Manal Siddiqui

The Dynesys lumbar spinal stabilization system: a preliminary report on positional magnetic resonance imaging findings.

Study Design. We present the positional magnetic resonance imaging findings of a prospective case series of patients undergoing surgery with the Dynesys spinal stabilization device (Zimmer, Inc., Warsaw, IN). Objective. To explore the biomechanical impact of the Dynesys device in vivo. Summary of Background Data. Spinal fusion surgery is widely used for painful degenerative conditions of the lumbar spine that have not responded to conservative measures. It often produces good outcomes but can be associated with adjacent segment hypermobility that may lead to further degeneration and pain. Previous cadaveric biomechanical studies claim that the Dynesys Dynamic Spinal Stabilization System allows some lumbar movement, behaving similar to a normal spine in extension but similar to rigid fixation in flexion. Methods. Twenty-four patients with dominant low back pain, with or without leg pain, were treated with the Dynesys. All patients underwent positional magnetic resonance imaging before surgery and 9 months after surgery. Measurements were made to assess the differences at the operated level, adjacent level, and whole lumbar spine. Results. There was a statistically significant reduction in flexion-extension range of movement of both the whole lumbar spine by 13.37° (P = 0.002) and at the instrumented segments by 4.08° (P < 0.001) following surgery. There was an insignificant reduction in range of movement at the level above instrumentation (P = 0.807). Mean anterior disc height at the instrumented level reduced by 0.7 mm following insertion of the Dynesys (P < 0.027). Mean posterior disc height reduced by 0.3 mm (P = 0.453). In a neutral posture, the Dynesys had no significant impact on lordosis or inclination of operated or adjacent levels. Contrary to cadaveric study findings, the Dynesys appears to restrict extension more than flexion with respect to a neutral posture. Conclusions. In vivo, the Dynesys Stabilization System allows movement at the instrumented level, albeit reduced, with no significant increased mobility at the adjacent segments. There was reduction of the anterior disc height without a significant increase of the posterior disc height.

One-year results of X STOP interspinous implant for the treatment of lumbar spinal stenosis

Study Design. Prospective observational study. Objective. To prospectively assess the clinical outcome of patients with symptomatic lumbar spinal stenosis before and at periodic intervals after X Stop implantation and to compare the data with previous studies. Summary of Background Data. The X Stop Interspinous Process Distraction Device is a relatively new interspinous implant designed for patients with symptomatic spinal stenosis particularly neurogenic claudication. Previously, a randomized study has shown a 75% improvement in symptoms and physical function at 1-year post-X Stop implantation for lumbar spinal stenosis. The only other study is a preliminary report of only 10 patients with variable intervals of clinical outcome assessment. Method. Forty consecutive patients were enrolled and surgically treated with X Stop implantation. The X Stop device was implanted at the stenotic segment, which was either at 1 or 2 levels in each patient. They were clinically evaluated at the preoperative, 3-month, 6-month, and 1-year stage with clinical questionnaires (Zurich Claudication Questionnaire, Oswestry Disability Index, and SF-36). Results. Sixteen patients failed to complete all the questionnaires at all time intervals and hence were excluded, leaving 24 patients who had completed all questionnaire at all time interval. By 12 months, 54% of these 24 patients reported clinically significant improvement in their symptoms, 33% reported clinically significant improvement in physical function, and 71% expressed satisfaction with the procedure. 29% of the patients required caudal epidural after 12 months after surgery for recurrence of their symptoms of neurogenic claudication. Conclusion. The results of this prospective observational study indicate that X Stop offers significant short-term improvement over a 1-year period. It is a safe, effective, and less invasive alternative for treatment of lumbar spinal stenosis. Our results, however, are less favorable than the previous multicenter, randomized study.

The Positional Magnetic Resonance Imaging Changes in the Lumbar Spine Following Insertion of a Novel Interspinous Process Distraction Device

Study Design. Patients 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). Objective. To visualize the effect of the device in vivo. Summary of Background Data. Previous 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. Methods. Using 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. Results. In 12 patients with 17 distracted levels, the area of the dural sac at these levels increased from 77.8 to 93.4 mm2 after surgery in the standing position (P = 0.006), with increase in the exit foramens, but no change in lumbar posture. Conclusions. This study shows that the X STOP device increases the cross-sectional area of the dural sac and exit foramens without causing changes in posture.

Influence of X Stop on Neural Foramina and Spinal Canal Area in Spinal Stenosis

Study Design. Measurements of cross sections of exit foramen and spinal canal were performed before and after placement of X Stop in physiologic postures using positional MR scanner at the stenosed level in patients with lumbar spinal stenosis. Objective. To quantify the effect of the implant in vivo on the lumbar spine at the instrumented levels in various postures. Summary of Background Data. Dimensions of the spinal canal and neural foramen decrease from flexion to extension. Symptoms of spinal stenosis occur typically in standing or extension. The X Stop device is designed to distract the posterior elements of the stenotic segment and place it in flexion to treat neurogenic claudication. We think that the device will improve the dimension of the canal in standing and extension. Methods. Twenty-six patients with lumbar spine stenosis underwent a one- or two-level X Stop procedure. All had preoperative and postoperative positional MRI in standing, supine, and sitting flexion and extension. Measurements were carried out on the images acquired. Results. Significant increase in the dimensions of the neural foramen and canal area were demonstrated after surgery. Conclusions. The X Stop device improves the degree of central and foraminal stenosis in vivo.

Effects of X-STOP device on sagittal lumbar spine kinematics in spinal stenosis.

The X-Stop device is designed to distract the posterior elements of the stenotic segment and place it in flexion to treat neurogenic claudication. Previous biomechanical studies on X Stop have been done in vitro on cadavers looking at disc pressures and segmental range of movements. The objective of this study is to understand the sagittal kinematics in vivo of the lumbar spine at the instrumented and adjacent levels. Twenty-six patients with lumbar spine stenosis underwent 1 or 2 level X-Stop procedure. All had pre- and postoperative positional magnetic resonance imaging (MRI) in standing, supine, and sitting in flexion and extension. Measurements of disc heights, endplate angles, segmental and lumbar range of movement were performed after placement of X Stop at the stenosed level in patients with lumbar spinal stenosis. No significant changes were seen in disc heights, segmental and total lumbar spine movements postoperatively. The X-Stop device does not affect the sagittal kinematics of the lumbar spine in vivo.

Positional MRI changes in supine versus sitting postures in patients with degenerative lumbar spine.

Introduction Back pain is associated with a degree of alteration in the alignment and movement of the lumbar spine. The purpose of this study is to investigate how the degree of lumbar segmental degeneration affects sagittal changes in the lumbar spine as it shifts from the supine to the sitting (load-bearing) posture. Materials and Methods Thirty patients with chronic low back pain were enrolled (14 male and 16 female patients); mean age 44.5 years. Their lumbar spines were initially investigated by conventional supine magnetic resonance imaging (MRI) followed later by positional MRI in the seated posture. Of the 150 discs studied, 87 were classified as healthy grade 1, 16 as grade 2, 34 as grade 3, and 13 as grade 4. Results As the lumbar spine was loaded from the supine to the sitting position, the end-plate angles were decreased significantly as the degeneration was increased. There were also significant changes in the anterior and middle disc heights between the supine and the sitting postures irrespective of the degree of degeneration. The overall lumbar lordosis did not significantly change between the two postures. Conclusions We have found that the changes in the segmental motion were related to the degree of degeneration. With positional MRI, we were able to demonstrate changes in healthy and degenerative discs in the weight-bearing position. More similar studies are needed to understand the complex kinematics of the lumbar spine.