Sunday 1 January 2012

Fusion and adjacent segment degeneration

Sagittal MRI cervical spine shows:
C5-6 Congenital fusion, as the intervening C5-6 disc is rudimentary with concavity of combined anterior surfaces of C5 and C6 - 'wasp waist' sign.
Absent normal cervical lordosis.
Marked degenerative changes at adjacent levels particularly C4-5 and C6-7.
No significant canal stenosis or cord compression.

In this case I've tried to focus on the relation between fusion of vertebral bodies let it be congenital or post discectomy and the advancement of degenerative changes at adjacent levels.

Development of adjacent segment degeneration (ASD) secondary to fusion :
The mechanical and shearing motion exerted by the lever moment at adjacent levels.
Increased intra discal pressures at adjacent levels which is proved in vitro during normal load testing.
Combination of these two mechanisms is postulated as being responsible for hypermobility and accelerating degenerative changes in the pathogenesis of ASD.                               

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