Risk factors for underestimating lumbar spinal canal stenosis severity using MRI: A retrospective analysis.

STUDY

DESIGN

A retrospective analysis.

PURPOSE: This study aimed to identify the risk factors for underestimating the severity of lumbar spinal canal stenosis (LCS) using magnetic resonance imaging (MRI).

OVERVIEW OF LITERATURE: In recent years, the indications for surgery for LCS have been increasingly determined by MRI alone, without myelography. However, as most MRI scans are performed in the supine position, it is challenging to detect dynamic stenosis using MRI alone. Thus, if the diagnosis is based on MRI alone without myelography, the severity of LCS may be underestimated.

METHODS

We retrospectively investigated 100 patients diagnosed with LCS using both MRI and myelography who underwent decompression surgery. We defined the discordant group as those with mild stenosis on MRI but severe stenosis on myelography and the concordant group as those with comparable myelography and MRI assessments. Univariate logistic regression analysis was performed to determine whether spinopelvic parameters and intervertebral mobility were risk factors for underestimation on MRI. The independent risk factors were investigated using multivariate logistic regression analysis.

RESULTS

Of the 100 patients diagnosed with LCS using MRI, 10 were judged to have more severe stenosis on myelography than on MRI. Univariate logistic regression analysis indicated a higher prevalence of posterior slippage in the discordant group (p = 0.02). Multivariate logistic regression analysis showed that posterior slippage in the extension position was an independent predictor of MRI underestimation (p = 0.01).

CONCLUSIONS

The presence of posterior slippage was an independent risk factor for underestimating the severity of spinal canal stenosis on MRI. Therefore, myelography might be recommended for LCS patients with posterior slippage.