Diagnosis-Specific Thresholds of the Minimal Clinically Important Difference and Patient Acceptable Symptom State for KOOS After Total Knee Arthroplasty

UPDATE

This article was updated on May 1, 2024 because of a previous error, which was discovered after the preliminary version of the article was posted online. The byline that had read "Ahmed K. Emara, MD 1 *, Ignacio Pasqualini, MD 1 *, Alison K. Klika, MS 1 , Melissa N. Orr, BS 1 , Pedro J. Rullán, MD 1 , Nicolas S. Piuzzi, MD 1 , and the Cleveland Clinic Arthroplasty Group†" now reads "Ahmed K. Emara, MD 1 *, Ignacio Pasqualini, MD 1 *, Yuxuan Jin, MS 1 , Alison K. Klika, MS 1 , Melissa N. Orr, BS 1 , Pedro J. Rullán, MD 1 , Nicolas S. Piuzzi, MD 1 , and the Cleveland Clinic Arthroplasty Group†".

BACKGROUND

Literature-reported minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) thresholds for patient-reported outcome measures demonstrate marked variability. The purpose of this study was to determine the minimal detectable change (MDC), MCID, and PASS thresholds for the Knee injury and Osteoarthritis Outcome Score (KOOS) Pain subdomain, Physical Function Short Form (PS), and Joint Replacement (JR) among patients with osteoarthritis (OA) who underwent primary total knee arthroplasty (TKA).

METHODS

A prospective cohort of 6,778 patients who underwent primary TKA was analyzed. Overall, 1-year follow-up was completed by 5,316 patients for the KOOS Pain, 5,018 patients for the KOOS PS, and 4,033 patients for the KOOS JR. A total of 5,186 patients had an OA diagnosis; this group had an average age of 67.0 years and was 59.9% female and 80.4% White. Diagnosis-specific MDCs and MCIDs were estimated with use of a distribution-based approach. PASS values were estimated with use of an anchor-based approach, which corresponded to a response to a satisfaction question at 1 year postoperatively.

RESULTS

The MCID thresholds for the OA group were 7.9 for the KOOS Pain, 8.0 for the KOOS PS, and 6.7 for the KOOS JR. A high percentage of patients achieved the MCID threshold for each outcome measure (KOOS Pain, 95%; KOOS PS, 88%; and KOOS JR, 94%). The MDC 80% to 95% confidence intervals ranged from 9.1 to 14.0 for the KOOS Pain, 9.2 to 14.1 for the KOOS PS, and 7.7 to 11.8 for the KOOS JR. The PASS thresholds for the OA group were 77.7 for the KOOS Pain (achieved by 73% of patients), 70.3 for the KOOS PS (achieved by 68% of patients), and 70.7 for the KOOS JR (achieved by 70% of patients).

CONCLUSIONS

The present study provided useful MCID, MDC, and PASS thresholds for the KOOS Pain, PS, and JR for patients with OA. The diagnosis-specific metrics established herein can serve as benchmarks for clinically meaningful postoperative improvement. Future research and quality assessments should utilize these OA-specific thresholds when evaluating outcomes following TKA. Doing so will enable more accurate determinations of operative success and improvements in patient-centered care.

LEVEL OF EVIDENCE

Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Trends in prevalence and complications for smokers who underwent total hip arthroplasty from 2011 to 2019: an analysis of 243,163 patients

BACKGROUND

Smoking is an established risk factor for postoperative complications after total hip arthroplasty (THA). It is unknown if the decreasing prevalence of adult smoking in the United States is reflected in the elective THA patient population. We aimed to investigate recent trends in: (1) the prevalence of smoking pre-THA, stratified by patient demographics; and (2) rates of 30-day complications and increased healthcare utilisation post-THA in smokers versus non-smokers.

METHODS

Patients who underwent primary elective THA (2011-2019) were identified using the National Surgical Quality Improvement Program database. A total of 243,163 cases (Smokers: n = 30,536; Non-smokers: n = 212,627) were included. Trends analyses were performed for smoking prevalence across the study period. Smokers were propensity score-matched (1:1) to a cohort of non-smokers (n = 29,628, each), and rates of 30-day complications, readmission, and non-home discharge were compared.

RESULTS

The rate of preoperative smoking significantly decreased from 14.0% in 2011 to 11.6% in 2019 (p-trend = 0.0286). When stratified, a significant decreasing trend in smoking was found for males and all races; within races, American-Indian/Alaska-Native race had the sharpest decline (2011:36.3% vs. 2019:23.2%). No significant change in 30-day complication rates among smokers or non-smokers was observed (p-trend > 0.05), but non-home discharge significantly decreased for both smokers (p-trend = 0.001) and non-smokers (p-trend < 0.001). After matching, higher rates of superficial surgical site infections (SSI) (0.9% vs. 0.5%; p < 0.001), deep SSI (0.5% vs. 0.3%; p < 0.001), wound disruption (0.2% vs. 0.1%; p = 0.006), and readmission (4.2% vs. 3.1%; p = <0.001) were found in smokers versus non-smokers.

CONCLUSIONS

The present study is encouraging that national efforts to reduce the prevalence of smoking may be successful within the THA population, but there is a persistently elevated risk of postoperative complications in smokers after THA.

What Are the Diagnosis-Specific Thresholds of Minimal Clinically Important Difference and Patient Acceptable Symptom State in Hip Disability and Osteoarthritis Outcome Score After Primary Total Hip Arthroplasty?

BACKGROUND

This study aimed to determine the minimal clinically important difference (MCID) and Patient Acceptable Symptom State (PASS) thresholds for Hip Disability and Osteoarthritis Outcome Score (HOOS) pain, physical short form (PS), and joint replacement (JR) 1 year after primary total hip arthroplasty stratified by preoperative diagnosis of osteoarthritis (OA) versus non-OA.

METHODS

A prospective institutional cohort of 5,887 patients who underwent primary total hip arthroplasty (January 2016 to December 2018) was included. There were 4,184 patients (77.0%) who completed a one-year follow-up. Demographics, comorbidities, and baseline and one-year HOOS pain, PS, and JR scores were recorded. Patients were stratified by preoperative diagnosis: OA or non-OA. Minimal detectable change (MDC) and MCIDs were estimated using a distribution-based approach. The PASS values were estimated using an anchor-based approach, which corresponded to a response to a satisfaction question at one year post surgery.

RESULTS

The MCID thresholds were slightly higher in the non-OA cohort versus OA patients. (HOOS-Pain: OA: 8.35 versus non-OA: 8.85 points; HOOS-PS: OA: 9.47 versus non-OA: 9.90 points; and HOOS-JR: OA: 7.76 versus non-OA: 8.46 points). Similarly, all MDC thresholds were consistently higher in the non-OA cohort compared to OA patients. The OA cohort exhibited similar or higher PASS thresholds compared to the non-OA cohort for HOOS-Pain (OA: ≥80.6 versus non-OA: ≥77.5 points), HOOS-PS (OA: ≥83.6 versus non-OA: ≥83.6 points), and HOOS-JR (OA: ≥76.8 versus non-OA: ≥73.5 points). A similar percentage of patients achieved MCID and PASS thresholds regardless of preoperative diagnosis.

CONCLUSIONS

While MCID and MDC thresholds for all HOOS subdomains were slightly higher among non-OA than OA patients, PASS thresholds for HOOS pain and JR were slightly higher in the OA group. The absolute magnitude of the difference in these thresholds may not be sufficient to cause major clinical differences. However, these subtle differences may have a significant impact when used as indicators of operative success in a population setting.

Understanding the 30-day mortality burden after revision total hip arthroplasty

BACKGROUND

Revision total hip arthroplasty (THA) is a challenging procedure that burdens the healthcare system. Despite being associated with worse outcomes relative to its primary counterpart, postoperative mortality after revision THA remains ill-defined. The present study aimed to (1) establish the overall 30-day mortality rate after revision THA and (2) explore the mortality rate stratified by age, comorbidity burden, and aseptic versus septic failure.

METHODS

The American College of Surgeons - National Surgical Quality Improvement Program (ACS-NSQIP) database was retrospectively reviewed for all patients who underwent revision THA from 2011 to 2019. A total of 23,501 patients were identified and grouped into mortality (n = 161) and mortality-free (n = 23,340) cohorts. Patient demographics, comorbidities, and aseptic/septic failure were evaluated.

RESULTS

The overall 30-day mortality was 0.69%. The mortality rate by age group (normalised per 1000 patients) was 0 (18-39 years [Y]), 0.67 (40-49 Y), 1.10 (50-59 Y), 2.58 (60-69 Y), 6.15 (70-79 Y) 19.32 (80-89 Y), and 58.22 (90+Y) (p < 0.001). The mortality rate by ASA classification (normalised per 1000 patients) was 0 (ASA I), 1.47 (ASA II), 6.94 (ASA III), 45.42 (ASA IV), and 200 (ASA V) (p < 0.001). The 30-day mortality rate for the septic and aseptic cohorts was 1.03% and 0.65%, respectively (p = 0.038). CCI scores (p < 0.001), diabetes (p < 0.001), systematic sepsis (p < 0.001), poor functional status (p < 0.001), BMI < 24.9 kg/m2 (p < 0.001), and dirty/infected wounds (p < 0.001) were all associated with increased mortality risk.

CONCLUSIONS

1 in 145 patients will suffer mortality during the 30 days after revision THA. PJI-related revision THA was associated with 1.5-fold increase in 30-day mortality rate compared to its aseptic counterpart. Certain patient determinants and baseline comorbidities, as measured by ASA and CCI scores, were associated with higher 30-day mortality rates. Therefore, it is imperative to identify such risk factors and implement perioperative patient optimisation pathways to mitigate the risk among vulnerable patients.

Preoperative Veteran RAND-12 Mental Composite Score of >60 Associated With Increased Likelihood of Patient Satisfaction After Total Hip Arthroplasty

BACKGROUND

The present study aimed to determine the distribution of Veterans RAND 12-Item health survey (VR-12) mental component scores (MCS) of patients undergoing primary total hip arthroplasty (THA) and the thresholds of VR-12 MCS scores that predict higher health care utilizations and 1-year patient-reported outcome measures (PROMs).

METHODS

A prospective cohort of 4,194 primary THA patients (January 2016 to December 2019) were included. Multivariable and cubic spline regression models were used to test for associations between preoperative VR-12 MCS and postoperative outcomes, including: 90-day hospital resource utilization (nonhome discharge, prolonged length of stay [LOS](ie, ≥3 days), all-cause readmission), attainment of patient acceptable symptom state (PASS) at 1-year postoperative and substantial clinical benefit (SCB) in the hip disability osteoarthritis outcome score (HOOS)-pain and HOOS-physical short form.

RESULTS

Lower VR-12 MCS was associated with older age, obesity, Black race, women, and smokers (all P < .001). Preoperative VR-12 MCS<20 was associated with more than twice the odds of nonhome discharge (odds ratio [OR]:2.31) and prolonged LOS (OR: 3.46). VR-12 MCS >60 was associated with higher odds of achieving PASS (OR: 2.00) and SCB in HOOS-joint related (JR) (OR: 1.16). Starting VR-12 MCS ≤40, there were exponentially higher odds of worse outcomes.

CONCLUSION

Low preoperative VR-12 MCS, specifically less than 40, may predict increased health care utilization. Furthermore, preoperative VR-12 MCS>60 predicts greater satisfaction at 1 year and higher odds of achieving SCB in HOOS-JR. Quantifiable thresholds for VR-12 MCS may aid in shared decision-making and patient counseling in setting expectations or may guide specific care pathway interventions to address mental health during THA.

LEVEL OF EVIDENCE

II.

Dissatisfaction After Total Hip Arthroplasty Associated With Preoperative Patient-Reported Outcome Phenotypes

BACKGROUND

Patient satisfaction is indicative of the quality of care in the value-driven healthcare model. The Patient Acceptable Symptom State (PASS) is a dichotomous outcome tool measuring the highest level of symptom beyond which a patient considers him/herself well. The purpose of the present study was to identify combined preoperative phenotypes of PROMs associated with not achieving PASS at 1 year following total hip arthroplasty (THA) and to associate such phenotypes with hospital utilization parameters.

METHODS

A prospective institutional cohort of 4,034 patients who underwent primary THA for osteoarthritis (OA) with 1-year follow-up was included. Preoperative scores on Hip Disability and Osteoarthritis Outcome Score (HOOS)-pain, HOOS physical short form-(PS), and Veteran's Rand-12 (VR-12) mental component summary-(MCS) were used to develop phenotypes. Associations between preoperative 'phenotype' and 1-year PASS, discharge disposition, prolonged length of stay, 90-day readmission, and 1-year reoperation were evaluated using multivariate regression.

RESULTS

10.6% (427/4,043) reported their state as 'not satisfactory' at 1 year. The phenotypes were the only preoperative factors to demonstrate the increased likelihood of 1-year dissatisfaction. Only phenotypes with lower than average preoperative MCS demonstrated this association. Low scores in all presently measured PROMs (Pain-PS-MCS-) was associated with double the odds of 1-year dissatisfaction (P < .001), 2.43 times the odds of nonhome discharge and 2.2 times the odds of prolonged LOS.

CONCLUSIONS

Patients with lower preoperative scores across multiple PROMs have increased odds of dissatisfaction after THA; and assessing pain, function, and MCS concomitantly (as phenotypes) may support identifying patients at risk for not achieving a satisfactory outcome.

Neighborhood Socioeconomic Disadvantages Associated With Prolonged Lengths of Stay, Nonhome Discharges, and 90-Day Readmissions After Total Knee Arthroplasty

BACKGROUND

Low socioeconomic status and neighborhood context has been linked to poor health care outcomes after total knee arthroplasty (TKA). The area deprivation index (ADI) addresses this relationship by ranking neighborhoods by socioeconomic disadvantage. We examined the following relationships of the ADI among TKA recipients: (1) patient demographics, (2) lengths of stay (LOS), (3) nonhome discharges, and (4) 90-day readmissions, emergency department visits, and reoperations.

METHODS

We reviewed a consecutive series of primary TKAs from 2018 through 2020 at a tertiary health care system. A total of 3928 patients who had complete ADI data were included. A plurality of patients (14.9%) were categorized within ADI 31-40, below the national median ADI of 47. Associations between the national ADI decile and 90-day postoperative health care utilization metrics were evaluated using multivariate regressions (adjusted for patient demographics and comorbidities).

RESULTS

The 91-100 ADI cohort was disproportionately African American, female, younger, and smokers. Compared with ADI 31-40 (reference), the ADI 61-70 cohort was associated with higher odds of LOS ≥3 days (odds ratio [OR] = 1.6 [1.08-2.36], P = .019) and nonhome discharges (OR = 1.73 [1.08-2.75], P = .021). The ADI 91-100 cohort was associated with the highest odds of prolonged LOS (OR = 2.27; [1.47-3.49], P < .001), nonhome discharges (OR = 3.49 [2.11-5.78], P < .001), and all-cause readmissions (OR: 1.79, [1.02-3.14], P = .044). No significant associations were found between the ADI and 90-day emergency department visits or reoperations (P > .05).

CONCLUSION

A higher ADI was associated with prolonged LOS, nonhome discharge status, and 90-day readmissions after TKA. This index highlights potential areas of intervention for assessing health care outcomes.

Combinations of Preoperative Patient-Reported Outcome Measure Phenotype (Pain, Function, and Mental Health) Predict Outcome After Total Knee Arthroplasty

BACKGROUND

Value-driven healthcare models prioritize patient-perceived benefits to quantify the quality of care through patient-reported outcome measures (PROMs). The Patient Acceptable Symptom State (PASS) is the highest level of symptom beyond which a patient considers his/her condition satisfactory. We identified preoperative phenotypes of PROMs associated with not achieving PASS at 1 year following total knee arthroplasty (TKA) and explored the relationships between such phenotypes with hospital utilization parameters.

METHODS

A prospective institutional cohort of 5,274 primary TKAs for osteoarthritis from 2016 to 2019 with 1-year follow-up were included. Preoperative scores on Knee Disability and Osteoarthritis Outcome Score (KOOS) Pain, KOOS-Physical function Short form (PS), and Veterans RAND 12-Item Health Survey (VR-12) Mental Component Summary (MCS) were used to develop patient phenotypes. Associations between preoperative "phenotype" and 1-year PASS, discharge disposition, length of stay, 90-day readmission, and 1-year reoperation were evaluated using multivariate regression.

RESULTS

In total, 16.3% (n = 862) of patients reported their state as "not acceptable" at 1 year. A combination of low scores in each of the presently examined PROMs was associated with the highest odds of 1-year dissatisfaction (odds ratio 2.18, 95% confidence interval 1.74-2.74). The PROM phenotypes were the greatest drivers compared to sociodemographic variables in predicting satisfaction. Combinations of low scores in VR-12 MCS and KOOS-PS were significantly associated with both non-home discharge status and prolonged length of stay.

CONCLUSION

Patients with combined lower preoperative scores across multiple PROMs (KOOS-Pain <41.7, KOOS-PS <51.5, and VR-12 MCS <52.8) have increased odds of dissatisfaction after TKA. Measuring pain, function, and mental health concurrently as phenotypes may help identify TKA patients at risk for not achieving a satisfactory outcome at 1 year.

PLAN and AM-PAC "6-Clicks" Scores to Predict Discharge Disposition After Primary Total Hip and Knee Arthroplasty

BACKGROUND

Determination of the appropriate post-discharge disposition after total hip (THA) and knee (TKA) arthroplasty is a challenging multidisciplinary decision. Algorithms used to guide this decision have been administered both preoperatively and postoperatively. The purpose of this study was to simultaneously evaluate the predictive ability of 2 such tools-the preoperatively administered Predicting Location after Arthroplasty Nomogram (PLAN) and the postoperatively administered Activity Measure for Post-Acute Care (AM-PAC) "6-Clicks" basic mobility tools-in accurately determining discharge disposition after elective THA and TKA.

METHODS

The study included 11,672 patients who underwent THA (n = 4,923) or TKA (n = 6,749) at a single large hospital system from December 2016 through March 2020. PLAN and "6-Clicks" basic mobility scores were recorded for all patients. Regression models and receiver operator characteristic curves were constructed to evaluate the tools' prediction concordance with the actual discharge disposition (home compared with a facility).

RESULTS

PLAN scores had a concordance index of 0.723 for the THA cohort and 0.738 for the TKA cohort. The first "6-Clicks" mobility score (recorded within the first 48 hours postoperatively) had a concordance index of 0.813 for the THA cohort and 0.790 for the TKA cohort. When PLAN and first "6-Clicks" mobility scores were used together, a concordance index of 0.836 was observed for the THA cohort and 0.836 for the TKA cohort. When the PLAN and "6-Clicks" agreed on home discharge, higher rates of discharge to home (98.0% for THA and 97.7% for TKA) and lower readmission rates (5.1% for THA and 7.0% for TKA) were observed, compared with when the tools disagreed.

CONCLUSIONS

PLAN and "6-Clicks" basic mobility scores were good-to-excellent predictors of discharge disposition after primary total joint arthroplasty, suggesting that both preoperative and postoperative variables influence discharge disposition. We recommend that preoperative variables be collected and used to generate a tentative plan for discharge, and the final decision on discharge disposition be augmented by early postoperative evaluation.

CLINICAL RELEVANCE

The determination of post-discharge needs after THA and TKA remains a complex clinical decision. This study shows how simultaneously exploring the predictive ability of preoperative and postoperative assessment tools on discharge disposition after total joint arthroplasty may be a useful aid in a value-driven health-care model.

A Call for a Standardized Approach to Reporting Patient-Reported Outcome Measures: Clinical Relevance Ratio

A shift toward a value-driven health-care model has made prospective collection of patient-reported outcome measures (PROMs) inextricably tied to measuring the success of orthopaedic surgery and patient satisfaction. While progress has been made in optimizing the utilization of PROM data, including establishing appropriate PROMs for a procedure and determining the clinical importance of unique tools, if these PROMs are not accurately analyzed and reported, a proportion of patients who do not reach the clinical thresholds may go unnoticed. Furthermore, parameters are unclear for setting a statistically and clinically important PROM threshold along with a minimum period for follow-up data collection.In this forum, we walk through simulated data sets modeling PROMs with the example of total joint arthroplasty. We discuss how the commonly used method of reporting PROMs by mean change can overestimate the treatment effects for the cohort as a whole and fail to capture distinct populations that are below a clinically relevant threshold. We demonstrate that when a study's outcome is PROMs, clinical importance should be reported using clinical thresholds such as the minimum clinically important difference (MCID), the smallest change in the treatment outcome that a patient perceives as beneficial, and the patient acceptable symptom state (PASS), the highest level of symptoms beyond which a patient considers himself or herself well. Finally, we propose a standardized reporting of PROMs that incorporates both the MCID and the PASS, and introduce a "clinical relevance ratio," which relies on a clinically relevant threshold to dichotomize outcomes and reports the number of patients achieving clinical importance at a given time point divided by the total number of patients included in the study. Unlike other common PROM-reporting approaches, the clinical relevance ratio is not skewed by patients who are lost to follow-up with increased time.

What Is the 30-Day Mortality Burden After Elective Total Hip Arthroplasty? An Analysis of 194,062 Patients

BACKGROUND

This study aims to answer the following questions regarding elective total hip arthroplasty (THA): What is (1) the overall 30-day mortality rate; (2) the mortality rate when stratified by age, comorbidities, and preoperative diagnosis; and (3) the distribution of patient demographics, comorbidities, and preoperative diagnoses between the mortality and mortality-free cohorts?

METHODS

The American College of Surgeons National Surgical Quality Improvement Program database was reviewed for all patients undergoing elective primary THA (2011-2018). A total of 194,062 patients were categorized based on the incidence of 30-day mortality (mortality: n = 206 vs mortality-free: n = 193,856). Patient demographics, comorbidities, and preoperative diagnosis (osteoarthritis [OA] vs non-OA) were recorded. Age category, American Society of Anesthesiologists (ASA) score, and modified Charlson Comorbidity Index (CCI) scores were normalized per 1000 and stratified by preoperative diagnosis.

RESULTS

The 30-day mortality rate was 0.11%. The percentage of deaths per age group (normalized per 1000) was 0% (18-29 years), 0% (30-39 years), 0.049% (40-49 years), 0.052%(50-59 years), 0.071% (60-69 years), 0.133% (70-79 years), and 0.352% (80-89 years). The percentage of deaths per ASA score was 0% (ASA I), 0.035% (ASA II), 0.174% (ASA III), and 1.008% (ASA IV). The percentage of deaths per CCI score was 0.09% (CCI = 0), 0.23% (CCI = 1), 0.74% (CCI = 2), 3.21% (CCI = 3), 4.76% (CCI = 4), and 0.57% (CCI ≥ 5). Non-OA diagnoses were significantly more frequent in the mortality cohort (16.0% vs 7.6%; P < .001).

CONCLUSION

The risk of mortality was highest in patients aged 80-89, patients of ASA class IV, patients with a CCI score of 4, and patients with a non-OA diagnosis. The overall rate of death was higher in the non-OA cohort compared to the OA cohort.

LEVEL OF EVIDENCE

III.

Comorbidity indices in orthopaedic surgery: a narrative review focused on hip and knee arthroplasty

Comorbidity indices currently used to estimate negative postoperative outcomes in orthopaedic surgery were originally developed among non-orthopaedic patient populations.

While current indices were initially intended to predict short-term mortality, they have since been used for other purposes as well.

As the rate of hip and knee arthroplasty steadily rises, understanding the magnitude of the effect of comorbid disease on postoperative outcomes has become increasingly more important.

Currently, the ASA classification is the most commonly used comorbidity measure and is systematically recorded by the majority of national arthroplasty registries.

Consideration should be given to developing an updated, standardized approach for comorbidity assessment and reporting in orthopaedic surgery, especially within the setting of elective hip and knee arthroplasty.

Cite this article: EFORT Open Rev 2021;6:629-640. DOI: 10.1302/2058-5241.6.200124

Patient Reported Outcome Measures: Challenges in the Reporting!

MINI-ABSTRACT

Patient-reported outcome measures are increasingly important in the era of value-based healthcare. We use the example of total joint arthroplasty to demonstrate how current reporting measures may hide poorer outcomes. There is thus a need for a standardized approach in reporting patient-reported outcome measure tied to clinically relevant thresholds.

An Update on Venous Thromboembolism Rates and Prophylaxis in Hip and Knee Arthroplasty in 2020

Patients undergoing total hip and knee arthroplasty are at high risk for venous thromboembolism (VTE) with an incidence of approximately 0.6-1.5%. Given the high volume of these operations, with approximately one million performed annually in the U.S., the rate of VTE represents a large absolute number of patients. The rate of VTE after total hip arthroplasty has been stable over the past decade, although there has been a slight reduction in the rate of deep venous thrombosis (DVT), but not pulmonary embolism (PE), after total knee arthroplasty. Over this time, there has been significant research into the optimal choice of pharmacologic VTE prophylaxis for individual patients, with the objective to reduce the rate of VTE while minimizing adverse side effects such as bleeding. Recently, aspirin has emerged as a promising prophylactic agent for patients undergoing arthroplasty due to its similar efficacy and good safety profile compared to other pharmacologic agents. However, there is no evidence to date that clearly demonstrates the superiority of any given prophylactic agent. Therefore, this review discusses (1) the current prevalence and trends in VTE after total hip and knee arthroplasty and (2) provides an update on pharmacologic VTE prophylaxis in regard to aspirin usage.

The EXTrauterine Environment for Neonatal Development Supports Normal Intestinal Maturation and Development

BACKGROUND AND AIMS

The Extra-Uterine Environment for Neonatal Development (EXTEND) aims to avoid the complications of prematurity, such as NEC. Our goal was to determine if bowel development occurs normally in EXTEND-supported lambs, with specific emphasis on markers of immaturity associated with NEC.

METHODS

We compared terminal ileum from 17 pre-term lambs supported on EXTEND for 2- 4 weeks to bowel from age-matched fetal lambs that developed in utero. We evaluated morphology, markers of epithelial integrity and maturation, enteric nervous system structure, and bowel motility.

RESULTS

EXTEND-supported lamb ileum had normal villus height, crypt depth, density of mucin-containing goblet cells, and enteric neuron density. Expression patterns for I-FABP, activated caspase-3 and EGFR were normal in bowel epithelium. Transmural resistance assessed in Ussing chambers was normal. Bowel motility was also normal as assessed by ex vivo organ bath and video imaging. However, Peyer's patch organization did not occur normally in EXTEND ileum, resulting in fewer circulating B cells in experimental animals.

CONCLUSION

EXTEND supports normal ileal epithelial and enteric nervous system maturation in pre-term lambs. The classic morphologic changes and cellular expression profiles associated with NEC are not seen. However, immune development within the EXTEND supported lamb bowel does not progress normally.

The KDEL receptor has a role in the biogenesis and trafficking of the epithelial sodium channel (ENaC)

Endoplasmic reticulum protein of 29 kDa (ERp29) is a thioredoxin-homologous endoplasmic reticulum (ER) protein that regulates the biogenesis of cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial sodium channel (ENaC). ERp29 may promote ENaC cleavage and increased open probability by directing ENaC to the Golgi via coat complex II (COP II) during biogenesis. We hypothesized that ERp29's C-terminal KEEL ER retention motif, a KDEL variant that is associated with less robust ER retention, strongly influences its regulation of ENaC biogenesis. As predicted by our previous work, depletion of Sec24D, the cargo recognition component of COP II that we previously demonstrated to interact with ENaC, decreases ENaC functional expression without altering β-ENaC expression at the apical surface. We then tested the influence of KDEL ERp29, which should be more readily retrieved from the proximal Golgi by the KDEL receptor (KDEL-R), and a KEEL-deleted mutant (ΔKEEL ERp29), which should not interact with the KDEL-R. ENaC functional expression was decreased by ΔKEEL ERp29 overexpression, whereas KDEL ERp29 overexpression did not significantly alter ENaC functional expression. Again, β-ENaC expression at the apical surface was unaltered by either of these manipulations. Finally, we tested whether the KDEL-R itself has a role in ENaC forward trafficking and found that KDEL-R depletion decreases ENaC functional expression, again without altering β-ENaC expression at the apical surface. These results support the hypothesis that the KDEL-R plays a role in the biogenesis of ENaC and in its exit from the ER through its association with COP II. The cleavage of the extracellular loops of the epithelial sodium channel (ENaC) α and γ subunits increases the channel's open probability and function. During ENaC biogenesis, such cleavage is regulated by the novel 29-kDa chaperone of the ER, ERp29. Our data here are consistent with the hypothesis that ERp29 must interact with the KDEL receptor to exert its regulation of ENaC biogenesis. The classically described role of the KDEL receptor is to retrieve ER-retained species from the proximal Golgi and return them to the ER via coat complex I machinery. In contrast, our data suggest a novel and important role for the KDEL receptor in the biogenesis and forward trafficking of ENaC.