Preoperative hemoglobin thresholds for increased risk of "medical" complications in fast-track total hip and knee arthroplasty, a secondary analysis of a machine-learning algorithm.

BACKGROUND: There is increasing evidence that gender-specific hemoglobin thresholds may not be ideal in the surgical population. Thus, preoperative anemia defined as a hemoglobin of <13.0 g/dL is a well-established risk factor in elective surgery. However, few studies have investigated the specific influence of preoperative hemoglobin within a machine-learning model using data from an optimized fast-track surgical setup. STUDY DESIGN AND METHODS: A secondary analysis on the specific influence of preoperative hemoglobin level on a machine-learning model developed for identifying patients at increased risk of a length of stay (LOS) of >4 day or readmissions due to medical complications in fast-track total hip and knee arthroplasty within a well-defined fast-track protocol. To evaluate the effect of hemoglobin on the model we calculated SHaply Additive Explanation (SHAP) values for the 3913 patients from our previous test-dataset and stratified by gender and total hip and knee arthroplasty, respectively. RESULTS: The study period ran from January 2017 to August 2017. Median LOS was 1 day and mean preoperative Hb was 15.5 g/dL (SD:1.5), lower in women (14.9 vs. 16.2 g/dL) and with 30.5% of women versus 12.0% of men having a Hb of <13.0 g/dL. There was a steep increase in SHAP value with a preoperative Hb < 14.8 g/dL, and irrespective of gender age and procedure type. DISCUSSION: A machine-learning model found a hemoglobin threshold of <14.8 g/dL for increased risk of impaired recovery, regardless of gender or age, supporting reevaluation of preoperative anemia thresholds in the elective surgical setting.

Peripheral nerve-blocks and associations with length of stay and readmissions in fast-track total hip and knee arthroplasty.

BACKGROUND: Peripheral nerve blocks (PNB) have recently been recommended in total hip (THA) and knee (TKA) arthroplasty as they may reduce pain, morphine consumption, length of stay (LOS) and complications. However, whether PNBs are associated with early discharge within an enhanced recovery protocol including multimodal analgesia is uncertain. METHODS: An observational multicenter study from January to August 2017 in six Danish Arthroplasty Centers with established fast-track protocols. Prospective recording of preoperative characteristics and information on PNB, LOS and readmissions through the Danish National Patient Registry and medical records. Multiple logistic regression was used to investigate associations between PNB and a LOS >1 day, LOS >4 days, and 30-days readmissions. We also reported on mobilization, pain, opioid and fall-related complications leading to LOS >4 days or readmissions. RESULTS: A total of 2027 (58.6%) THA and 1432 (41.4%) TKAs with a median LOS of 1 day (IQR 1-2) and 5.3% (CI:4.6-6.1) 30-days readmission rate were identified. PNB was used in 40.7% (CI:38.2-43.3) of TKA and 2.7% (CI:2.0-3.5) of THA, but with considerable interdepartmental variation (0.0-89.0% for TKA). There was no association between PNB and LOS >1 day (OR:1.19 CI:0.82-1.72; p = .354), LOS >4 days (OR:1.4 CI:0.68-2.89; p = .359) or 30-days readmissions (OR:1.02 CI:0.63-1.65; p = .935) in TKA. Logistic regression in THA was not possible due to limited use of PNB. In TKA there were 12 (2.1% CI:1.2-3.6) with and 1 (0.1% CI:0.02-0.7) without a PNB, who had mobilization, pain or opioid-related complications, and 5 (0.9% CI:0.4-2.0) versus 4 (0.5% CI:0.2-1.2) who fell. Correspondingly, 2 (3.7% CI:1.0-12.6) and 11 (0.6% CI:0.3-1.0) of THA patients had these complications, while 0 (0.0% CI:0.0-6.6) and 17 (0.8% CI:0.5-1.3) fell. CONCLUSION: Routine use of peripheral nerve blocks was not associated with early discharge or 30-days readmissions in fast-track THA and TKA. Future studies should focus on benefits of PNB in high-risk patients.

Machine-learning vs. logistic regression for preoperative prediction of medical morbidity after fast-track hip and knee arthroplasty-a comparative study.

BACKGROUND: Machine-learning models may improve prediction of length of stay (LOS) and morbidity after surgery. However, few studies include fast-track programs, and most rely on administrative coding with limited follow-up and information on perioperative care. This study investigates potential benefits of a machine-learning model for prediction of postoperative morbidity in fast-track total hip (THA) and knee arthroplasty (TKA). METHODS: Cohort study in consecutive unselected primary THA/TKA between 2014-2017 from seven Danish centers with established fast-track protocols. Preoperative comorbidity and prescribed medication were recorded prospectively and information on length of stay and readmissions was obtained through the Danish National Patient Registry and medical records. We used a machine-learning model (Boosted Decision Trees) based on boosted decision trees with 33 preoperative variables for predicting "medical" morbidity leading to LOS > 4 days or 90-days readmissions and compared to a logistical regression model based on the same variables. We also evaluated two parsimonious models, using the ten most important variables in the full machine-learning and logistic regression models. Data collected between 2014-2016 (n:18,013) was used for model training and data from 2017 (n:3913) was used for testing. Model performances were analyzed using precision, area under receiver operating (AUROC) and precision recall curves (AUPRC), as well as the Mathews Correlation Coefficient. Variable importance was analyzed using Shapley Additive Explanations values. RESULTS: Using a threshold of 20% "risk-patients" (n:782), precision, AUROC and AUPRC were 13.6%, 76.3% and 15.5% vs. 12.4%, 74.7% and 15.6% for the machine-learning and logistic regression model, respectively. The parsimonious machine-learning model performed better than the full logistic regression model. Of the top ten variables, eight were shared between the machine-learning and logistic regression models, but with a considerable age-related variation in importance of specific types of medication. CONCLUSION: A machine-learning model using preoperative characteristics and prescriptions slightly improved identification of patients in high-risk of "medical" complications after fast-track THA and TKA compared to a logistic regression model. Such algorithms could help find a manageable population of patients who may benefit most from intensified perioperative care.

Gastrointestinal complications after fast-track total hip and knee replacement: an observational study in a consecutive 36,932 patient cohort.

INTRODUCTION: Gastrointestinal complications after total hip (THA) and knee arthroplasty (TKA) have been reported to be between 0.3 and 2.6% with bleeding and C. difficile infection in 0-1%, and 0.1-1.7%, respectively. The use of enhanced recovery or "fast-track" protocols have focused on optimizing all aspects of perioperative care resulting in reduced length of hospital stay (LOS) and potentially also gastrointestinal complications. This study is a detailed analysis on the occurrence of postoperative gastrointestinal complications resulting in increased hospital stay or readmissions in a large consecutive cohort of fast-track THA and TKA with complete 90 days follow-up. MATERIALS AND METHODS: This is an observational study on a consecutive cohort of primary unilateral THAs and TKAs performed between January 2010 and August 2017 in nine Danish high-volume fast-track centers. Discharge summaries and relevant patient records were reviewed in patients with readmissions within 90 days or LOS > 4 days caused by gastrointestinal complications. RESULTS: The cohort included 36,932 patients with 58.3% females and 54.1% THAs. Mean age and BMI were 68 years and 28. Median postoperative LOS was 2 days. Only n: 276 (0.75 %) had a LOS > 4 days or a readmission within 90 days due to a gastrointestinal complication (CI 0.67%-0.84%). Of these, only 34 (0.09%) were graded as severe ileus or gastrointestinal bleeding. CONCLUSIONS: The risk of GI-complications within the first 90 postoperative days after fast-track THA and TKA was low (0.75%).

Machine learning classifiers do not improve prediction of hospitalization > 2 days after fast-track hip and knee arthroplasty compared with a classical statistical risk model.

Background and purpose: Prediction of postoperative outcomes and length of hospital stay (LOS) of patients is vital for allocation of healthcare resources. We investigated the performance of prediction models based on machinelearning algorithms compared with a previous risk stratification model using traditional multiple logistic regression, for predicting the risk of a LOS of > 2 days after fast-track total hip and knee replacement. Patients and methods: 3 different machine learning classifiers were trained on data from the Lundbeck Centre for Fast-track Hip and Knee Replacement Database (LCDB) collected from 9,512 patients between 2016 and 2017. The chosen classifiers were a random forest classifier (RF), a support vector machine classifier with a polynomial kernel (SVM), and a multinomial Naïve-Bayes classifier (NB). Results: Comparing performance measures of the classifiers with the traditional model revealed that all the models had a similar performance in terms of F1 score, accuracy, sensitivity, specificity, area under the receiver operating curve (AUC), and area under the precision-recall curve (AUPRC). A feature importance analysis of the RF classifier found hospital, age, use of walking aid, living alone, and joint operated on to be the most relevant input features. None of the classifiers reached a clinically relevant performance with the input data from the LCDB. Interpretation: Despite the promising prospects of machine-learning practices for disease and risk prediction, none of the machine learning models tested outperformed the traditional multiple regression model in predicting which patients in this cohort had a LOS > 2 days.

Postoperative Morbidity and Mortality in Diabetic Patients After Fast-Track Hip and Knee Arthroplasty: A Prospective Follow-up Cohort of 36,762 Procedures.

BACKGROUND: Diabetes increases the risk of adverse outcomes in surgical procedures, including total hip and knee arthroplasty (THA/TKA), and the prevalence of diabetic patients undergoing these procedures is high, ranging from approximately 8% to 20%. However, there is still a need to clarify the role of diabetes and antihyperglycemic treatment in a fast-track THA/TKA setting, which otherwise may decrease morbidity. Consequently, we investigated the association between diabetes and antihyperglycemic treatment on length of stay (LOS) and complications following fast-track THA/TKA within a multicenter fast-track collaboration. METHODS: We used an observational study design on data from a prospective multicenter fast-track collaboration on unselected elective primary THA/TKA from 2010 to 2017. Complete follow-up (>99%) was achieved through The Danish National Patient Registry, antihyperglycemic treatment established through the Danish National Database of Reimbursed Prescriptions and types of complications leading to LOS >4 days, 90-day readmission or mortality obtained by scrutinizing health records and discharge summaries. Patients were categorized as nondiabetic and if diabetic into insulin-, orally, and dietary-treated diabetic patients. RESULTS: A total of 36,762 procedures were included, of which 837 (2.3%) had insulin-treated diabetes, 2615 (7.1%) orally treated diabetes, and 566 (1.5%) dietary-treated diabetes. Overall median LOS was 2 (interquartile range [IQR]: 1-3) days, and mean LOS was 2.4 (standard deviation [SD], 2.5) days. The proportion of patients with LOS >4 days was 6.0% for nondiabetic patients, 14.7% for insulin-treated, 9.4% for orally treated, and 9.5% for dietary-treated diabetic patients. Pharmacologically treated diabetes (versus nondiabetes) was independently associated with increased odds of LOS >4 days (insulin-treated: odds ratio [OR], 2.2 [99.6% confidence interval {CI}, 1.3-3.7], P < .001; orally treated: OR, 1.5 [99.6% CI, 1.0-2.1]; P = .002). Insulin-treated diabetes was independently associated with increased odds of "diabetes-related" morbidity (OR, 2.3 [99.6% CI, 1.2-4.2]; P < .001). Diabetic patients had increased renal complications regardless of antihyperglycemic treatment, but only insulin-treated patients suffered significantly more cardiac complications than nondiabetic patients. There was no increase in periprosthetic joint infections or mortality associated with diabetes. CONCLUSIONS: Patients with pharmacologically treated diabetes undergoing fast-track THA/TKA were at increased odds of LOS >4 days. Although complication rates were low, patients with insulin-treated diabetes were at increased odds of postoperative complications compared to nondiabetic patients and to their orally treated counterparts. Further investigation into the pathogenesis of postoperative complications differentiated by antihyperglycemic treatment is needed.

Influence of day of surgery and prediction of LOS > 2 days after fast-track hip and knee replacement.

Background and purpose - Enhanced recovery programs have reduced length of stay (LOS) after hip and knee arthroplasty (THA/TKA). Although risk factors disposing to prolonged LOS are well documented, there is limited information on the role of weekday of surgery. This study analyzed the role of weekday of surgery and other potential risk factors for LOS > 2 days.Patients and methods - We included 10,576 unselected consecutive procedures between January 2016 and August 2017 within a multicenter fast-track THA/TKA collaboration with prospective collection of preoperative characteristics. We used multiple regression analysis of potential risk factors for LOS > 2 days followed by construction of a simple risk score from 0 to 15 points based on the calculated odds ratios.Results - Mean LOS was 1.9 (SD 1.8) days, with 80% of patients having surgery from Monday to Wednesday. Of these, 17% (95% CI 16-18) had a LOS > 2 days vs. 19% (CI 17-21) in those operated on Thursday and Friday. Patients were scheduled evenly throughout the week regardless of risk of LOS > 2 days and despite the fact that 38% (CI 35-40) of patients with ≥ 6 points (16% of the total population) had a LOS > 2 days compared with 14% (CI 13-14) in those with < 6 points. In these "high-risk" patients, the fraction with LOS > 2 days increased when having surgery on Thursdays or Fridays (43% CI 38-49) compared with Monday to Wednesday (37% CI 34-39).Interpretation - A detailed preoperative risk assessment may be helpful to plan the weekday of surgery in order to decrease LOS and weekend hospitalization.

Days alive and out of hospital after fast-track total hip and knee arthroplasty: an observational cohort study in 16 137 patients.

BACKGROUND: Days alive and out of hospital (DAH) has been proposed as a pragmatic outcome measure of surgical quality. However, there is a lack of procedure specific data or data within an optimised fast-track protocol. Furthermore, information about influence of follow-up duration and types of complications on DAH is limited. METHODS: Observational multicentre cohort study of patients undergoing fast-track total hip (THA) and knee arthroplasty (TKA). Prospective information on comorbidity and complete 90 days follow-up was undertaken through the Danish National Patient Register and chart review. RESULTS: For 16 137 procedures, of which 18.6% were high-risk (≥2 preoperative risk factors), the median length of stay was 2 days (inter-quartile range [IQR], 2-3), and 30- and 90-day readmission rates were 5.7% and 8.1%, respectively. Median DAH30 and DAH90 days were 27 (26-28) and 87 (85-88) vs 28 (27-28) and 88 (87-89) (P<0.001) in high-vs low-risk patients, respectively. The fraction with DAH ≤25 at 30 days and DAH ≤85 at 90 days was increased in high-vs low-risk patients: 23.3% vs 6.8% (odds ratio [OR]=4.16; 95% confidence interval [CI], 3.73-4.65) and 26.0% vs 8.6% (OR=3.75; 95% CI, 3.38-4.16). There were relatively fewer 'surgical' complications in high- vs low-risk patients with DAH30 ≤25 (14.6% vs 25.8%) (OR=0.49; 95% CI, 0.37-0.65) and DAH90 ≤85 (16.9% vs 31.89%) (OR=0.43; 95% CI, 0.34-0.56). About 2% of patients had readmissions, but DAH was >25 and >85 at 30 and 90 days after operation, respectively. CONCLUSION: Median DAH in fast-track THA/TKA patients is 28 at 30 days and 88 at 90 days after surgery. DAH in high-risk patients was only slightly reduced compared with low-risk patients, but they have relatively more 'medical' complications.

Incidence and Risk Factors for Stroke in Fast-Track Hip and Knee Arthroplasty-A Clinical Registry Study of 24,862 Procedures.

BACKGROUND: Postoperative stroke is a severe complication with a reported 30-day incidence of 0.4%-0.6% after total hip (THA) and knee arthroplasty (TKA). However, most data are based on diagnostic codes and with limited details on perioperative care, including the use of fast-track protocols. We investigated the incidence of and preoperative and postoperative factors for stroke after fast-track THA/TKA. METHODS: We used an observational study design of elective fast-track THA/TKA patients with prospective collection of comorbidity and complete 90-day follow-up. Medical records were evaluated for events potentially disposing to stroke. Identification of relevant preoperative risk factors was done by multivariable logistic regression. Incidence of stroke was compared with a Danish background population. RESULTS: Of 24,862 procedures with a median length of stay of 2 (interquartile range, 2-3) days, we found 27 (0.11%; 95% confidence interval [CI], 0.08%-0.16%) and 43 strokes (0.17%, 95% CI, 0.13%-0.23%) ≤30 and ≤90 days after surgery, respectively. Preoperative risk factors for stroke ≤30 days were age ≥ 85 years (odds ratio [OR], 4.3; 95% CI, 1.1-16.3) and anticoagulant treatment (OR, 3.1; 95% CI, 1.2-7.9). Preoperative anemia was near significant (OR, 2.1; 95% CI, 0.98-4.6, P = .055). Eight strokes ≤30 days were preceded by a cardiovascular event within the second postoperative day. Incidence of stroke after postoperative day 30 was similar to a Danish background population. CONCLUSION: Risk of postoperative stroke in fast-track THA and TKA was low but may be further reduced with increased focus on avoiding perioperative cardiovascular events and in patients with preoperative anticoagulants or anemia.

Myocardial infarction following fast-track total hip and knee arthroplasty-incidence, time course, and risk factors: a prospective cohort study of 24,862 procedures.

Background and purpose - Acute myocardial infarction (MI) is a leading cause of mortality following total hip and knee arthroplasty (THA/TKA). The reported 30-day incidence of MI varies from 0.3% to 0.9%. However, most data derive from administration and insurance databases or large RCTs with potential confounding factors. We studied the incidence of and potential modifiable risk factors for postoperative MI in a large, multicenter optimized "fast-track" THA/TKA setting. Patients and methods - A prospective cohort study was conducted on consecutive unselected elective primary unilateral THA and TKA, using prospective information on comorbidities and complete 90-day follow-up from the Danish National Patient Registry. Evaluation of discharge summaries and medical records was undertaken in cases of suspected MI. Logistic regression analyses were carried out for identification of preoperative risk factors. Results - Of 24,862 procedures with a median length of stay 2 (IQR 2-3) days, 30- and 90-day incidence of MI was 31 (0.12%) and 48 (0.19%). Preoperative risk factors for MI ≤30 days were age >85 years (OR 7.4, 95% CI 2.3-24), insulin-dependent diabetes mellitus (IDDM) (3.6, CI 1.1-12), cardiovascular disease (2.4, CI 1.1-5.0) and hypercholesterolemia (2.3, CI 1.1-5.1). Of 31 patients with MI ≤30 days 9 were treated with vasopressors for intraoperative hypotension and 27 had postoperative anemia. Interpretation - Fast-track THA and TKA had a low 30-day MI incidence. Focus on patients with age >85, IDDM, cardiovascular disease, and hypercholesterolemia may further reduce the 30-day incidence of MI. The role of postoperative anemia and intraoperative hypotension are other areas for further improvement.

The Role of Psychiatric Diagnoses for Outcome After Hip and Knee Arthroplasty.

BACKGROUND: Surgical patients receiving psychopharmacologic treatment have been associated with adverse outcomes in total hip and knee arthroplasty (THA and TKA). The purpose of this study was to investigate whether a specific high-risk group of patients receiving psychopharmacologic treatment could be identified based upon a nationwide psychiatric diagnosis register. METHODS: From 7 different orthopedic centers, 8288 THA and TKA patients were included from January 2010 to November 2012 of which 943 (11.4%) received psychopharmacologic treatment. Patients receiving preoperative psychopharmacologic treatment were divided into 2 groups based on the presence or absence of a psychiatric diagnosis in a nationwide administrative database and analyzed with respect to length of hospital stay (LOS >4 days) and 30- and 90-day readmissions using multivariable logistic regression models. RESULTS: A total of 191 patients receiving psychopharmacologic treatment were registered with a psychiatric diagnosis while 752 patients received psychopharmacologic treatment without a registered psychiatric diagnosis. No significantly increased risk was found in patients with a preoperative registered psychiatric diagnosis compared to patients without, with regard to LOS >4 days (odds ratio [OR], 1.19; P = .51), 30-day readmission (OR, 0.56; P = .086), or 90-day readmission (OR, 0.81; P = .446), respectively. However, both groups had an increased risk of LOS >4 days and readmissions compared to a control population without psychopharmacologic treatment or any registered psychiatric diagnoses. CONCLUSION: No further risk was found for psychopharmacologically treated THA/TKA patients with an additional hospital-related psychiatric diagnosis compared to patients without, suggesting that the psychopharmacologic treatment per se is an outcome risk factor independent of severity of the psychiatric disorder.

Thromboembolic and major bleeding events in relation to perioperative bridging of vitamin K antagonists in 649 fast-track total hip and knee arthroplasties.

Background - The benefit of preoperative bridging in surgical patients with continuous anticoagulant therapy is debatable, and drawing of meaningful conclusions may have been limited by mixed procedures with different thromboembolic and bleeding risks in most published studies. Patients and methods - This was an observational cohort treatment study in consecutive primary unilateral total hip and knee arthroplasty patients between January 2010 and November 2013 in 8 Danish fast-track departments. Data were collected prospectively on preoperative comorbidity and anticoagulants in patients with preoperative vitamin K antagonist (VKA) treatment. We performed 30-day follow-up on in-hospital complications and re-admissions through the Danish National Patient Registry and patient records. Results - Of 13,375 procedures, 649 (4.7%) were in VKA patients with a mean age of 73 (SD 9) years and a median length of stay of 3 days (IQR: 2-4). Preoperative bridging was used in 430 (67%), while 215 (33%) were paused. Of 4 arterial thromboembolic events (ATEs) (0.6%), 2 were in paused patients and 2 were in bridged patients (p = 0.6). Of 3 venous thromboembolic events (VTEs) (0.5%), 2 were in paused patients and 1 was in a bridged patient (p = 0.3). Of 8 major bleedings (MBs) (1.2%), 1 was in a paused patient and 7 were in bridged patients (p = 0.3), 5 of whom received therapeutic bridging. Similar results were found in a propensity-matched cohort. Interpretation - In contrast to recent studies in mixed surgical procedures, no statistically significant differences in ATE, VTE, or MB were found between preoperative bridging and pausation of VKA patients. However, the higher number of thromboembolic events in paused patients and the higher number of major bleedings in bridged patients warrant more extensive investigation.

Increased risk of intraoperative and early postoperative periprosthetic femoral fracture with uncemented stems.

Background and purpose - The use of uncemented fixation in total hip arthroplasty (THA) is increasing. Registry studies have indicated an increased risk of revision of uncemented implants due to early periprosthetic femoral fracture. In this paper, we describe the incidence and predisposing factors for intraoperative and early postoperative (≤ 90 days) periprosthetic femoral fractures after cemented and uncemented THA. Patients and methods - This was a prospective observational study in 8 Danish high-volume centers from February 2010 to November 2013. We used the 90-day follow-up from the Danish National Patient Registry and patient records. We obtained intraoperative information from the Danish Hip Arthroplasty Registry and from surgical notes. Results - Of 7,169 primary consecutive THAs, 5,482 (77%) were performed using uncemented femoral components. The total incidence of periprosthetic femoral fractures ≤ 90 days postoperatively was 2.1% (n = 150). 70 fractures were detected intraoperatively (46 required osteosynthesis). 51 postoperatively detected fractures occurred without trauma (42 of which were reoperated) and 29 were postoperative fall-related fractures (27 of which were reoperated). 134 fractures (2.4%) were found in uncemented femoral components and 16 (0.9%) were found in cemented femoral components (p < 0.001). Uncemented femoral stem (relative risk (RR) = 4.1, 95% CI: 2.3-7.2), medically treated osteoporosis (RR =2.8, CI: 1.6-4.8), female sex (RR =1.6, CI: 1.1-2.2), and age (RR =1.4 per 10 years, CI: 1.2-1.6) were associated with increased risk of periprosthetic femoral fracture when analyzed using multivariable regression analysis. Interpretation - Uncemented femoral components were associated with an increased risk of early periprosthetic femoral fractures, especially in elderly, female, and osteoporotic patients.

Postoperative Morbidity and Discharge Destinations After Fast-Track Hip and Knee Arthroplasty in Patients Older Than 85 Years.

BACKGROUND: Elderly patients are at risk of increased length of hospital stay (LOS), postoperative complications, readmission, and discharge to destinations other than home after elective total hip arthroplasty (THA) and total knee arthroplasty (TKA). Recent studies have found that enhanced recovery protocols or fast-track surgery can be safe for elderly patients undergoing these procedures and may result in reduced LOS. However, detailed studies on preoperative comorbidity and differentiation between medical and surgical postoperative morbidity in elderly patients are scarce. The aim of this study was to provide detailed information on postoperative morbidity resulting in LOS >4 days or readmissions <90 days after fast-track THA and TKA in patients ≥85 years. METHODS: This is a descriptive, observational study in consecutive unselected patients ≥85 years undergoing fast-track THA/TKA. The primary outcome was the causes of postoperative morbidity leading to an LOS of >4 days. Secondary outcomes were 90-day surgically related readmissions, discharge destination, 90-day mortality, and role of disposing factors for LOS >4 days and 90-day readmissions. Data on preoperative characteristics were prospectively gathered using patient-reported questionnaires. Data on all admissions were collected using the Danish National Health Registry, ensuring complete follow-up. Any cases of LOS >4 days or readmissions were investigated through review of discharge forms or medical records. Backward stepwise logistic regression was used for analysis of association between disposing factors and LOS >4 days and 90-day readmission. RESULTS: Of 13,775 procedures, 549 were performed in 522 patients ≥85 years. Median age was 87 years (interquartile range, 85-88) and median LOS of 3 days (interquartile range, 2-5). In 27.3% procedures, LOS was >4 days, with 82.7% due to medical causes, most often related to anemia requiring blood transfusion and mobilization issues. Use of walking aids was associated with LOS >4 days (odds ratio [OR], 1.99; 95% confidence interval [CI], 1.26-3.15; P = 0.003), whereas preoperative anemia showed borderline significance (OR, 1.52; 95% CI, 0.99-2.32; P = 0.057). Thirty-eight patients (6.9%) were not discharged directly home, of which 68.4% had LOS >4 days. Readmission rates were 14.2% and 17.9% within 30 and 90 days, respectively, and 75.5% of readmissions within 90 days were medical, mainly due to falls and suspected but disproved venous thromboembolic events. Preoperative anemia was associated with increased (OR, 1.81; 95% CI, 1.13-2.91; P = 0.014) and living alone with decreased (OR, 0.50; 95% CI, 0.31-0.80; P = 0.004) risk of 90-day readmissions. Ninety-day mortality was 2.0%, with 1.0% occurring during primary admission. CONCLUSIONS: Fast-track THA and TKA with an LOS of median 3 days and discharge to home are feasible in most patients ≥85 years. However, further attention to pre- and postoperative anemia and the pathogenesis of medical complications is needed to improve postoperative outcomes and reduce readmissions.

Does BMI influence hospital stay and morbidity after fast-track hip and knee arthroplasty?

Background and purpose - Body mass index (BMI) outside the normal range possibly affects the perioperative morbidity and mortality following total hip arthroplasty (THA) and total knee arthroplasty (TKA) in traditional care programs. We determined perioperative morbidity and mortality in such patients who were operated with the fast-track methodology and compared the levels with those in patients with normal BMI. Patients and methods - This was a prospective observational study involving 13,730 procedures (7,194 THA and 6,536 TKA operations) performed in a standardized fast-track setting. Complete 90-day follow-up was achieved using national registries and review of medical records. Patients were grouped according to BMI as being underweight, of normal weight, overweight, obese, very obese, and morbidly obese. Results - Median length of stay (LOS) was 2 (IQR: 2-3) days in all BMI groups. 30-day re-admission rates were around 6% for both THA (6.1%) and TKA (5.9%), without any statistically significant differences between BMI groups in univariate analysis (p > 0.4), but there was a trend of a protective effect of overweight for both THA (p = 0.1) and TKA (p = 0.06). 90-day re-admission rates increased to 8.6% for THA and 8.3% for TKA, which was similar among BMI groups, but there was a trend of lower rates in overweight and obese TKA patients (p = 0.08 and p = 0.06, respectively). When we adjusted for preoperative comorbidity, high BMI in THA patients (very obese and morbidly obese patients only) was associated with a LOS of >4 days (p = 0.001), but not with re-admission. No such relationship existed for TKA. Interpretation - A fast-track setting resulted in similar length of hospital stay and re-admission rates regardless of BMI, except for very obese and morbidly obese THA patients.

Revision of infected knee arthroplasties in Denmark.

Background and purpose - The surgical treatment of periprosthetic knee infection is generally either a partial revision procedure (open debridement and exchange of the tibial insert) or a 2-stage exchange arthroplasty procedure. We describe the failure rates of these procedures on a nationwide basis. Patients and methods - 105 partial revisions (100 patients) and 215 potential 2-stage revision procedures (205 patients) performed due to infection from July 1, 2011 to June 30, 2013 were identified from the Danish Knee Arthroplasty Register (DKR). Failure was defined as surgically related death ≤ 90 days postoperatively, re-revision due to infection, or not reaching the second stage for a planned 2-stage procedure within a median follow-up period of 3.2 (2.2-4.2) years. Results - The failure rate of the partial revisions was 43%. 71 of the partial revisions (67%) were revisions of a primary prosthesis with a re-revision rate due to infection of 34%, as compared to 55% in revisions of a revision prosthesis (p = 0.05). The failure rate of the 2-stage revisions was 30%. Median time interval between stages was 84 (9-597) days. 117 (54%) of the 2-stage revisions were revisions of a primary prosthesis with a re-revision rate due to infection of 21%, as compared to 29% in revisions of a previously revised prosthesis (p = 0.1). Overall postoperative mortality was 0.6% in high-volume centers (> 30 procedures within 2 years) as opposed to 7% in the remaining centers (p = 0.003). Interpretation - The failure rates of 43% after the partial revision procedures and 30% after the 2-stage revisions in combination with the higher mortality outside high-volume centers call for centralization and reconsideration of surgical strategies.

Psychiatric Disorders and Psychopharmacologic Treatment as Risk Factors in Elective Fast-track Total Hip and Knee Arthroplasty.

BACKGROUND: Psychiatric disorder (PsD) is rarely considered when evaluating perioperative risk factors. Studies on PsD are often limited by use of administrative coding, incomplete follow-up, and lack of preoperative data on psychopharmacological treatment. METHODS: A multicenter study with prospective registration on preoperative comorbidity, complete 90-day follow-up, and information on dispensed prescriptions on psychopharmacological treatment (excluding benzodiazepines). All departments used similar fast-track approaches and discharge to home. Evaluation of postoperative morbidity was based on discharge records. Odds ratios for length of stay (LOS) more than 4 days and surgery-related readmissions were calculated using multiple logistic regression adjusting for potential confounders. RESULTS: Of 8,757 procedures, 1,001 (11.4%) were in PsD patients. Of these, 43.4% used selective serotonin inhibitors (SSRIs), 31.6% used other antidepressants, 8.5% used a combination, and 16.5% used antipsychotics. PsD was associated with increased risk of LOS more than 4 days (16.5 vs. 7.3%; odds ratio, 1.90; 95% CI, 1.52 to 2.37), regardless of treatment with SSRIs (2.19; 1.62 to 2.97), other antidepressants (1.81; 1.25 to 2.61), or antipsychotics (1.90; 1.62 to 3.16). PsD was associated with increased 30- (9.9 vs. 5.1%; 1.93; 1.49 to 2.49) and 90-day surgery-related readmissions (12.8 vs. 7.4%; 1.68; 1.34 to 2.10), significant for SSRIs (1.97; 1.38 to 2.82 and 1.77; 1.29 to 2.43), other antidepressants (2.24; 1.51 to 3.32 and 1.82; 1.27 to 2.61), and antipsychotics (1.85; 1.03 to 3.31, 30 days only). In PsD patients, pain (1.4%), postoperative anemia (1.1%), and pulmonary complications (1.1%) were the most frequent causes of LOS more than 4 days. Hip displacements (2.8%) and falls (1.9%) were the most frequent readmissions, and 90-day surgery-related mortality was 0.7% with and 0.2% without PsD. CONCLUSIONS: Psychopharmacologically treated PsD is a risk factor for postoperative morbidity after fast-track arthroplasty, regardless of treatment type. This may be due to PsD per se and/or drug-related side effects.

Postoperative morbidity and mortality in type-2 diabetics after fast-track primary total hip and knee arthroplasty.

BACKGROUND: Diabetes is a risk factor for postoperative morbidity, which includes total hip and knee arthroplasty. However, no previous studies have been done in a fast-track setting with optimized perioperative care, including spinal anesthesia, multimodal opioid-sparing analgesia, early mobilization, and discharge to home, which improved postoperative outcome. METHODS: We performed an observational cohort study using prospective data in primary total hip and total knee arthroplasty with a standardized fast-track approach. Eight hundred ninety type 2 diabetics were successfully propensity matched with 7165 nondiabetics. Subanalyses on antihyperglycemic treatment were done using the Danish National Database of Reimbursed Prescriptions for information on dispensed prescriptions 6 months preoperatively. Length of hospital stay (LOS), 90-day readmissions, and mortality were found through the Danish National Health Registry and medical charts. Multiple logistic regression analyses on LOS > 4 days and readmissions were used to further adjust for demographics, comorbidity, and department of surgery. To further evaluate the clinical relevance of type 2 diabetes, we estimated the number of surgical type 2 diabetics needed for 1 more occurrence of LOS > 4 days or readmissions (adjusted number needed to harm [NNH]). RESULTS: Although more type 2 diabetics (11.3%) than nondiabetics (8.1%) had LOS > 4 days (unadjusted P = 0.001), there was no association between type 2 diabetes and LOS > 4 days when adjusting for covariates (odds ratio: 1.19 [0.93-1.54]; P = 0.172). Correspondingly, the NNH was 78 but ranged between 31 and infinity. Type 2 diabetes was not associated with 30- (1.02 [0.75-1.39]; P = 0.897) or 90-day readmissions (1.22 [0.87-1.71]; P = 0.254), and with an NNH of 957 (59-∞) and 115 (35-∞), respectively. Insulin-treated type 2 diabetes was associated with increased risk of specific "diabetes-related" morbidity (1.95 [1.13-3.35]; P = 0.016). CONCLUSIONS: Type 2 diabetes per se has limited influence on postoperative morbidity in fast-track total hip and knee arthroplasty.

Early morbidity after simultaneous and staged bilateral total knee arthroplasty.

PURPOSE: The aim of this nationwide study was to investigate the early morbidity after bilateral simultaneous and staged total knee arthroplasty (TKA) in order to clarify potential benefits of a well-established fast-track regime. METHODS: The Danish National Patient Registry was searched for all bilateral simultaneous and staged TKA procedures from 2010 to 2011. The staged procedures were defined as two separate procedures done within 0-6 months or within 7-18 months. RESULTS: A total of 157 patients had bilateral simultaneous TKA, 346 patients had bilateral staged TKA within 0-6 months and 292 patients had bilateral staged TKA within 7-18 months. The median length of stay in hospital (LOS) was 4 days (interquartile range, IQR: 3) after bilateral simultaneous TKA versus cumulated LOS of 6 days (IQR: 3) in both of the bilateral staged groups (p < 0.001). There were no deaths after bilateral simultaneous TKA versus three deaths (0.9 and 1.0 %) in each of the bilateral staged groups within 90 days of surgery (n.s.). The total readmission rate within 30 days of surgery was lower after bilateral simultaneous TKA (7 %, CI 4.0-12.0) and bilateral staged TKA within 0-6 months (9 %, CI 6.4-12.4) compared with 14 % (CI 11.5-20.1) after bilateral staged TKA within 7-18 months. CONCLUSIONS: The results from this nationwide study indicate that bilateral simultaneous TKA can safely be performed in a fast-track set-up.