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E2414. Predicting Postoperative Disability Score Improvement in Patients With Lumbar Interbody Fusion Using Postoperative CT
Authors
  1. Tae Yang Choi; National Health Insurance Service Ilsan Hospital
  2. Min-Yung Chang; National Health Insurance Service Ilsan Hospital
  3. Seung Hyun Lee; National Health Insurance Service Ilsan Hospital
Objective:
To investigate the CT image predictor of improvement of disability score on postoperative CT scan in patients with one-level transforaminal lumbar interbody fusion.

Materials and Methods:
This retrospective study enrolled 78 patients (mean age: 64.1 years; 30 men and 48 women) treated for degenerative disease with one-level transforaminal lumbar interbody fusion from February 2012 to December 2018, and who had both pre- and postoperative CTs with at least two years of routine follow-up. Postoperative disability was assessed as Oswestry Disability Index (ODI) on each clinical follow-up and we used ratio of ODI (postoperative ODI divided by initial ODI) with cutoff 0.82, to classify patients into improvement (less than 0.82) and non-improvement groups (0.82 or more). Fusion degree, recent compression fracture, new disc herniation, hardware failure (including screw loosening, interbody cage subsidence, and hardware fracture), and adjacent segment disease (ASD; newly developed moderate to severe spinal stenosis, or segmental instability, or deterioration =2 grades on the UCLA grade scale) were assessed on postoperative CT scan. We used univariate statistical analyses for qualitative and quantitative data, and mixed effect logistic regression analyses to find image predictors on this longitudinal data set.

Results:
Total 587 clinical plus radiographic follow-up examinations, and 311 CT examinations follow-up were performed on 78 patients with mean 3.5 postoperative years. Recent compression fracture was observed in nine patients and was significantly associated with high (poor) ODI ratio (p < 0.001). New disc herniation was observed in eight patients, and screw or rod fracture was observed in four patients, and also associated with poor ODI ratio (p < 0.001, for both). All three CT features were predictive of non-improvement group on mixed effect logistic regression analyses (p < 0.001 for all three features). Achievement of interbody bone fusion, screw loosening, and interbody cage subsidence were frequently seen, but not associated with the post-operative disability. Development of ASD was borderline significant (p = 0.006). Among clinical and demographic factors, long postoperative date, and low (good) initial ODI were associated with poor post-operative ODI score.

Conclusion:
Recent compression fracture, new disc herniation, and hardware (screw or rod) fracture were independent CT imaging predictors for the poor post-operative disability score. Achievement of interbody bone fusion, screw loosening, interbody cage subsidence were frequently seen, but not associated with poor disability scale.