Incidence and Cost of Ankle Sprains in United States Emergency Departments

Research Team Members: Shweta Shah, Abbie Thomas, Josh Noone, Chris Blanchette, and Erik Wikstrom

ankleWhy did you do this study?

Injury associated with physical activity is a leading reason that people stop being physically active. Physical inactivity is clearly linked to a decreased quality of life and significant long-term health problems including obesity, osteoarthritis, and cardiovascular disease among others. Lateral ankle sprains, the most common injury sustained during sport, accounts for 60% of all sport related injuries. Unfortunately, up to 75% of people who sprain their ankle will develop residual symptoms, often termed “chronic ankle instability” which has been shown to significantly alter an individual’s health and function by causing him or her to become less active over their life span and linked with the development of ankle osteoarthritis.

Previous research has demonstrated that lateral ankle sprains are also a common injury in active-duty U.S. military service members, U.S. military cadets, the general European population, and the general U.S. population. For example, about 625,000 lateral ankle sprains were seen in U.S. emergency departments annually between 2002 and 2006. Despite this evidence, lateral ankle sprains are often incorrectly considered a minor injury with no lasting consequences by the general public, portions of the health care community, and policy makers. This problem is due, in part, to a lack of data regarding the financial impact of lateral ankle sprains in the U.S. and the only available estimate is severely outdated (1984). Therefore, our study aimed to generate a more recent estimate of the national incidence of lateral ankle sprains and the costs associated with lateral ankle sprains seen in U.S. emergency departments. We also determined the most common procedures undertaken for this injury to determine if there are unnecessary costs being charged to the patient.

ed-flow-pic1What did you do and what did you find in this study?

We accessed the Nationwide Emergency Department Sample (NEDS) to assess cross-sectional data on acute ankle sprain visits. This is a nationwide data set developed as a part of the Healthcare Cost and Utilization Project, a federal-state-industry partnership sponsored by the Agency for Healthcare Research and Quality. Only emergency department cases with a primary diagnosis of a lateral ankle sprain were included regardless of injuries and/or illnesses reported. Patient age was classified into categories ranging from pediatric (<13 years) to geriatric admissions (≥65 years) and mean emergency department charges were calculated based on the charge data provided for each visit. We then generated descriptive statistics (i.e. counts, frequencies, averages) to assess population characteristics for lateral ankle sprains across different age groups and across sex. The Clinical Classifications Software (CCS) for services and procedures was applied to group the most common procedures into meaningful categories.


Figure 1

How do these findings impact the public?

The estimated nationwide incidence of lateral ankle sprains was 932,868 (Figure 1). This is 300,000 more lateral ankle sprains on an annual basis than previously estimated. Of these, 57% of lateral ankle sprains were to females, which supports previous research suggesting that females may be at an increased risk for sustaining lateral ankle sprains. On average, a lateral ankle sprain patient was charged $1,211 for their emergency department visit which equates to >$1.1 billion in annual health care charges. Interestingly, almost 90% of lateral ankle sprain patients received some form of diagnostic radiology (e.g. an x-ray) in order to rule out a fracture (Figure 2). Unfortunately, most of these procedures are unnecessary because research shows that only about 15% of these would have a fracture and because fractures can be successfully ruled out by using the Ottawa Ankle Rules.


Figure 2

It is important to note, that the $1.1 billion charged to patients only represents the financial impact of immediately treating lateral ankle sprains in emergency departments. This figure does not consider charges accrued by individuals who sought immediate care from family physicians or other health care providers. This figure also does not consider the costs of future therapy, treatment for long-term symptoms, or human capital costs (i.e. time lost from work, etc.) which make up 69-87% of the total costs associated with lateral ankle sprains.

The high incidence and cost of lateral ankle sprains demonstrate the importance of developing effective prevention strategies that target those at greatest risk. These data also highlight the need to continue to educate emergency department providers about how they could refine their clinical practice to manage unnecessary costs while acutely treating lateral ankle sprains.