Purpose

No clinical CT based classification system is currently in use for Lumbar Foraminal Stenosis. MRI scanners are not easily available, are expensive and may be contraindicated in an increasing number of patients. This study aims to propose and evaluate the reproducibility of a novel CT based classification for lumbar foraminal stenosis.

Materials and Methods

The grading was developed as 4 grades. Normal foramen – Grade 0, Anteroposterior(AP)/Superoinferior (SI)(single plane) fat compression – Grade 1, Both AP/SI compression (two planes) – Grade 2 (both AP and SI) without distortion of nerve root, Grade 2 with distortion of nerve root – Grade 3.

800 lumbar foramen of a cohort of 100 random patients over the age of 60 who had undergone both CT and MRI scans were reviewed by two radiologists independently to assess agreement of the novel CT classification against the MRI based grading system of Lee et al. Interobserver(n=400) and intraobserver agreement(n=160) was also evaluated. Agreement analysis was performed using the Weighted Kappa statistic.

Results

100 patients (M:F = 45:55) with a mean age of 68.5 years (range 60 – 83 years were included in the study. The duration between CT and MRI scans was 98 days(range 0 – 540, SD – 108). There was good correlation between CT and MRI with Kappa scores (k=0.81) and intraobserver Kappa of 0.89 and 0.98 for the two readers.

Conclusion

The novel CT based classification correlates well with the MRI grading system and can safely and accurately replace it where required.