Preoperative Radiographic Predictors of Subsequent Fusion after Lumbar Decompression Surgery.

ABSTRACT

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The purpose of this study is to determine which demographic, surgical, and radiographic preoperative characteristics are most associated with the need for subsequent fusion after decompression lumbar spinal surgery. SUMMARY OF BACKGROUND DATA There is a relatively high rate of the need for repeat decompression or fusion after an index decompression procedure for degenerative spine disease. Nevertheless, there is a dearth of literature identifying risk factors for lumbar fusion following decompression surgery. METHODS: Patients 18 years or older receiving a primary lumbar decompression surgery within the levels of L3-S1 between 2011 and 2020 were identified. All patients had preoperative radiographs and 2 years of follow-up data. Chart review was performed for surgical characteristics and demographics. The sagittal parameters included lumbar lordosis (LL), segmental lordosis (SL), anterior disc height (aDH), posterior disk height (pDH), sacral slope (SS), and pelvic tilt (PT). Pelvic incidence (PI=PT+SS) and pelvic incidence minus lumbar lordosis (PI-LL) were calculated. In addition, the Roussouly classification was determined for each patient. Bivariant and multivariant analyses were performed. RESULTS: Of the 363 patients identified in this study, 96 patients had a fusion after their index decompression surgery. Multivariable analysis identified involvement of L4-L5 level in the decompression (odds ratio (OR)=1.83 (1.09-3.14), P=0.026), increased L5-S1 segmental lordosis (OR=1.08 (1.03-1.13), P=0.001), decreased SS (OR=0.96 (0.93-0.99), P=0.023), and decreased endplate obliquity (OR=0.88 (0.77-0.99), P=0.040) as significant independent predictors of fusion after decompression surgery. CONCLUSIONS: This is one of the first studies to assess preoperative sagittal parameters in conjunction with demographic variables to determine predictors of the need for fusion after index decompression. We demonstrated that decompression at L4-L5, greater L5-S1 segmental lordosis, decreased sacral slope, and decreased endplate obliquity were associated with higher rates of fusion after decompression surgery.