Resident Physician University of California, San Francisco San Francisco, California, United States
Introduction: Patient reported outcomes (PROs) are key indicators of efficacy after spinal surgery. Typically, several different PRO questionnaires are combined to provide clinicians with a holistic understanding of patient mobility, pain, quality of life, and satisfaction. While each PRO provides useful and complementary information, the extent to which these outcomes vary and the underlying clinical dimensions they contribute to is not known.
Methods: Six hundred eight patients undergoing surgery for grade I degenerative lumbar spondylolisthesis were recruited as part of the Quality Outcomes Database. The Oswestry Disability Index (ODI), EuroQol-5D (EQ-5D), patient satisfaction index, and numeric rating scale back pain (NRSBP) and leg pain (NRSLP) were acquired at least 24 months postoperatively. Principal components analysis was performed to identify latent clinical outcomes dimensions.
Results: Across all time points, the first principal component (PC1) accounted for 61.1% – 68.3% of the variance in outcomes while the second (PC2) accounted for 12.1% – 13.7%. The ODI, followed by the EQ-5D and pain metrics, had the largest absolute loadings on PC1, indicating they contribute to a similar clinical dimension. Conversely, the patient satisfaction index loaded most heavily on PC2, implying that the index, in part, captures a dimension separate from metrics of disability and quality of life. The ODI demonstrated strong relationships to each PRO including the NRSBP (OR = 1.09, 95% CI [1.08-1.10], p< 0.0001), NRSLP (OR = 1.07, 95% CI [1.07-1.08], p< 0.0001), patient satisfaction index (OR = 1.06, 95% CI [1.05-1.07], p< 0.0001), and EQ-5D (R-squared = 0.55, p< 0.0001).
Conclusion : Most of the variance in PROs after spinal surgery can be captured by a single dimension represented by disability and quality of life metrics, of which the ODI remains a key contributor. Additional PRO questionnaires including the patient satisfaction index provide distinct yet complementary information.
