All patients undergoing THA between 2005 and 2015 were identified in the registry using primary Current Procedural Terminology code 27130. Patients were split into 2 groups based on whether or not they chronically used corticosteroids preoperatively for a medical condition. A patient was considered a chronic corticosteroid user if he/she used oral or parenteral corticosteroids within 30 days before the index procedure for >10 of the preceding 30 days. Those who received a 1-time steroid pulse or those who used topical or inhaled steroids were not considered as steroid users in this study.
BASELINE CHARACTERISTICS AND PERIOPERATIVE OUTCOMES
Baseline patient and operative characteristics, including patient age, gender, body mass index (BMI), functional status, American Society of Anesthesiologists (ASA) class, anesthesia type, operative duration, and medical comorbidities including hypertension, COPD, diabetes mellitus, and smoking history, were compared between both groups. Perioperative outcomes that were assessed in this study include death, renal, respiratory, and cardiac complications, deep vein thrombosis or pulmonary embolism, stroke, sepsis, return to the operating room, urinary tract infection (UTI), wound dehiscence, superficial and deep SSI, need for a blood transfusion within 72 hours of index surgical procedure, and hospital readmissions. Renal complications were defined as acute or progressive renal insufficiency; respiratory complications were defined as failure to wean from the ventilator, need for intubation after the index procedure, and the occurrence of pneumonia; and cardiac complications were defined as myocardial infarction or cardiac arrest requiring cardiopulmonary resuscitation. Patients were excluded if they had missing baseline or operative characteristic data, an unclean wound classification at the time of admission, or if their THA was considered emergent.
STATISTICAL ANALYSIS
A propensity score-matched comparison was performed to adjust for differences in baseline and operative characteristics between the 2 cohorts in this study. In the current study, the propensity score was defined as the conditional probability that a patient chronically used preoperative corticosteroids for a medical condition, as a function of age, BMI, gender, ASA class, functional status, medical comorbidities, anesthesia type, and operative duration. A 1:1 matching with tight calipers (0.0001), and nearest-neighbor matching was used to generate 2 equally-sized, propensity-matched cohorts based on steroid status.26 Nearest-neighbor matching identifies patients in both cohorts with the closest propensity scores for inclusion in propensity-matched cohorts. This matching is continued until 1 group runs out of patients to match. Baseline patient and operative characteristics for the unadjusted and propensity-matched groups were compared using Pearson’s χ2 analysis. Outcomes after THA by steroid status were also compared in both unadjusted and propensity-matched groups. Finally, all patients who were readmitted were identified, and the reason for readmission was determined using the International Classification of Disease Ninth (ICD-9) and Tenth (ICD-10) edition codes. Patients were classified as having an infectious readmission only if the ICD code clearly stated an infectious etiology. For instance, a patient with an intestinal infection due to Clostridium difficile (ICD-9 008.45) was counted as a gastrointestinal infection, whereas diarrhea without a distinctly specified etiology (ICD-9 787.91, ICD-10 R19.7) was counted as a gastrointestinal medical complication. Readmission data was only available in ACS-NSQIP from 2011 to 2015, constituting 92.5% of all patients included in this study. We used SPSS version 23 (IBM Corporation) for all statistical analyses, and defined a significant P value as <.05.
RESULTS
BASELINE PATIENTS AND OPERATIVE CHARACTERISTICS
In total, we identified 101,532 patients who underwent THA (Table 1). O these, 3714 (3.7%) chronically used corticosteroids preoperatively, whereas 97,818 (96.3%) did not.
When the unadjusted cohorts were compared, patients using corticosteroids were more likely to be female, less likely to obese, more likely to have hypertension, diabetes mellitus, COPD, higher ASA class, undergone THA with general anesthesia, and have a dependent functional status (P < .001 for all comparisons). After propensity matching, 2 equally sized cohorts of 3618 patients each were generated based on steroid status and no differences in baseline and operative characteristics were identified between the 2 groups.
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