The use of an interspinous implant in conjunction with a graded facetectomy procedure

Study Design. The range of motion (ROM) of lumbar cadaver spines was measured during flexion, extension, axial rotation, and lateral bending following graded facetectomies and implantation of an X STOP interspinous spacer implant. Objective. The study was performed undertaken to understand better the influence of the interspinous spacer implant on the kinematics of the lumbar spine following graded facetectomies. Summary of the Background Data. Lateral lumbar spinal stenosis is often treated with a unilateral or bilateral facetectomy procedure. Previous biomechanical research has shown that a facetectomy may increase the ROM during flexion and axial rotation. Methods. Seven cadaver spines (L2 - L5) were tested in flexion, extension, axial rotation, and lateral bending, and the individual ROM of each motion segment was measured. Specimens were tested intact and following 3 graded facetectomies (i.e., unilateral medial facetectomy [UMF], unilateral total facetectomy [UTF], and bilateral total facetectomy [BTF]), with and without the X STOP. Results. A BTF caused a significant increase in ROM during flexion and axial rotation but not extension and lateral bending. The UMF and UTF did not affect the ROM during any of the 4 motions. The interspinous implant: (1) significantly decreased the flexion ROM for the intact, UMF, UTF, and BTF treatments; (2) significantly decreased the extension ROM for the intact, UMF, and BTF treatments but not the UTF (P < 0.13); (3) had no significant effect on the axial rotation ROM; and (4) significantly increased the lateral bending ROM for the UMF, UTF, and BTF treatments. Conclusions. The results suggest that the implant may be used in conjunction with a UMF or UTF. However, the X STOP should not be used in conjunction with BTF.