Describing the size of lumbar disc herniations using computed tomography. A comparison of different size index calculations and their relation to sciatica.

Abstract

The study compared different methods to measure the absolute and relative size of lumbar disc herniations on computed tomography scans and their relation to sciatica. Computed tomography (CT) examinations were done before and at 3 and 24 months after nonoperative treatment in 30 patients with lumbar disc herniations. The size of the herniation was described by different indexes and related to the degree of sciatica. One index was formed by the area of the herniation in relation to the spinal canal (A-index), whereas two indexes were formed by linear measurements of the herniation in relation to the spinal canal in either two (ST-index) or one direction (S-index). Each index was correlated significantly to the degree of sciatica. The area of the herniations decreased markedly over time. Linear measurements of the herniation in two perpendicular directions provide a practical and accurate way of describing the size of lumbar disc herniations.