Risk factors for hospital admission in patients undergoing outpatient anterior cruciate ligament reconstruction: A national database study

Publication Date


Journal Title

J Orthop


© 2020 Professor P K Surendran Memorial Education Foundation Introduction: Anterior Cruciate Ligament Reconstructions (ACLR) are routinely performed in an outpatient setting with low 90-day readmission rates (2.3%); however, admissions rates in the immediate perioperative period have been previously reported as high as 13.1%. Despite the surprisingly high number of patients requiring immediate perioperative admission, there has been a lack of recent literature specifically examining the associated risk factors for admission. Methods: Using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, a query for patients who underwent ACLR from 2011 through 2018 was performed using Current Procedural Terminology codes. The following concomitant procedures were included: meniscectomy, meniscal repair, diagnostic arthroscopy, loose body removal, synovectomy, chondroplasty, abrasion chondroplasty, drilling for osteochondritis dissecans. Demographics including age, sex, race, body mass index (BMI) and comorbidities were collected. Perioperative factors collected were anesthesia type and operative times. Patient demographic and perioperative data were compared using Fisher's exact test and Pearson's chi-square test. Multivariate logistic regressions were used to calculate odds ratios (OR) and 95% confidence intervals (CI) of independent risk factors for postoperative admission. Holm-Bonferroni method yielded adjusted p-value thresholds for significance. Results: Of the 20,819 patients undergoing ACLR with and without concomitant procedures, 3.8% of patients were admitted to the hospital in the immediate postoperative period. Following multivariate regression analysis, increased odds of admission were demonstrated with the use of regional anesthesia alone (OR = 2.77, 95%CI: 2.22–3.44; p < 0.001), increasing concurrent procedures (Table 1), and obesity classes II (OR = 1.62, 95%CI: 1.26–2.10; p < 0.001) and III (OR = 1.81, 95%CI: 1.33–2.47; p < 0.001). Subsequent subgroup analysis of the isolated ACLR procedures (N = 9,423) demonstrated a 3.3% postoperative admission rate. Multivariate regressions demonstrated increased odds of admission with regional anesthesia use only (OR = 2.62, 95%CI: 1.90–3.60; p < 0.001), obesity class II (OR = 2.22, 95%CI: 1.51–3.26; p < 0.001), and increasing minutes of operative time (OR = 1.01, 95%CI: 1.01–1.01; p < 0.001). Table 2 demonstrates increasing rates and odds of admission with increasing operative time in hours. Conclusion: Anterior Cruciate Ligament Reconstructions are routinely performed in an outpatient setting; nevertheless, a subset of ACLR patients is admitted postoperatively. We found an increased risk of admission with the use of regional anesthesia alone, increasing concurrent procedures and obesity classes II and III. A further understanding of patient risk factors for those undergoing ACLR allows orthopedic surgeons to better develop a preoperative plan and discuss patient expectations, which will lead to more efficient resource allocation and improved patient satisfaction.

Volume Number



436 - 441

Document Type



Faculty; Northwell Researcher; Northwell Resident


School of Medicine; Northwell Health

Primary Department

Orthopedic Surgery





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