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|Year : 2014 | Volume
| Issue : 4 | Page : 417-422
Endoscopic anterior decompression in cervical disc disease
Yad Ram Yadav, Vijay Parihar, Shailendra Ratre, Yatin Kher
Department of Neurosurgery, Netaji Subhash Chandra Bose Medical College, Jabalpur, Madhya Pradesh, India
|Date of Submission||26-May-2014|
|Date of Decision||25-Jun-2014|
|Date of Acceptance||10-Aug-2014|
|Date of Web Publication||19-Sep-2014|
Yad Ram Yadav
105 Nehru Nagar, Opposite Medical College, Jabalpur - 482 003, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Background: Although microscopic anterior cervical discectomy with or without fusion are common surgical procedures for treatment of cervical herniated discs, loss of disc height, pseudarthrosis, and adjacent disc degeneration are some of the problems associated with it. This study is aimed to evaluate results of endoscopic microforaminotomy in cervical disc diseases. Materials and Methods: A prospective study of 50 patients of mono segmental soft or hard disc causing myeloradiculopathy was undertaken. A visual analogue scale (VAS) for neck and arm pain and functional outcomes using the Nurick grading system were assessed. There were 28, 12, 8, and 2 patients at C5-6, C6-7, C4-5, and C3-4 levels disc diseases, respectively. Patients with two or more level disc, instabilities, disc extending more than half vertebral body height, and previous operation at the same segment were excluded. Results: Age ranged from 21 to 67 years. Average postoperative reduction in disc height, operating time, and blood loss was 1.1 mm, 110 minutes, and 30 ml, respectively. Average pre-operative VAS score for arm pain and Nurick grading was 7.6 and 2.7, which improved to 1.9 and 0.82, respectively. All patients improved; 1, 2, 3 grade improvement was seen in 10, 27, and 10 patients, respectively. There was no significant complication or any mortality. Conclusion: Although longer follow up of large number of patients is required, endoscopic microforaminotomy is a safe and an effective alternative to microscopic anterior discectomy with or without fusion.
Keywords: Cervical pain, cervical spondylosis, cervical vertebrae, discectomy, herniated disc, intervertebral disc, intervertebral disc degeneration, neckpain, prolapsed disc
|How to cite this article:|
Yadav YR, Parihar V, Ratre S, Kher Y. Endoscopic anterior decompression in cervical disc disease. Neurol India 2014;62:417-22
| » Introduction|| |
The surgical management of cervical disc has evolved considerably over the past decades, and no surgical treatment is without associated morbidity or limitations.  Anterior cervical decompression and fusionis a common surgical procedure in cervical disc herniations. Loss of disc heights, pseudarthrosis, and degeneration of adjacent segmentsare the reported disadvantage of such procedures. , Modifications to reduce these disadvantages have been described: Anterior cervical decompression without fusion, , anterior foraminotomy using various techniques, , endoscopic anterior decompression  microscopic- or endoscopic-assisted posterior keyhole foraminotomy, , and cervical disc prosthesis. 
Full-endoscopic anterior microforaminotomy for compressive myelopathy preserves motion segment. Fusion is not required in this procedure. Manipulation of the cervical nerve root is also not required to access anteriorly located offending structure. We report our initial experience of endoscopic anterior decompression in single level cervical disc diseases.
| » Materials and Methods|| |
This is a prospective study of 50 patients with monosegmental soft or hard disc causing compressive myelopathy. Detailed history and neurologic examination was performed. Severity of neck and arm pain was assessed using visual analogue scale (VAS). Functional outcomes were assessed using the Nurick grading system.  There were 28, 12, 8, and 2 patients at C5-6, C6-7, C4-5, and C3-4 levels, respectively. Myelopathy with unilateral or bilateral radiculopathy showing soft or hard mono-segmental disc herniation was included in the study. Patients with two or more level disc, instabilities, disc extending more than half vertebral body height, and previous operation at the same segment were excluded from study. Any losses of operated or adjacent disc height, and cervical Cobb angle were recorded. All patients underwent pre-operative cervical spine X-rays and magnetic resonance imaging (MRI) scans [Figure 1]. Vertebral artery injury is a real worry in this procedure. Detailed analysis of MRI images to find the exact position of vertebral artery was undertaken as the artery may be anomalous in its course and may be situated outside the foramen transversarium. Postoperative MRI scan was also performed at 3 months after surgery [Figure 2] or earlier if needed. Dynamic X-rays to detect any instability were also done. Any evidence of spontaneous vertebral body fusion was also recorded.
|Figure 1: Preoperative MRI scan showing large C 5– 6 disc in T2 sagittal (a, b), T2 axial (c), and T1 sagittal images (d)|
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|Figure 2: Postoperative MRI scan showing good decompression (arrow in A and F) in T2 mid-sagittal (a), Axial T2 (b-d), Small operative bone window at C5-6 (e), Mid-sagittal T1 images (f)|
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The same surgeon performed all operations under general anesthesia. Patients were placed in supine position on table without any traction. The neck was kept in slightly extended position. The surgeon stood on the side of the approach and video monitors were placed opposite to the surgeon. Skin incision was marked under fluoroscopic guidance. Skin incision of about 2.5-3.0 cm was given, which was about two-third medial and one-third lateral to the medial border of sternocleidomastoid. Skin incision was towards the symptomatic or more symptomatic side or on right side when there was symmetrical compression. Localization was done using C arm. Trachea and esophagus were retracted medially and carotid sheath laterally. Pre-tracheal and pre-vertebral fascia were dissected. Correct level was again confirmed. Destandau set (Karl Storz GmbH and Co. KG Tuttlingen) was placed. Medial portion of the longuscolli muscle was excised to expose the lateral part of desired level. Part of the uncinate processes below and the uncus abovewas removed with a high-speed drill using diamond burrs of 3-mm tip to achieve anterior microforaminotomy. An uncinate process is a hook-shaped process on the lateral borders of the superior surface of the third to the seventh cervical and first thoracic vertebrae. Uncovertebral joint or Luschka ' s joint is formed between uncinate process bellow and the uncus above. The uncinate process projects upward from the superior surface of the vertebral body below as a lip, and the uncus projects downward from the inferior surface of vertebral body above [Figure 3]a. A piece of thin cortical bone was left behind to protect the vertebral artery until the posterior longitudinal ligament is exposed. This lateral remnant of the uncinate process can also be fractured at the base after gentle dissection from vertebral artery. The posterior longitudinal ligament was incised and removed with 1-mmKerrison punch. Sub-ligamentous or an extruded disc herniation, if present, was removed. The central part of the disc and opposite side root was also decompressed [Figure 4]. Although the central disc and opposite side root can be decompressed using lateral foraminotomy approach by angulating scope medially, it is not required for the central disc without radiculopathy. The entry point can be medial and foraminotomy may not be required in such cases [Figure 3]b. This also decreases the risk of vertebral artery injury.
|Figure 3: (a) Uncinate process is a hook-shaped process on the lateral borders of the superior surface of lower cervical vertebra where asuncus projects downward from the inferior surface of superior vertebral body. (b) Square area on lateral surface of vertebral bodies shows route of entry for anterior cervical foraminotomy while circular area of entry can be used for central disc|
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|Figure 4: Endoscopic procedure showing dissection of soft tissues over the desired uncinate process and disc space (a), coagulation of medial part of longuscolli (b and c), Removal of lateral part of disc (d), Drilling of uncinate process (e), Exposure of part of disc and posterior longitudinal ligament (f and g), Well decompressed dural sac (h and i)|
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| » Results|| |
Age of patients ranged from 21 to 67 years (mean, 45 years). There were 39 male and 11 female patients. Preoperative mean VAS scores for arm and neck pain were 7.6 and 3.2, which at 3-month postoperative followup were 1.9 and 1.1, respectively. There were 3, 5, 7, 24, and 11 patients in preoperative grade 0, 1, 2, 3, and 4, respectively, with an average grade of 2.7. There were 22, 15, and 13 patients in postoperative grade of 0, 1, and 2, respectively, with an average of 0.82. All patients improved after surgery including the 3 patients in grade 0 with radiculopathy. Improvement of grade by 1, 2, and 3 was seen in 10, 27, and 10 patients, respectively.
Six patients showed progression of pre-existing adjacent disc degeneration. There was no spontaneous fusion in any patient at the operated level. The cervical Cobb angel before surgery ranged from 3.5 to 11.4 (mean, 6.3) that remained from 3.2 to 13.6 (mean, 6.1) after surgery. Preoperative segmental Cobb angle ranged from 0.5 to 6.7 (mean, 2.1), which also did not change significantly at 3 months post operatively (range, 0.0-6.9; mean, 2.0). Loss in disc height ranged from 0.9 to 1.3 mm (mean, 1.1 mm). Operating time and blood loss ranged from 90 to 150 minutes (mean, 110 minutes) and 20 to 100 ml (mean, 30 ml), respectively [Table 1]. Mean hospital stay was 2 days (range, 1-3 days). There was no mortality, hematoma, reoperation, or any postoperative deterioration. There was no esophageal, vertebral artery, or root injury. Transient difficulty in swallowing occurred in two patients. Followup ranged from 3 to 18 months.
|Table 1: Patients demography, results of surgery, advantages and limitations of the procedure|
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| » Discussion|| |
Anterior foraminotomy using various techniques through the uncinate process or the vertebral body part allows direct decompression of the anteriorly lying offending tissue without manipulation of root with motion-segment preserving technique. , Endoscopic anterior decompression without fusion through the disc space (transdiscal) has been found to be safe and effective.  Ruetten et al. observed comparable rate of complications and revisions in endoscopic technique and in conventional anterior discectomy and fusion group.  Microscope- or endoscope-assisted posterior keyhole foraminotomy is effective in selected patients when pathologic changes are primarily posterior with acceptable preoperative lordosis. Posterior cervical endoscopic discectomy may be a promising alternative for the physically/socially active patients with preservation of motion segment.  The cervical disc prosthesis is intended to combine decompression and reconstruction of the intervertebral space while preserving segment mobility.  Although heated debates continue about the comparison of anterior cervical discectomy (ACD), anterior cervical discectomy with fusion (ACDF), and anterior cervical discectomy and fusion with instrumentation (ACDFI), prospective randomized controlled trials have demonstrated similar clinical outcomes between the three procedures, with slightly increased segmental kyphosis and decreased disc height with ACD. Although there was loss of disc height and alteration in cervical spine alignment, neither compromised clinical outcome in the first year following anterior cervical decompression without fusion. ,
Endoscopic surgeries are being increasingly used in spine,  skull base, and cranial surgeries. Although microscopic anterior cervical discectomy is gold standard, endoscopic anterior decompression can be used as an alternative to microscopic technique that allows similar decompression with smaller bony opening, and better visualization of whole cord and roots especially contralateral root. Recent reviews have also shown that the endoscopic disc surgery can achieve same clinical results in symptomatic cervical and lumbar disc herniations as the microsurgical techniques without increasing complication rates.  Fully endoscopic microforaminotomy as an alternative to ACDF or ACD has been found to be safe and effective in our series without any mortality or significant complications. Operative time was comparable to other conventional anterior cervical disc surgery techniques. Blood loss and hospital stay was also short in our study. In our study, there was a 1.1-mm reduction in disc height without any significant change in Cobb angle. Similar results of non-significant increase in the segmental kyphosis angle and disc height reduction were observed in endoscopic group and conventional discectomy and fusion group.  This could be due to very small amount of the disc removed in the endoscopic group. Generally, conventional discectomy and fusion involves complete discectomy with curettage of the end plate, which probably promotes some sinking. Although there is no comparison regarding disc height reduction and kyphosis angle in anterior discectomy without fusion and anterior endoscopic technique in the available literature, endoscopic group should fare well because of less disc and bone removal.
Patients with significant reduction in disc height with associated foramen stenosis need grafting and fusion to increase disc height and to treat foramen stenosis. Such patients are not ideal cases for endoscopic microforaminotomy surgery. Although multilevel disc disease of more than one disc can be operated using endoscopic microforaminotomy, it takes more time. Instabilities and previous operation at the same segment are also unsuitable for this approach. Although posterior part of the end cartilage and part of the posterior vertebral body can be removed, compression extending more than middle of the vertebral body is not ideal for microforaminotomy. Although there was no vertebral artery injury in our series, it is a real worry in anterior microforaminotomy.
Rarely intra-operative bleeding may cause frequent soiling of lens tip, which can be controlled by cold saline or adrenalin saline lavage, elevation of head end, placing saline-soaked cotton patties, and gelatin sponge with or without prothrombin, etc.  Inner tube with telescope can be removed and hemostasis can be achieved with the help of microscope using the outer tube of the set. Rarely conversion to an open surgery may be required when a hemorrhage is unmanageable. Telescope should be angled medially and proper orientation of camera should be maintained throughout the procedure. Well-supported hand with pen type precision grip should be used [Figure 5]. If power grip is required to use some instrument such as Kerrison punch, a second hand support or addition of precision grip by a second hand should be used to improve precision [Figure 6].
|Figure 5: Avoid unsupported hand holding drill hand piece (a), hand should be resting on the sheath of the endoscopic set to improve precision (b)|
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|Figure 6: (a) Power grip (arrow) should be avoided because of poor precision compared to pen type of precision grip. If this power grip is required to use some instrument such as Kerrison punch, addition of pen type of precision grip (arrows) by other hand improves precision (b and c)|
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Staining of lens tip by blood, bone dust, fluid, tissue, etc., excessive moisture content in the air medium, telescope out of focus, improper connection from scope to the monitor and damaged lens can give rise to poor image quality.  Telescope tip should be kept as much away as possible from the operative site using maximum magnification to avoid lens soiling during drilling. Endoscopic tube should be kept as vertical as possible; excessive angulation of sheath allows surrounding tissue to enter in it that may obscure proper visualization.
The number of patients in this study was small and the follow up was also short. Long-term results in large number of patients including change in disc height and Cobb angle need to be evaluated. Other limitations of this operation are the limited possibility to extend the operation in the event of unforeseen difficulties, possibility of recurrences, and a difficult learning curve. Practice on model, hands-on cadaver dissection, watching live surgery, and simulators can shorten learning curve.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]