The pedicle-facet angle and tropism in the sagittal plane in degenerative spondylolisthesis: a computed tomography study using multiplanar reformations techniques.

STUDY

DESIGN

A case-control study.

OBJECTIVE

To analyze the facet joint orientation in the sagittal plane [pedicle-facet angle (P-F angle)] and facet tropism, and clarify the relationship between P-F angle and the amount of vertebral slipping in degenerative spondylolisthesis (DS) patients on multislice computed tomography using multiplanar reformations techniques.

SUMMARY OF BACKGROUND DATA: Some studies have indicated a correlation between DS and an increased sagittal orientation of the facet joints. However, the facet orientation has not been fully elucidated and it had been measured only in the transverse plane of computed tomography and magnetic resonance imaging. Although the P-F angle had been measured on the plain radiographs, accurate measurement was difficult to obtain because of the technical limitations.

METHODS

A total of 156 patients, who came to our hospital for low back pain and/or sciatica were divided into 2 groups. The DS group comprised of 78 patients with DS at L4-L5, and the control group comprised of 78 patients without spondylolisthesis. The P-F angle and tropism were measured in the sagittal plane on multi-slice computed tomography using multiplanar reformations techniques.

RESULTS

The P-F angles at L4-L5 were 117.02±6.89 degrees (left), 115.95±6.02 degrees (right) in the DS group and 106.71±3.19 degrees (left), 105.58±3.07 degrees (right) in the control group, respectively (P₁<0.01, P(r)<0.01). The facet tropism at L4-L5 in the DS group was significantly increased, compared with that in the control group (P=0.004). The mean P-F angle at L4-L5 did not correlate with the amount of vertebral slipping (r=0.176, P=0.122).

CONCLUSIONS

The P-F angle was the highest at L4-L5 both in the DS and the control group, which might explain the fact that L4 vertebra is more likely to slip forward. The P-F angle of the slipped vertebra alone was more horizontally inclined and facet tropism in the sagittal plane may relate well to DS.