Radiographic indices for lumbar developmental spinal stenosis

Abstract

INTRODUCTION: Reoperation is not an uncommon event in spinal stenosis. Developmental spinal stenosis (DSS) has been previously defined by magnetic resonance imaging (MRI) via the axial anteroposterior (AP) bony spinal canal diameter. X-rays are superior due to its availability and cost compared with MRI. However, currently there is no definition of DSS based on X-rays. This study aimed to develop radiographic indices for diagnosing DSS. METHODS: This was a prospective cohort of 148 subjects consisting of those undergoing surgery for lumbar spinal stenosis (patient group; n=66) and asymptomatic subjects recruited openly from the general population (control group; n=82). All subjects underwent MRI for diagnosing DSS and radiographs for measuring parameters used for creating the indices. All measurements were performed by 2 independent investigators. Receiver operating characteristic (ROC) analysis was used to determine the cut-off values for diagnosing DSS using radiographs. RESULTS: All 66 subjects from the patient group were diagnosed with DSS on MRI. The ROC analysis suggested sagittal vertebral body width to pedicle width ratio (SBW:PW) as having the strongest sensitivity (92%) and specificity (99%) for diagnosing DSS. Cut-off indices for SBW:PW were level-specific: 2.0 at L1, 2.0 at L2, 2.2 at L3, 2.2 at L4, 2.5 at L5, and 2.8 at S1. CONCLUSION: This is the first study to define DSS on plain radiographs based on comparisons between a clinically relevant patient group and a control group. Individuals with DSS can be identified by a simple radiograph using a screening tool allowing for better cost-saving means for clinical diagnosis or research purposes.