Background Data: Spondylolisthesis refers to the forward displacement of one vertebra relative to another. Whether degenerative spondylolisthesis (DS) leads to instability was controversial in the literature. DS was conventionally considered to be instable but some papers have reported that there was no evidence that the range of motions (ROMs) of the vertebrae with DS were increased compared with normal vertebrae. Purpose: The aim of the work was to study motor characteristics of the vertebral segments with lumber degenerative spondylolisthesis in elderly patients after
surgical management. Study Design: This is a prospective study. Patients and Methods: Thirty patients (age more than 55 years) with lumbar DS and failed conservative measures for at least three months before surgical treatment
were included. Vertebral kinematics obtained using dynamic plain X. ray; also MRI and/or CT scan of lumbosacral spine were done. During functional postures, vertebral instability was studied. All cases operated upon from May 2013 to
December 2013 in the Neurosurgery Department of Banha University hospital and followed up 6 months for at least. Patients were grouped into 2 groups according to vertebral instability: Group A (fifteen cases ) and Group B (fifteen cases) chosen without privilege to sex , or weight, but suffering from midline low back pain and/ or claudication that were proven to be attributed to spondylolisthesis. Clinical follow-up: done immediately, at 3 and 6 months intervals. The evaluation included the Japanese Orthopedic Association (JOA). Preoperative and last postoperative standing were done to measure the degree of slip and percentage of slip. Results: Adequate lumbar decompression alone in cases of Group A (with no
evident range of motion) showed good outcome with less complications when compared with cases of Group B(showing instability) treated with decompression  with posterolateral instrumented fusion using bilateral pedicle screw fixation.Conclusion: Lumbar DS is a degenerative disease of lumbar spine results in neural compression but does not result necessarily in vertebral instability, some cases of lumbar DS may need only neural decompression as re-stabilization process may have occurred but other cases show instability which required decompression with instrumented fusion. (2014ESJ082)