Interspinous Process Research Articles

P20. Positional MRI changes in the lumbar spine following insertion of a novel interspinous process distraction device

BACKGROUND CONTEXT: Clinical, radiologic, and cadaveric studies have demonstrated reduction in area of the dural sac and exit foramina as the lumbar spine moves from flexion into extension. Patients with spinal stenosis develop symptoms of radiculopathy and/or neurogenic claudication in erect or extended postures which are relieved by sitting or stooping. Clinical studies on the X-Stop device have shown improvement in the claudication outcomes. The device can be implanted under local anaesthetic, avoiding the high morbidity or mortality associated with spinal decompressions and/or fusions.

Avulsion of the L4 Spinous Process: An Unusual Injury in a Professional Rugby Player

A case of L4 spinous process avulsion following a hyperflexion injury treated with surgical excision. To show that single photon emission computerized tomography is essential for the diagnosis and that excision can provide a successful outcome. The avulsion resulted from a forced hyperflexion injury at the L4/5 area, where the interspinous ligament provides a high resistance to flexion. A 29-year-old international rugby football player injured his low back during a match. Plain radiography and magnetic resonance imaging did not reveal the injury. Single photon emission computerized tomography and computerized tomography showed the lesion. Initial conservative therapy failed to control the symptoms, and, therefore, late excision was performed with pain-free return to contact sports at 3 months. Few cases of interspinous process avulsions have been described, and, to our knowledge, this is the first reported case of rugby football player who had a successful outcome with late surgical excision.

A Multicenter, Prospective, Randomized Trial Evaluating the X STOP Interspinous Process Decompression System for the Treatment of Neurogenic Intermittent Claudication

A randomized, controlled, prospective multicenter trial comparing the outcomes of neurogenic intermittent claudication (NIC) patients treated with the interspinous process decompression system (X STOP) with patients treated nonoperatively. To determine the safety and efficacy of the X STOP interspinous implant. Patients suffering from NIC secondary to lumbar spinal stenosis have been limited to a choice between nonoperative therapies and decompressive surgical procedures, with or without fusion. The X STOP was developed to provide an alternative therapeutic treatment. METHODS.: 191 patients were treated, 100 in the X STOP group and 91 in the control group. The primary outcomes measure was the Zurich Claudication Questionnaire, a patient-completed, validated instrument for NIC. At every follow-up visit, X STOP patients had significantly better outcomes in each domain of the Zurich Claudication Questionnaire. At 2 years, the X STOP patients improved by 45.4% over the mean baseline Symptom Severity score compared with 7.4% in the control group; the mean improvement in the Physical Function domain was 44.3% in the X STOP group and -0.4% in the control group. In the X STOP group, 73.1% patients were satisfied with their treatment compared with 35.9% of control patients. The X STOP provides a conservative yet effective treatment for patients suffering from lumbar spinal stenosis. In the continuum of treatment options, the X STOP offers an attractive alternative to both conservative care and decompressive surgery.

Insertion loads of the X STOP interspinous process distraction system designed to treat neurogenic intermittent claudication

An interspinous process implant has been developed to treat patients suffering from neurogenic intermittent claudication secondary to lumbar spinal stenosis. As most patients who suffer from spinal stenosis are over the age of 50 and may have weaker bones, it is imperative to know how bone mineral density (BMD) correlates with lateral spinous process strength. The study was undertaken to characterize the lateral failure loads of the spinous process, correlate the failure loads to BMD, and compare the failure loads to the loads required to insert an interspinous process implant. Spinous process lateral failure loads were assessed, correlated to BMD, and compared to the loads required to insert an interspinous process implant. Mean spinous process failure loads were significantly greater than the lateral insertion load of the interspinous process implant. There was a significant relationship between the BMD and spinous process failure load. The technique used to insert the interspinous implant poses little risk to spinous process failure. There is ample margin of safety between the insertion loads and spinous process failure loads. The significant relationship between BMD and spinous process failure load suggests that patients with lower BMD must be approached with more caution during the implant insertion procedure.

The Effect of an Interspinous Process Implant on Facet Loading During Extension

Facet loading parameters of lumbar cadaver spines were measured during extension before and after placement of an interspinous process implant. The study was undertaken to quantify the influence of an interspinous implant on facet loading at the implanted and adjacent levels during extension. Facet loading is increased during extension and decreased during flexion. Previous studies have demonstrated that interspinous process decompression relieves disc pressure at the implanted level and does not alter disc pressure at the adjacent levels. Facet joints are believed to play a key role in back pain, especially in patients with collapsed discs and increased motion segment mobility resulting in increased facet loading. Seven cadaver spines (L2-L5) were loaded to 15 Nm of extension and 700 N compression with and without an interspinous process implant (X STOP) placed between the L3-L4 spinous processes. Pressure-sensitive film was placed in the facet joints of the implanted and adjacent levels. After loading, the film was digitally analyzed for peak pressure, average pressure, contact area, and force. These values were compared between the intact and implanted specimens at the adjacent and implanted levels using a paired t test (P < 0.05). The implant significantly reduced the mean peak pressure, average pressure, contact area, and force at the implanted level. The mean peak pressure, average pressure, contact area, and force at the adjacent levels were not significantly different between the intact and implanted specimens with the exception of contact area at the L2-L3 level. Interspinous process decompression will unlikely cause adjacent level facet pain or accelerated facet joint degeneration. Furthermore, pain induced from pressure originating in the facets and/or posterior anulus of the lumbar spine may be relieved by interspinous pro-cess decompression. Clinical results from patients with a component of lower back pain suggest that this is a valid conclusion.

The Treatment Mechanism of an Interspinous Process Implant for Lumbar Neurogenic Intermittent Claudication

The spinal canal and neural foramina dimensions of cadaver lumbar spines were quantified during flexion and extension using magnetic resonance imaging before and after placement of an interspinous process implant. To quantify the effect of the implant on the dimensions of the spinal canal and neural foramina during flexion and extension. Lumbar neurogenic intermittent claudication symptoms are typically exacerbated during extension and relieved during flexion. It is understood that the dimensions of the spinal canal and neural foramen increase in flexion and decrease in extension. The authors hypothesized that an interspinous process implant would significantly prevent narrowing of the canal and foramina in extension and have no significant effect in flexion. Eight L2-L5 specimens were positioned to 15 degrees of flexion and 15 degrees of extension using a positioning frame. Each specimen was magnetic resonance imaged with and without an interspinous implant (X STOP) placed between the L3-L4 spinous processes. Canal and foramina dimensions were compared between the intact and implanted specimens using a repeated measures analysis of variance with a level of significance of 0.05. In extension, the implant significantly increased the canal area by 18% (231-273 mm), the subarticular diameter by 50% (2.5-3.7 mm), the canal diameter by 10% (17.8-19.5 mm), the foraminal area by 25% (106-133 mm), and the foraminal width by 41% (3.4-4.8 mm). The results of this study show that the X STOP interspinous process implant prevents narrowing of the spinal canal and foramina in extension.

Effect of an interspinous implant on loads in the lumbar spine / Einfluss eines interspinösen Implantats auf die Belastungen der Lendenwirbelsäule

Interspinous process implants are increasingly used to treat canal stenoses. Little information exists about the effects of implant height and stiffness on the biomechanical behavior of the lumbar spine. Therefore, a three-dimensional nonlinear finite element model of the osseoligamentous lumbar spine (L1 to L5) was created with a slightly degenerated disc at L3/L4. An interspinous implant was inserted at that segment. Implants with different heights and stiffnesses were studied. The model was loaded with the upper body weight and muscle forces to simulate walking and 25 degrees extension. Implant forces are influenced strongly by the height and negligibly by the elastic modulus of the implant. Intersegmental rotation at implant level is markedly reduced, while intradiscal pressure is slightly increased. Implant size and stiffness have only a minor effect on intradiscal pressure. The maximum von Mises stress in the vertebral arch is strongly increased by the implant.

117. Interspinous process decompression (IPD) significantly improves symptom severity in neurogenic intermittent claudication patients

BACKGROUND CONTEXT: Symptoms of neurogenic intermittent claudication (NIC) secondary to lumbar spinal stenosis (LSS) which include leg pain, tingling, numbness and weakness, are exacerbated in lumbar extension and relieved in standing flexion or sitting. For patients with mild to moderate NIC who have failed to respond to non-operative treatment modalities, decompressive laminectomy is often considered. A surgical option is interspinous process decompression (IPD), by which an implant is placed between the spinous processes of the affected level(s) preventing compression of the neural structures at the affected level(s) during extension.

115. Interspinous process decompression (IPD) significantly improves physical function in neurogenic intermittent claudication patients: a prospective randomized multicenter study

115. Interspinous process decompression (IPD) significantly improves physical function in neurogenic intermittent claudication patients: a prospective randomized multicenter study

63. A prospective randomized multicenter study of lumbar neurogenic intermittent claudication patients treated conservatively with a laminectomy or with interspinous process decompression

63. A prospective randomized multicenter study of lumbar neurogenic intermittent claudication patients treated conservatively with a laminectomy or with interspinous process decompression

Interspinous devices for lumbar stenosis – a review of the literature

Interspinous process distraction devices are emerging as a treatment for lumbar spinal canal and foraminal stenosis. Lifetime risk is around 10%. The number of patients who could potentially benefit from such surgery is large and is projected to rise. A literature search was undertaken of relevant bibliographic databases, limited to four main languages. High level searching was performed using relevant web-based resources. . The literature review indicated that interspinous devices are effective, in the short term, in treating claudication related to spinal stenosis. There was however, a lack of medium and long-term outcome data, particularly with respect to durability of symptom relief and the risks of device migration or dislocation. There was also little published comparison against alternative conventional surgery. Interspinous devices are a promising new technology, the results of longer-term clinical follow-up studies are needed to define more clearly their role in the management of lumbar spinal stenosis.

The conservative surgical treatment of lumbar spinal stenosis in the elderly.

Canal stenosis is now the most common indication for lumbar spine surgery in elderly subjects. Degenerative disc disease is by far the most common cause of lumbar spinal stenosis. It is generally accepted that surgery is indicated if a well-conducted conservative management fails. A meta-analysis of the literature showed on average that 64% of surgically treated patients for lumbar spinal stenosis were reported to have good-to-excellent outcomes. In recent years, however, a growing tendency towards less invasive decompressive surgery has emerged. One such procedure, laminarthrectomy, refers to a surgical decompression involving a partial laminectomy of the vertebra above and below the stenotic level combined with a partial arthrectomy at that level. It can be performed through an approach which preserves a maximum of bony and ligamentous structures. Another principle of surgical treatment is interspinous process distraction This device is implanted between the spinous processes, thus reducing extension at the symptomatic level(s), yet allowing flexion and unrestricted axial rotation and lateral flexion. It limits the further narrowing of the canal in upright and extended position. In accordance with the current general tendency towards minimally invasive surgery, such techniques, which preserve much of the anatomy, and the biomechanical function of the lumbar spine may prove highly indicated in the surgical treatment of lumbar stenosis, especially in the elderly.

Determination of inter-spinous process distance in the lumbar spine. Evaluation of reference population to facilitate detection of severe trauma.

Fracture of a spinal segment with minimal or no compression of the vertebral body can be highly unstable. Screening for such an injury in the lumbar spine is often obstructed in a multi-injured patient, because of difficulty in obtaining adequate sagittal radiographs. The position of the spinous processes in relation to each other is the key for proper evaluation of the status of the posterior stabilising structures. The amount of separation or axial rotation of the posterior part of the vertebra that can occur before failure of the posterior structures has not been unambiguously defined. Despite this, it can be assumed that severe separation of the spinous processes indicates a more or less pronounced loss of mechanical support. An analysis of how the posterior spinous processes relate to each other on an anteroposterior (AP) radiograph could obviate this problem. A new, simple and reproducible radiographic tool is presented for screening of an eventual rupture of posterior structures of the lumbar spine. This method is based on measurements of the variation in interspinal process distance between adjacent levels in lumbar spine in a normal population. Two hundred normal AP radiographs of non-injured thoracolumbar spine were studied. The interspinal process distance was measured as the distance between the cranial ends of the adjacent projections of spinous processes on AP radiographs. The mean values and 99% confidence limits for changes in the interspinal process distances between adjacent spinal levels were determined and analysed in relation to age, gender and spinal segment level. An upper limit of a normal difference in distance between the spinous processes at two adjacent levels was determined to be 7-10 mm, depending on age and location in the lumbar spine. A difference in interspinal process distance exceeding 7 mm between two adjacent lumbar levels should alert a surgeon to severe and unstable injury.

Traumatic instability of the lumbar spine. A dynamic in vitro study of flexion-distraction injury.

This in vitro study determined the effect on the lumbar spine of a dynamic flexion-distraction loading simulating a lap seatbelt injury. The proportion by which the forces and the moments contributed to the injury of the lumbar spinal segment in such a situation was analyzed. The remaining stability of the injured lumbar motion segment was determined together with the threshold for lumbar spine instability in such an injury. Based on the experimental results in this study, radiographic guidelines for instability criteria in lumbar and thoracolumbar dislocations in the sagittal plane without concomitant compression fracture of the middle column were proposed. A number of check-lists and guidelines were suggested for the diagnosis of spinal instability after trauma, but no conclusive system was established. Those systems were mostly based on experiments performed on spinal segments after sequential ablation of ligaments and facet joints followed by static, unidirectional physiologic loading. We believed that there was a need for more profound knowledge of spinal injury and for instability criteria of lumbar spinal injuries based on more realistic experimental data simulating the clinical situation. In our injury model, we decided to study the biomechanic outcome of a flexion-distraction injury similar to seatbelt type injury seen in frontal motor vehicle collisions. Twenty lumbar functional spinal units were first loaded statically with a physiologic flexion-shear load to determine angulations and displacements under noninjurous conditions. Dynamic flexion-shear loading to injury with two different load pulses was then applied. Static physiologic load was then again applied to determine any permanent residual deformation. The viscoelastic effect of loading rate on translatory and angular displacements and the values for translatory and angulation displacements at first sign of injury (yield) and at failure were determined. Radiographic guidelines for instability criteria in lumbar and thoracolumbar fracture-dislocations without concomitant posterior vertebral body compression are proposed: 1. Instability exists if there is a kyphosis of the lumbar motion segment > or = 12 degrees (impending instability) or > or = 19 degrees (total instability) on lateral radiographs. 2. Relative increase in interspinous process distance > or = 20 mm (impending instability), > or = 33 mm (total instability) on anteroposterior radiographs.

腰椎変性疾患に対する椎間関節及びきょく突起間固定を用いた運動文節固定法

There have been reports of several complications such as neuologic injury due to inaccurate pedicular screw insertion, breakage of the screw or rods and loosening of the screws using transpedicular screw instrumentation.With a safer and easier technique to achieve a solid stabilization, as in transpeduncular fixation, we employed the combination of inter-spinous process fusion (ISPF) and translaminar facer screw fixation technique (TFSF).Features of the TFSF technique include the following (1) by having direct screw insertion to the facet, stabilization of the whole range of motion of the moter segment can be obtained. (2) is a relatively easy technique, with no major inherent risk.However disadvantages include the fact that spinous processes and lamina are not as strong as rhe pedicle, making this procedure not recommended for use in osteoporosis.To overcome this disadvantage we simultaneously employed this technique with TLSF, and treated 19 cases of unstable lumbar disc lesion in this series.The average age of patients was 53 years (range from 30 years to 72 years).The follow-up period was 6-18 months (mean 9.8 months).Ten patients had retrolisthesis with or without lumbosacral transitional vertebrael, 5 failed lumbar disc surgery, 3 cases had degenerative spondylolisthesis and 1 unstable disc with congenital kyphoscoliosis.The spinous processes in patients with osteoporosis were reinforced by two strut bones bilaterally and then a wire inserted.These patients tended to get quicker consolidation than the group who were stabilized with only the ISPF technique. At the present time there have been no screw or wire breakages and no neurological complications.

不安定性を有する腰椎変性疾患に対するキョク突起間固定を主とした運動分節固定の治療成績

We report on three different types of inter-spinous process fusion (ISPF) thechniques which were used to stabilize the lumbar disc lesions in 144 patients with symptomatic segmental instability.Fourty-four patients received on H-shaped bone graft between the upper and lower interspinous processes of the lesioned disc. Both spinous processes and grafted bone were then fixed by wire (or tetron tape).After 2 or 3 weeks of bed-immobilization, patients were permitted to stand and to walk with a body cast.Movement of the fused segment was recognized by functional X-ray in two patients. Of them, one had reconstructive surgery for pain, at which time it was shown that one of the two grafted bones had abnormal movement, but the others was almost consolidated.To obtain earlier and stronger stabilization, and to reduce the period of bed rest ceramic artificial bone and facet fusion were also carried out in several cases.The improved facet fusion technique was believed to achieve more effective stabilization with the H-graft technique.

The biomechanics of lumbar facetectomy under compression-flexion.

Alterations of posterior spinal elements including the facet joints are commonly associated with a variety of lumbar operative procedures. Under continuous physiologic compression-flexion load application L2-L3 and L4-L5 functional units were tested as intact preparations and then sequentially altered with unilateral facetectomy, bilateral facetectomy, posterior ligament transection, and partial discectomy. Using a method of continuous motion analysis, the movement of the individual spinal components (disc, facet joint, interspinous process distance) were statistically compared between the various surgical alterations. Higher physiologic loads produced significant increases in overall deflection from BF to BFL alterations indicating a preference to preserve the posterior ligaments for this surgical approach. Although insignificant changes in the force-deflection response from one surgical alteration to the next sequential alteration were noted, statistically significant increases in localized facet joint motion may suggest the potential for acceleration of segmental degenerative changes.

ImDroved Postoperative Course After Spinous Process Segmental Instrumentation of Thoracolumbar Fractures

This article compares the postoperative course of 40 patients who had Harrington instrumentation with 40 patients who had Harrington instrumentation and interspinous process segmental instrumentation of unstable thoracolumbar fractures and reviews the findings. The two groups of patients were otherwise homogeneous, and average operative time, total blood loss, and days to oral intake were similar for both groups of patients. On average, however, patients undergoing interspinous process segmental instrumentation were out of bed sooner (4.5 versus 7.7 days, P less than 0.0001), discharged sooner (32 versus 38 days, P less than 0.079), and brace-free earlier (2.1 versus 5.9 months, P less than 0.001) and had fewer fixation-related complications than did patients undergoing Harrington instrumentation alone. Comparison of average hospital costs documented a savings of $5,160 for the typical patient undergoing interspinous process segmental instrumentation.

Fusion of scoliosis by Harrington distraction rod: Interspinous process and sublaminar wiring compared in 42 cases

Forty-two consecutive patients with scoliosis who between 1981 and 1988 underwent posterior Harrington distraction rod and interspinous process or sublaminar wiring were retrospectively reviewed. No difference was found between the techniques with respect to age, sex, curve pattern, curve magnitude, levels fused, operative time, blood loss, correction, and loss of correction at the 1-year and 2-year follow-up. The interspinous process wiring was superior to the sublaminar wiring as regards ease of technique, early ambulation, few complications, and a more effective means for maintaining the correction without postoperative immobilization.

Dural Penetration by Interspinous Process Segmental Spine Instrumentation

A case of pseudo-meningocele complicating posterior spine fusion with interspinous process segmental spinal instrumentation is presented. The L rod rotated postoperatively 90 degrees and penetrated the dura. The presenting symptoms were pain accompanied by fixed lumbar and hip flexion contractures that improved dramatically after removal of the penetrating part. The unusual course as well as the treatment and recommendation for prevention are discussed.