Effect of adverse events on low back surgery outcome: twenty-four-month follow-up results from a Food And Drug Administration investigational device exemptiontrial.

STUDY DESIGN: This study was based on a post hoc analysis of data collected from a prospective FDA-regulated trial comparing total disc replacement to fusion surgery.

OBJECTIVE: he purpose of this study was to determine if the occurrence of adverse events (AEs) had an impact on outcomes of low back surgery.

SUMMARY OF BACKGROUND DATA: AEs are rigorously recorded during clinical trials primarily to evaluate the safety of the investigational device. AEs include a wide variety of events including those that are not typically thought of as complications related to the treatment intervention. During the course of a study, many physical events may happen to a patient including injuries from motor vehicle accidents, falling, various joint injuries, cancer onset, gastrointestinal problems, etc. Although these are generally thought of as having nothing to do with the patient's spine surgery, the potential detrimental impact of these AEs on the patient's overall well being may negatively effect responses to outcome assessments used to evaluated the clinical outcome of the spine surgery.

METHODS: Data were collected from an FDA-regulated prospective randomized clinical trial comparing lumbar fusion to total disc replacement. AE and clinical data were analyzed for 155 patients who had reached 24-month follow-up. The number of active AEs, along with event severity (mild, moderate, or severe), and its relationship to surgery (unrelated, possibly related, or causative) were recorded. Clinical outcome was based on VAS, Oswestry, and overall satisfaction at 24-month follow-up. Data were analyzed using ANOVA.

RESULTS: There were significant relationships between the presence of active AEs and improvement on VAS pain scores, Oswestry scores, and patient satisfaction (P < 0.05; ANOVA with post hoc Tukey) at 24-month follow-up. Patients with no active adverse events had more than 70% improvement on their VAS and Oswestry scores. Significantly less improvements was seen in the VAS and Oswestry scores for patients with 2 or more active AEs, moderate or severe AEs, and AEs classified as related to the study intervention. Patients with AEs classified as being related to the study intervention were significantly less satisfied than those with no AEs or AEs classified as unrelated to the surgery.

CONCLUSION: This study was the first to investigate the impact of active AEs on clinical outcome of spinal surgery. While AEs are recorded to evaluate the safety of new treatments, this study found that AEs also play a role in explaining some of the variation in treatment outcome.