Volumes of Degenerated Lumbar Intervertebral Disks Determined From Volumetric Image Analysis

Jason A. Heth, MD
J Haller, PhD
T Ryken, MD (Iowa City, IA)

Introduction:

Intervertebral disk degeneration is a common problem resulting in significant disability. While medical and less invasive surgeries are often successful in relieving pain and disability, other individuals progress to worsened pain syndromes. Current operative strategies to treat further disk degeneration include interbody instrumentation with and placement of prosthetic disks. Optimal instrumentation design requires better understanding of the shape of the degenerated intervertebral disk. The purpose of this study was to extract in–vivo lumbar disks from CT images of the degenerated lumbar disk space and measure their volumes.

Methods:

Lumbar spine CTs were obtained from three patients undergoing lumbar surgery. Analyze imaging analysis software (Mayo Biomedical Imaging Laboratory) was utilized for image analysis. For each disk level, the disk was extracted, or segmented, out of each sagitally–reconstructed slice using Analyze's segmentation tools. These two dimensional disk slices were assembled into a three–dimensional volume. The volumes were then measure in cm3.

Results:

Volumes of two disk spaces at each level from T12–L1 through L5–S1 were compiled: T12–L1 10.9+/–1.5 (average+/–standard deviation), L1–L2 13.3+/–4.7, L2–3 14.8+/–1.72, L3–4 17.1 +/– 0.6, L4–5 14.1 +/– 7.2, and L5–S1 14.5+/–7.4, all in cm3.

Discussion/Conclusions:

These are initial results in volumetric analysis of diseased intervertebral disks. Future directions of this work include correlation with radiographic degree of disk degeneration with measured volumes and surface analysis of the vertebral endplates. This may serve to improve instrumentation interaction with adjacent vertebral bodies.