Chapter 6: Low Back Pain

INTRODUCTION

Despite countless recent advances in diagnosis and treatment, low back pain remains one of the most challenging conditions in all of orthopedics. The results of both surgical and nonsurgical treatments often fall short of patient expectations, making low back pain a frustrating diagnosis for patients and providers alike. The goal of this chapter is to provide a practical, logical, and evidence-based approach to patients with this challenging condition.

ANATOMY

The basic unit in the anatomy of the spine is the vertebra (Figure 6-1). A single vertebra has a solid mass of bone anteriorly called the vertebral body and a complicated array of bony spines and prominences posteriorly called the posterior elements. In the middle, there is an open passageway called the spinal canal. The spinal canal starts at the foramen magnum, the opening at the base of the skull where the brain stops and the spinal cord begins, and it continues all the way down to the coccyx. Adjacent vertebrae are stacked one on top of the other, and together, they form the skeletal structure of our spines: a long sheath of bony “armor” to protect our fragile spinal cord and nerve roots and a structural frame to support our body mass (Figure 6-2). For most of the lumbar spine, the spinal canal contains a collection of nerve roots, not the spinal cord. Figure 6-3 shows that the spinal cord ends at approximately the level of the second lumbar vertebra, and that, below this level, the spinal canal contains a bundle of nerve roots called the cauda equina. Each vertebra is linked to the vertebrae above and below it by firm but flexible connections that allow motion in this otherwise-rigid bony column. In the front, the tissue that connects adjacent vertebrae is called the intervertebral disk. Each disk consists of a tough, rubbery peripheral ring known as the annulus fibrosus and a soft, jelly-like center known as the nucleus pulposus (Figure 6-4). Behind the spinal canal, the posterior elements of adjacent vertebrae form articulated connections known as the facet joints.