title: Decompression for degenerative spondylolisthesis and spinal stenosis at L4-5. The effects on facet joint morphology.
abstract: Anatomic variations exist in the facet joint orientation, shape, and size at L4-5. This morphology is further modified by degenerative changes in spinal stenosis and degenerative spondylolisthesis. This study explored the morphologic alteration of "pedicle-to-pedicle" decompression on the facet joints in normal patients, spinal stenosis patients, and degenerative spondylolisthesis patients. Using computerized digitization, computed tomographic scan images of the facet joint at L4-5 and the medial border of the pedicle at L5 were superimposed. The facet joint orientation, coronal dimension, percentage, and absolute reduction in coronal dimension after pedicle-to-pedicle decompression, and residual coronal dimension after decompression at L4-5 were measured for the three groups. There is a significantly reduced coronal dimension of the facet joint in degenerative spondylolisthesis patients compared with spinal stenosis and normal patients (P < 0.01). The average reduction of the facet joint coronal dimension is 34% (SD 30%) in degenerative spondylolisthesis, and 36% (SD 25%) in spinal stenosis. The smaller preoperative coronal dimension in degenerative spondylolisthesis leads to a significantly reduced residual coronal dimension in degenerative spondylolisthesis compared with normal patients (5.9 mm [SD 4.3 mm] vs. 9.3 mm [SD 3.5 mm]), respectively. Wide variations in facet joint reduction and residual facet joint coronal dimension exist. The significantly reduced coronal dimension after decompression in degenerative spondylolisthesis may be correlated to a trend to further anterior displacement if it is treated with decompression alone. Case-specific assessment of residual facet joint morphology after decompression in both spinal stenosis and degenerative spondylolisthesis patients should be integrated into decisions about fusion for stability at the L4-5 level.
authors.affiliation: Department of Orthopaedics and Rehabilitation, McClure Musculoskeletal Research Center, University of Vermont, Burlington.
authors.forename: L J
authors.initials: LJ
authors.lastname: Grobler
authors.forename: P A
authors.initials: PA
authors.lastname: Robertson
authors.forename: J E
authors.initials: JE
authors.lastname: Novotny
authors.forename: J W
authors.initials: JW
authors.lastname: Ahern
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008297:Male; D011856:Radiographic Image Enhancement; D013130:Spinal Stenosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D013168:Spondylolisthesis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed