How Do Functional Comorbidities Affect PROMIS-PF Scores Following Lumbar Fusion Surgery?

Study Design. A retrospective review. Objective. The purpose of this study is to trend PROMIS PF scores following lumbar fusion surgery, and to investigate how the presence of functional comorbidities affects PROMIS PF scores. Additionally, we compare trends in PROMIS PF scores to the Oswestry Disability Index (ODI) and to PROMIS Pain Interference (PI) scores. Summary of Background Data. National Institute of Health’s (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function (PF) domain has been validated in spine surgery. However, little is known about how PROMIS-PF scores are affected by functional comorbidities and how these scores change in patients recovering from lumbar fusion surgery over time. In this study, we hypothesize that functional comorbidities negatively affect recovery. Methods. We retrospectively identified 1,893 patients who underwent thoracolumbar, lumbar, or lumbosacral fusion for degenerative conditions between 01/02/2014 and 01/07/2022. We summarized PF at 3-month intervals for 2 years following surgery between those with and without functional comorbidity, defined as the presence of congestive heart failure (HF), chronic obstructive pulmonary disease (COPD), cerebrovascular disease (CVD), or paraplegia. Mixed effects multivariable regressions were used to model between group trends in PF through 2 years post-operatively controlling for age, gender, indication, and surgical invasiveness. The minimally clinically important difference (MCID) was defined as 5+ point improvement from baseline in PF. Results. The cohort includes 1,224 (65%) patients without functional comorbidity and 669 (35%) with functional comorbidity. The mean age was 65.0 and Charlson index was 1.0 in the cohort without functional comorbidity compared to 65.4 and 3.8 in the cohort with functional comorbidity ( P =0.552 and P <0.001 respectively). The groups were otherwise similar with respect to surgical invasiveness index, vertebral levels, and spine diagnosis (all P >0.05). At 24 months post operatively, the functional comorbidity group had a 2.5 point lower absolute PF score and a 1.3 point less improvement from baseline ( P =0.012 and 0.190 respectively). 19.3% of patients in the functional comorbidity group achieved the MCID compared to 80.9% in patients without a functional comorbidity ( P <0.001). Conclusion. Based on PROMIS PF scores, patients with functional comorbidities do not recover to the same extent and are less likely to achieve an MCID compared to patients without baseline functional comorbidities. PROMIS-PF can help benchmark patients along their recovery, and other metrics may be needed to better understand the recovery of patients with functional comorbidities.