Prospective analysis of adverse events in surgical treatment of degenerative spondylolisthesis.

Background Context: Surgical adverse event (AE) monitoring is imprecise, of uncertain validity, and tends toward underreporting. Reports focus on specific procedures rather than outcomes in the context of presenting diagnosis. Specific intraoperative (intraop) or postoperative (postop) AEs that may be independently associated with degenerative spondylolisthesis (DS) have never been reported.

Purpose: The primary purpose was to assess the AE profile of surgically treated patients with L4-L5 DS. The secondary goal was to identify potential risk factors that correlate with those AEs.

Study Design/setting: Prospective cohort and academic quaternary spine center.

Patient Sample: Ninety-two patients with L4-L5 DS were treated surgically, discharged from Vancouver General Hospital between January 1, 2009 and December 31, 2010.

Outcome Measures: Incidence rates and odds ratios.

Methods: Prospective AE data were analyzed using univariate analyses, forward selection regression models, and Spearman correlation coefficients. Results were compared with outcomes reported in the Spine Patient Outcomes Research Trial.

Results: No AEs were seen in 57.6% of patients, one AE in 17.4%, and two or more AEs in 17.4%. Dural tears (6.5%) and intraop bone-implant interface failure requiring revision (3.3%) were the most common intraop AEs. Postoperatively, the most frequent AEs were urinary tract infection (10.9%), delirium (5.4%), neuropathic pain (4.4%), deep wound infection (3.3%), and superficial wound infection (3.3%). The odds of an intraop AE increased by 9% (95% confidence interval [CI] 1-18) per year of age at admission. Adjusted Charlson comorbidity index (CCI) did not correlate with number of AEs experienced. The odds of postop delirium correlated with CCI (odds ratio [OR] 3.39, 95% CI 1.12-10.24) and dural tear (OR 35.84, 95% CI 1.72-747.45). Length of stay was statistically significant and was influenced by two or more AEs, CCI, postop loss of correction, cerebrospinal fluid leak, deep wound infection, noninfected wound drainage, and gender.

Conclusions: Risk of intraop AEs, but not postop AEs, increased with increasing age. Having multiple comorbidities does not predispose to more AEs. Infections predominate among the postop AEs. Patients at increased risk of delirium or of having an increased length of hospital stay may more easily be predicted. Studies specifically designed to prospectively assess AEs have the potential to more accurately identify postop AE rates.