Association Between Wait Time and 30-Day Mortality in Adults Undergoing Hip Fracture Surgery

Abstract

Importance: Although wait times for hip fracture surgery have been linked to mortality and are being used as quality-of-care indicators worldwide, controversy exists about the duration of the wait that leads to complications.

Objective: To use population-based wait-time data to identify the optimal time window in which to conduct hip fracture surgery before the risk of complications increases.

Design, setting, and participants: Population-based, retrospective cohort study of adults undergoing hip fracture surgery between April 1, 2009, and March 31, 2014, at 72 hospitals in Ontario, Canada. Risk-adjusted restricted cubic splines modeled the probability of each complication according to wait time. The inflection point (in hours) when complications began to increase was used to define early and delayed surgery. To evaluate the robustness of this definition, outcomes among propensity-score matched early and delayed surgical patients were compared using percent absolute risk differences (RDs, with 95% CIs).

Exposure: Time elapsed from hospital arrival to surgery (in hours).

Main outcomes and measures: Mortality within 30 days. Secondary outcomes included a composite of mortality or other medical complications (myocardial infarction, deep vein thrombosis, pulmonary embolism, and pneumonia).

Results: Among 42 230 patients with hip fracture (mean [SD] age, 80.1 years [10.7], 70.5% women) who met study entry criteria, overall mortality at 30 days was 7.0%. The risk of complications increased when wait times were greater than 24 hours, irrespective of the complication considered. Compared with 13 731 propensity-score matched patients who received surgery earlier, 13 731 patients who received surgery after 24 hours had a significantly higher risk of 30-day mortality (898 [6.5%] vs 790 [5.8%]; % absolute RD, 0.79; 95% CI, 0.23-1.35) and the composite outcome (1680 [12.2%]) vs 1383 [10.1%]; % absolute RD, 2.16; 95% CI, 1.43-2.89).

Conclusions and relevance: Among adults undergoing hip fracture surgery, increased wait time was associated with a greater risk of 30-day mortality and other complications. A wait time of 24 hours may represent a threshold defining higher risk.

Figure 1.. Probability of the Primary Outcome According to Wait Times for Surgery as a Continuous Variable

Probabilities (95% CIs) models used restricted cubic splines adjusting for age, sex, year, income quintile, rurality, transfer from any health care institution, Deyo-Charlson score, history of frailty, diabetes, heart failure, chronic obstructive pulmonary disease, myocardial infarction, or hypertension, fracture and surgery type, Injury Severity Score, surgeon volume and experience, hospital volume and type, and surgery duration. Analysis conducted among 41 186 of 42 230 patients. C statistic was 0.756. Variance inflation factors were 4 or less for included variable included, indicating an absence of collinearity. Probabilities of the primary outcome according to wait times for surgery are presented for patients with average fracture, physician, and hospital system characteristics in the cohort.

Figure 2.. Probability of the Primary, Secondary, and Negative Tracer Outcomes (Involving Hardware Removal and Hip Dislocation)

Probabilities (95% CIs) models used restricted cubic splines. Variables in the adusted models are listed in the “Outcomes” section of the Methods and in Figure 1. Analysis conducted among 41 186 of 42 230 patients. Probabilities of each outcome according to wait times for surgery are presented for the patient with average fracture, physician, and hospital system characteristics in the cohort.