Yuexin Chen

Leveraging Electronic Medical Records for Surveillance of Surgical Site Infection in a Total Joint Replacement Population

OBJECTIVE To evaluate whether a hybrid electronic screening algorithm using a total joint replacement (TJR) registry, electronic surgical site infection (SSI) screening, and electronic health record (EHR) review of SSI is sensitive and specific for SSI detection and reduces chart review volume for SSI surveillance. DESIGN Validation study. SETTING A large health maintenance organization (HMO) with 8.6 million members. METHODS Using codes for infection, wound complications, cellullitis, procedures related to infections, and surgeon-reported complications from the International Classification of Diseases, Ninth Revision, Clinical Modification, we screened each TJR procedure performed in our HMO between January 2006 and December 2008 for possible infections. Flagged charts were reviewed by clinical-content experts to confirm SSIs. SSIs identified by the electronic screening algorithm were compared with SSIs identified by the traditional indirect surveillance methodology currently employed in our HMO. Positive predictive values (PPVs), negative predictive values (NPVs), and specificity and sensitivity values were calculated. Absolute reduction of chart review volume was evaluated. RESULTS The algorithm identified 4,001 possible SSIs (9.5%) for the 42,173 procedures performed for our TJR patient population. A total of 440 case patients (1.04%) had SSIs (PPV, 11.0%; NPV, 100.0%). The sensitivity and specificity of the overall algorithm were 97.8% and 91.5%, respectively. CONCLUSION An electronic screening algorithm combined with an electronic health record review of flagged cases can be used as a valid source for TJR SSI surveillance. The algorithm successfully reduced the volume of chart review for surveillance by 90.5%.

Outcomes of Routine Use of Antibiotic-Loaded Cement in Primary Total Knee Arthroplasty

The routine use of antibiotic-loaded bone cement (ALBC) in primary total knee arthroplasty (TKA) is controversial. Outcomes were recorded in patients who underwent primary TKA from May 2003 to March 2007 using a community-based total joint registry. Infection rates were compared in patients undergoing TKA with ALBC and regular cement. A total of 22 889 primary TKA were performed, with 2030 cases (8.9%) using ALBC. Two thousand four hundred forty-nine patients were diabetic (10.7%), with ALBC used in 295 cases (12%). The rate of deep infection was 1.4% for ALBC TKA (28 cases) and 0.7% (154 cases) with regular cement (P = .002). Among patients with diabetes, the infection rate was 1.7% (5 cases) with ALBC and 0.9% (19 cases) with regular cement (P = .199). In patients whom surgeons considered higher risk for infection, ALBC did not appear to reduce TKA infection rates. The routine use of antibiotic-laden cement warrants further investigation.

Risk Factors Associated With 30-day Readmissions After Instrumented Spine Surgery in 14,939 Patients: 30-day readmissions after instrumented spine surgery

Study Design. A retrospective review of instrumented spine registry from an integrated US healthcare system. Objective. Investigate the 30-day readmission rate and risk factors after instrumented spine surgery. Summary of Background Data. Published readmission rates range from 2% to over 20%. We were interested in learning which patients were at greatest risk, when did readmissions occur, and why. Method. 30-day readmission rates were determined for 14,939 patients after an index spine procedure between 1/2009 and 3/2013. Data were analyzed with descriptive statistics, univariate, and multivariate logistic regression analysis. Result. The average age of the cohort was 59 (SD = 13.4) and 52% were female. The 30-day readmission rate was 5.5% (821/14,939). The temporal pattern for readmission was: 17% (140) at week 1, 48% (394) at week 2, 72% (591) at week 3, and 100% (821) at week 4. The leading causes were wound complications (infection, hematoma, dehiscence, seroma), sepsis, pain management, pneumonia, and pulmonary emboli/deep venous thrombosis. In a multivariate model, readmission risk factors were: malignancy (OR 2.99, 95% CI: 1.56, 5.73), operative time more than 400 minutes (OR 2.59, 95% CI: 1.66, 4.02), operative time 300–399 minutes (OR 2.33, 95% CI: 1.54–3.52), hospital stay 6–10 days (OR 2.03, 95% CI: 1.31–3.14), hospital stay more than 10 days (OR 1.85, 95% CI: 1.1, −3.08), surgical complications (OR 1.67, 95% CI: 1.18, 2.36), operative time 200–299 (OR 1.52, 95% CI: 1.04, 2.22), depression (OR 1.48, 95% CI: 1.14, 1.93), rheumatoid arthritis (OR 1.45, 95% CI: 1.05, 2.01), deficiency anemia (OR 1.30, 95% CI: 1.05, 1.61), and hypothyroidism (OR 1.29, 95% CI: 1.01, 1.64). Conclusion. Surgical complications (dural tear, deep infections, superficial infections, epidural hematoma), malignancy, lengthy operative times, and lengthy initial hospitalizations are all risk factors for 30-day readmission. These findings should be considered during preoperative assessment and surgical planning. Level of Evidence: 3

Statistics in Brief: An Introduction to the Use of Propensity Scores

Randomized controlled trials (RCTs) are considered the gold standard of clinical research because randomization reduces the risk of extraneous factors influencing results of a study [2]. Nonetheless, high-quality, observational studies are at times more desirable than experimental studies (such as RCTs) owing to the their capacity to evaluate rare events, fewer ethical challenges with conducting the study, feasibility attributable to lower costs or infrastructure needs, and sometimes greater generalizability of the findings because of less-strict inclusion or exclusion criteria for patients and surgeons. Most orthopaedic studies are observational and retrospective [4, 7, 24]. Confounding exists when a third variable, which is not the exposure or outcome of interest, changes the relationship between the exposure and outcome being studied. For a variable to be a confounder, it must be (1) associated with the exposure of interest in the study, and (2) associated with the outcome. For a more real-life example, consider a study evaluating differences in time to revision between ceramic-on-ceramic and metal-on-polyethylene bearings used in THAs. The surgeon’s choice of bearing surface is likely not random; younger patients preferentially receive ceramic-on-ceramic bearings as opposed to metal-onpolyethylene bearings. If age also is related to the outcome (revision) in the study population, then age is regarded as a confounder. If the effect of age is not incorporated in the analysis, the estimate of the treatment effect (eg, odds ratio) will be biased. Confounding can be addressed using several methods with similar objectives during either the design or analysis phases of a study. Examples of methods used during the design of a study include restriction or matching, whereas those used during analysis include stratification, regression adjustment, instrumental variables techniques, and propensity score techniques. The purpose of this article is to describe confounding and how its effects can be minimized in observational studies with propensity score techniques. We provide guidance for when and how to use propensity scoring in studies.

Injury pathology at the time of anterior cruciate ligament reconstruction associations with self-assessment of knee function.

Objective:To evaluate the association of preoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) and structural injuries reported at the time of anterior cruciate ligament reconstruction (ACLR). Design:Cross-sectional study. Setting:Three medical centers in California. Participants:Primary ACLRs (N = 636) performed between January 2009 and June 2010. Independent Variables:The 5 KOOS subscales: pain, other symptoms, activities of daily living (ADL), function in sport and recreation (Sport/Rec), and quality of life (QoL). Main Outcome Measures:Associated injuries (cartilage, medial meniscus, lateral meniscus, other ligaments), identified at the time of ACLR. Results:Sixty-eight percent of the cohort was male and the median age was 26 years. No gender differences in KOOS were observed. No KOOS differences were observed by race, except in Sport/Rec. Younger patients reported higher KOOS. Pain and ADL scores were not associated with any concurrent injury. A 10-point increase in KOOS symptoms subscale was associated with 22% higher likelihood of isolated ACL, 13% lower likelihood of medial meniscus injury, and 10% lower likelihood of lateral meniscus. A 10-point increase in the KOOS Sport/Rec subscale score was associated with 8% higher likelihood of isolated ACL and 9% lower likelihood of medial meniscus injury. A 10-point increase in the KOOS QoL subscale was associated with 15% lower likelihood of medial meniscus injury. Conclusions:Weak associations between the symptoms, Sports/Rec, and QoL subscales and structural injuries at ACLR were observed. The KOOS and its subscales are not useful as indicators of the pattern or severity of preoperative injury of patients presenting for ACLR.

Bone morphogenetic protein (BMP-2) usage and cancer correlation: An analysis of 10,416 spine fusion patients from a multi-center spine registry

• This is an independent, non-industry supported study—one of the few that exists in the literature.

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.

Does pre-coating total knee tibial implants affect the risk of aseptic revision?

We evaluated the impact of pre-coating the tibial component with polymethylmethacrylate (PMMA) on implant survival in a cohort of 16 548 primary NexGen total knee replacements (TKRs) in 14 113 patients. In 13 835 TKRs a pre-coated tray was used while in 2713 TKRs the non-pre-coated version of the same tray was used. All the TKRs were performed between 2001 and 2009 and were cemented. TKRs implanted with a pre-coated tibial component had a lower cumulative survival than those with a non-pre-coated tibial component (p = 0.01). After adjusting for diagnosis, age, gender, body mass index, American Society of Anesthesiologists grade, femoral coupling design, surgeon volume and hospital volume, pre-coating was an independent risk factor for all-cause aseptic revision (hazard ratio 2.75, p = 0.006). Revision for aseptic loosening was uncommon for both pre-coated and non-pre-coated trays (rates of 0.12% and 0%, respectively). Pre-coating with PMMA does not appear to be protective of revision for this tibial tray design at short-term follow-up.

Analysis of mitral valve replacement outcomes is enhanced by meaningful clinical use of electronic health records.

OBJECTIVE Cardiac surgical mortality has improved during the last decade despite the aging of the population. An integrated US health plan developed a heart valve registry to track outcomes and complications of heart valve operations. This database was used for longitudinal evaluation of mitral valve (MV) outcomes from 1999 to 2008 at four affiliated hospitals. METHODS We identified 3130 patients in the Apollo database who underwent 3180 initial MV procedures. Internal administrative and Social Security Administration databases were merged to determine survival rates. Electronic health records were searched to ascertain demographics, comorbidities, and postoperative complications. Cox regression was used to evaluate mean survival and identify risk factors. RESULTS The procedures included 1160 mechanical valve replacements, 1159 tissue valve replacements, and 861 annuloplasties. The mean age of patients undergoing these procedures was 58 ± 11 years, 69 ± 12 years, and 62 ± 12 years, respectively. Mean survival was 8.9 ± 0.1 years for mechanical valve replacement, 7.0 ± 0.1 years for tissue valve replacement, and 7.7 ± 0.1 years for annuloplasty. Early in the study, there was a preference for implanting mechanical MVs. Beginning in 2003, more patients received tissue valve replacements rather than mechanical valves. Over time, there was an increasing trend of annuloplasty. Cox regression analysis identified the following risk factors for increased ten-year mortality: tissue valve implantation; advanced age; female sex; nonelective, nonisolated procedure; diabetes; postoperative use of banked blood products; previous cardiovascular intervention; dialysis; and longer perfusion time. Hospital location, reoperation, preoperative anticoagulation, and cardiogenic shock were not statistically significant risk factors. CONCLUSIONS When controlling for other risk factors, we observed a lower long-term survival rate for tissue valve replacement compared with mechanical valve replacement. Integrating electronic health records with existing electronic databases provided near-real-time analysis of longitudinal cardiac surgical outcomes.

Does chronic kidney disease affect the mortality rate in patients undergoing spine surgery

The number of patients with chronic kidney disease (CKD) and their life expectancy has been increasing. With time number of patients undergoing spine surgery has also been on a rise. This study we did a retrospective review of registry data to investigate the mortality rate of chronic kidney disease patients following spine surgery using a large, multi-center spine registry. 12,276 consecutive spine-fusion patients from January 2009 to December 2012 were included and mortality rates in patients with CKD compared to those with normal kidney function following spine surgery. Logistic regression was usedto evaluate risk of mortality following spine surgery. The average age of the cohort was 59 (SD=13.4). 53% were female. Patients who had stage 3, 4 or 5 CKD were older than non-CKD patients (mean=71,SD=9.2 vs. 59, SD=13.3). After adjusting for confounding variables, patients with stage 3 or 4 CKD had higher mortality rates than patients with normal kidney function (OR 1.78, 95% CI 1.3-2.45) Hemodialysis-dependent patients (stage 5 CKD) had even higher rates of mortality compared to patients with normal function (OR 4.18, 95% CI1.87-9.34). our findings suggest that spine surgery is associated with significantly higher mortality rates in patients with CKD compared to patients with normal kidney function. Understanding the additional morbidity and mortality of spine surgery in this medically complicated group of patients is imperative for accurate preoperative risk assessment.