• Manal Siddiqui, Malcolm Nicol, Efthimios Karadimas, Frank Smith, and Douglas Wardlaw.
• Department of Radiology, Woodend Hospital, Aberdeen, Scotland.
• Spine. 2005 Dec 1; 30 (23): 2677-82.

Study DesignPatients with symptomatic lumbar spinal stenosis underwent magnetic resonance imaging to study changes in the lumbar spine in various postures before and after implantation of the X STOP Interspinous Process Distraction Device (St. Francis Medical Technologies, Concord, CA).ObjectiveTo visualize the effect of the device in vivo.Summary Of Background DataPrevious studies have shown vertebral canal and exit foraminal area to reduce from flexion to extension. Recently, reports on improved kinematics in vitro at the implantation level of the X STOP device have also been published.MethodsUsing positional magnetic resonance imaging, patients were scanned before and 6 months after surgery. Images were taken with the patient in sitting flexed, extended, neutral, and standing positions. The total range of motion of the lumbar spine and individual segments were measured, along with changes in disc height, areas of the exit foramens, and dural sac.ResultsIn 12 patients with 17 distracted levels, the area of the dural sac at these levels increased from 77.8 to 93.4 mm after surgery in the standing position (P = 0.006), with increase in the exit foramens, but no change in lumbar posture.ConclusionsThis study shows that the X STOP device increases the cross-sectional area of the dural sac and exit foramens without causing changes in posture.

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