Digital computed tomography affords new measurement possibilities in lumbar stenosis

The problem of lumbar stenosis has been analysed at length in the literature as the number of patients with low back pain of this aetiology continues to increase. The aim of this study was:1. to carry out a prospective study assessing the dimensions of spinal canal on the basis of CT data and to compare patient data with a control group.2. to determine if the sagittal and transverse dimensions and surface area of the spinal canal are sufficiently sensitive and robust measures of spinal canal stenosis at L3, L4 and L5 levels.

The investigational group consisted of 176 patients (93 men, 83 women). A total of 528 vertebral levels were evaluated and compared with a control group consisting of 42 persons. Digital CT scans were obtained with a precision of 0.01 mm and 0.01 mm2. A discriminative function algorithm was used to classify cases according to the level of stenosis.

The mean sagittal dimension at L3 was 13.26 mm and the mean transverse dimension was 23.36 mm, with a surface area of 244.39 mm2. At L4, the mean sagittal dimension was 14.12 mm, the mean transverse dimension was 24.60 mm, and the surface area was 267.70 mm2. At L5, the mean sagittal dimension was 14.76 mm, the mean transverse dimension was 31.38 mm, and the surface area was 303.99 mm2. The most important factors influencing the quality of classification were height, width and surface area. Student's t test with a significance level at p=0.05 revealed statistically significant differences. The accuracy of classification in discriminative analysis was 92.66%.

The proposed indicators of the sagittal and transverse dimensions and surface area of the spinal canal were useful in assessing quantitative changes with this investigational technique. The sagittal dimension had the greatest sensitivity in the evaluation of stenosis.