Are Case Volume and Facility Complexity Level Associated With Postoperative Complications After Hip Fracture Surgery in the Veterans Affairs Healthcare System?
Authors: Wong Jimmy K. , Kim T. Edward , Mudumbai Seshadri C. , Memtsoudis Stavros G. , Giori Nicholas J. , Howard Steven K. , Oka Roberta K. , King Robert , Mariano Edward R. 
Published: September 2018

Abstract

Background
Hospital-related factors associated with mortality and morbidity after hip fracture surgery are not completely understood. The Veterans Health Administration (VHA) is the largest single-payer, networked healthcare system in the country serving a relatively homogenous patient population with facilities that vary in size and resource availability. These characteristics provide some degree of financial and patient-level controls to explore the association, if any, between surgical volume and facility resource availability and hospital performance regarding postoperative complications after hip fracture surgery.

Questions/purposes
(1) Do VHA facilities with the highest complexity level designation (Level 1a) have a disproportionate number of better-than-expected performance outliers for major postoperative complications compared with lower-complexity level facilities? (2) Do VHA facilities with higher hip fracture surgical volume have a disproportionate number of better-than-expected performance outliers for major postoperative complications compared with lower-volume facilities?

Methods
We explored the Veterans Affairs Surgical Quality Improvement Project (VASQIP) database from October 2001 to September 2012 for records of hip fracture surgery performed. Data reliability of the VASQIP database has been previously validated. We excluded nine of the 98 VHA facilities for contributing fewer than 30 records. The remaining 89 VHA facilities provided 23,029 records. The VHA designates a complexity level to each facility based on multiple criteria. We labeled facilities with a complexity Level 1a (38 facilities)–the highest achievable VHA designated complexity level—as high complexity; we labeled all other complexity level designations as low complexity (51 facilities). Facility volume was divided into tertiles: high (> 277 hip fracture procedures during the sampling frame), medium (204 to 277 procedures), and low (< 204 procedures). The patient population treated by low-complexity facilities was older, had a higher prevalence of severe chronic obstructive pulmonary disease (26% versus 22%, p < 0.001), and had a higher percentage of patients having surgery within 2 days of hospital admission (83% versus 76%, p < 0.001). High-complexity facilities treated more patients with recent congestive heart failure exacerbation (4% versus 3%, p < 0.001). We defined major postoperative complications as having at least one of the following: death within 30 days of surgery, cardiac arrest requiring cardiopulmonary resuscitation, new q-wave myocardial infarction, deep vein thrombosis and/or pulmonary embolism, ventilator dependence for at least 48 hours after surgery, reintubation for respiratory or cardiac failure, acute renal failure requiring renal replacement therapy, progressive renal insufficiency with a rise in serum creatinine of at least 2 mg/dL from preoperative value, pneumonia, or surgical site infection. We used the observed-to-expected ratio (O/E ratio)—a risk-adjusted metric to classify facility performance—for major postoperative complications to assess the performance of VHA facilities. Outlier facilities with 95% confidence intervals (95% CI) for O/E ratio completely less than 1.0 were labeled “exceed expectation;” those that were completely greater than 1.0 were labeled “below expectation.” We compared differences in the distribution of outlier facilities between high and low-complexity facilities, and between high-, medium-, and low-volume facilities using Fisher’s exact test.

Results
We observed no association between facility complexity level and the distribution of outlier facilities (high-complexity: 5% exceeded expectation, 5% below expectation; low-complexity: 8% exceeded expectation, 2% below expectation; p = 0.742). Compared with high-complexity facilities, the adjusted odds ratio for major postoperative complications for low-complexity facilities was 0.85 (95% CI, 0.67–1.09; p = 0.108).
We observed no association between facility volume and the distribution of outlier facilities: 3% exceeded expectation and 3% below expectation for high-volume; 10% exceeded expectation and 3% below expectation for medium-volume; and 7% exceeded expectation and 3% below expectation for low-volume; p = 0.890). The adjusted odds ratios for major postoperative complications were 0.87 (95% CI, 0.73–1.05) for low- versus high-volume facilities and 0.89 (95% CI, 0.79–1.02] for medium- versus high-volume facilities (p = 0.155).

Conclusions
These results do not support restricting facilities from treating hip fracture patients based on historical surgical volume or facility resource availability. Identification of consistent performance outliers may help health care organizations with multiple facilities determine allocation of services and identify characteristics and processes that determine outlier status in the interest of continued quality improvement.

Level of Evidence
Level III, therapeutic study.