Interspinous Device Research Articles

Clinical evaluation of a lumbar interspinous dynamic stabilization device (the Wallis system) with a 13-year mean follow-up

The authors determined current health status of patients who had been included in a long-term survivorship analysis of a lumbar dynamic stabilizer. Among 133 living patients, 107 (average age at surgery, 44.2 +/- 9.9 years) completed health questionnaires. All patients had initially been scheduled for decompression and fusion for canal stenosis, herniated disc, or both. In 20 patients, the implant was removed, and fusion was performed. The other 87 still had the dynamic stabilizer. Satisfaction, Oswestry disability index, visual analog scales for back and leg pain, short-form (SF-36) quality-of-life physical composite score, physical function, and social function were significantly better (p < or = 0.05) in the patients who still had the dynamic stabilization device. SF-36 scores of the fused subgroup were no worse than those reported elsewhere in patients who had primary pedicle-screw enhanced lumbar fusion. This anatomy-sparing device provided a good 13-year clinical outcome and obviated arthrodesis in 80% of patients.

Effect of a novel interspinous implant on lumbar spinal range of motion

Interspinous devices have been introduced to provide a minimally invasive surgical alternative for patients with lumbar spinal stenosis or foraminal stenosis. Little is known however, of the effect of interspinous devices on intersegmental range of motion (ROM). The aim of this in vivo study was to investigate the effect of a novel minimally invasive interspinous implant, InSwing, on sagittal plane ROM of the lumbar spine using an ovine model. Ten adolescent Merino lambs underwent a destabilization procedure at the L1-L2 level simulating a stenotic degenerative spondylolisthesis (as described in our earlier work; Spine 15:571-576, 1990). All animals were placed in a side-lying posture and lateral radiographs were taken in full flexion and extension of the trunk in a standardized manner. Radiographs were repeated following the insertion of an 8-mm InSwing interspinous device at L1-L2, and again with the implant secured by means of a tension band tightened to 1 N/m around the L1 and L2 spinous processes. ROM was assessed in each of the three conditions and compared using Cobb's method. A paired t-test compared ROM for each of the experimental conditions (P < 0.05). After instrumentation with the InSwing interspinous implant, the mean total sagittal ROM (from full extension to full flexion) was reduced by 16% from 6.3 degrees to 5.3 +/- 2.7 degrees. The addition of the tension band resulted in a 43% reduction in total sagittal ROM to 3.6 +/- 1.9 degrees which approached significance. When looking at flexion only, the addition of the interspinous implant without the tension band did not significantly reduce lumbar flexion, however, a statistically significant 15% reduction in lumbar flexion was observed with the addition of the tension band (P = 0.01). To our knowledge, this is the first in vivo study radiographically showing the advantage of using an interspinous device to stabilize the spine in flexion. These results are important findings particularly for patients with clinical symptoms related to instable degenerative spondylolisthesis.

Risk Factors and Surgical Treatment for Symptomatic Adjacent Segment Degeneration after Lumbar Spine Fusion

The present study analyzed the risk factors, prevalence and clinical results following revision surgery for adjacent segment degeneration (ASD) in patients who had undergone lumbar fusion. Over an 8-year period, we performed posterior lumbar fusion in 81 patients. Patients were followed a minimum of 2 years (mean 5.5 years). During that time, 9 patients required revision surgery due to ASD development. Four patients underwent autogenous posterolateral arthrodesis and extended transpedicle screw fixation, 4 patients underwent decompressive laminectomy and interspinous device implantation, and 1 patient underwent simple decompression. Of the 9 of patients with clinical ASD, 33.3% (3 of 9) of patients did not have radiographic ASD on plain radiographs. Following revision surgery, the clinical results were excellent or good in 8 patients (88.9%). Age > 50 years at primary surgery was a significant risk factor for ASD development, while number of fusion levels, initial diagnosis and type of fusion were not. The incidence of ASD development after lumbar surgery was 11.1% (9 of 81) in this study. Age greater than 50 was the statistically significant risk factor for ASD development. Similar successful clinical outcomes were observed after extended fusion with wide decompression or after interspinous device implantation. Given the latter procedure is less invasive, the findings suggest it may be considered a treatment alternative in selected cases but it needs further study.

Biomechanical Evaluation of an Interspinous Stabilizing Device, Locker

A biomechanical study. To evaluate the biomechanical properties of a novel dynamic interspinous device named Locke There has been no biomechanical study on this device. Five human cadaveric lumbar spine specimens (L2-S1) were tested in the following sequence: (1) intact state; (2) after removal of the interspinous ligaments of L3-L4; (3) after application of the Locker at the interspinous space; (4) after destabilization of the L3-L4 motion segments; and (5) after reapplication of the Locker to the destabilized segments. Range of motion (ROM) and intradiscal pressure were measured by a video-based motion capture system and needle transducers. Applied to the intact spine, the Locker significantly reduced the ROM of the segment in extension and flexion without significant effect on lateral bending and/or axial rotation. When applied to the destabilized segment, it significantly reduced the ROM in all directions of movement except in axial rotation, where it failed to restore the ROM of the segment. The ROM of adjacent segments was not significantly affected by the application of the Locker. Pressures at the posterior anulus and central nucleus were decreased by application of the Locker. The Locker showed a significant stabilizing effect on the spinal motion segment both in the intact and destabilized spine without any significant effect on adjacent segments. It also decreased the pressures of the posterior anulus and central nucleus significantly. However, in the destabilized spine, it showed no stabilizing effect in axial rotation. This biomechanical property should be considered in clinical application.

P108. Five Year Outcomes in Patients Treated with the X-STOP Interspinous Process Device for Neurogenic Intermittent Claudication Due to Lumbar Spinal Stenosis

BACKGROUND CONTEXT: Patients with neurogenic intermittent claudication (NIC) secondary to lumbar spinal stenosis experience pain, decrements in physical function and quality of life. The X-STOP interspinous process device (IPD) is a minimally invasive treatment option. Results of a multicenter randomized trial demonstrated that 2-year treatment success with the X-STOP IPD was significantly better compared with non-surgical care.

P41. Two Year Clinical Results of X-Stop Interspinous Decompression Device in the Management of Symptomatic Lumbar Canal Stenosis

P41. Two Year Clinical Results of X-Stop Interspinous Decompression Device in the Management of Symptomatic Lumbar Canal Stenosis

Biomechanical effect of different lumbar interspinous implants on flexibility and intradiscal pressure

Interspinous implants are used to treat lumbar spinal stenosis or facet joint arthritis. The aims of implanting interspinous devices are to unload the facet joints, restore foraminal height and provide stability especially in extension but still allow motion. The aim of this in vitro study was to compare four different interspinous implants--Colfex, Wallis, Diam and X-Stop--in terms of their three-dimensional flexibility and the intradiscal pressure. Twenty-four human lumbar spine specimens were divided into four equal groups and tested with pure moments in flexion/extension, lateral bending and axial rotation: (1) intact, (2) defect, (3) after implantation. Range of motion and the intradiscal pressure were determined. In each implant-group the defect caused an increase in range of motion by about 8% in lateral bending to 18% in axial rotation. Implantation had similar effects with all four implants. In extension, Coflex, Wallis, Diam, and X-Stop all overcompensated the instability caused by the defect and allowed about 50% of the range of motion of the intact state. In contrast, in flexion, lateral bending and axial rotation the values of the range of motion stayed about the values of the defect state. Similarly the intradiscal pressure after implantation was similar to that of the intact specimens in flexion, lateral bending and axial rotation but much smaller during extension. All tested interspinous implants had a similar effect on the flexibility: they strongly stabilized and reduced the intradiscal pressure in extension, but had almost no effect in flexion, lateral bending and axial rotation.

Clinical Symposium II: Interspinous-based Dynamic Stabilization.

Interspinous-based dynamic stabilization has become a popular form of treatment in recent years. Though many companies have developed innovative designs for interspinous spacer devices, there are many questions yet to be answered. Some of these devices have considerably more clinical experience than

Self-rated evaluation of outcome of the implantation of interspinous process distraction (X-Stop) for neurogenic claudication

The treatment of lumbar spinal stenosis is either conservative or surgical decompression. Recently, an interspinous decompression device (X-Stop) has been developed as an alternative. Patients treated with an X-Stop between 2003 and 2006 are subject of this study. The SF-36 Health Survey and Zürich Questionnaires are used. The data of pre- and post-operative self-rated questionnaires are collected and analysed by independent investigators. The data were statistically analysed. A good outcome was defined when the mean score at the ZQ for satisfaction was at maximal 2.0, and the mean improvement of the severity score was at least 0.5, and also for vitality score. For relations between outcome and gender, smoking, BMI, orthopaedic co-morbidity, number of implanted X-Stops were sought. The change in SF-36 scales was related to the outcome. Sixty-five patients did undergo implantation of an X-Stop. The mean age was 64.4 +/- 10.0 years (range: 37.0-85.0 years). 31.1% Of the patients had a good outcome. A good outcome was not related to smoking, BMI, number of implanted X-Stops. However, a good outcome was related to the absence of orthopaedic co-morbidity or male gender. Patients with a good outcome had significantly a better improvement of the scales of the SF-36 concerning physical pain or impairment. The X-Stop does improve the clinical situation. However, a good outcome is achieved less often than previously reported. Probable explanations are discussed.

High failure rate of the interspinous distraction device (X-Stop) for the treatment of lumbar spinal stenosis caused by degenerative spondylolisthesis

The X-Stop interspinous distraction device has shown to be an attractive alternative to conventional surgical procedures in the treatment of symptomatic degenerative lumbar spinal stenosis. However, the effectiveness of the X-Stop in symptomatic degenerative lumbar spinal stenosis caused by degenerative spondylolisthesis is not known. A cohort of 12 consecutive patients with symptomatic lumbar spinal stenosis caused by degenerative spondylolisthesis were treated with the X-Stop interspinous distraction device. All patients had low back pain, neurogenic claudication and radiculopathy. Pre-operative radiographs revealed an average slip of 19.6%. MRI of the lumbosacral spine showed a severe stenosis. In ten patients, the X-Stop was placed at the L4–5 level, whereas two patients were treated at both, L3–4 and L4–5 level. The mean follow-up was 30.3 months. In eight patients a complete relief of symptoms was observed post-operatively, whereas the remaining 4 patients experienced no relief of symptoms. Recurrence of pain, neurogenic claudication, and worsening of neurological symptoms was observed in three patients within 24 months. Post-operative radiographs and MRI did not show any changes in the percentage of slip or spinal dimensions. Finally, secondary surgical treatment by decompression with posterolateral fusion was performed in seven patients (58%) within 24 months. In conclusion, the X-Stop interspinous distraction device showed an extremely high failure rate, defined as surgical re-intervention, after short term follow-up in patients with spinal stenosis caused by degenerative spondylolisthesis. We do not recommend the X-Stop for the treatment of spinal stenosis complicating degenerative spondylolisthesis.

Interspinous Process Distraction Devices for Spinal Stenosis

Interspinous process distraction devices represent a relatively new option for minimally invasive surgical treatment of lumbar spinal stenosis. The X STOP device is the first such implant to receive FDA approval for this indication, and promising results from initial clinical studies have encouraged development of multiple alternative implant designs. These devices are designed for placement between adjacent spinous processes and function to create relative segmental flexion at the treated level, indirectly increasing the cross-sectional area of the spinal canal as well as the neuroforamina. This technology is an option for patients with neurogenic claudication aggravated by standing or walking and relieved by sitting. Short-term clinical results appear comparable to laminectomy and superior to nonoperative treatment. Long-term clinical follow-up data are not yet available.

Interspinous Process Devices in the Lumbar Spine

A growing number of interspinous process devices have been introduced to the lumbar spine implant market. Implant designs vary from static spacers to dynamized devices. Furthermore, they are composed of a range of different materials including bone allograft, titanium, polyetheretherketone, and elastomeric compounds. The common link between them is the mechanical goal of distracting the spinous processes to affect the intervertebral relationship. In contrast, the purported clinical goals are more variable, ranging from treatment of degenerative spinal stenosis, discogenic low back pain, facet syndrome, disk herniations, and instability. Though some clinical data exist for some of these devices, defining the indications for these minimally invasive procedures will be crucial. Indications should emerge from thoughtful consideration of data from randomized controlled studies.

149. Spinal Stenosis Decompression and Coflex™ Interspinous Stabilization: Clinical Results from an International Multicenter Retrospective Study

BACKGROUND CONTEXT: Degenerative spinal stenosis is a severely disabling disease common in the elderly with patient symptoms usually including bilateral radicular pain that radiates to the buttocks and posterior thighs, intermittent neurogenic claudication, sensation disturbance and loss of strength in the lower extremities. The coflex™ interspinous stabilization device (Paradigm Spine) is a functionally dynamic implant (compressible in extension) used to stabilize the motion segment after direct surgical decompression of moderate to severe stenosis without concomitant fusion.

Interspinous Process Devices in the Lumbar Spine

Contemporary Spine Surgery: September 2007 - Volume 8 - Issue 9 - p 8 doi: 10.1097/01.CSS.0000285190.82679.a3

92. Non-fusion DIAM Interspinous Distraction Device For Low Back Pain: 24 Months Follow-up

92. Non-fusion DIAM Interspinous Distraction Device For Low Back Pain: 24 Months Follow-up

Foreign body reaction due to polyethylene’s wear after implantation of an interspinal segment

Different interspinous implants are used as minimal invasive intervention in the management of degenerative disorders of the lumbar spine. We present a case with foreign body reaction due to polyethylene's wear after a device for intervertebral assisted motion (DIAM) implantation. We conclude that the polyethylene interspinous devices can cause biological response, therefore; the surgeons and the companies should carefully watch their patients following application of such devices.

Failure of the Wallis Interspinous Implant to Lower the Incidence of Recurrent Lumbar Disc Herniations in Patients Undergoing Primary Disc Excision

Ipsilateral recurrent disc herniation after lumbar discectomy is a significant problem in the management of lumbar disc disease and may necessitate repeat surgical intervention. A population-based study in Finland found that about 14% of all primary lumbar discectomies required additional surgical interventions. Interspinous devices, which have been shown to unload the posterior anulus, may reduce the occurrence of recurrent herniations. We report our short-term experience with the use of the Wallis device in the management of patients with lumbar disc herniation undergoing primary disc excision. Thirty-seven consecutive patients (23 males and 14 females, average age 36 y) underwent primary lumbar disc excision followed by fixation of the segment with the Wallis implant during a period of 1 year. Indications for implanting the Wallis device were a voluminous disc herniation and preservation of at least 50% of disc space height. Surgery was performed at level L4-5 in most patients. Average follow-up after surgery was 16 months (range 12 to 24). The last 14 patients were also evaluated by the preoperative and postoperative Oswestry Disability Index (ODI) questionnaire, the SF-36 survey, and by a visual analog scale (VAS) for back and leg pain. The average ODI dropped from 43 to 12.7. The average VAS for back pain dropped from 6.6 to1.4 and the average Vas for leg pain dropped from 8.2 to 1.5. Five patients (4 males and 1 female) with relapsing leg pain were diagnosed by contrast-enhanced magnetic resonance imaging as suffering from recurrent herniation (5/37, 13%). All reherniations occurred at level L4-5 level between 1 and 9 months after the index surgery. Two of the 5 patients subsequently underwent additional discectomy and fusion. The current Wallis implant is probably incapable of reducing the incidence of recurrent herniations, but it still may be useful in patients with discogenic back pain due to early degenerative disc disease.

Interspinous Process Devices in the Lumbar Spine

A growing number of interspinous process devices have been introduced to the lumbar spine implant market. Implant designs vary from static spacers to dynamized devices. Furthermore, they are composed of a range of different materials including bone allograft, titanium, polyetheretherketone, and elastomeric compounds. The common link between them is the mechanical goal of distracting the spinous processes to affect the intervertebral relationship. In contrast, the purported clinical goals are more variable, ranging from treatment of degenerative spinal stenosis, discogenic low back pain, facet syndrome, disk herniations, and instability. Though some clinical data exist for some of these devices, defining the indications for these minimally invasive procedures will be crucial. Indications should emerge from thoughtful consideration of data from randomized controlled studies.

One-Year Results of X STOP Interspinous Implant for the Treatment of Lumbar Spinal Stenosis

Prospective observational study. 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. 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. 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). 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. 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.

Long-term actuarial survivorship analysis of an interspinous stabilization system

In 1986, an interspinous dynamic stabilization system (the prototype of the current Wallis implant) was designed to stiffen unstable operated degenerate lumbar segments with a hard interspinous blocker to limit extension and a tension band around the spinous processes to secure the implant and limit flexion. Restoring physiological mechanical conditions to the treated level(s) while preserving some intervertebral mobility was intended to treat low-back pain related to degenerative instability without increasing stress forces in the adjacent segments. The procedure was easily reversible. If low back pain persisted or recurred, the device was removed and stability was achieved using fusion. The intermediate-term results were promising, but the long-term safety and efficacy of this dynamic interspinous stabilization device has not been previously documented. We retrospectively reviewed the hospital files of all the patients (n = 241) who had this dynamic stabilization system implanted between 1987 and 1995, contacting as many as possible to determine the actuarial survivorship of the system. In this manner, 142 of the 241 patients (58.9%) were contacted by telephone. The endpoints used for the survivorship analysis were 'any subsequent lumbar operation' and 'implant removal'. At 14 years follow-up, values of actuarial survivorship with 95% confidence interval were 75.9 +/- 8.3 and 81.3 +/- 6.8% for the endpoints 'any subsequent lumbar operation' and 'implant removal', respectively. There was no difference in survivorship of multiple-level implants with respect to single-level devices. Although the conclusions of the present study must be tempered by the 41% attrition rate, these findings support the long-term safety of this system, and possibly long-term protective action against adjacent-level degeneration by motion preservation. Outcomes at least equivalent to those of fusion were observed without the primary drawbacks of fusion.