Treatment of the Moderate Lumbar Spinal Stenosis with an Intespinous Distraction Device IMPALA®

© 2013 Haso Sefo et al.; licensee University of Sarajevo Faculty of Health Studies. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. UNIVERSITY OF SARAJEVO FACULTY OF HEALTH STUDIES ABSTRACT


INTRODUCTION
Lumbar spinal stenosis (LSS) is a condition involving the narrowing of either the spinal canal or neural foramina. Th e stenosis is caused by hypertrophy of the ligament fl avum and facet joints, osteophytes, spondylolisthesis and disc protrusion, which results in nerve compression in one or more motion segments (1). Th e most common symptom associated with LSS is neurogenic intermittent claudication (NIC) and typically concerns patients at the age of 50 or above. NIC is defi ned as pain or numbness in the buttocks, thighs and/or legs brought on by either prolonged standing or exercise in the erect posture. Th e symptom is typically relieved by various manoeuvres that fl ex the lumbar spine, such as bending forward or sitting, which increases the spinal canal signifi cantly. Th e best treatment of NIC due to lumbal stenosis remains controversial. Nonoperative therapy like epidural steroid injections, nonsteroidal anti-infl ammatory medication, analgesics, physical therapy, and spinal manipulation, is frequently performed. Decompressive surgery with or without fusion is the current 'gold standard'treatment for moderate to severe symptomatic LSS (1)(2)(3)(4). Th e fi rst interspinous device, the Wallis system (Abbott Spine), was developed in 1986 and used in patients with recurrent disc herniation. Recently, a new class of spinal devices called interspinous spacers (ISPs) has been introduced. Th e painful repercussions of lumbar stenoses can often be mitigated by a combination of decompression and widening of the intervertebral foramen. Th is permanent widening is achieved by an interspinous spacer (5,6). IMPALA® made by Signus fulfi ls this function. It is a threepart implant which is inserted between two spinous processes. Th e natural structures are left largely intact in this procedure: the supraspinous ligament is retained and the bony structures are not damaged. Th us mobility is maintained in fl exion and rotation. Pain occurring in extension is alleviated. Th e positive aspects of using IMPALA® are: tensioning the interspinous ligaments, separating the posterior elements with accompanying unloading of the facet joints, reducing facetal pain, widening the intervertebral foramen and thus decompressing the vertebral canal and relieving the load on the disc, reducing disc pain and reducing the riskof prolapse. IMPALA®is made of PEEK-OPTIMA®, a biocompatible plastic which combines several advantages. Th e elasticity module is similar to that of cortical bone. In addition, plastic ensures artefact-free MRT imaging. Appropriate markers are incorporated to enable the position of the implant to be determined by X-ray. Th e indication for IMPALA® includes radiologically confi rmed, moderate stenoses of the vertebral canal in the L1-S1 region, of varying genesis, with neurological impairment, resulting in claudication and/or radicular symptoms. Th e procedure is limited to a maximum of two levels (7).

Patients
Th e study included a total of 11 adult patients with moderate lumbar spinal stenosis, who consecutively underwent placement of interspinous distraction device at 1 or 2 levels between October 2011 and February 2013 at Department of neurosurgery, Clinical Center University of Sarajevo. Lumbar spinal stenosis in all patients was confi rmed by MRI scans. All patients had lateral and AP standing roentgenograms of the lumbar spine before sur-gery as well as after surgery (Figure 1). Clinical evaluations were performed preoperatively and 3-months after surgery using the Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) (8). In our institution, patients are admitted for 24 hours before the day of the procedure. Th e patient is out of bed few hours after surgery and discharged on second postoperative day. Usually, the patients had regular follow up at 1 and 3 months.

Operative techniques
Th e operation is typically performed under general anaesthetic. It is advantageous if the patient is completely relaxed. Th e patient is placed in the genupectoral position on a radiolucent table. After identifi cation of the segment aff ected and radiological assessment, an incision is made in the midline. Th e segment to be operated on is exposed on one side, leaving the supraspinous ligament intact. With the aid of the curettes, the interspinous ligament can then be opened and the muscles detached on the opposite side. Th is makes a unilateral approach possible. Th e distractor is then inserted as far as possible between the spinous processes. Complete muscular relaxation is necessary to attain optimal distraction at the coronal level. Th e distraction should relieve the load on the posterior elements of the vertebral column and result in foraminal decompression. Th e appropriate size of implant is determined using the distractor in the locked position and the trial instrument. Th e aim is to use the largest size of implant possible. Th ereafter, interspinous distractor was inserted tightly into the interspinous space Th e implant is fi nally secured by attaching the locking plate. A fi nal X-ray check is made on two planes.

RESULTS
A total of 11 patients (7 female and 4 male) with spinal stenosis were included in the study. Th e mean age was 52 (range 42-63). In 7 patients (L4-L5 level), in 2 patients, (L3-L4 and L4-L5 levels) and in 2 patients (L4-L5 and L5-S1 levels) were implanted (Table 1). Th e mean preoperative VAS was 7.09 and fell to 2.27 a 3-months after surgery (Figure 2).Th e mean preoperative ODI was 59.45 fell to 20.72 3-months after surgery (Figure 3). Th ere was a signifi cant improvement in the VAS and ODI scores.

DISCUSSION
Th e interspinous implantation is less invasive than laminectomy as a gold standard in classical surgical treatment of spinal stenosis. In general, materials are well tolerated. Th ere were no broken or permanently deformed implants in any of the cases. Th ere was just one case of migration of interspinous-device because of placement of smaller size of device and that patient was underwent to surgery again. Compared with literature-reported outcomes of laminectomy surgery there are signifi cant diff erences in operative time, estimated blood loss, hospital stay, complication rate and reoperation rates favouring the interspinous-device (10-15).     In our study there was signifi cant improvement of symptoms according VAS and ODI scores after interspinous-device placement. It was also conformed in a prospective and randomized multi-center study made by Zuckerman et al. (16) showed also a success rate of 59% at 1 year postsurgery with an interspinous implant. Th is result was much better than that of 12% in the control patients who were treated only conservatively.

CONCLUSIONS
Using the IMPALA® device in patients with moderate lumbar spinal stenosis is a minimal invasive and safe procedure. Clinical symptoms were improved 3 months after surgery. Th e decompression of the lumbar spine with IMPALA® bridges the cleft between usual conservative therapy and aggressive surgical treatment methods reducing symptoms with minimal surgical risks.