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MILD (minimally invasive lumbar decompression) is an FDA cleared percutaneous, fluoroscopically guided procedure developed as a less destabilizing bone and tissue sparing alternative to more invasive surgical decompression options.
The removal of hypertrophied ligamentum flavum tissue during the mild procedure creates spinal canal space, thereby reducing intraspinal pressures, relieving nerve compression and alleviating complaints associated with neurogenic claudication.
The traditional treatment algorithm for spinal stenosis ranges from the least invasive conventional therapies to the most invasive surgeries with fusion (Figure 38-1).
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Lumbar spinal stenosis secondary to ligamentum flavum hypertrophy on MRI or CT imaging
Symptomatic neurogenic claudication in patients with lumbar spinal stenosis
The absence of spinal instability
The absence of grade II or greater spondylolisthesis
The absence of severe foraminal or lateral stenosis presumed to be causing the symptoms
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There are no FDA contraindications for the mild procedure. However, relevant clinical contraindications are listed:
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Spinal instability
Severe neurologic deficit
The absence of a laminar shelf at the level to be treated
Inability to appreciate the epidurogram at level and side to be treated
Infection
Conventional surgical contraindications such as bleeding disorders and/or active anticoagulation, as well as, systemic or local infections should be considered.
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Interlaminar space
Ligamentum flavum
Facet joint
Intervertebral disc
Epidural space
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PATHOPHYSIOLOGY OF SPINAL STENOSIS
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Degenerative changes in the lumbar spine include hypertrophy of the ligamentum flavum, facet joint arthritic changes, and bulging intervertebral discs.
There is structural narrowing of the vertebral canal resulting in nerve root compression and symptomatic neurogenic claudication.
Neurogenic claudication presents as severe pain in the lower back, buttocks, and/or legs that progressively worsens as the individual stands or walks and is relieved with forward flexion—releasing pressure on the neural elements.
Neurogenic claudication symptoms do not follow specific dermatomal patterns and, unless associated with severe stenosis, usually are not associated with neurologic deficits.
Patients often complain of lower extremity numbness or paresthesiae.
Pain is typically not initiated with nonweight bearing positions such as sitting or lying supine.
Compared to vascular claudication, patients with neurogenic claudication present with pain during prolonged erect standing and walking, but tolerate cycling due to flexed positioning, and also have palpable pedal pulses.
In combination with patient symptomatology, radiologic evidence often used to define spinal stenosis is a canal area of less than 100 mm2.
As confirmed radiologically, the most common level affected by lumbar spinal stenosis is L4-5, followed by L3-4, L5-S1, L2-3, and L1-2 (see anatomical Figure 38-2).
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As the vertebral canal ...