The Effect of the Pedicle-Facet Angle on Degenerative Cervical Spondylolisthesis

OBJECTIVE To measure the orientation of the facet joints of cervical spine (C-spine) segments in the sagittal plane, known as the pedicle-facet (P-F) angle, and to use these measurements to evaluate the relationship between the P-F angle and the amount of vertebral anterolisthesis in patients with degenerative cervical spondylolisthesis (DCS). METHODS A retrospective case-control study was performed including 30 age- and sex-matched patients with DCS and 30 control participants. Anterior-posterior and lateral view radiographs of the C-spine were obtained in a standing position. The P-F angle at all cervical levels and the amount of anterolisthesis at C4-5 were measured from lateral view plain radiographs. RESULTS The P-F angles at C4-5 were 141.14±7.14° for the DCS group and 130.53±13.50° (p=0.012) for the control group, and at C5-6 were 137.46±8.53° for the DCS group and 128.53±16.01° for the control group (p=0.001). The mean P-F angle at C4-5 did not correlate with the amount of anterolisthesis (p=0.483). The amount of anterior slippage did correlate with age (p<0.001). CONCLUSION The P-F angle was intrinsically higher at C4-5, compared to C5-6, in both the DCS and control groups, which might explain the increased likelihood for anterolisthesis of C4. Higher P-F angles in the DCS group may be a predisposing factor to slippage. The P-F angle may interact with age to increase incidence of anterolisthesis with increasing age.