Lateral lumbar spinal canal stenosis: Classification, Pathologic anatomy and surgical decompression

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Introduction

1. 3 Types of lumbar spinal stenosis (LSS)

     1) spinal canal

     2) nerve root canal

     3) intervertebral foramen

     # but misunderstanding concerning the terminology, pathology, method of surgery for LSS

2. Many different terminologies of LSS

     1) lateral recess stenosis

     2) foraminal canal stenosis

     3) subarticular stenosis

     4) subpedicular stenosis

     5) intervertebral foramen stenosis

     6) lateral gutter stenosis

3. Many different terminologies of surgical methods for LSS

     1) foraminotomy

     2) foraminectomy

     3) partial facetectomy

     4) total facetectomy

     5) total laminectomy

4. Purpose

     1) facilitate communication among disciplines

           by classifying the lateral lumbar spinal canal into three zones

           by illustrating common pathologic conditions

     2) illustrate the technique of surgical decompression of pathologic conditions in each zome

Entrance zone stenosis

Why does the Entrance zone stenosis happen?

     1) hypertrophic osteoarthritis of facet joint, particularly involving superior articular process

     2) developmental variations of the facet joints (shape, size or orientation)

     3) developmental short pedicle

     4) osteophytic ridge or bulging annulus of disc anterior to the nerve root

Mid zone stenosis

Why does the Mid zone stenosis happen?

     1) osteophyte formation under the pars interarticularis where ligamentum flavum is attached

     2) fibrocartilagenous or bursal tissue hypertrophy at a spondylolytic defect

     *very difficult to detect the pathological condition under pars interarticularis on roentgenographic examination and cannot be easiy recognized pre-operatively

Exit zone stenosis

Why does the Exit zone stenosis happen?

     1) hypertrophic osteoarthritis changes of facet joints with subluxation

     2) osteophytic ridge formation along the superior margin of the disc

Discussion

1. Previous Studies

     1) Puttti >> Lateral lumbar spinal canal is an important location for the pathogenesis of ganglionities, funniculitis and plexitis to cause sciatic pain

     2) Sicard >> lateral foraminal canal can be said as the crossroad of neurologia

     3) Putti >> described various pathologic conditions of lateral lumbar spinal canal caused by facet joint

     4) Kirkaldy-Willis and McIvor >> 3 types of spinal stenosis

           a. Spinal canal

           b. nerve root canal

           c. intervertebral foramen

2. Details

     1) Entrance zone & Exit zone >> considerable attention from clinicians

     2) Mid zone >> very difficult to demonstrate by various radiologic techniques

           -different symptoms when DRG is compressed or entrapped

     3) In stenotic condition with facet joint subluxation and hypertrophy, DRG is located more medially and proximally under the area where the lamia meets the base of the inferior articular process.

     4) in lateral lumbar spinal canal stenosis, single spinal nerve >> entrapped at 3 different zones across 2 spinal motion segments

     5) pathologic conditions at a single level >> entrap 2 different spinal nerves within 2 different zone of lateral lumbar spinal canal