.9 (11.5) years. Leading up to surgery 55.5% had unchanged BMI, and postoperatively 48.2% had unchanged BMI. Multivariate logistic regression revealed that those who lost BMI preoperatively were more likely to gain BMI postoperatively (odds ratio [OR] 3.28, confidence interval [CI] 1.83-5.97, P = .005), but those who gained >5% BMI preoperatively had no association with BMI change postoperatively. Those in a higher BMI class preoperatively were less likely to gain BMI preoperatively (Class 3 obese patients: OR 0.001, CI 0.0002-0.004, P < .001). African American patients were more likely to gain BMI preoperatively (OR 2.32, CI 1.16-4.66, P = .017). We did not detect an association between BMI change and postoperative clinical outcomes. CONCLUSION: In World Health Organization Class 2 or 3 obese patients, most maintained BMI between their first preoperative and final postoperative visit. Preoperatively, Class 3 obese patients were less likely to gain weight than Class 2 obese patients. The primary predictor of postoperative weight gain was preoperative weight loss. Weight change preoperatively and postoperatively were not associated with worse clinical outcomes.

Prosthetic Knee Infection With Coagulase-Negative Staphylococcus: A Harbinger of Poor Outcomes.

BACKGROUND: Coagulase-negative staphylococci (CoNS) are biofilm-producing pathogens whose role in periprosthetic joint infection (PJI) is increasing. There is little data on the prognosis and treatment considerations in the setting of PJI. We sought to evaluate the clinical characteristics, outcomes, and complications in these patients. METHODS: This is a retrospective cohort study of adult patients at a single tertiary medical center from 2009 to 2020 with culture-proven CoNS PJI after total knee arthroplasty, as diagnosed by Musculoskeletal Infection Society criteria. The primary outcome was treatment success, with failure defined as recurrent CoNS PJI, recurrent PJI with a new pathogen, and/or chronic oral antibiotic suppression at one year postoperatively. RESULTS: We identified 55 patients with a CoNS total knee arthroplasty PJI with a mean follow-up of 29.8 months (SD: 16.3 months). The most commonly isolated organism was Staphylococcus epidermidis (n = 36, 65.5%). The overall prevalence of methicillin resistance was 63%. Surgical treatment included surgical debridement, antibiotics, and implant retention in 25 (45.5%) cases and two-stage revision (22 articulating and eight static antibiotic-impregnated spacers). At one-year follow-up, only 47% of patients had successful management of their infection. The surgical debridement, antibiotics, and implant retention cohort had the higher rate of treatment failure (60.0%) compared to two-stage revision (46.7%). CONCLUSION: These results indicate a poor rate of success in treating CoNS PJI. This likely represents the interplay of inherent virulence through biofilm formation and decreased antibiotic efficacy.

Resilience and pain catastrophizing among patients with total knee arthroplasty: a cohort study to examine psychological constructs as predictors of post-operative outcomes.

BACKGROUND: Patients' psychological health may influence recovery and functional outcomes after total knee arthroplasty (TKA). Pain catastrophizing, known to be associated with poor function following TKA, encompasses rumination, magnification, and helplessness that patients feel toward their pain. Resilience, however, is an individual's ability to adapt to adversity and may be an important psychological construct that supersedes the relationship between pain catastrophizing and recovery. In this study we sought to identify whether pre-operative resilience is predictive of 3-month postoperative outcomes after adjusting for pain catastrophizing and other covariates. METHODS: Patients undergoing TKA between January 2019 and November 2019 were included in this longitudinal cohort study. Demographics and questionnaires [Brief Resilience Scale (BRS), Pain Catastrophizing Scale (PCS), Knee injury and Osteoarthritis Outcome Score, Junior (KOOS, JR.) and Patient-Reported Outcomes Measurement Information System Physical and Mental Health (PROMIS PH and MH, respectively)] were collected preoperatively and 3 months postoperatively. Multivariable regression was used to test associations of preoperative BRS with postoperative outcomes, adjusting for PCS and other patient-level sociodemographic and clinical characteristics. RESULTS: The study cohort included 117 patients with a median age of 67.0 years (Q1-Q3: 59.0-72.0). Fifty-three percent of patients were women and 70.1% were white. Unadjusted analyses identified an association between resilience and post-operative outcomes and the relationship persisted for physical function after adjusting for PCS and other covariates; in multivariable linear regression analyses, higher baseline resilience was positively associated with better postoperative knee function (ß = 0.24, p = 0.019) and better general physical health (ß = 0.24, p = 0.013) but not general mental health (ß = 0.04, p = 0.738). CONCLUSIONS: Our prospective cohort study suggests that resilience predicts postoperative knee function and general physical health in patients undergoing TKA. Exploring interventions that address preoperative mental health and resilience more specifically may improve self-reported physical function outcomes of patients undergoing TKA.

Do Fixed or Mobile Bearing Implants Have Better Survivorship in Medial Unicompartmental Knee Arthroplasty? A Study From the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: During the last 5 years, there has been an increase in the use of unicompartmental knee arthroplasty (UKA) to treat knee osteoarthritis in Australia, and these account for almost 6% of annual knee replacement procedures. However, there is debate as to whether a fixed bearing or a mobile bearing design is best for decreasing revision for loosening and disease progression as well as improving survivorship. Small sample sizes and possible confounding in the studies on the topic may have masked differences between fixed and mobile bearing designs. QUESTIONS/PURPOSES: Using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), we selected the four contemporary designs of medial compartment UKA: mobile bearing, fixed modular, all-polyethylene, and fixed molded metal-backed used for the treatment of osteoarthritis to ask: (1) How do the different designs of unicompartmental knees compare with survivorship as measured by cumulative percentage revision (CPR)? (2) Is there a difference in the revision rate between designs as a function of patient sex or age? (3) Do the reasons for revision differ, and what types of revision procedures are performed when these UKA are revised? METHODS: The AOANJRR longitudinally maintains data on all primary and revision joint arthroplasties, with nearly 100% capture. The study population included all UKA procedures undertaken for osteoarthritis between September 1999 and December 2018. Of 56,628 unicompartmental knees recorded during the study period, 50,380 medial UKA procedures undertaken for osteoarthritis were included in the analysis after exclusion of procedures with unknown bearing types (31 of 56,628), lateral or patellofemoral compartment UKA procedures (5657 of 56,628), and those performed for a primary diagnosis other than osteoarthritis (560 of 56,628). There were 50,380 UKA procedures available for analysis. The study group consisted of 40% (20,208 of 50,380) mobile bearing UKA, 35% (17,822 of 50,380) fixed modular UKA, 23% (11,461 of 50,380) all-polyethylene UKA, and 2% (889 of 50,380) fixed molded metal-backed UKA. There were similar sex proportions and age distributions for each bearing group. The overall mean age of patients was 65 ± 9.4 years, and 55% (27,496 of 50,380) of patients were males. The outcome measure was the CPR, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the first revision. Hazard ratios from Cox proportional hazards models, adjusted for sex and age, were performed to compare the revision rates among groups. The cohort was stratified into age groups of younger than 65 years and 65 years and older to compare revision rates as a function of age. Differences among bearing groups for the major causes and modes of revision were assessed using hazard ratios. RESULTS: At 15 years, fixed modular UKA had a CPR of 16% (95% CI 15% to 17%). In comparison, the CPR was 23% (95% CI 22% to 24%) for mobile bearing UKA, 26% (95% CI 24% to 27%) for all-polyethylene UKA, and 20% (95% CI 16% to 24%) for fixed molded metal-backed UKA. The lower revision rate for fixed modular UKA was seen through the entire period compared with mobile bearing UKA (hazard ratio 1.5 [95% CI 1.4 to 1.6]; p < 0.001) and fixed molded metal-backed UKA (HR 1.3 [95% CI 1.1 to 1.6]; p = 0.003), but it varied with time compared with all-polyethylene UKA. The findings were consistent when stratified by sex or age. Although all-polyethylene UKA had the highest revision rate overall and for patients younger than 65 years, for patients aged 65 years and older, there was no difference between all-polyethylene and mobile bearing UKA. When compared with fixed modular UKA, a higher revision risk for loosening was shown in both mobile bearing UKA (HR 1.7 [95% CI 1.5 to 1.9]; p < 0.001) and all-polyethylene UKA (HR 2.4 [95% CI 2.1 to 2.7]; p < 0.001). The revision risk for disease progression was higher for all-polyethylene UKA at all time points (HR 1.4 [95% CI 1.3 to 1.6]; p < 0.001) and for mobile bearing UKA after 8 years when each were compared with fixed modular UKA (8 to 12 years: HR 1.4 [95% CI 1.2 to 1.7]; p < 0.001; 12 or more years: HR 1.9 [95% CI 1.5 to 2.3]; p < 0.001). The risk of revision to TKA was higher for mobile bearing UKA compared with fixed modular UKA (HR 1.4 [95% CI 1.3 to 1.5]; p < 0.001). CONCLUSION: If UKA is to be considered for the treatment of isolated medial compartment osteoarthritis, the fixed modular UKA bearing has the best survivorship of the current UKA designs. LEVEL OF EVIDENCE: Level III, therapeutic study.

Outpatient Total Joint Arthroplasty: The New Reality.

As perioperative protocols have improved, there has been a reduction in the rates of key complications after hip and knee arthroplasty. Likewise, as we have been able to make patients more comfortable postoperatively, hospital length of stay has decreased and in some centers, hip and knee arthroplasty is now routinely performed as an outpatient. While the number of surgeons offering this option and patients choosing to have procedures performed as an outpatient grows, many questions revolve around this movement. This article will review the data supporting outpatient arthroplasty, the business and legal aspects involved, if surgeons can align with their hospital to offer these services, and how tightly knit and highly organized teams are key to the success of safely offering hip and knee arthroplasty on an outpatient basis.

A Preoperative Risk Prediction Tool for Discharge to a Skilled Nursing or Rehabilitation Facility After Total Joint Arthroplasty.

BACKGROUND: Discharge to rehabilitation or a skilled nursing facility (SNF) after total joint arthroplasty remains a primary driver of cost excess for bundled payments. An accurate preoperative risk prediction tool would help providers and health systems identify and modulate perioperative care for higher risk individuals and serve as a vital tool in preoperative clinic as part of shared decision-making regarding the risks/benefits of surgery. METHODS: A total of 10,155 primary total knee (5,570, 55%) and hip (4,585, 45%) arthroplasties performed between June 2013 and January 2018 at a single institution were reviewed. The predictive ability of 45 variables for discharge location (SNF/rehab vs home) was tested, including preoperative sociodemographic factors, intraoperative metrics, postoperative labs, as well as 30 Elixhauser comorbidities. Parameters surviving selection were included in a multivariable logistic regression model, which was calibrated using 20,000 bootstrapped samples. RESULTS: A total of 1786 (17.6%) cases were discharged to a SNF/rehab, and a multivariable logistic regression model demonstrated excellent predictive accuracy (area under the receiver operator characteristic curve: 0.824) despite requiring only 9 preoperative variables: age, partner status, the American Society of Anesthesiologists score, body mass index, gender, neurologic disease, electrolyte disorder, paralysis, and pulmonary circulation disorder. Notably, this model was independent of surgery (knee vs hip). Internal validation showed no loss of accuracy (area under the receiver operator characteristic curve: 0.8216, mean squared error: 0.0004) after bias correction for overfitting, and the model was incorporated into a readily available, online prediction tool for easy clinical use. CONCLUSION: This convenient, interactive tool for estimating likelihood of discharge to a SNF/rehab achieves excellent accuracy using exclusively preoperative factors. These should form the basis for improved reimbursement legislation adjusting for patient risk, ensuring no disparities in access arise for vulnerable populations. LEVEL OF EVIDENCE: III.

Cost of Aseptic Revision Total Knee Arthroplasty at a Tertiary Medical Center.

BACKGROUND: Revision total knee arthroplasty (TKA) involves varying levels of case complexity and costs depending on the following: (1) number of components revised, (2) duration of operating room time, and (3) length of hospital stay. However, the cost associated with different types of aseptic TKA revisions, based on number and type of components revised, is not well described. We sought to determine differences in cost associated with different revision types, and to correlate this with average national hospital and surgeon reimbursement based on current Centers for Medicare and Medicaid Services data. METHODS: This is a retrospective review of aseptic revision TKAs performed at a single tertiary referral center from 2015 to 2018. Patient demographic data, operating room time, and direct surgery and total hospital costs obtained from an internal accounting database (Enterprise Performance Systems, Inc) were collected. Patients were stratified by the components revised (polyethylene liner only, tibia only, femur only, or both femur and tibia). We hypothesized that direct surgery and total hospital costs would increase as case complexity increased from poly exchange to single-component revisions and both-component revisions. RESULTS: In total, 106 patients were included (19 poly exchanges, 10 tibia-only revisions, 13 femur-only revisions, and 64 both-component revisions). Operating room time was significantly lower for poly exchange than all other groups (P < .001). Direct surgery and total hospital costs were significantly lower for poly exchange than all other groups (P < .001), and were significantly lower for tibia-only and femur-only revisions compared to both-component revisions (P < .001). Average national surgeon reimbursement by Medicare decreased as a percentage of direct surgery cost as case complexity increased from poly exchange to tibia-only, femur-only, and both-component revisions. Total hospital cost per average Diagnosis Related Group weight was lowest for single-component revisions and highest for both-component revision. CONCLUSION: There are significant differences in cost associated with aseptic TKA revisions based on number and type of components revised. These differences may not be accurately reflected in reimbursement, and often represent a burden to those who treat complex revisions.

A Case Complexity Modifier Is Warranted for Primary Total Knee Arthroplasty.

BACKGROUND: The Center for Medicare and Medicaid Services is faced with a challenge of decreasing the cost of care for total knee arthroplasty (TKA) but must make efforts to prevent patient selection bias in the process. Currently, no appropriate modifier codes exist for primary TKA based on case complexity. We sought to determine differences in perioperative parameters for patients with complex primary TKA with the hypothesis that they would require increased cost of care, prolonged care times, and have worse postoperative outcome metrics. METHODS: We performed a single-center retrospective review from 2015 to 2018 of all primary TKAs. Patient demographics, medial proximal tibial angle (mPTA), lateral distal femoral angle (lDFA), flexion contracture, cost of care, and early postoperative outcomes were collected. Complex patients were defined as those requiring stems or augments, and multivariable logistic regression analysis and propensity score matching were performed to evaluate perioperative outcomes. RESULTS: About 1043 primary TKAs were studied, and 84 patients (8.3%) were deemed complex. For this cohort, surgery duration was greater (P < .001), cost of care higher (P < .001), and patients had a greater likelihood for 90-day hospital return. Deviation of mPTA and lDFA was significantly greater preoperatively before and after propensity score matching. Cut point analysis demonstrated that preoperative mPTA <83o or >91o, lDFA <84o or >90o, flexion contracture >10o, and body mass index >35.7 were associated with complex procedures. CONCLUSION: Complex primary TKA may be identifiable preoperatively and those cases associated with prolonged operative time, excess hospital cost of care, and increased 90-day hospital returns. This should be considered in future reimbursement models to prevent patient selection bias, and a complexity modifier is warranted.