Contraindication of Minimally Invasive Lateral Interbody Fusion for Percutaneous Reduction of Degenerative Spondylolisthesis: A New Radiographic Indicator of Bony Lateral Recess Stenosis Using I Line

STUDY DESIGN: Retrospective cohort study. PURPOSE: This study aimed to evaluate aggravated lateral recess stenosis and clarify the indirect decompression threshold by combined lateral interbody fusion and percutaneous pedicle screw fixation (LIF/PPS). OVERVIEW OF LITERATURE: No previous reports have described an effective radiographic indicator for determining the surgical indication for LIF/PPS. METHODS: A retrospective review of 185 consecutive patients, who underwent 1- or 2-level lumbar fusion surgery for degenerative spondylolisthesis (DS). According to their symptomatic improvement, they were placed into either the “recovery” or “no-recovery” group. Preoperative computed tomography (CT) images were evaluated for the position of the superior articular processes at the slipping level, followed by a graded classification (grades 0–3) using the impingement line (I line), a new radiographic indicator. All 432 superior articular facets in 216 slipped levels were classified, and both groups’ characteristics were compared. RESULTS: There were 171 patients (92.4%) in the recovery group and 14 patients in the no-recovery group (7.6%). All patients in the no-recovery group were diagnosed with symptoms associated with deteriorated bony lateral recess stenosis. All superior articular processes of the lower vertebral body in affected levels reached and exceeded the I line (I line-; grade 2 and 3) on preoperative sagittal CT images. In the recovery group, most superior articular processes did not reach the I line (I line+; grade 0 and 1; p=0.0233). CONCLUSIONS: In DS cases that are classified as grade 2 or greater, the risk of aggravated bony lateral recess stenosis due to corrective surgery is high; therefore, indirect decompression by LIF/PPS is, in principle, contraindicated.