Vertebral displacement ( Spinal Instability )

We have three types which are:

1-Spondylolisthesis which means anterior displacement of the vertebra above on the vertebra below.

Grades  of Spondylolisthesis :

-Starting from second degree, we assume fracture of the pars because the vertebra above can not move more than half the length of the vertebra below with destruction of the pars.

Pseudo disc bulge:

-This is seen due to compression of the lower disc by the posterior edge of the sliding upper vertebra ( it does not conform to the edges of the vertebra as seen in the true disc bulge ).

 

• Grade 1: 0-25% vertebral slippage
• Grade 2: 25-50% vertebral slippage
• Grade 3: 50-75% vertebral slippage
• Grade 4: 75-100% vertebral slippage
• Grade 5: vertebral disc has slipped completely off

 

Causes:

*Lytic type: Due to pars defect.

*Degenerative type: Due to osteoarthritis.

2-Retrolisthesis which means posterior displacement of the vertebra above on the vertebra below.