General Session: Thoraco-Lumbar Degenerative

Presented by: R. Rampersaud

Author(s):

R. Rampersaud(1,2),(3), K. Sundararajan(3), R. Amritanand(4), B. Ravi(1,5), K. David(4)

(1) University of Toronto, Surgery - Orthopaedics, Toronto, ON, Canada
(2) Krembil Research Institute, Toronto, ON, Canada
(3) University Health Network, Toronto, ON, Canada
(4) Christian Medical College Vellore, Department of Orthopaedics, Spinal Disorders Surgery Unit, Vellore, India
(5) Sunnybrook Research Institute, Holland Musculoskeletal Research Program, Toronto, ON, Canada

Abstract

Introduction: There is considerable debate regarding the selection of patients with DLS who may not require a fusion. Fusion, however, there is little debate, that indiscriminate fusion can add significant cost and increased morbidity in this aging demographic. The primary objective of our study was to determine which demographic, clinical and radiographic parameters may predict hypermobile spondylolisthesis, the need for fusion, and 2 year outcomes in LSS patients.

Methods: Retrospective cohort of 299 consecutive surgical LSS patients from a single surgeon. All patients underwent a minimally invasive decompression (leg-dominant symptoms with or without DLS) or decompression and fusion (back-dominant symptoms & 4+ mm of motion in DLS patients). Patient demographics including age, gender and BMI were recorded. Pelvic incidence (PI), mean facet angle (FA), mean facet fluid width (FFW), disc height, lumbar lordosis from L1-S1 (LL), and loading translation (LT; defined as any increase in anterior translation from supine MRI to standing x-ray, i.e. mobile spondylolisthesis) were measured from pre-operative MRIs and standing radiographs. Outcomes were presence of DLS with and without mobility, fusion vs. decompression alone, reoperation, and 2 year change in Oswestry Disability Index (ODI). Outcomes were compared using ODI and reoperation rate. Pre-operative Visual Analogue Scale (VAS) scores for leg and back pain were also collected. T-test, chi-squared test, and Fisher's exact test analyses were used to assess bivariate relationships. Multiple logistic regression was used to determine predictor variables where appropriate.

Results: Controlling for age, the odds of a surgical LSS patient having a DLS (n=199) were significantly higher in women (adjusted OR [95% CI] = 2.02 [1.1,3.7]) with higher PI (1.06 [1.0,1.1] per degree) and larger mean facet fluid width (1.99 [1.4,3.1] per mm). The odds of DLS were lower with increasing (i.e. more horizontal) mean FA (0.96 [0.9,1.0] per degree) and LL (0.97 [0.95,1.0] per degree). Compared to patients without DLS, those with DLS had no significant differences in either reoperation rate or post-operative ODI change.
No baseline characteristics were associated with spinal instability among patients with DLS.
Fusion surgery was more likely in women (OR=2.55 [1.4,4.8]), patients with a DLS (3.25 [1.6,6.9]), and low disc height (2.22 [1.2,4.0]), controlling for age. There was no significant difference in re-operation rate or ODI change in patients who received fusion versus decompression alone, either in the full sample of LSS patients or in patients with DLS.
Patients who had a reoperation (n=53) were younger (p< 0.01) and had worse pre-operative back pain (p< 0.01). Higher baseline ODI and leg pain were associated with reaching MCID for ODI. No other baseline demographic or radiographic variables were associated with reoperation risk or change in ODI.

Conclusions: Based on the senior author's surgical selection criteria, women with higher PI, DLS, and reduced standing disc height are more likely to receive a fusion. However, fusion versus decompression alone did not predict outcome or re-operation. Overall, this study shows that the radiographic parameters assessed do not independently correlate with clinical, patient-reported outcomes or re-operation in LSS patients regardless of the presence of DLS. The DLS patients selected for decompression alone achieved similar clinical and patient-reported outcomes compared to those without DLS.