Clinical outcomes after lumbar fusion complicated by deep wound infection: a case-control study

Abstract

Study design: A propensity score-matched case-control study.

Objective: To evaluate the 2-year clinical outcomes of patients who have undergone instrumented spinal fusions complicated by deep wound infections and compare them with a propensity score-matched control group who did not have infections.

Summary of background data: Postoperative infection after instrumented spinal fusion is a major complication, often resulting in substantial short-term morbidity. However, there is little literature reviewing how these patients do in the longer term after their infection has been managed.

Methods: Thirty patients were identified who underwent instrumented lumbar spinal fusion with complete preoperative and 2-year postoperative outcome measures and had acute (#3 mo) postoperative deep wound infections necessitating irrigation and debridement. Outcome measures included the Oswestry Disability Index, 36-Item Short Form Health Survey Physical and Mental composite summaries, and numeric rating scales (0-10) for back and leg pain. A noninfected control group was identified using propensity score-matching techniques based on demographics, baseline clinical outcome measures, and surgical characteristics. Two-year postoperative outcome measures of both groups were compared. The proportion of patients achieving the minimum clinically important difference for the outcome measures was also assessed. Independent t tests were used to compare continuous variables, and Fisher exact test was used to compare categorical variables between the 2 groups.

Results: Consistent with the propensity score-matching technique, there were no significant demographic or surgical differences between the 2 study groups at baseline. Oswestry Disability Index, 36-Item Short Form Health Survey Physical Composite Summary, and back and leg pain scores were statistically significantly better at 2 years postoperative than at baseline in both groups. However, at 2 years postoperative, the infection group had a statistically significantly worse back pain score compared with the control group (6.45 vs. 4.70, P = 0.020). Also, a greater proportion of patients in the control group (18, 60%) achieved minimum clinically important difference for Oswestry Disability Index than those in the infection group (8, 27%, P = 0.018).

Conclusion: This study demonstrates that patients with acute postoperative deep wound infections after instrumented lumbar spinal fusion have improved outcome measures after surgery but have greater back pain and a decreased probability of achieving minimum clinically important difference.