- Spine Center, Department of Neurosurgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, South Korea
Spine Center, Department of Neurosurgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, South Korea
DOI:10.4103/2152-7806.128915Copyright: © 2014 Hur J. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Hur J, Kim J, Shin M, Ryu K. Minimally invasive posterior cervical decompression using tubular retractor: The technical note and early clinical outcome. Surg Neurol Int 15-Mar-2014;5:34
How to cite this URL: Hur J, Kim J, Shin M, Ryu K. Minimally invasive posterior cervical decompression using tubular retractor: The technical note and early clinical outcome. Surg Neurol Int 15-Mar-2014;5:34. Available from: http://sni.wpengine.com/surgicalint_articles/minimally-invasive-posterior-cervical-decompression-using-tubular-retractor-the-technical-note-and-early-clinical-outcome/
Background:The aim of this work is to present a novel decompression technique that approaches cervical spine posteriorly, but through minimal invasive method using tubular retractor avoiding detachment of posterior musculature.
Methods:Six patients underwent minimally invasive posterior cervical decompression using the tubular retractor system and surgical microscope. Minimally invasive access to the posterior cervical spine was performed with exposure through a paramedian muscle-splitting approach. With the assistance of a specialized tubular retraction system and deep soft tissue expansion mechanism, multilevel posterior cervical decompression could be accomplished. This approach also allows safe docking of the retractor system on the lateral mass, thus avoiding the cervical spinal canal during exposure. A standard operating microscope was used with ×10 magnification and 400 mm focal length. The hospital charts, magnetic resonance imaging studies, and follow-up records of all the patients were reviewed. Outcome was assessed by neurological status and visual analog scale (VAS) for neck and arm pain.
Results:There was no significant complication related to operation. The follow-up time was 4-12 months (mean, 9 months). Muscle weakness improved in all patients; sensory deficits resolved in four patients and improved in two patients. Analysis of the mean VAS for radicular pain and VAS for neck pain showed significant improvement.
Conclusions:The preliminary experiences with good clinical outcome seem to promise that this minimally invasive technique is a valid alternative option for the treatment of cervical spondylotic myelopathy.
Keywords: Cervical spondylotic myelopathy, cervical spine, minimal invasive technique, tubular retractor
Cervical spondylotic myelopathy (CSM) is one of the most common disorders of the cervical spine characterized by development and progression of degenerative changes associated with aging process. Patients with cervical spinal stenosis have tendency to suffer chronic myelopathy and also have high risk of acute spinal cord injury following to trauma. In most cases, cervical canal stenoses result from normal degenerative processes of ventral cord compression by bulging discs and osteophytes and posterior compression from facet hypertrophy and ligamentum flavum thickening. The average diameter of normal cervical canal on plain radiograph is 17 mm, whereas symptomatic stenosis occurs when diameter is less than 13 mm.[
Various anterior and posterior approaches for the treatment of CSM and studies showing many different results comparing anterior approach and posterior approach have been reported.[
Recently, with the wide spread of minimally invasive techniques, there has been renewed interest in the posterior approach for cervical spine disorders.[
The purpose of this study is to describe the minimally invasive surgical technique accomplishing multilevel posterior cervical decompression using a tubular retractor system and to document the early clinical outcome for this minimal invasive surgery.
Six patients suffering from CSM underwent minimally invasive posterior cervical decompression using the tubular retractor and surgical microscope. The operations were performed between April 2012 and November 2012. The indication for surgery was i) presence of CSM confirmed by radiologic imaging studies, ii) presence of symptomatic myelopathy for more than 6 months, iii) compression ratio less than 0.4 indicating flattening of the cord, iv) transverse area of the cord less than 40 mm2, v) predominant dorsal cord compressing pathology such as ossification of ligament flavum, and vi) failure of conservative treatment over a period of 6 weeks. The exclusion criteria were cervical myelopathy with tumor, trauma, severe ossification of posterior longitudinal ligament (OPLL), herniated disc, rheumatoid arthritis, pyogenic spondylitis, and other combined spinal lesion. The pathologic level and extent of spinal cord compression was confirmed by magnetic resonance imaging (MRI) and postmyelography computed tomography (CT). In addition, cervical MRI was performed with three different neck positions (neutral, flexion, and extension) in all patients to determine whether the spinal canal was more dominantly compressed by posterior than anterior pathology. Cases with more dominant anterior compression (such as multilevel interverterbal disc bulging) were excluded from the study and underwent alternative anterior approach surgery. Demographic and intraoperative data of patients are listed in
The hospital charts, radiologic imaging studies, and follow-up records of all the patients were carefully reviewed. Outcome was assessed preoperatively and postoperatively by Japanese Orthopedic Association scoring system for cervical myelopathy[
All parameters were analyzed statistically. The data were expressed as mean and standard deviation (mean ± SD). A result was considered statistically significant if the P value was less than 0.05.
Before surgery, the patient must have dynamic radiographs to rule out obvious instability and MRI or postmyelography CT to define the extent of the surgery. Routine medical and laboratory evaluations are obtained. The anesthesia team must be informed prior to the surgery for the need of possible fiberoptic intubation. The operation is done under general anesthesia and interoperative somatosensory evoked potentials (SEP) monitoring was done in all patients.
Patient is settled to prone position and head fixation with Mayfield head fixator in a slightly flexed position. The Mayfield attachment to the operation bed was fully extended to prevent interference with C-arm fluoroscopic localization. Skin preparation and drapping was done with usual sterile manners. 14-16 mm minimal skin incision is made in a vertical fashion above targeted level approximately 1.5-2 cm lateral to the spinous process [
After subcutaneous dissection, fascia is incised sharply for the entire length of the skin incision. If more than one level is to be decompressed, it is helpful to extend the incision cranially and caudally to allow manipulation of the working channel. Once facial incision was done, gentle finger dissection followed to the extensor muscles of the posterior neck until lamina and facet joint were palpated. Cheek retractors may be used to allow gentle spreading of the fascia and the fibers of the paraspinal muscles overlying the lamina and facet to facilitate dilation and exposure. Serial dilators of the Insight tubes system (Synthes GmbH, Oberdorf, Switzerland) were applied under gentle controlled motion avoiding slippage into the wide interlaminar space. Then 16 mm tubular retractor is positioned safely on lateral mass and secured to the flexible arm of the Insight retractor mounted to the table side rail [
After docking tubular retractor, operating microscope is introduced [
A drain was placed at operated level to prevent epidural hematoma after surgery. Since there is no muscle deflected, ambulation encouraged in all patients after 4 h of operation without a neck support.
Six patients underwent minimally invasive posterior cervical decompression using the tubular retractor system and surgical microscope. The follow-up time was 4-12 months (mean, 9 months). Average intraoperative blood loss was 61 (±33) ml, average operating time was 1.7 (±0.3) h, and the average length of hospital stay was 1.4 (±0.5) days, respectively [
A 65-year-old female visited our clinic complaining neck pain and severe right side radicular arm pain with hand grip weakness for 12 months. She was conservatively treated at local clinic for 8 months without improvement. The cervical MRI showed right side neural foraminal stenosis from C3 to C6 levels and central spinal canal stenosis from C4 to C6 levels with myelopathy due to ossification of ligament flavumm (OLF). Cervical dynamic (flexion-extension) MRI showed aggravation of canal stenosis by posterior pathology on extension [
(a) Preoperative flexion/extension MRI shows severe canal stenosis with myelopathy from C3 to C7 levels due to OLF. Canal stenosis aggravates within neck extension. Preoperative 3D reconstructed CT shows occified ligament flavum. (b) Postoperative MRI shows enlarged spinal canal on both flexion and extension image. 3D reconstructed CT image shows hemilaminectomy on C4, C5, C6 vertebrae with bilaterally decompressed by ULBD technique
Cervical spinal decompression is usually performed from an anterior or posterior approach depending on various factors, including extent of disease, sagittal curvature of cervical spine, prior surgery, general condition of the patient, skill and familiarity of the surgeon, severity of canal compression, and intervertebral mobility at maximum compressed level. The anterior approach offers a simpler route to the spine and a means to decompress the ventral spinal cord, which is often the site of pathology. Disadvantages include potential complications involving the anterior neck structures, dysphagia, recurrent laryngeal nerve injury, and adjacent segment degeneration following loss of one or more motion segments.
On the other hand, posterior decompression technique gives more space for the thecal sac and avoids many of the hazards of the anterior exposure. However, anterior compressing pathologies such as disc herniation, osteophytes, or OPLL could be neglected. Although a simple multilevel laminectomy or laminoplasty is a relatively straightforward procedure, it often results in more postoperative neck pain and longer hospitalization. In addition, cerebrospinal fluid (CSF) leakage, wound problems, postoperative kyphosis, and instability are not uncommon.
With the recent advent of more specialized instruments and access devices, minimally invasive spinal surgery has proven to be a useful tool for the treatment of spinal disease while minimizing soft tissue damage. Application of this novel technique to the cervical spine followed naturally, and posterior minimal invasive cervical approach was performed recently in many institutes to determine the feasibility and efficacy of such procedures. Recent studies using a transmuscular working channel to perform a minimally invasive decompression for radiculopathy and myelopathy concluded that the basic technique was safe and feasible.[
Although there are a few reports of posterior cervical decompression by different minimally invasive techniques, we have introduced more challenging “ULBD” technique to minimize paraspinal muscle injury and extent of laminotomy. Moreover, the routine three-position cervical MRI for cervical spondylotic myelopathic patients was performed to evaluate characteristics of canal compression pathology and to aid surgeon's decision in selecting appropriate surgical technique. The cervical dynamic MRI is useful to determine more accurately the number of levels where the spinal cord is compromised, and to better evaluate narrowing of the canal.[
The tubular retractor provides wide visualization through the small skin incision and successive angulations of the working channel into a more medial position allow access to the contralateral dorsal spinal canal, which is superior to that of the unilateral open technique. Visualization of the spinal canal, ligamentum flavum, and existing nerve root interface is facilitated by operating microscope (Zeiss Pentero surgical microscope, Jena, Germany) to provide three-dimensional view and with the microscope-assisted procedure we could accomplish bilateral decompression via a unilateral approach, the so-called “unilateral approach and bilateral decompression (ULBD)”.[
The minimally invasive posterior cervical decompression using the tubular retractor technique had many advantages such as small skin incision, gentle tissue dissection, excellent visualization, and ability to achieve results equivalent to conventional open techniques. Open posterior cervical approach requires paraspinal muscles dissection and partial facetectomy. Stripping of the muscles may damage their innervation and blood supply, which may cause postoperative neck pain with temporary or persistent functional disturbances and possibly affecting stability in multiple level procedures.[
On the other hand, minimally invasive decompression has higher risk of dura and nerve injury, CSF leakage and postoperative seroma formation compared with conventional laminectomy or laminoplasty.[
Furthermore, spinal canal enlarging is somewhat limited compared with conventional posterior techniques in that one is not able to push down the dura to obtain a better view as in lumbar surgeries. Decompression of canal stenosis, which occurred due to posterior pathologic lesion such as OLF, has great efficacy with this technique, but in case of anterior cervical pathologic lesions or multilevel canal stenoses with more than three segments, and developmental canal stenosis, anterior approach or conventional laminoplasty may be a better alternative option. Without the benefit of a wide viewing area as in conventional open surgery, the risk of incomplete decompression also exists, especially with the inexperienced hands.
This study demonstrates the feasibility of decompressing the cervical spinal canal using a unilateral tubular technique. Minimal invasive surgery techniques involve a very steep learning curve and considerable experience is required to decompress the neural structures adequately. The operation field of tubular retractor is limited, making it difficult to appreciate the amount of bony work that has been performed. Furthermore under the microscopic view it could be more disorienting. Ensuring a satisfactory canal decompression, while maintaining the integrity of neural elements clearly, requires hard training and experience. Long-term follow-up studies with larger sample series are required to determine its benefits compared with traditional open laminectomy.
In our preliminary clinical series aided by tubular retractor system based on minimally invasive spinal surgery, we demonstrate relatively safe procedures and good outcomes despite the limited number of patients and short follow-up periods. These techniques have the theoretical advantages of reducing morbidity, blood loss, perioperative pain, and length of hospital stay associated with conventional open posterior spinal exposure. This minimally invasive posterior technique could be considerable alternative in choosing a surgical method for cervical myelopathy. However, steep learning curve is required for this minimally invasive technique and risk of possible complications such as dura and nerve injury, CSF leakage, and postoperative seroma formation do exists. More studies are required to determine the exact benefits compared with open surgery.
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