Introduction Symptoms of neurogenic intermittent claudication in spinal stenosis are explained by the narrowing of the spinal canal in the extended (upright) position and widening in the sitting (flexed) position. The XStop inter-spinous process distraction device is a new product that is designed to hold the affected segments in a flexed posture. This prospective study looks at the changes in the lumbar spine in a variety of postures from pre- to post insertion.

Methods Using a positional magnetic resonance imaging (pMRI) scanner, patients were scanned before and six months after the insertion of the device. Images were taken in sitting flexed and extended, and standing positions. The change in the total range of movement of the lumbar spine and in the individual operated segments was measured along with changes in the surface areas of the exit foramen, the dural sac, and the disc height.

Results 12 patients with 17 levels distracted have been scanned and measured. The cross sectional area of the dural sac at the level of the stenosis has increased from a mean of 77.8 mm² to 93.4 mm² in the standing position (p=0.006) and from 84.56mm² to 107.35mm² on extension (p=0.008). There were no statistically significant changes in the range of movement of the whole lumbar spine, or at levels adjacent to the device.

Discussion This study demonstrates that the X Stop device increases the cross sectional surface area of the spinal canal at the stenosed level, without causing extensive changes in the posture of the lumbar spine.

Introduction The Dynesys device uses transpedicular screws linked by a cord and spacers. It is claimed that the advantage is that it allows some motion, in all directions, in the operative levels. In vitro laboratory biomechanical studies show that the movement permitted is similar to rigid fusions.

This study measures the changes in the lumbar spine in different postures, pre- and after insertion of the device.

Material-method In our study 20 patients with dominant low back pain, with or without leg pain, were treated with Dynesys system. Stress discography was made to evaluate the symptomatic level

All had a positional MRI preoperatively and nine months post-operatively in flexion-extension-lateral bending.

The patients were divided in to two groups:

Group(A) with 8 patients in which Dynesys was used with fusion (disc-height< 40 %)

Group(B) with 12 patients was the Dynesys-only group (disc-height=40–90%).

Results The operated levels were 42, 10 of those were fused levels. The results showed that there was a statistically significant difference in flexion-extension range of movement of the whole lumbar spine (mean= −13.45)(p< 0.005), but it wasn’t significant in the level above (mean=0.056)(p=0.972) and at a single instrumented segment was (mean=−4.06°)(p< 0.05)

The changes in the anterior disc height was (mean= −1.18)(p< 0.05) and to the posterior (mean=0.37)(p=0.134). In bending were (mean=−0.87°)(p=0.18) for left and (mean=−0.24°)(p=0.75) for the right

Discussion This study shows that in the Dynesys stabilizing system allows small range of movement at the instrumented levels, with no significant increased mobility in the adjacent levels. Also the device acted to compress the anterior annulus

Introduction Symptoms of neurogenic intermittent claudication in spinal stenosis are explained by the narrowing of the spinal canal in the extended (upright) position and widening in the sitting (flexed) position. The X-Stop® inter-spinous process distraction device (St. francis Medical Technologies) is a new product designed to hold the affected segments in a flexed posture. This prospective study looks at the changes in the lumbar spine in a variety of postures from pre- to post-insertion.

Method Using positional MRI (pMRI), patients were scanned before and six months after operation. Images were taken in sitting flexed, extended, neutral, and standing positions. The total range of motion of the lumbar spine and of the individual operated segments were measured, along with changes in disc height, areas of the exit foramina, and dural sac.

21 patients (11 males; 10 females) were included in the study. Age ranged from 57 – 88 years. All had symptomatic lumbar spinal stenosis- single level- 13 (L2/3-1; L3/4-3; L4/5-9); double level 8(L3/4, L4/5 – 7; L4/5, L5/ S1 – 1).

Results The mean area of the dural sac at the operated levels increased from 89.25mm2 to 108.96mm2 (p< 0.001) in the standing posture and from 103.96mm2 to 124.94mm2 (p< 0.001) in extension postoperatively. The area of the exit foramina in extension increased from 79.15mm2 to 100.41mm2 (p< 0.001) on the left side and from 80.86mm2 to 98.74mm2 (p< 0.001) on the right side. The overall changes in the range of movement of the individual segments or of the lumbar spine were statistically insignificant.

Discussion Previous, radiologic (Willen J, et al; Spine 1997) and cadaveric studies have demonstrated reduction in area of the dural sac and exit foramina as the lumbar spine moves from flexion into extension. Our study is the first to quantify these changes in symptomatic patients with lumbar spinal stenosis using postional MRI. This study supports previous studies using positional MRI scanner in patients with lumbar spinal stenosis and also demonstrates that the X-Stop device increases the cross-sectional area of the spinal canal and exit foramina by distracting the spinous processes of the operated level without significantly affecting overall posture of the lumbar spine.

Introduction The Dynesys® stabilisation system (Zimmer Spine) uses transpedicular screws linked by a cord and spacers; the advantage claimed is that it allows some motion, in all directions, in the operated levels. In vitro laboratory biomechanical studies show that the movement permitted is similar to rigid fixation systems.

This study measures the changes in the lumbar spine in different postures, pre- and after insertion of the device. Methods In our study 25 patients with dominant low back pain, with or without leg pain, were treated with Dynesys system, 14 females and 11 males with mean age 43.5 yrs. Discography was done to evaluate the symptomatic painful level. All patients had a positional magnetic resonance imaging (pMRI) scans preoperatively and nine months post-operatively in standing; sitting flexion and extension, and left and right bending postures. The patients were initially divided into two groups. The first (Group A) with 14 patients in which only Dynesys was used (disc height 40–90%) and the second (group B) with 11 patients in which Dynesys was used with fusion (disc height < 40 %).

Results The operated levels were 51, 13 of which were fused. The results of the pMRI measurements showed that the mean range of movement of the lumbosacral angle reduced by 10.3° from pre-op of 39.2° to postop. of 28.9° (p= 0.016) in group A while in group B it reduced by 13.7° from 36.2° preop. to 22.5° postoperatively (p= 0.02).

The range of movement of the end plate angle at the instrumented segments in group A reduced from 5.6° preoperatively to 2.6° with a difference of 3.0° (p=0.016) while in group B it reduced from 6.7° to 2.5° postoperatively with a difference of 4.2°(p=0.008). The range of movement of the end plate angle at adjacent level in group A changed from 8.8° preop. to 7.2° with a reduction of 1.6° (p=0.427) while in group B it increased from 6.9° to 8.6°, difference of 1.7° (p=0.149)

The mean anterior disc height in group A reduced by 1.2mm (p< 0.005) from 10.1mm to 8.9mm postoperatively, and the posterior one was increased from 6.5mm to 8.9mm with a difference of 0.6mm (p= 0.013). In group B the anterior disc height was reduced by 1.1mm (pre-op 10.4mm to post-op 9.3mm; p=0.049) and the posterior one by 0.16mm (pre-op 6.98mm to post-op 6.82mm; p=0.714)

Discussion This study shows that in the Dynesys stabilising system allows a small range of movement at the instrumented levels, with no significant increased mobility in the adjacent levels. Also the device acted to compress the anterior annulus more than to distract the posterior annulus.