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Lumbar 5 hypoplasia and wedging and (pseudo-) anterolisthesis in patients with spondylolysis. Study with MRI 2007

General Spine

Guido E Wilms, MD, PhD
Baudouin Maldague, MD, PhD, Non ASSR Member
Philippe Demaerel, MD,PhD, Non ASSR Member

Scientific Paper

Purpose

To describe the findings on MRI in patients with spondylolysis and hypoplasia of lumbar vertebra L5 with regard to the presence and degree of anterolisthesis.

Methods & Materials

We studied the MR-images of 22 patients with bilateral L5 spondylolysis and hypoplasia and posterior wedging of L5. The anteroposterior diameter of L4, L5 and S1 were measured and compared. The degree of posterior wedging of L5 was calculated. The degree of anterolisthesis was determined as well as the myelographic repercussion on MR-myelography.

Results

The mean difference between the anteroposterior diameter of L4 and L5 was 3,75 mm or 10,6 % shortening of L5 compared to L4. The mean difference between the anteroposterior diameter of L5 and S1 was 4,25 mm or 11,9 % shortening of L5 compared to S1. The mean percentage posterior wedging was 24,5 %. In 13 patients there was no anterior vertebral slipping. True anterolisthesis grade 1 was seen in 5 and anterolisthesis grade 2 in 4 patients. Myelographic repercussion of the "anterolisthesis" was only seen in the 4 patients with grade 2 anterolisthesis. It is important to note that L5 hypoplasia was only seen in patients with bilateral spodylolysis.

Conclusion

L5 hypoplasia and wedging in patients with bilateral spondylolyis does not necessarily lead to true anterior vertebral slipping but can be at the base of pseudospondylolisthesis.
Spondylolisthesis can only be diagnosed if both the anterior and poterior margins of the vertebral body are displaced forward.
L5 hypoplasia seems another reliable sign of bilateral spondylolysis.

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