Variance estimation of the risk difference when using propensity-score matching and weighting with time-to-event outcomes.

Observational studies are increasingly being used in medicine to estimate the effects of treatments or exposures on outcomes. To minimize the potential for confounding when estimating treatment effects, propensity score methods are frequently implemented. Often outcomes are the time to event. While it is common to report the treatment effect as a relative effect, such as the hazard ratio, reporting the effect using an absolute measure of effect is also important. One commonly used absolute measure of effect is the risk difference or difference in probability of the occurrence of an event within a specified duration of follow-up between a treatment and comparison group. We first describe methods for point and variance estimation of the risk difference when using weighting or matching based on the propensity score when outcomes are time-to-event. Next, we conducted Monte Carlo simulations to compare the relative performance of these methods with respect to bias of the point estimate, accuracy of variance estimates, and coverage of estimated confidence intervals. The results of the simulation generally support the use of weighting methods (untrimmed ATT weights and IPTW) or caliper matching when the prevalence of treatment is low for point estimation. For standard error estimation the simulation results support the use of weighted robust standard errors, bootstrap methods, or matching with a naïve standard error (i.e., Greenwood method). The methods considered in the article are illustrated using a real-world example in which we estimate the effect of discharge prescribing of statins on patients hospitalized for acute myocardial infarction.

Partition testing for real-world evidence studies.

Traditional approaches to hypothesis testing in comparative post-approval safety and effectiveness studies of medical products are often inadequate because of a limited scope of possible inferences (e.g., superiority or inferiority). Often there is interest in simultaneously testing for superiority, equivalence, inferiority, non-inferiority, and non-superiority, which can be achieved using a partition testing framework. Partition testing only requires selection of an equivalence margin and calculation of a two-sided Wald confidence interval. In addition to permitting a broader range of inferences, the strengths of the approach include: mitigating publication bias, avoiding use of a clinically irrelevant nil hypothesis, and more transparent and impartial appraisal of the clinical importance of a study's findings by pre-specifying an equivalence margin. However, a challenge in implementing the approach can be the process for identifying an equivalence margin. The methodology is illustrated using a published study of the safety of Ondansetron for the off-label treatment of nausea and vomiting during pregnancy. Applying the method to the study results would have led to a conclusion that women exposed to Ondansetron in comparison to those that are not, are equivalent with respect to risk of cardiac malformations and oral clefts. These conclusions are more in line with the magnitude of the observed effects than the conclusions resulting from a traditional inferiority/superiority testing conducted by the study authors.

Variance estimation when using propensity-score matching with replacement with survival or time-to-event outcomes.

Propensity-score matching is a popular analytic method to estimate the effects of treatments when using observational data. Matching on the propensity score typically requires a pool of potential controls that is larger than the number of treated or exposed subjects. The most common approach to matching on the propensity score is matching without replacement, in which each control subject is matched to at most one treated subject. Failure to find a matched control for each treated subject can lead to "bias due to incomplete matching." To avoid this bias, it is important to identify a matched control subject for each treated subject. An alternative to matching without replacement is matching with replacement, in which control subjects are allowed to be matched to multiple treated subjects. A limitation to the use of matching with replacement is that variance estimation must account for both the matched nature of the sample and for some control subjects being included in multiple matched sets. While a variance estimator has been proposed for when outcomes are continuous, no such estimator has been proposed for use with time-to-event outcomes, which are common in medical and epidemiological research. We propose a variance estimator for the hazard ratio when matching with replacement. We conducted a series of Monte Carlo simulations to examine the performance of this estimator. We illustrate the utility of matching with replacement to estimate the effect of smoking cessation counseling on survival in smokers discharged from hospital with a heart attack.

Propensity score methods for time-dependent cluster confounding.

In observational studies, subjects are often nested within clusters. In medical studies, patients are often treated by doctors and therefore patients are regarded as nested or clustered within doctors. A concern that arises with clustered data is that cluster-level characteristics (e.g., characteristics of the doctor) are associated with both treatment selection and patient outcomes, resulting in cluster-level confounding. Measuring and modeling cluster attributes can be difficult and statistical methods exist to control for all unmeasured cluster characteristics. An assumption of these methods however is that characteristics of the cluster and the effects of those characteristics on the outcome (as well as probability of treatment assignment when using covariate balancing methods) are constant over time. In this paper, we consider methods that relax this assumption and allow for estimation of treatment effects in the presence of unmeasured time-dependent cluster confounding. The methods are based on matching with the propensity score and incorporate unmeasured time-specific cluster effects by performing matching within clusters or using fixed- or random-cluster effects in the propensity score model. The methods are illustrated using data to compare the effectiveness of two total hip devices with respect to survival of the device and a simulation study is performed that compares the proposed methods. One method that was found to perform well is matching within surgeon clusters partitioned by time. Considerations in implementing the proposed methods are discussed.

Postmarket surveillance of arthroplasty device components using machine learning methods.

PURPOSE: While joint arthroplasty is generally a safe and effective procedure, there are concerns that some devices are at increased risk of failure. Early identification of total hip arthroplasty devices with increased risk of failure can be challenging because devices consist of multiple components, hundreds of distinct components are currently used in surgery, and any estimated effect needs to address confounding due to device and patient factors. The purpose of this study was to assess the effectiveness of machine learning approaches at identifying recalled components listed by the US Food and Drug Administration using data from a US total joint arthroplasty registry. METHODS: An open cohort study was conducted using data (January 1, 2001, to December 31, 2015) from 74 520 implantations and 348 unique components in the Kaiser Permanente Total Joint Replacement Registry. Exposures of interest were device components used in elective primary total hip arthroplasty. The outcome was time to first revision surgery, defined as exchange, removal, or addition of any component. Machine learning methods included regularized/unregularized Cox models and random survival forest. RESULTS: Among the recalled components detected were ASR acetabular shell/large femoral head, Durom acetabular shell/Metasul large femoral head, and Rejuvenate modular neck stem. The three components not identified were characterized by small numbers of devices recorded in the registry. CONCLUSIONS: The novel approaches to signal detection may improve postmarket surveillance of frequently used arthroplasty devices, which in turn will improve public health.

Survival and Reintervention Risk by Patient Age and Preoperative Abdominal Aortic Aneurysm Diameter after Endovascular Aneurysm Repair.

BACKGROUND: Endovascular aneurysm repair (EVAR) has become the standard of care for abdominal aortic aneurysm (AAA), but questions remain regarding the benefit in high-risk and elderly patients. The purpose of this study was to examine the effect of age, preoperative AAA diameter, and their interaction on survival and reintervention rates after EVAR. METHODS: Our integrated health system's AAA endograft registry was used to identify patients who underwent elective EVAR between 2010 and 2014. Of interest was the effect of patient age at the time of surgery (≤80 vs. >80 years old), preoperative AAA diameter (≤5.5 cm vs. >5.5 cm), and their interaction. Primary endpoints were all-cause mortality and reintervention. Between-within mixed-effects Cox models with propensity score weights were fit. RESULTS: Of 1,967 patients undergoing EVAR, unadjusted rates for survival at 4 years after EVAR was 76.1%, and reintervention-free rate was 86.0%. For mortality, there was insufficient evidence for an interaction between age and AAA size (P = 0.309). Patient age >80 years was associated with 2.53-fold higher mortality risk (hazard ratios [HR] = 2.53; 95% confidence intervals [CI], 1.73-3.70; P < 0.001), whereas AAA > 5.5 cm was associated with 1.75-fold higher mortality risk (HR = 1.75; 95% CI, 1.26-2.45; P = 0.001). For reintervention risk, there were no significant interactions or main effects for age or AAA diameter. CONCLUSIONS: Age and AAA diameter are independent predictors of reduced survival after EVAR, but the effect is not amplified when both are present. Age >80 years or AAA size >5.5 cm did not increase the risk of reintervention. No specific AAA size, patient age, or combination thereof was identified that would contraindicate AAA repair.

An international comparison of THA patients, implants, techniques, and survivorship in Sweden, Australia, and the United States.

Background and purpose - International comparisons of total hip arthroplasty (THA) practices and outcomes provide an opportunity to enhance the quality of care worldwide. We compared THA patients, implants, techniques, and survivorship in Sweden, Australia, and the United States. Patients and methods - Primary THAs due to osteoarthritis were identified using Swedish (n = 159,695), Australian (n = 279,693), and US registries (n = 69,641) (2003-2015). We compared patients, practices, and implant usage across the countries using descriptive statistics. We evaluated time to all-cause revision using Kaplan-Meier survival curves. We assessed differences in countries' THA survival using chi-square tests of survival probabilities. Results - Sweden had fewer comorbidities than the United States and Australia. Cement fixation was used predominantly in Sweden and cementless in the United States and Australia. The direct anterior approach was used more frequently in the United States and Australia. Smaller head sizes (≤ 32 mm vs. ≥ 36 mm) were used more often in Sweden than the United States and Australia. Metal-on-highly cross-linked polyethylene was used more frequently in the United States and Australia than in Sweden. Sweden's 5- (97.8%) and 10-year THA survival (95.8%) was higher than the United States' (5-year: 97.0%; 10-year: 95.2%) and Australia (5-year: 96.3%; 10-year: 93.5%). Interpretation - Patient characteristics, surgical techniques, and implants differed across the 3 countries, emphasizing the need to adjust for demographics, surgical techniques, and implants and the need for global standardized definitions to compare THA survivorship internationally.

Meta-analysis of individual registry results enhances international registry collaboration.

Background and purpose - Although common in medical research, meta-analysis has not been widely adopted in registry collaborations. A meta-analytic approach in which each registry conducts a standardized analysis on its own data followed by a meta-analysis to calculate a weighted average of the estimates allows collaboration without sharing patient-level data. The value of meta-analysis as an alternative to individual patient data analysis is illustrated in this study by comparing the risk of revision of porous tantalum cups versus other uncemented cups in primary total hip arthroplasties from Sweden, Australia, and a US registry (2003-2015). Patients and methods - For both individual patient data analysis and meta-analysis approaches a Cox proportional hazard model was fit for time to revision, comparing porous tantalum (n = 23,201) with other uncemented cups (n = 128,321). Covariates included age, sex, diagnosis, head size, and stem fixation. In the meta-analysis approach, treatment effect size (i.e., Cox model hazard ratio) was calculated within each registry and a weighted average for the individual registries' estimates was calculated. Results - Patient-level data analysis and meta-analytic approaches yielded the same results with the porous tantalum cups having a higher risk of revision than other uncemented cups (HR (95% CI) 1.6 (1.4-1.7) and HR (95% CI) 1.5 (1.4-1.7), respectively). Adding the US cohort to the meta-analysis led to greater generalizability, increased precision of the treatment effect, and similar findings (HR (95% CI) 1.6 (1.4-1.7)) with increased risk of porous tantalum cups. Interpretation - The meta-analytic technique is a viable option to address privacy, security, and data ownership concerns allowing more expansive registry collaboration, greater generalizability, and increased precision of treatment effects.

Is There a Difference in Revision Risk Between Metal and Ceramic Heads on Highly Crosslinked Polyethylene Liners?

BACKGROUND: The most common bearing surface used among primary THAs worldwide is a metal or ceramic femoral head that articulates against a highly crosslinked ultrahigh-molecular-weight polyethylene (HXLPE) acetabular liner. Despite their widespread use, relatively little is known about the comparative effectiveness of ceramic versus metal femoral heads with respect to risk of revision and dislocation as well as the role of head size in this relationship. QUESTIONS/PURPOSES: The purpose of this study was to evaluate the risk of (1) all-cause revision in metal versus ceramic femoral heads when used with an HXLPE liner, including an evaluation of the effect of head size; and (2) dislocation in metal versus ceramic femoral heads when used with an HXLPE liner as well as an assessment of the effect of head size. METHODS: Data were collected as part of the Kaiser Permanente Total Joint Replacement Registry between 2001 and 2013. Patients in this study were on average overweight (body mass index = 29 kg/m2), 67 years old, mostly female (57%), and had osteoarthritis (93%) as the primary indication for surgery. The material of the femoral head (metal, ceramic) was crossed with head size (< 32, 32, 36, > 36 mm), yielding eight device groupings. Only uncemented devices were evaluated. The primary outcome was all-cause revision (n = 28,772) and the secondary outcome was dislocation within 1 year (n = 19,623). Propensity scores were used to adjust for potential confounding at the implant/patient level using between-within semiparametric survival models that control for surgeon and hospital confounding and adjust estimates for the within-cluster correlation among observations on the response. RESULTS: For all-cause revision, there was no difference between ceramic versus metal (reference) heads in combination with an HXLPE liner (hazard ratio [HR] = 0.82 [0.65-1.04], p = 0.099). Smaller metal head sizes of < 32 mm were associated with increased risk of revision relative to 36 mm (HR = 1.66 [1.20-2.31], p = 0.002, adjusted p = 0.025). For dislocation, ceramic heads increased risk relative to metal at < 32 mm only (HR = 4.39 [1.72-11.19], p = 0.002, adjusted p = 0.020). Head sizes < 32 mm were associated with increased risk of dislocation relative to 36 mm for metal (HR = 2.99 [1.40-6.39], p = 0.005, adjusted p = 0.047) and ceramic heads (HR = 15.69 [6.07-40.55], p < 0.001, adjusted p < 0.001). CONCLUSIONS: The results did not provide evidence for use of one femoral head material over another when used with HXLPE liners for the outcome of revision, but for dislocation, metal performed better than ceramic with < 32-mm heads. Overall, the findings suggest increased risk of revision/dislocation with head sizes < 32 mm. LEVEL OF EVIDENCE: Level III, therapeutic study.

Midterm-Adjusted Survival Comparing the Best Performing Unicompartmental and Total Knee Arthroplasties in a Registry.

BACKGROUND: Recent literature suggests that the difference in revision risk between unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) can be influenced by surgeon volume and other confounders. We hypothesized that implant selection might decrease the relative risk of revision in an adjusted model. METHODS: We selected the best performing (BP) primary UKAs and TKAs performed for osteoarthritis between January 2001 and December 2012 collected through a joint replacement registry. We compared aseptic and all-cause risk of revision using a surgeon-stratified Cox regression model with propensity score adjustment. RESULTS: One thousand fifty-four UKAs were compared with 74,185 TKAs. The rate for all-cause revision was lower for UKAs (2.1%) than for TKAs (2.4%), whereas the rate for aseptic revision was higher for UKAs (2.0%) than TKAs (1.4%). The adjusted risk of aseptic revision was not significantly higher for UKA than TKA (hazard ratio = 2.02 [0.68, 5.96], P = .203) or all-cause revision (hazard ratio = 1.24 [0.52, 2.98], P = .603). CONCLUSION: When comparing the survivorship of the BP UKAs to the BP TKAs in our registry, the adjusted risk of revision remained higher for UKAs than for TKAs, although the difference did not reach statistical significance.

Comparative Effectiveness and Safety of Drug Prophylaxis for Prevention of Venous Thromboembolism After Total Knee Arthroplasty.

BACKGROUND: Rates of venous thromboembolism in contemporary studies of primary total knee arthroplasty (TKA) have been reported to be as high as 3.5%. Although drug prophylaxis is effective, the best option among these regimens is not well established. The purpose of this study was to evaluate the comparative effectiveness and safety of aspirin, low-molecular-weight heparin, synthetic pentasaccharide factor Xa inhibitors, and vitamin K antagonist. METHODS: Data were from a US total joint replacement registry, with 30,499 patients receiving unilateral TKA from May 16, 2006, to December 31, 2013. Patients received either aspirin (324-325 mg daily), enoxaparin (40-60 mg daily), fondaparinux (2.5 mg daily), or warfarin (all doses) and were followed up 90 days postoperatively on several outcomes: deep vein thrombosis, pulmonary embolism, major bleeding, wound complications, infection, and death. RESULTS: There was no evidence that fondaparinux, enoxaparin, or warfarin were superior to aspirin in the prevention of pulmonary embolism, deep vein thrombosis, or venous thromboembolism or that aspirin was safer than these alternatives. However, enoxaparin was found to be as safe as aspirin with respect to bleeding, and fondaparinux was as safe as aspirin for risk of wound complications. CONCLUSION: Among TKA patients, we did not find evidence for decreased effectiveness or increased safety with use of aspirin, but enoxaparin had comparable safety to aspirin for bleeding and fondaparinux had comparable safety to aspirin for wound complications.

Bilateral Simultaneous vs Staged Total Knee Arthroplasty: A Comparison of Complications and Mortality.

BACKGROUND: The purpose of this study was to compare the complications and mortality between bilateral simultaneous total knee arthroplasty (BTKA-Simultaneous) and bilateral staged TKA (BTK-Staged) while adjusting for differences in patient, surgeon, and hospital characteristics. METHODS: An integrated health care system total joint registry was used to compare patients undergoing BTKA-Simultaneous to BTKA-Staged. For outcomes related to revision and infection, the sample included 11,118 patients, and for outcomes of death, acute myocardial infarction, stroke, and venous thromboembolism, a subsample of 7991 patients with comorbidity data was selected. RESULTS: Overall death and complications in both groups were rare. The complication rates for BTKA-Simultaneous and BTKA-Staged were comparable: aseptic revision (1.17% vs 0.9%), septic revision/deep infection (0.8% vs 0.7%), death (0.28% vs 0.1%), and adverse events (2.49% vs 1.97%). In the adjusted models, there were no significant differences in any of the outcomes between the 2 groups. CONCLUSION: There is a lack of evidence to support superiority of either BTKA-Simultaneous or BTKA-Staged.

Similar mortality with general or regional anesthesia in elderly hip fracture patients.

BACKGROUND AND PURPOSE: There is continuing confusion among practitioners with regard to the optimal choice of anesthetic type for repair of hip fractures. We investigated whether type of anesthetic was associated with short-term mortality after hip fracture surgery. PATIENTS AND METHODS: We conducted a retrospective cohort study of patients with surgically treated hip fractures, performed between January 1, 2009 and December 31, 2012. Exposure of interest was anesthesia type (general, spinal/neuroaxial, and mixed). Endpoints were 30-, 90-, and 365-day post-surgery mortality. Multivariable conditional logistic regression models were used and odds ratios (ORs) and 95% confidence intervals (CIs) are reported. RESULTS: Of the 7,585 participants, 5,412 (71%) were women and the median age was 80 (IQR: 72-85) years old. Of the total cohort, 4,257 (56%) received general anesthesia, 3,059 (40%) received spinal/neuroaxial, and 269 (4%) received mixed anesthesia. Overall, the incidence of 30-, 90-, and 365-day mortality was 4% (n = 307), 8% (n = 583), and 15% (n = 1,126), respectively. When compared with general anesthesia, the 365-day odds of mortality was marginally lower in patients with spinal/neuroaxial anesthesia (OR = 0.84, CI: 0.70-1.0), but it was similar in patients with mixed anesthesia (OR = 1.3, CI: 0.70-2.3). No other statistically significant differences were observed. INTERPRETATION: Regarding mortality, this study does not support specific recommendations regarding the type of anesthetic in surgery of fractured hips.

Is there a difference in total knee arthroplasty risk of revision in highly crosslinked versus conventional polyethylene?

BACKGROUND: Highly crosslinked polyethylene (HXLPE) was introduced to reduce wear and associated osteolysis in total knee arthroplasty (TKA). However, there is limited clinical evidence that HXLPE is more effective than conventional polyethylene (CPE) in TKA. QUESTIONS/PURPOSES: (1) Do primary TKAs with HXLPE tibial inserts have a lower risk of revision (all-cause, aseptic, and septic) than TKAs with CPE tibial inserts? (2) In NexGen TKA (Zimmer Inc, Warsaw, IN, USA) bearings, do HXLPE tibial inserts have a lower risk of revision (all-cause, aseptic, and septic) than CPE tibial inserts? (3) In Press-Fit Condylar TKA (PFC or PFC Sigma; DePuy Inc, Warsaw, IN, USA), do HXLPE tibial inserts have a lower risk of revision (all-cause, aseptic, and septic) than procedures performed with CPE tibial inserts? METHODS: The Kaiser Permanente Total Joint Replacement Registry was used to identify primary TKAs (N = 77,084) performed during the study period (April 2001 to December 2011) with cobalt-chromium alloy on CPE (CoCr-CPE) and CoCr-HXLPE bearings. The registry has 95% voluntary participation and less than 9% were loss to followup during the 10-year study period. A total of 60,841 (79%) had CoCr-CPE bearings, 11,048 (14%) had CoCr-HXLPE bearings, and 5195 (7%) were unknown. Specific knee implant designs (NexGen, Zimmer and PFC-Sigma, DePuy Inc) were also evaluated. These implants represented 41% (31,793) and 49% (37,457), respectively, of the 77,084 TKAs of known implant types registered during that period; implant selection was at the discretion of the attending surgeon. Descriptive statistics and marginal Cox regression models with propensity score adjustments were applied to compare risk of revision for CoCr-CPE versus CoCr-HXLPE TKA bearings. RESULTS: At 5 years followup, cumulative incidence of revision for CoCr-CPE and CoCr-XLPE were 2.7% and 3.1%, respectively. Adjusted risks of all-cause (hazard ratio [HR], 1.05; 95% confidence interval [CI], 0.86-1.29; p = 0.620), aseptic (HR, 1.01; 95% CI, 0.77-1.32; p = 0.954), and septic revision (HR, 1.11; 95% CI, 0.81-1.51; p = 0.519) did not differ in patients with CoCr-XLPE bearings compared with CoCr-CPE. Within TKAs with NexGen components, the adjusted risks of all-cause (HR, 1.14; 95% CI, 0.86-1.51; p = 0.354), aseptic (HR, 1.14; 95% CI, 0.79-1.65; p = 0.493), and septic revision (HR, 1.14; 95% CI, 0.76-1.73; p = 518) were similar in patients with CoCr-XLPE compared with those with CoCr-CPE bearings. Finally, within the TKAs with PFC components, the adjusted risks of all-cause (HR, 0.80; 95% CI, 0.49-1.30; p = 0.369), aseptic (HR, 0.62; 95% CI, 0.62-1.14; p = 0.123), and septic revision (HR, 0.97; 95% CI, 0.51-1.85; p = 0.929) were also similar in patients with CoCr-XLPE compared with those with CoCr-CPE bearings. CONCLUSIONS: In this large study, we did not find differences in risk of revision for CoCr-HXLPE compared with CoCr-CPE bearings at 5 years followup. In selecting HXLPE in TKA, clinicians should consider the increased cost and lack of available evidence of performance for greater than 10 years followup. Future studies are necessary to evaluate longitudinal outcomes of CoCr-HXLPE versus conventional TKA bearings. LEVEL OF EVIDENCE: Level III, therapeutic study.

Anterior and Anterolateral Approaches for THA Are Associated With Lower Dislocation Risk Without Higher Revision Risk.

BACKGROUND: Lack of consensus continues regarding the benefit of anteriorly based surgical approaches for primary total hip arthroplasty (THA). The purpose of this study was to evaluate the risk of aseptic revision, septic revision, and dislocations for various approaches used in primary THAs from a community-based healthcare organization. QUESTIONS/PURPOSES: (1) What is the incidence of aseptic revision, septic revision, and dislocation for primary THA in a large community-based healthcare organization? (2) Does the risk of aseptic revision, septic revision, and dislocation vary by THA surgical approach? METHODS: The Kaiser Permanente Total Joint Replacement Registry was used to identify primary THAs performed between April 1, 2001 and December 31, 2011. Endpoints were septic revisions, aseptic revisions, and dislocations. The exposure of interest was surgical approach (posterior, anterolateral, direct lateral, direct anterior). Patient, implant, surgeon, and hospital factors were evaluated as possible confounders. Survival analysis was performed with marginal multivariate Cox models. Hazard ratios (HRs) and 95% confidence intervals (CIs) are reported. A total of 42,438 primary THAs were available for analysis of revision outcomes and 22,237 for dislocation. Median followup was 3 years (interquartile range, 1-5 years). The registry's voluntary participation is 95%. The most commonly used approach was posterior (75%, N = 31,747) followed by anterolateral (10%, N = 4226), direct anterior (4%, N = 1851), and direct lateral (2%, N = 667). RESULTS: During the study period 785 hips (2%) were revised for aseptic reasons, 213 (0.5%) for septic reasons, and 276 (1%) experienced a dislocation. The revision rate per 100 years of observation was 0.54 for aseptic revisions, 0.15 for septic revisions, and 0.58 for dislocations. There were no differences in adjusted risk of revision (either septic or aseptic) across the different THA approaches. However, the anterolateral approach (adjusted HR, 0.29; 95% CI, 0.13-0.63, p = 0.002) and direct anterior approach (adjusted HR, 0.44; 95% CI, 0.22-0.87, p = 0.017) had a lower risk of dislocation relative to the posterior approach. There were no differences in any of the outcomes when comparing the direct anterior approach with the anterolateral approach. CONCLUSIONS: Anterior and anterolateral surgical approaches had the advantage of a lower risk of dislocation without increasing the risk of early revision. LEVEL OF EVIDENCE: Level III, therapeutic study.

Two-Day Length of Stay is Not Inferior to 3 Days in Total Knee Arthroplasty with Regards to 30-Day Readmissions.

The impact of a shortened length of stay (LOS) following total knee arthroplasty (TKA) on the risk of readmission is not well documented despite recent trends towards shorter hospitalization. We retrospectively compared the adjusted risk of 30-day readmission following TKA between patients with 2-, 3- and 4-day LOS using current postoperative care protocols. A total of 23,655 consecutive primary, unilateral TKAs operated between 01/01/2009 and 12/31/2011 were studied retrospectively using non-inferiority testing. The main outcome was 30-day readmission. Two-day LOS decreased the odds of readmission by a factor of 0.96, with an upper bound one-sided 95% confidence interval of 1.10. After adjusting for other variables, LOS of 2 days is not inferior to 3 days with respect to the risk of 30-day readmission.

Risk factors for total hip arthroplasty aseptic revision.

The purpose of this study was to evaluate patient, operative, implant, surgeon, and hospital factors associated with aseptic revision after primary THA in patients registered in a large US Total Joint Replacement Registry. A total of 35,960 THAs registered from 4/2001-12/2010 were evaluated. The 8-year survival rate was 96.7% (95% CI 96.4%-97.0%). Females had a higher risk of aseptic revision than males. Hispanic and Asian patients had a lower risk of revision than white patients. Ceramic-on-ceramic, ceramic-on-conventional polyethylene, and metal-on-conventional polyethylene bearing surfaces had a higher risk of revision than metal-on-highly cross-linked polyethylene. Body mass index, health status, diabetes, diagnosis, fixation, approach, bilateral procedures, head size, surgeon fellowship training, surgeon and hospital volume were not revision risk factors.

Leadership, organizational climate, and working alliance in a children's mental health service system.

The goal of this study was to examine the relationships of transformational leadership and organizational climate with working alliance, in a children's mental health service system. Using multilevel structural equation modeling, the effect of leadership on working alliance was mediated by organizational climate. These results suggest that supervisors may be able to impact quality of care through improving workplace climate. Organizational factors should be considered in efforts to improve public sector services. Understanding these issues is important for program leaders, mental health service providers, and consumers because they can affect both the way services are delivered and ultimately, clinical outcomes.

Risk factors for total knee arthroplasty aseptic revision.

Using a Total Joint Replacement Registry, patient, operative, implant, surgeon, and hospital risk factors associated with aseptic revision after primary total knee arthroplasty (TKA) were evaluated. From 04/2001 to 12/31/2010 64,017 primary TKA cases, followed for a median time of 2.9 years, were registered and included in the analysis. Patients were predominantly female, white, with osteoarthritis, and obese. The crude aseptic revision rate is 1.3% (N=826). The cumulative survival for aseptic revision at 8 years is 97.6% (95% CI 97.3%-97.8%). Adjusted models revealed that age, race, body mass index, diabetic status, bilateral procedures, high-flex implants, and the LCS mobile bearing knee are associated with risk of revision. Gender, general health status, diagnosis, surgeon fellowship training, surgeon volume, hospital volume, fixation, and bearing surface material were not associated with risk of aseptic revision. Recognition of surgical factors associated with TKA failures can help the surgeons with their choices of surgical techniques and implants.

Alternative bearings in total knee arthroplasty: risk of early revision compared to traditional bearings: an analysis of 62,177 primary cases.

BACKGROUND AND PURPOSE: There is no substantial clinical evidence for the superiority of alternative bearings in total knee arthroplasty (TKA). We compared the short-term revision risk in alternative surface bearing knees (oxidized zirconium (OZ) femoral implants or highly crosslinked polyethylene (HXLPE) inserts) with that for traditional bearings (cobalt-chromium (CoCR) on conventional polyethelene (CPE)). The risk of revision with commercially available HXLPE inserts was also evaluated. METHODS: All 62,177 primary TKA cases registered in a Total Joint Replacement Registry between April 2001 and December 2010 were retrospectively analyzed. The endpoints for the analysis were all-cause revisions, septic revisions, or aseptic revisions. Bearing surfaces were categorized as OZ-CPE, CoCr-HXLPE, or CoCr-CPE. HXLPE inserts were stratified according to brand name. Confounding was addressed using propensity score weights. Marginal Cox-regression models adjusting for surgeon clustering were used. RESULTS: The proportion of females was 62%. Average age was 68 (SD 9.3) years, and median follow-up time was 2.8 (IQR 1.2-4.9) years. After adjustments, the risks of all-cause, aseptic, and septic revision with CoCr-HXLPE and OZ-CPE bearings were not statistically significantly higher than with traditional CoCr-CPE bearings. No specific brand of HXLPE insert was associated with a higher risk of all-cause, aseptic, or septic revision compared to CoCr-CPE. INTERPRETATION: At least in the short term, none of the alternative knee bearings evaluated (CoCr-HXLPE or OZ-CPE) had a greater risk of all-cause, aseptic, and septic revision than traditional CoCr-CPE bearings.