More than 60% of people in developed countries will
experience spinal pain at some time in their lives. Back pain is
the most common complaint of patients referred to pain clinics.
The pain is nonspecific in about 85% of the cases, and
onset of symptoms is most often between the ages of 35 and 55 years.
According to some sources, 15% to 45% of all adults
experience lower back pain, and 1 in 20 people present with a new
episode annually. Back pain absorbs approximately 40% of
the cost of workers’ compensation, which was estimated
as $24 billion in 1990 and is considerably higher today.
Risk factors for spinal pain include trauma, heavy physical labor,
frequent twisting, bending, vibrations, pulling and pushing, and
repetitive motion, especially that involving static postures. Psychological
features such as anxiety, depression, job dissatisfaction, and stress
also can play an important role.
The spine consists of 7 cervical, 12 thoracic, and 5 lumbar vertebrae
in addition to sacrum and coccyx. They articulate anteriorly through
the disks and posteriorly through the left and right synovial facet
joints. Anterior to the ligamentum flavum and covering the facet
(apophyseal) joint is a variable amount of vascularized adipose
tissue, which directly contacts the dural sleeve of the nerve root.
The sleeve is located so close to the facet that it is possible,
inadvertently, to inject medication directly into the cerebrospinal
fluid. The articular surfaces of the facets are covered by cartilage.
Joints are lined by synovium and contain variable amounts of fluid.
The fibrous joint capsule forms superior and inferior joint recesses
and blends anteromedially with the ligamentum flavum. It is located
close to the neural foramen and the nerve root. Enlarged and osteophytic joints
can contribute to significant narrowing of the neuroforaminal opening
and can cause radicular symptoms.
Computed tomography (CT), magnetic resonance imaging (MRI), and
intra-articular contrast medium can be used to demonstrate these
anatomic features. The volume of injectate that can be accommodated
by the facet joints varies as follows: cervical, 0.5 mL to 1.0 mL;
thoracic, 0.4 mL to 0.6 mL; and lumbar, 1.0 mL to 2 mL.
In the upper lumbar spine, approximately 80% of the
facet joints are curved and 20% are flat. This situation
is reversed in the lower lumbar spine, where approximately 80% of
the joints are flat. The upper lumbar facets are oriented more strongly
in the sagittal plane, and by the L5 to Sl level, they rotate obliquely.
The lumbar facet joints are oriented 45 degrees from the sagittal
plane, but because of the curvature of the joints, the posterior
part of the joint is close to the sagittal plane. Lumbar facet syndrome
has been considered to be a significant source of lower back pain.
The thoracic facet joints are almost parallel to the coronal
plane. They extend superiorly and inferiorly from the junctions
of the laminae and pedicles and are oriented ...