Anatomy of the lumbar spinal canal.

1. In the lumbar spinal canal of the achondroplast there is decreased cross-sectional area. In addition the intervertebral foramina are narrow. These changes result in reduced area for the dural sac and exiting spinal nerves. 2. There is associated thoracolumbar kyphosis and a lumbosacral hyperlordosis. These sagittal plane changes result in increased tension on the dural sac and nerves. 3. With aging there is disc degeneration with disc space narrowing and osteophyte formation. In addition facet hypertrophy with osteophyte formation are common. These degenerative changes further reduce the size of an already compromised spinal canal and intervertebral foramina. The above understanding of the normal spinal and anatomy in the achondroplast, and the added effects of aging allow the surgeon to plan a logical treatment regimen for neurological problems in the achondroplast.