Venous Thromboembolic Events After Spinal Fusion: Which Patients Are at High Risk?

Background: Postoperative venous thromboembolic events (VTEs), which include pulmonary emboli and deep venous thromboses, are potentially preventable causes of death. The aim of this study was to investigate the patient and procedure-related risk factors for the occurrence of VTEs in patients undergoing spinal fusion.

Methods: We used ICD-9-CM (International Classification of Diseases, 9th Revision, Clinical Modification) procedure codes to identify patients in the Nationwide Inpatient Sample (NIS) database for 2001 through 2010 who were treated with spinal fusion. The occurrence of a symptomatic VTE was identified with use of ICD-9-CM diagnosis codes. Patient demographics, hospital characteristics, and comorbidities in the VTE and non-VTE groups were analyzed, and independent risk factors for VTE were identified.

Results: A total of 710,154 spinal fusion procedures were identified in the NIS from 2001 to 2010, and 3525 (0.50%) of these patients were recorded as having 3777 VTEs, consisting of 2038 deep venous thromboses (0.29%) and 1739 pulmonary emboli (0.24%). Patients with a VTE were older on average (57.63 years compared with 52.88 years for patients without a VTE) and more often male (VTE incidence, 0.58% compared with 0.42% for female) and black (VTE incidence, 0.78% compared with 0.47% for white). Postoperative VTE occurrence was associated with a longer hospital stay (18.0 compared with 3.94 days) and higher total hospital charges ($207,253 compared with $66,823). A number of comorbidities and procedure-related factors were identified as independent risk factors for VTE.

Conclusions: We present a VTE Risk Index, based on the independent risk factors identified in this study, for the VTE following spinal fusion. In conjunction with current guidelines, this risk index can be used to guide clinical decision-making regarding VTE prophylaxis in patients undergoing spinal fusion.

Level of evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.