1366. Assessing the Differences in Characteristics of Patients Lost to Follow-up at 2 years: Results from the Multi-Site Quality Outcomes Database (QOD) Study of Impact of Fusion on Outcomes of Grade 1 Spondylolisthesis

Authors: Mohamad Bydon, MD, FAANS ; Praveen Mummaneni, MD; John Knightly, MD; Kevin Foley, MD; Jonathan Slotkin, MD; Eric Potts, MD; Mark Shaffrey; Christopher Shaffrey, MD; Michael Wang, MD; Paul Park, MD; Erica Bisson, MD; Anthony Asher, MD (Rochester, MN)


Loss to follow up has been shown to bias outcome assessment among studies utilizing clinical registries. Previous studies has investigated the reasons why patients are lost to follow up; however, little is known about characteristics of patients that are lost to follow up and how they compare to patients who are captured. Herein, we analyzed patients enrolled in a national surgical registry and compared the baseline characteristics of patients captured with those lost to follow up at 2 years.


We queried the Quality Outcomes Database for patients with grade 1 lumbar degenerative spondylolisthesis undergoing a surgical intervention between July 2014 and June 2016. Only those patients enrolled in a multi-side study investigating the impact of fusion on clinical and Patient Reported Outcomes (PROs) among patients with grade 1 spondylolisthesis were evaluated.


Of the 608 patients undergoing enrolled in the study, 84% (n=511) were successfully followed for 2 years. Patients who were captured were more likely to be unemployed (50.5%,n=258 vs 40.2%,n=39,p=0.04) and at baseline had lower back-pain (VAS-BP 6.5±2.7 vs 7.3±2.4, p=0.021), lower leg-pain (VAS-LP 6.4±2.8 vs 7.3±2.6, p=0.006), lower ODI-score (45.86±16.8 vs 51.04±18.1, p=0.007) and higher EQ-5D-score (0.54±0.22 vs 0.41±0.24, p=0.004) but longer operative time (180.2 minutes±87.3 vs 157.8±78, p=0.020). Patients lost to follow-up were more likely to be smokers (16.5%,n=16 vs 10.6%, n=54, p=0.032) and have a history of depression (26.8%,n=26 vs 19%,n=97, p=0.05). Proportion of patients undergoing a fusion surgery did not differ between the two groups (78.4%,n=134 vs 80.5%,n=504).


 To execute future, high-quality study, it is important to identify patients undergoing surgery for spondylolisthesis who might be lost to follow up after surgical intervention. In a large, prospective registry, we found that those who were lost to follow up were more likely to be smokers and depressed