Identifying Subsets of Patients with Single-level Degenerative Disc Disease for Lumbar Fusion: the Value of Prognostic Tests in Surgical Decision Making

Background Context: Fusion surgery for degenerative disc disease (DDD) has become a standard of care, albeit not without controversy. Outcomes are inconsistent and a superiority over conservative treatment is debatable. Proper patient selection is key to clinical success, and a comprehensive understanding of prognostic tests does not currently exist.

Purpose: This study aimed to investigate the value of prognostic tests and sociodemographic factors in predicting outcomes following lumbar fusion surgery for DDD.

Study Design: This is a retrospective analysis of prospectively collected data.

Patient Sample: We included patients who underwent fusion surgery for DDD between 2010 and 2016.

Outcome Measures: The outcome measures included pre- and postoperative visual analog scale and Oswestry Disability Index scores.

Materials And Methods: Prospectively collected patient data were reviewed for preoperative tests, perioperative data, and clinical outcomes. Prognostic tests used were discography, pantaloon cast test (PCT), Modic changes, and a summary of physical symptoms, coined "loading factor." By means of multivariate stepwise regression, prognostic factors that were useful in predicting outcomes were identified.

Results: A total of 91 patients fit the inclusion criteria, with a mean follow-up of 33±16 months. Discography, Modic changes, and loading factor were of no value for predicting outcome scores (p>.05). A positive PCT predicted improved outcomes in back pain severity, but only in patients without prior surgery (p=.02). Demographic factors that showed a consistent reduction in back pain were female sex (p=.021) and no prior surgery at index level (p=.009). No other sociodemographic factors were of predictive value (p>.05).

Conclusions: In patients without prior surgery, the PCT appears to be the most promising prognostic tool. Other prognostic selection tools such as discography and Modic changes yield disappointing results. In this study, female patients and those without prior spine surgery appear to be most likely to benefit from fusion surgery for DDD.