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Scott D. Daffner, MD
Alexander R. Vacaro, MD ABSTRACT The presentation of spinal
curvature as a new presentation after the completion of skeletal maturity
is termed adult lumbar degenerative scoliosis, and affects 6% of those
older then 50 years. The
scoliosis is divided into 2 categories:
Primary degenerative curves develop from focal disc degeneration
and asymmetric collapse leading to coronal plane rotation and malalignment.
The apex is usually at L2-3 or L3-4, and the curve is usually shorter than
what is seen with idiopathic curves.
Secondary curves, the second type, may be due to intrinsic spine
processes, or factors close to it. Congenital
anomalies such as facet asymmetry in an anatomic fashion, or degenerative
progression due to an already present idiopathic scoliosis.
The presence of lumbar scoliosis
creates an asymmetric spinal loading via shear forces that predispose to
an increase in coronal curve magnitude and axial torque, which in turn
adds to the rotational deformity. In
young, growing patients these forces can lead to asymmetric growth, or in
skeletally mature patients, asymmetric remodeling.
Coronal plane deformity can arise
due to unilateral spondylolysis, post-traumatic or post-inflammatory
conditions. The most common
extra-spinal contributing factor is a leg length discrepancy, which leads
to pelvic obliquity, spinal curve, and progressive unilateral disc
degeneration. Osteoporosis
has often been implicated as a cause of adult degenerative scoliosis, but
there have been studies that have not found a correlation between
progressive curve development and bone demineralization.
They did, however, find a relationship with regards to progressive
degenerative disc disease. The clinical presentation of a
patient with this condition will be complaints of pain, due to muscular
discomfort, facet joint arthrosis, or disc degeneration.
The pain is usually on the convex side of the curve, which may be
due to nerve root stretching. Standing and exertion usually increase the pain, and sitting
does not often relieve the pain. Often,
lying down is the only way to unload the spinal segments.
There may be radicular complaints, as end plate spurring and facet
hypertrophy cause stenosis along the path of the nerve root.
Usually, these symptoms are on the concave side of the curve due to
compression, but can also occur on the convex side due to nerve root
stretching. The most common
neurological deficit seen, according to one study, was sensory deficits in
the L4-5 roots, followed by calf atrophy, then buttock and thigh atrophy.
Lee and colleagues documented that
lateral spinal canal stenosis in the lumbar spine can be divided into
three categories, and are most commonly found at the L4-5 level.
The first is impingement at the entrance zone, which is the
most cephalad portion of the canal, located inferomedially to the superior
articular process. Osteophytes along the medial border of the superior articular
process can impinge on the nerve in this region. The second is the midzone, which lies inferior to the
pars interarticularis and below the pedicle.
The ventral motor nerve root and larger dorsal root ganglion are
located here, and osteophytes under the pars along with spondylotic
deformities/hypertrophy of the fibrocatilaginous and bursal tissue can
cause nerve impingement. The
third zone is the exit zone, which is the area that immediately
surrounds the intervertebral foramen and contains the peripheral nerve.
Hypertrophic changes at the facet joint, subluxation, and
osteophyte formation can all impinge the root at this level. Even though the nerve may escape
impingement at the level of the foramen, it can still become impinged in a
condition called far out syndrome.
Here, the L5 transverse process can impinge the root against the
superior portion or the ala of the sacrum.
This can occur either from rotation and narrowing at the L5-sacral
interface, or from extensive slippage during spondylolisthesis. Nonoperative treatment can include analgesics, anti-inflammatories, PT, medial treatment of the osteoporosis, and rarely bracing. Injections often relieve the radicular symptoms, but not the more common complaint of axial back pain. Multiple injections can only give short-term relief, and their actual effectiveness is still a matter of debate. Surgery usually aims to restore lordosis, maintain stability, and decompress the nerve roots in cases of severe neurological deficits. In cases where osteoporosis occurs, the anchoring system may not be strong due to the demineralization of the bone. The L5-sacral joint is rarely fused in these patients, but other levels are usually fused to prevent collapse of the curve. COMMENTS We have all seen these patients at
one time or another in the clinic. The
scoliosis component is not often identified in the prescription.
Instead, the diagnosis of LBP or even stenosis is used.
However, obtaining a written copy of the radiograph can help us
identify the shape and degree of the curve, in order to modify our
treatment accordingly. While we cannot change the bony curve, we can loosen up the
concave soft tissue to reduce the curve and rotation component.
If a leg length discrepancy is present, either as a cause or an
effect, we can adjust via a shoe lift to reduce the curve and neural
compression. Also, other
standard treatments, including level specific mobilization, traction, and
strengthening all can benefit these patients.
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