Original Research

Hip Fracture and the Weekend Effect: Does Weekend Admission Affect Patient Outcomes?

Am J Orthop. 2015 October;44(10):458-464

Reduced hospital staffing on weekends is a hypothesized risk factor for adverse health outcomes—commonly referred to as the weekend effect.

We conducted a study on the effect of weekend admission on short-term outcomes among US hip fracture patients. We selected Nationwide Inpatient Sample (1998–2010) patients with a principal diagnosis of femoral neck fracture and grouped them by day of admission (weekend or weekday). We used multivariate logistic and linear regression analyses, controlling for age, race, sex, number of comorbidities, and other risk factors, to calculate odds ratios (ORs) of mortality and perioperative complications as well as mean difference in length of hospital stay.

Our study population included 96,892 weekend and 248,097 weekday admissions. Compared with patients admitted on weekdays, patients admitted on weekends had lower mortality (OR, 0.94; 95% confidence interval [CI], 0.89-0.99) and shorter mean hospital stay (estimate, 3.74%; 95% CI, 3.40-4.08) but did not differ in risk of perioperative complications (OR, 1.00; 95% CI, 0.98-1.02).

Weekend admission did not predict death, perioperative complications, longer hospital stay, or other adverse short-term outcomes. Our study data do not support a weekend effect among hip fracture admissions in the United States.

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References

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Weekend admission has been hypothesized to be a risk factor for increased patient mortality and complications during hospital stays—commonly referred to as the weekend effect.¹ Reduced hospital staffing on weekends, particularly of senior-level physicians and ancillary nursing services, may affect the quality of diagnosis and management for patients admitted for traumatic and emergent conditions. Investigators have found increased mortality in weekend admissions for stroke,² subdural hematoma,³ gastrointestinal bleeding,^4,5 atrial fibrillation,⁶ and pulmonary embolism.⁷ Investigators have not found increased mortality in weekend admissions for hip fracture, though the majority of the data was derived from European patient populations, which may be subject to management and staffing strategies different from those for US patients.^8-10 Furthermore, data on this topic in US patients are limited to a multispecialty study of 50 different admission diagnoses, which used 1 year of data from a single US state.¹

We conducted a study to comprehensively assess the effect of weekend admission on adverse outcomes during hospital stays. The literature suggests that surgery for hip fracture can be delayed up to 48 hours without significant additional risk of death,^11-13 allowing orthopedic departments to stabilize routine hip fracture admissions on weekends and operate whenever limited surgical teams become available. Surgical delay has not been thoroughly analyzed by day of admission among US patients,¹⁴ but the combined potential of more conservative preoperative management and the availability of fewer senior physicians and ancillary providers may result in worse outcomes for weekend versus weekday admissions.

Materials and Methods

Study Population

Part of the Healthcare Cost and Utilization Project, the Nationwide Inpatient Sample (NIS) provides a 20% representative sample of annual US hospital admissions.¹⁵ For these admissions, the NIS includes data related to demographic and clinical variables, such as International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis and procedure codes, as well as descriptive variables for the hospitals where the patients were admitted. The NIS is publicly available to researchers. As its health information is deidentified, we did not have to obtain institutional review board approval for this study.

Ascertainment of Cases

Our initial study population, drawn from the period 1998–2010, consisted of 821,531 patients with a principal ICD-9-CM diagnosis of femoral neck fracture (820.0-820.9). To best capture the typical presentation of hip fracture, we excluded:

Patients with open femoral neck fractures (820.1, 820.3, 820.9).

Patients who did not have open reduction and internal fixation (ORIF) (79.35), hemiarthroplasty (81.52), closed reduction and internal fixation (CRIF) (79.15), internal fixation (78.55), or total hip arthroplasty (THA) (81.51) as their primary surgical procedure.

Patients admitted from sources other than the emergency department.

Patients who underwent surgery before admission.

Patients whose admission type was not classified as emergency or urgent.

Ascertainment of Covariates

For all patients, we extracted data on exposure of interest, day of admission (weekend or weekday), and demographic variables including age, sex, race (white, black, Hispanic, other, missing), and insurance (Medicare, Medicaid, private, other). We used the Elixhauser method to determine 30 different comorbidities from ICD-9-CM diagnosis coding¹⁶ and sorted patients by total number of comorbidities (0, 1, 2, 3 or 4, ≥5). As has been done before,¹⁷ we excluded blood loss anemia, coagulopathy, and fluid and electrolyte disorders from this comorbidity calculation, as these conditions can be secondary to trauma. We also extracted data on the admission itself, including hospital region (Northeast, Midwest, South, West), hospital bed size (small, medium, large), hospital teaching status (nonteaching, teaching), and hospital location (rural, urban). We used diagnosis codes to categorize fracture location as “not otherwise specified” (820.8), intracapsular (820.0), or extracapsular (820.2).

Because of low frequencies, we collapsed 2 race designations (Native American, Asian or Pacific Islander) into the “other race” category and 2 insurance designations (self-pay, no charge) into the “other insurance” category. For a substantial number of patients, race information was missing, so we included “missing” as its own category in analyses. Patients who were missing data on day of admission, age, sex, insurance, or hospital characteristics were excluded from our final cohort, as missing frequencies for each variable were small.

Ascertainment of Outcomes

For all patients, we extracted data on death status at discharge and length of hospital stay. We log-transformed length of stay because of its right skew, assigning the value of 12 hours to patients admitted and discharged the same day. Perioperative complications were calculated using ICD-9-CM codes as defined by a recent study of orthopedics-related complications by Lin and colleagues.¹⁸ There were 14 possible complications, including acute renal failure (584.5-9), tachycardia (427), wound hemorrhage (719.15, 998.31-2), wound disruption (998.3, 998.31-2), wound infection (682.6, 686.9, 891, 891.1-2, 894, 894.1-2, 998.5, 998.51, 998.6, 998.83, 998.59), deep vein thrombosis (453.4, 453.41-2, 453.9), acute myocardial infarction (410, 410.01, 410.11, 410.2, 410.21, 410.3, 410.31, 410.4, 410.41, 410.5, 410.51, 410.6, 410.9, 410.91, 997.1), pneumonia (480-480.9, 481, 482-482.9, 483, 483.1, 483.8, 484, 484.1, 484.3, 484.5-8, 485, 486, 487, 507), pulmonary embolism (415.11, 415.19), sepsis (995.91-2), stroke (997.02), urinary tract infection (599, 997.5), implant infection (996.66-7, 996.69), and incision and débridement (86.04, 86.09, 86.22, 86.28, 86.3). In our statistical analyses, we examined both the risk of having a complicated admission (≥1 perioperative complication) and the risk of having each specific complication.