Study Overview
Objective. To determine the association between wait times for hip fracture surgery and outcomes after surgery and to identify the optimal time window for conducting hip fracture surgery.
Design. Observational cohort study.
Setting and participants. The study was conducted using population-based health administrative databases in Ontario, Canada. The databases collected information on health care services, physician and hospital information, and demographic characteristics in Ontario. The investigators used the databases to identify adults undergoing hip fracture surgery between April 2009 and March 2014. Excluded were adults who are non-Ontario residents, those with elective hospital admissions, those with prior hip fractures, and patients without hospital arrival time data. Other exclusion criteria include age younger than 45 years, those with delay in surgery longer than 10 days, surgery performed by a nonorthopedic surgeon, and those at hospitals with fewer than 5 hip fracture surgeries during the study period.
The primary independent variable was wait time for surgery, calculated from time from emergency department arrival until surgery and rounded in hours. Other covariates included in the analysis were patient characteristics including age, sex and comorbid conditions using the Deyo-Charlson comorbidity index, the Johns Hopkins Collapsed Aggregated Diagnosis Groups, and other validated algorithms. In addition, other conditions associated with hip fracture were included—osteomyelitis, bone cancer, other fractures, history of total hip arthroplasty, and multiple trauma. Additional covariates included median neighborhood household income quintile as a proxy for socioeconomic status, patient’s discharge disposition, and rural status. Characteristics of the procedure including procedure type, duration and timing (working vs. after hours) were assessed. Surgeon- and hospital-related factors included years since orthopedic certification as a proxy for surgeon experience and number of hip fracture procedures performed in the year preceding the event for surgeon and hospital. Other hospital characteristics included academic or community-based hospital, hospital size, and hospital’s capacity for performing nonelective surgery.
Main outcome measures. The main outcome measure was mortality within 30 days of being admitted for hip fracture surgery. Other secondary outcomes included mortality at 90 and 365 days after admission, medical complications within 30, 90, and 365 days, and a composite of mortality and any complications at these timeframes. Complications included myocardial infarction, deep vein thrombosis, pulmonary embolism and pneumonia. Statistical analysis include modeling for the probability of complications according to the time elapsed from emergency department arrival to surgery using risk adjusted spline analyses. The association between surgical wait time and mortality was graphically represented to visualize an inflection point when complications begin to rise. The area under the receiver operating characteristic curve was calculated at time thresholds around the area of inflection and the time producing the maximum area under the curve was selected as the threshold to classify patients
as receiving early or delayed surgery. Early and delayed patients were matched using propensity score with 1:1 matching without replacement. Outcomes were compared between early and delayed groups after matching and absolute risk differences were calculated using generalized estimating equations.
Main results. A total of 42,230 adults were included, with a mean age of 80.1 (SD 10.7) years; 70.5% were women. The average time from arrival to emergency room to surgery was 38.8 (SD 28.8) hours. The spline models identified an area of inflection at 24 hours when the risk of complications begins to rise. The investigators used 24 hours as a time point to classify patients into early or delayed surgery group. 33.6% of patients received early surgery and 66.4% had delayed surgery. Propensity score matching yielded a sample of 13,731 in each group. Patients with delayed surgery compared with early surgery had higher 30-day mortality (6.5% vs. 5.8%, absolute risk difference 0.79%), rate of pulmonary embolism (1.2% vs. 0.7%, absolute risk difference 0.51%), rate of myocardial infarction (1.2% vs. 0.8%, absolute risk difference 0.39%), and rate of pneumonia (4.6% vs. 3.7%, absolute risk difference 0.95%). For the composite outcome, 12.1% vs. 10.1% had mortality or complications in the delayed group and the early group respectively with an absolute difference of 2.16%. Outcomes at 90 days and 365 days were similar and remained significant. In subgroups of patients without comorbidity and those receiving surgery within 36 hours the results remained similar.
Conclusion. Early hip fracture surgery, defined as within 24 hours after arrival to emergency room, is associated with lower mortality and complications when compared to delayed surgery.
Commentary
Hip fracture affects predominantly older adults and leads to potential devastating consequences. Older adults who experience hip fracture have increased risk of functional decline, institutionalization, and death [1]. As hip fracture care often include surgical repair, many studies have examined the impact of timing of surgery on hip fracture outcomes, as the timing of surgery is a potentially modifiable factor that could impact patient outcomes [2]. Prior smaller cohort studies have demonstrated that delayed surgery may impact outcomes but the reasons for the delay, such as medical complexity, may also play a role in increasing the risk of adverse outcomes [3]. The current study adds to the previous literature by examining a large population-based cohort, thereby allowing for analysis that takes into account medical comorbidities using matching methods and sensitivity analyses that examined a sample without comorbidities. The study also employs a different approach to defining early vs. delayed surgery by using analytical methods to determine when risk of complications begins to rise. The results indicate that early surgery is associated with better outcomes at 30 days and beyond and that delaying surgery beyond 24 hours is associated with poorer patient outcomes.
Patients with hip fracture require care from multiple disciplines and care across multiple settings. These care components may also have an impact on patient outcomes, particularly outcomes at 90 and 365 days; some examples include anesthesia care during hip fracture surgery [4], pain control, early mobilization, and delirium prevention [1,5]. A limitation of utilizing administrative databases is that some of these potentially important factors that may affect outcome may not be included and thus cannot be controlled for. It is conceivable that early surgery may be associated with care characteristics that may also be favorable to outcomes. Another limitation is that it is still difficult to tease out the effect of medical complexity at the
time of hip fracture presentation, which may impact both timing of surgery and patient outcomes, despite sensitivity analyses that limit the sample to those who had surgery within 36 hours and also those without medical comorbidities according to the administrative data, and adjusting for antiplatelet or anticoagulant medications. It is also important to note that a randomized controlled trial may further elucidate the causal relationship between timing of surgery and patient outcomes. Despite the limitations of the study, the results make a strong case for limiting surgical wait time to within 24 hours from the time when the patient arrives in the emergency room.
Applications for Clinical Practice
Similar to how hospitals organize their care for patients with acute myocardial infarction for early reperfusion, and for patients with acute ischemic stroke with early thombolytic therapy, hip fracture care may need to be organized and coordinated in order to reduce surgical wait time to within 24 hours. Timely assessments by an orthopedic surgeon, anesthesiologist, and medical consultants to prepare patients for surgery and making available operating room and staff for hip fracture patients are necessary steps to reach the goal of reducing surgical wait time.
—William W. Hung, MD, MPH