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INTRODUCTION

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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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Figure 38-1.

Lumbar spinal stenosis treatment algorithm.

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INDICATIONS

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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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CONTRAINDICATIONS

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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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RELEVANT ANATOMY

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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 narrows, ...

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