An Overview of the Spine

• Author: Samuel D. Hodge, Jr./Jack E. Hubbard
• Profession: Skilled litigator, is chair of the department of legal studies at Temple University/Professor of Neurology at the University of Minnesota
• Pages: 409-446

An Overview

of the Spine

Get knowledge

of the spine, for this

is the requisite for

many diseases.

Hippocrates,

469–377 B.C.

7

The spine is a complex and impressive collection of vertebrae, intervertebral disks, nerves,

a spinal cord, and soft tissues.1 The common perception that the spine is weak or vulner-

able and that we must be careful not to hurt it is incorrect. In reality, it is a very durable

and strong structure designed to do its job.2 Nevertheless, it can be a great source of pain.

In fact, back pain is a major health problem that extracts an enormous emotional and

financial toll. For instance, musculoskeletal problems cost the economy more than $215

billion annually, and each year 14 percent of the population suffers a back impairment

that will limit activities of daily living.3 Back symptoms are the second leading reason for

visits to physicians, and the most frequent cause for orthopedic and neurosurgical con-

sultations.4 They are also the most common reason for disability in individuals under the

age of 45.5 Further, in excess of 65 million Americans suffer from low back pain each year,

and 50 percent of those who experience an episode of low back pain will have a repeat

occurrence within one year.

These statistics are staggering and demonstrate the great care that must be exercised

in handling an injury claim involving the spine to ascertain the real cause of the problem.

To properly understand a claim involving the spine, it is helpful to gain an appreciation

of some of the basics about this anatomical area. For instance: What is the difference

between a herniated disk and a bulging disk? What are the different parts of the spine and

what are their functions?6 This chapter provides an overview of the spine and includes

a discussion of the bones that make up this structure, the cushions that allow the spine

to bend, and the soft tissues that hold the vertebral column together. Information about

spinal injuries and surgical repair techniques is also presented, as well as litigation tips to

assist the practitioner in presenting or defending a back injury claim. Subsequent chap-

ters provide a more detailed overview of the neck and low back since these anatomical

parts account for most injuries to this region of the body.

Anatomy of the Spine

The spine extends from the base of the skull to the pelvis and consists of a number of

bones, termed vertebrae. The vertebrae are stacked upon each other, with each separated

from the vertebrae above and below by soft cushion-like pads called intervertebral disks.

Figure 7-1.

Vertebrae are not uniform in size and generally become larger in a descending order

because of their increasing weight-bearing responsibilities. Figure 7-1. For the most part,

vertebrae have two major aspects—the body and the arch. Figure 7-2. The body of the ver-

tebra, the larger circular portion in the front (anterior), carries the weight of the spine and

is separated from each of the vertebrae above and below by an intervertebral disk. The

back portion (posterior) of a vertebra, the vertebral arch, is more delicate and designed to

410 ◆ CHAPTER 7

allow movement by forming pairs of synovial joints, or the moveable point of contact,

with the vertebrae above and below. These joints, called facets, are supplied by sensory

nerve fibers, making them a source of back pain. Protruding from the back of each ver-

tebral arch is a spinous process that serves as anchor points for the muscles that move the

spine. The posterior portion of these spines can be felt as hard bumps down the back.

Extending laterally out from each vertebral arch are two transverse processes. The vertebral

body and arch enclose a roughly oval-shaped space called the vertebral foramen. When the

vertebrae are stacked upon each other, these individual openings form the vertebral canal,

a long hollow tube, much like what happens when napkin rings are stacked upon each

other. Within the vertebral canal runs the spinal cord as it courses downward from the

brain through the cervical and thoracic vertebral levels to the T12 level. In the lumbar

levels, nerve fibers extend from the end of the spinal cord to course further downward to

go to the pelvic organs and legs. Between each adjacent vertebrae are openings on either

side, termed the intervertebral foramina (singular, foramen) through which spinal nerves

exit from the spinal cord to the structures of the body.

Major Regions of the Spine

There are five regions of the spine, consisting of a total of 26 vertebrae. At birth, however,

these bones number 33, but some fuse together with time. From top to bottom, these

regions are the cervical, thoracic, lumbar, sacrum, and coccyx.

The cervical spine consists of seven smaller and tightly stacked vertebrae, numbered

C1-C7, which support the head and provide a great deal of flexibility to the neck. Figure

7-3. The first cervical vertebra starts at the base of the skull, and the last one terminates

at the first prominent nodule, the spine of the seventh cervical vertebra, which can be

palpated on the back at the base of the neck. The neck is able to engage in two types of

movements: rotation and flexion/extension. Rotation is the ability to turn the head to the

FIGURE 7-1.

7-1a: Posterior view of the spine

superimposed upon the human

form. The spine is composed

of individual vertebrae separated

by intervertebral disks. Note that

the vertebrae increase in size,

progressing down to the lumbar

region, reflecting an increased

weight-bearing function.

Figure 7-1b: Side and back views

of the entire spine composed of

vertebrae that are stacked upon

each other separated by disks.

The five regions and the number

of vertebrae from top down are

cervical (7 vertebrae), thoracic (12

vertebrae), lumbar (5 vertebrae),

sacrum (5 sacral vertebrae fused),

and coccyx (3-5 vertebrae).

AN OVERVIEW OF THE SPINE ◆ 411

Vertebral

Vertebral

arch

arch

Vertebral

Vertebral

body

body

Spinous facet

Spinous facet

process

process

Transverse

Transverse

process

process

Vertebral

Vertebral

foramen

foramen

Vertebra

Vertebra

Vertebral

Vertebral

body

body

Spinous

Spinous

process

process

Vertebral

Vertebral

arch

arch

Intervertebral

Intervertebral

foramina

foramina

FIGURE 7-2.

7-2a: Top view of a vertebra

consisting of the large body located

in the front (ventral) and the

more delicate arch located toward

the back (posterior). These two

components form a central open-

ing, the vertebral (spinal) foramen.

When vertebrae are stacked on

top of each other like napkin

rings, the result is a long tube

termed the vertebral (spinal) canal

through which runs the spinal

cord. Each vertebra connects with

those above and below, forming

a joint termed a facet. Projecting

back from the midline of each

arch is the spinous process and from

the sides the transverse process that

serve as the attachment points for

muscles.

7-2b: Side view of three verte-

brae illustrating the intervetebral

foramina.

FIGURE 7-3.

Side view of the cervical portion

of the spine, revealing vertebrae

C1-C7. The spinous process of

C7 can be felt as a midline promi-

nence on the base of the neck.

spinous

spinous

process

process

a

b