Impact of associated injuries in conjunction with fracture of the axis vertebra on inpatient outcomes and postoperative complications: a Nationwide Inpatient Sample analysis from 2002 to 2011

Background Context There are limited data available on the impact of associated spinal (other spinal injuries [OSIs]) and extra-spinal injuries (ESIs) occurring in conjunction with fractures of the axis vertebra (C2) on clinical outcomes. Purpose This study aimed to compare outcomes in patients with isolated C2 fractures versus patients with associated injuries in conjunction with C2 fractures. Study Design/Setting A retrospective cohort study. Patient Sample A total of 30,472 adult patients with C2 fractures (International Classification of Diseases, Ninth Revision, Clinical Modification code 805.02) registered in the Nationwide Inpatient Sample (NIS) database (2002–2011) comprised the patient sample. Outcome Measures Inpatient mortality, unfavorable discharge, prolonged length of stay (LOS) and high-end hospital charges in the non-operative and operative cohorts, and postoperative complications (deep venous thrombosis [DVT]; acute renal failure [ARF]; respiratory complications and wound infections) for the operative cohort were the outcome measures. Methods Patients were stratified into four categories based on injury type: (1) isolated C2 fracture (n=10,135; 33.3%); (2) C2 fracture+OSI (8.7%); (3) C2 fracture+ESI (37.2%); and (4) C2 fracture+OSI+ESI (20.8%). Multivariable logistic regression fitted with generalized estimating equations using the sandwich variance-covariance matrix estimator to account for clustering of similar outcomes within hospitals was used to examine the association of primary endpoints for each of the associated injury categories with reference to isolated C2 fractures. Results Mean age of the cohort was 66.27±21.67 years and 52% were female. Of the cohort, 52% underwent surgical intervention for C2 fracture. In a pooled regression analysis involving the operative cohort, the risks for inpatient mortality (odds ratio [OR]: 3.77; 95% confidence interval [CI]: 3.02–4.70; p<.001), unfavorable discharge (OR: 1.83; 95% CI: 1.66–2.01; p<.001), prolonged LOS (OR: 1.33; 95% CI: 1.18–1.50; p<.001), high hospital charges (OR: 1.49; 95% CI: 1.31–2.69; p<.001), DVT (OR: 2.08; 95% CI: 1.61–2.68; p<.001), and ARF (OR: 1.46; 95% CI: 1.16–1.83; p=.001) were significantly higher in patients with additional injuries when compared with patients with C2 fractures alone. Likewise, increased chances of inpatient mortality (OR: 1.40; 95% CI: 1.21–1.62; p<.001), unfavorable discharge (OR: 1.24; 95% CI: 1.15–1.34; p<.001) and high hospital charges (OR: 1.31; 95% CI: 1.21–1.43; p<.001) were observed in a pooled analysis of patients with concomitant associated injuries in the non-operative cohort. Conclusions Associated injuries occurring concomitantly with C2 fractures adversely influence postoperative outcomes. In comparison to isolated C2 fractures, patients with associated injuries tend to have a greater propensity for higher health-care resource use because of more complicated and longer hospital inpatient stay.