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Minimally invasive anterior contralateral approach for the treatment of cervical disc herniation
Surgical Neurology 63 (2005) 210 – 219 www.surgicalneurology-online.com
Minimally invasive anterior contralateral approach for the treatment of cervical disc herniation Yunus Aydin, MDa, R. Alper Kaya, MDa,*, S. Meltem Can, MDa, Osman Tqrkmenog˘lu, MDa, Halit Cavusoglu, MDa, Ibrahim M. Ziyal, MDb b
Abstract
a Clinic of Neurosurgery, Sisli Etfal State Hospital, Istanbul 34077, Turkey Department of Neurosurgery, Hacettepe University Faculty of Medicine, Ankara 06100 Received 15 January 2004; accepted 22 March 2004
Background: During the practice of ipsilateral approach to the offending lesion in anterior simple discectomy, the authors realized that it achieves better surgical exposure of the opposite foraminal area. In addition, it was also realized that routine procedures for better visualization of the foraminal area, such as stripping longus colli muscles, further excising of the anterior longitudinal ligament, or using a spreader, which cause more invasive surgery during the standard anterior approach, are not necessary because the contralateral approach already achieves sufficient exposure of the target foraminal area. Objective: Evaluation of the results and effectiveness of this minimal invasive technique in patients with either soft or hard disc herniations. Methods: Between January 1994 and April 2002, 216 patients underwent anterior contralateral microdiscectomy without fusion for cervical disc herniation at 1 or 2 adjacent levels. Anterior contralateral microdiscectomy is a less invasive technique than standard anterior simple discectomy in which longus colli muscles are not stripped, and the lateral part of annulus fibrosis at the side of intervention and ventrolateral part of it at the opposite side are not removed. In addition, a mini Zenker handheld retractor is used for retraction of paravertebral soft tissues and a spreader is not used during the discectomy procedure. There were 182 patients diagnosed with radiculopathy and 34 patients with myelopathy. Assessments of the neurological status of patients with radiculopathy were done by physical examinations, and of those with myelopathy according to the modified Japanese Orthopaedic Association cervical spine functional assessment scale. These neurological assessments were repeated in the 18th month after surgery. In the follow-up period, the outcomes of surgery were also assessed for all patients in 4 categories, from failure to excellent. Results: Surgery outcomes generally have been good to excellent and none of the patients were made worse by the procedure. The outcomes were significantly better in the radiculopathy and soft disc herniation groups. Other positive outcome factors were short duration and sudden onset of symptoms, normal cervical curvature, and single-level disease. Follow-up radiological studies revealed fibrous healing with normal or slight loss of disc height in 199 (92.1%) patients and total obliteration of the involved disc space representing radiological fusion signs in 13 (6%) patients. The overall complications observed in this study were 2 spontaneous and 2 postinfection collapses of disc level, 1 excessive fibrosis of disc level, and 2 adjacent-level diseases. Conclusion: Anterior contralateral microdiscectomy without fusion achieves better exposure for resection of the offending foraminal or far lateral lesions, ventral osteophytes, or a disc fragment
* Corresponding author. Gokturk Cad. No: 46/14, Samat Apt. Gokturk/Kemerburgaz, Istanbul, Turkey. Tel.: +90 212 2343338; fax: +90 212 2416012. E-mail address: [email protected] (R.A. Kaya). 0090-3019/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2004.07.001
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under direct microscopic visualization. Collapse and instability of the involved disc level can also be avoided via this less invasive technique. D 2005 Elsevier Inc. All rights reserved. Keywords:
Anterior cervical discectomy; Contralateral approach
1. Introduction The surgical approach to cervical disc disease has gone through an evolution over several decades. There is now an extensive body of literature on the surgical treatment of this clinical entity. Recently, anterior approaches with or without interbody grafting have become customary in the surgical management of diseased intervertebral discs in the cervical spine. Although most clinical results are satisfactory, some probable complications with regard to graft and graft site after a fusion procedure, collapse or instability of the level involved after simple discectomy, and adjacent-level disease after both procedures have led surgeons to seek some variations in anterior approaches [15,20,23,34,39,40,42]. More recently, some studies have reported the application of cervical disc prosthesis for maintaining the functioning motion segment of the affected level after anterior cervical discectomy [2,12]. Although its early results are encouraging, comprehensive clinical studies describing long-term results are necessary for routine surgical use of this device. During the practice of anterior cervical discectomy the senior author recognized that the standard right-side exposure allowed much better visualization of the left foramina than the right one. Since 1994, we have used the anterior contralateral approach as a standard procedure at the opposite site of brachialgia in all cases. We started this study in 1994 to determine the results of our less invasive anterior cervical discectomy technique without fusion through contralateral approach.
2. Clinical materials and methods Between January 1994 and April 2002, 216 patients with cervical paramedian disc herniation who met the criteria of this study underwent anterior contralateral microdiscectomy without fusion. All patients who had one or more of the following criteria were included in this study: (1) the existence of radicular motor weakness, (2) the existence of long tract signs, (3) the persistence of radicular pain refractory to at least 3 weeks of conservative treatment, and (4) concordance between the patient’s signs and symptoms and magnetic resonance imaging (MRI) findings. Patients with advanced cervical spondylosis and/or 3-level disc herniations and those referred to our clinic for a second operation were not included in this study. Of these 216 patients, 133 were male and 83 were female, with ages ranging from 28 to 69 years (average, 42.6). The duration of the symptoms ranged from 1 week to 2 years, less than 3 months in 102 patients (47.2%), 3 to 12
months in 53 patients (24.5%), and more than 12 months in 61 patients (28.2%). There were 182 patients diagnosed with radiculopathy and 34 patients with myelopathy. The assessments of the neurological status of patients with radiculopathy were evaluated by physical examinations and of those with myelopathy according to the Japanese Orthopaedic Association (JOA) cervical spine functional assessment scale modified by Benzel et al [3] (Table 1). Table 1 JOA cervical spine myelopathy functional assessment scale, modified by Benzel et al [3] Score
Definition
Motor dysfunction score of the upper extremities 0 Inability to move hands 1 Inability to eat with a spoon but able to move hands 2 Inability to button shirt but able to eat with a spoon 3 Able to button shirt with great difficulty 4 Able to button shirt with slight difficulty 5 No dysfunction Motor dysfunction score of the lower extremities 0 Complete loss of motor and sensory function 1 Sensory preservation without ability to move legs 2 Able to move legs but unable to work 3 Able to walk on flat floor with a walking aid (ie, cane or crutch) 4 Able to walk up and/or down stairs with handrail 5 Moderate to significant lack of stability but able to walk up and/or down stairs without handrail 6 Mild lack of stability but able to walk with smooth reciprocation unaided 7 No dysfunction Sensory dysfunction score of the upper extremities 0 Complete loss of hand sensation 1 Severe sensory loss or pain 2 Mild sensory loss 3 No sensory loss Sphincter dysfunction score 0 1 2 3
Inability to micturate voluntarily Marked difficulty with micturation Mild to moderate difficulty with micturation Normal micturation
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Fig. 1. Illustrative drawing of anterior contralateral approach for cervical microdiscectomy. LCM indicates longus colli muscle; C, curette; PD, protruded disc; and *, remaining part of annulus fibrosis.
These were repeated at the 18th month postoperatively to determine the final neurological status of the patients. Preoperative radiological investigations were made with plain roentgenograms and MRI for all patients. The affected side was the right side in 83 patients (38.4%) and the left in 133 patients (61.5%). Single-level disc herniation was present in 162 (75%) patients and double level in 54 (25%) patients. The operative findings in a total of 270 discs removed were a ruptured disc in 109 (40.3%) segments, a soft protrusion in 58 (21.4%) segments, and a hard disc protrusion in 103 (38.1%) segments. The number of operated levels were as follows: C3-4, 7 patients (3.2%); C4-5, 28 patients (12.9%); C5-6, 129 patients (59.7%); C67, 102 patients (47.2%); and C7-T1, 4 patients (1.85%). 3. Surgical technique The operation is made in a similar fashion to anterior simple discectomy that has been previously described [5,7], but the approach is performed at the contralateral side of the radiculopathy with some modifications. The head is placed in a neutral position with a towel roll under the neck, thus preserving the cervical lordosis. The entire operation is performed with an operating microscope. A 2-cm transverse skin incision is made medial to the medial border of the sternocleidomastoid muscle. After splitting the platysma muscle longitudinally, the areolar tissue between the carotid sheath and the tracheoesophageal bundle is separated by finger dissection down to the anterior surface of the vertebral bodies. Since the automatic retractors are too wide
to work with the small incision, a 15-mm-wide mini Zenker handheld retractor is used to retract the skin, trachea, and esophagus medially. The proper level is verified by a C-arm scope. As opposed to the conventional technique, the longus colli muscles are not stripped. The anterior longitudinal ligament between the longus colli muscles is incised in a rectangular shape just next to the medial border of the ipsilateral muscle with a scalpel. The disc material is removed with microcurettes and punches down to the posterior longitudinal ligament (PLL) without using a spreader, and care is taken not to remove cartilaginous end plates. However, all the lateral border of the annulus fibrosus at the side of the intervention and the ventrolateral part at the opposite side are left intact (Fig. 1). If there are accompanying posterior osteophytes to the disc herniation, these are removed with microcurettes and/or an air drill to decompress the spinal canal, taking care not to remove cartilaginous end plates. The epidural space, foramen, and nerve root are controlled for free sequester after excision of the PLL. In cases of foraminal osteophytes or far lateral extruded disc fragments, partial uncinate joint excision is performed. The contralateral approach provides an additional advantage with direct microscopic visualization of the target area during this procedure. When decompression is confirmed with direct inspection under surgical microscope, the operation is completed. The operation takes about 40 minutes in soft protrusions and extends to 60 to 90 minutes per level in hard disc cases. The patient is allowed out of bed without a cervical collar 5 hours after surgery and is discharged within 24 hours. An exercise program is started after 3 weeks to strengthen the paracervical muscles. Patients are advised to return to their daily activities after 2 weeks. 4. Follow-up All patients were followed up regularly at 4 weeks and at 3-, 6-, 12-, and 18-month intervals. The mean follow-up time was 26.9 months, ranging from 6 to 108 months. The outcomes of surgery in the long-term follow-up examinations were categorized for all patients according to the criteria used by Hadley and Sonntag [14] (Table 2).
Table 2 Outcome criteria after anterior cervical discectomy without fusion according to Hadley and Sonntag [14] Excellent Good
Improved
Failed
Patient’s preoperative symptoms and signs completely resolved Patient has complete pain relief and return of motor power and muscle bulk but with residual sensory or reflex abnormality Patient with some residual motor, sensory, or reflex abnormality and residual pain (typically neck pain) but improved compared with preoperative symptoms and signs Patient unimproved (or worse) after surgery
Y. Aydin et al. / Surgical Neurology 63 (2005) 210 –219 Table 3 Relief of symptoms and signs in 182 patients with radiculopathy Symptoms and signs
Neck/interscapular pain Severe Slight or moderate Brachialgia Radicular motor deficit Radicular sensory deficit Reflex changes Muscle atrophy
No. of patients Preoperative
Postoperative (at the 18th month)
59 123 182 146 134 167 22
– 17 – 13 21 44 10
(32.4%) (67.5%) (100%) (80.2%) (73.6%) (91.7%) (12%)
(9.3%) (7.1%) (11.5%) (24.1%) (5.4%)
Conventional radiographs including flexion/extension views at the 3rd, 6th, 12th, and 18th month were taken routinely, and MRI and/or CT scans were taken according to the decision of the attending surgeon when needed. The routine radiological investigations at these time intervals were taken in 158 of 216 patients, and the remaining 18 after 6 months and 40 after 12 months refused to have control radiological investigations. The features studied on these imaging data included (1) the presence of a reduction in height of the interspace and spontaneous osseous union at the discectomy level, (2) the presence of abnormal motion at dynamic roentgenograms, (3) the presence of straight curvature or anterior angulation of the cervical spine, and (4) the relationship between the radiological investigations and neurological status of the patient. 5. Results All of the 216 patients recovered immediately after the operation, being free from radicular pain and having a normal range of motion of the neck. Hoarseness was not observed in any of the patients, and 9 (4.1%) complained of minimal temporary dysphagia immediately after the operation. The preoperative and late postoperative symptoms and signs at 18 months after operation of 182 patients with radiculopathy are summarized in Table 3. Of the 146
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patients with radicular motor weakness, 98 improved to normal within 4 weeks after discharge. For the other 48 patients for whom the duration of neurological deficit was longer than 6 months, the weakness of the concerned muscles did not necessarily improve within that time and they needed physical therapy. Nevertheless, there was still slight motor weakness in 13 patients even 1 year after the operation. The preoperative and postoperative modified JOA scores of the patients with myelopathy are shown in Fig. 2. Neurological deterioration was not observed after the operation in this group and there was a statistically significant difference between the pre and postoperative JOA scores ( P = .0001, Student t test=12.61). Follow-up radiological studies revealed fibrous healing with a slight loss of disc height in 199 (92.1%) patients (Fig. 3) and total obliteration of the involved disc space representing radiological fusion signs in 13 (6%) patients (Fig. 4). All patients except 3 showing spontaneous radiological fusion signs at the involved disc were in the hard disc lesion group. In this study, no fusion procedure was performed in any of the patients, but only 4 patients— 2 after discitis and 2 spontaneously—developed postdiscectomy collapse and kyphosis, causing recurrent brachialgia. They underwent a second operation for Smith-Robinson– type [38] fusion and plate-screw fixation. All of these second operations resulted in entire resolution of brachialgia and osseous union at their follow-ups. A functional instability of the cervical spine was not determined in any of the patients at follow-up dynamic roentgenograms. There was normal cervical lordosis in 149 patients (68.9%) and abnormal cervical curvature (ie, straightened cervical spine or slight kyphosis) in 67 patients (31%) preoperatively. Of the 149 patients with preoperative normal cervical curvature, 8 showed a slightly straightened cervical spine at initial controls but improved to normal at later follow-up; 34 patients with preoperative abnormal cervical curvature also improved to normal at follow-up, but the remaining 29 patients maintained their preoperative condition. On the other hand, there was no patient with
Fig. 2. The preoperative and follow-up (at the 18th month) JOA scores of patients with myelopathy (n = 34). ( P b .05)
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Fig. 3. A, The preoperative T2-weighted sagittal MRI showing disc herniation at C4-C5 and C5-C6 levels in a 56 year old patient. B, The preoperative lateral cervical roentgenogram. C, The postoperative lateral cervical roentgenogram shows a slight loss of the disc height with fibrous healing after 2-level microdiscectomy (78 months after the operation).
additional kyphosis postoperatively except 4 who developed collapse of the involved level. All 4 patients who received a second operation for fusion either because of spontaneous or postinfectious collapse of the level were in the group of abnormal cervical curvature preoperatively and had a hard disc disease. The total number of patients with normal cervical curvature or improving their preoperative cervical curvature was 183 (84.7%) at final follow-up. The results
generally have been good to excellent, and none of the patients were made worse by the procedure. Aside from the 4 patients representing collapse of the level, there were also 2 patients who showed failed outcome. One, who was a drug user, was reoperated on because the preoperative symptoms were not resolved. Although his postoperative magnetic resonance images did not show significant findings corresponding with his symptoms, a significant
Fig. 4. A, The preoperative T2-weighted sagittal MRI showing an extruded disc fragment at the C5-C6 level in a 35-year-old patient. B, The axial T2weighted MRI at the herniation level. C, The postoperative lateral cervical roentgenogram shows spontaneous fusion and normal cervical curvature 36 months after operation.
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Fig. 5. Outcomes of surgery according to symptoms and type of lesion.
interspace fibrotic tissue also covering the foraminal area was detected at his second operation. In this study, 2 patients represented adjacent-level disease at the late postoperative period. One with relapse of symptoms was reoperated on, and the other asymptomatic patient underwent additional follow-up and was not operated on. Thus, all of the complications observed were as follows: 2 spontaneous and 2 postinfection collapses of the level, 1 excessive fibrosis of the level, and 2 adjacentlevel disease (1 of them symptomatic). The clinical longterm results according to symptoms and types of lesions are shown in Fig. 5. The results were better in the radiculopathy and soft disc groups than those in the myelopathy and hard disc groups ( P = .0001, v 2 = 36.21, and P = .0001, v 2=26.84, respectively). The correlations between the long-term outcome and age, sex, duration, and onset of symptoms were also studied (Table 4). The number of patients with good or excellent outcome was higher in the group of patients younger than 50 and it was statistically significant ( P = .0001, v 2=22.61). There was
also a statistically significantly better outcome in patients with short duration and sudden onset of symptoms ( P = .0001, v 2=105.9 and P = .0001, v 2=41.97). On the other hand, the statistical analysis of the effect of the postoperative cervical curvature and the number of segments operated on (double or single) revealed that there was a significantly better results in patients with normal cervical curvature and single-level disease (Table 5). 6. Discussion There are several effective surgical options for the treatment of patients with symptomatic disc herniation of a cervical spine segment [1,5,7,15,17,20,23,38,39]. The posterior approach provided considerable success and was described in the treatment of cervical disc herniation by many early surgeons [1,17,22,28,44]. While generally satisfactory results were achieved in the management of lateral perforated discs, the results were often disastrous because of the need to retract the spinal cord to remove
Table 4 Correlation between the outcome and age, sex, and duration and onset of symptoms Groups
Age Sex Duration of symptoms Onset of symptoms
Excellent
N50 b50 Female Male b 3 mo N 3 mo Sudden Gradual
Good
Improved
Failed
Total
P
n
%
n
%
n
%
n
%
n
%
14 70 28 56 75 9 72 12
23.0 45.2 33.7 42.1 73.5 7.9 53.7 14.6
33 63 45 51 27 69 52 44
54.1 40.6 54.2 38.3 26.5 60.5 38.8 53.7
8 22 9 24 – 30 7 23
13.1 14.2 10.8 15.8 – 26.3 5.2 28.0
6 – 1 5 – 6 3 3
9.8 – 1.2 3.8 – 5.3 2.2 3.7
61 155 83 133 102 114 134 82
100 100 100 100 100 100 100 100
.0001 .116 .0001 .0001
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Table 5 Outcome according to follow-up cervical curvature and number of involved levels Excellent Normal curvature Abnormal curvature Single level Double level
Good
Improved
Failed
Total
P
n
%
n
%
n
%
n
%
n
%
84 – 70 14
46.9 – 43.2 29.8
84 12 78 18
46.9 36.4 48.1 38.3
11 15 12 11
6.1 45.5 7.4 23.4
– 6 2 4
– 18.2 1.2 8.5
179 33 162 47
100 100 100 100
midline disc herniations. However, the anterior surgical approach allows a thorough decompression of the ventral aspect of the cervical spinal cord and cervical nerve roots. Besides, the PLL can be opened via this approach to remove sequestered disc fragments or osteophytes that cause ventral or ventrolateral cord/root encroachment. Although the anterior approach has become customary as a preferred surgical choice for cervical disc disease because of its efficiency and simplicity, it has brought about a new controversy concerning the anterior discectomy with or without fusion [35,37,45]. The advocates of the anterior approach with interbody fusion propose that bone grafts are necessary to maintain biomechanical stability, to facilitate fusion, to promote the resorption of osteophytes, and to widen the neural foramina. However, the rate of graft and graft-site complications, reaching 18% in larger series [6,25,36], prompted several surgeons to perform discectomy without fusion. In particular, after the introduction of the operating microscope into anterior cervical procedures, many surgeons using the simple discectomy technique reported favorable results that were comparable to those obtained by the fusion technique [16,21,25,30,33]. It is asserted that anterior simple discectomy subsequently leads to bone fusion; thus, a bone graft is not necessary after such a procedure [19,29,31,35,41,46]. However, such a result can only be expected if all disc material and both end plates are thoroughly removed, which may result in the subsequent deterioration of preoperative cervical curvature leading to neck pain and/or stretch-mediated recurrent radiculopathy due to collapse of disc level. On the other hand, fusion formation at discectomy levels either spontaneously or via a graft results in the loss of a motion segment, leading to increased strain-induced mechanical stress on the adjacent segments. According to an experimental biomechanical in vitro study by Pospiech et al [32], the increased intradisc pressure may be one mediator for the acceleration of the degenerative changes. In 1997, Hilibrand et al [18] postulated that up to 25% of the patients who undergo cervical fusion might require treatment of adjacent-level disease within 10 years. DePalma et al [9], reported a series of 229 patients who underwent anterior cervical interbody fusion, describing a rate of 81% of adjacent-level disease. During the surgical technique used in this study both lateral borders of annulus fibrosis and end plates are preserved to maintain the height of disc level to avoid subsequent development of morbidities such as collapse of disc level and/or adjacent-level disease. According to the
.0001 .001
results of this study, the rate of the radiologically confirmed spontaneous fusion formation is 6% and postdiscectomy collapse is 1.8% (2 of them due to infection). The published incidence of complete bone fusion ranges from 28% to 100% [19,21,24,29,31,41,46] and collapse of the involved disc space from 1.5% to 43% [14,24] after anterior cervical discectomy without fusion. Comparing the results of our technique with those of the classical technique without bone graft application, the rate of the postdiscectomy collapse and spontaneous fusion formation is very low. Moreover, there was no patient having additional kyphosis postoperatively except 4 patients who developed collapse of the involved level. We observed adjacent-level disease in 2 patients, a figure that is also low in comparison to the published figures. During the classical ipsilateral anterior approach, usually an excessive dissection of anterior longitudinal ligament, more removal of both end plates and sometimes bone structures, and distraction of level with a spreader are necessary for the decompression of foraminal lesions. All of these procedures are factors creating subsequent problems such as collapse of the level or instability as mentioned earlier. To accomplish decompression of more limited anterior foraminal compressive lesions, anterolateral and transuncodiscal approaches have been introduced by Verbiest [42], Hakuba [15], and Lesoin et al [23]. In 1989, Snyder and Bernhardt [39] reported anterior fractional interspace decompression by performing lateral one-third discectomy and leaving the remainder of the disc untouched. More recently, a surgical technique to the same area was introduced: removing the buncovertebral jointQ— the uncinate process, the lateral portion of the cephalad end plate and lateral portion of the intervertebral disc—by Jho [20] and later by Tascioglu et al [40], and modification of this technique by Saringer et al [34]. All these modifications of the anterior approach to the cervical disc disease propose to achieve more foraminal exposure and to preserve the mobility of the involved cervical segment. Nevertheless, these approaches are useless in cases of ventral compression and may cause recurrent disc herniations. However, the contralateral anterior approach used in this study, while achieving more exposure to the foraminal area, also allows decompression of ventral compressions less invasively and at the same time prevents settling of the involved disc. Because our surgical approach attacks and eradicates the causative lesion where it grows, we did not encounter a recurrent disc prolapse in any of our patients.
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Contrary to some authors [8,29,43], we think it is essential to remove all of the posterior and lateral osteophytes. With contralateral anterior microsurgical technique, it is possible to eradicate them without causing settling of the level and injury to the neural structures. As mentioned in most of the relevant literature [13,19, 27,37,45,46], we insist on the routine resection of the PLL and direct visualization of the dura and the foramen to avoid postoperative deterioration due to missed free fragments, and probable swelling or calcification of the PLL in the postoperative long term as pointed out previously [4,5]. In agreement with the literature [5,11], in our series, patients with radiculopathy achieved a significantly better outcome than patients with myelopathy. Seventy-eight percent of patients with radiculopathy had ruptured disc or soft protrusion and 85.2% percent of patients with myelopathy had hard disc protrusion. In addition, patients with ruptured disc or soft protrusion had a significantly better outcome than the ones with hard disc protrusion. In concurrence with O’Laoire and Thomas [30] and Bertalanffy and Eggert [5], our results also support that compression due to prolapsed intervertebral disc carries better prognosis than compression due to a chronic degenerative disc disease. The results of the present study showed that patients with a sudden onset and a short duration of symptoms (less than 3 months) had a statistically significantly better outcome than those with a gradual onset and duration of symptoms (more than 3 months). Thus, we fully agree with the previous reports emphasizing an early operation to achieve a better outcome [5,10]. Vocal cord paresis has been reported in most references as transient, varying from 1.1% (4) up to 16% [26] that may occasionally be permanent (1%-2%) [8]. However, we did not observe such a complication in our series, and it seems to be the result of our minimally invasive microsurgical technique dealing with the intermittent application of a mini Zenker handheld retractor instead of an automatic large retractor.
7. Conclusions Anterior contralateral microdiscectomy accomplishes direct visualization and resection of the offending foraminal lesions, ventral osteophytes, or a disc fragment, and prevents settling of the involved disc. Because the surgical procedure does not necessitate a fusion procedure, fusionrelated complications with regard to graft and graft site are avoided. In addition, preserving the end plates and both lateral parts of annulus fibrosis during this surgical procedure prevent early spontaneous fusion, thus minimizing the adjacent-level disease. This minimally invasive technique achieves better postoperative comfort with a quite low complication rate and allows patients to resume full activity immediately after surgery.
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[23] Lesoin F, Biondi A, Jomin M. Foraminal cervical herniated disc treated by anterior discoforaminotomy. Neurosurgery 1987;21:334 - 8. [24] Lieu AS, Howng SL. Clinical results of anterior cervical discectomy without interbody fusion. Kaohsiung J Med Sci 1998;14(4):212 - 6. [25] Lunsford LD, Bissonette DJ, Janetta PJ, Sheptak PE, Zorub DS. Anterior surgery for cervical disc disease: Part 1. Treatment of lateral cervical disc herniation in 253 cases. J Neurosurg 1980;53:1 - 11. [26] Lunsford LD, Bissonette DJ, Zorub DS. Anterior surgery for cervical disc disease: Part 2. Treatment of cervical spondylotic myelopathy in 32 cases. J Neurosurg 1980;53:12 - 9. [27] Maurice-Williams RS, Elsmore A. Extended anterior cervical discectomy without fusion: a long-term follow-up study. Br J Neurosurg 1999;13:474 - 9. [28] Mosdal C, Overgaard J. Lateral cervical fasetectomy. The surgical pathology of radicular brachialgia. Acta Neurochir (Wien) 1984;70:199 - 205. [29] Murphy MG, Gado M. Anterior cervical discectomy without interbody bone graft. J Neurosurg 1972;37:71 - 4. [30] O’Laoire SA, Thomas DGT. Spinal cord compression due to prolapse of cervical intervertebral disc (herniation of nucleus pulposus). Treatment in 26 cases by discectomy without bone graft. J Neurosurg 1983;59:847 - 53. [31] Pointillart V, Cernier A, Vital JM, Senegas J. Anterior discectomy without interbody fusion for cervical disc herniation. Eur Spine J 1995;4(1):45 - 51. [32] Pospiech J, Stolke D, Wilke HJ, Claes LE. Intradiscal pressure recordings in the cervical spine. Neurosurgery 1999;44:379 - 85. [33] Rosenorn J, Hansen EB, Rosenorn MA. Anterior cervical discectomy with and without fusion. A prospective study. J Neurosurg 1983;59:252 - 5. [34] Saringer W, Nfbauer I, Reddy M, Tschabitscher M, Horaczek A. Microsurgical anterior cervical foraminotomy (uncoforaminotomy) for unilateral radiculopathy: clinical results of a new technique. Acta Neurochir 2002;144:685 - 94. [35] Savoluinen S, Rinne J, Hernesniemi J. A prospective randomized study of anterior single-level cervical disc operations with long-term follow-up: surgical fusion is unnecessary. Neurosurgery 1998;43(1): 51 - 5. [36] Savoluinen S, Usenius JP, Hernesniemi J. Iliac crest versus artificial bone grafts in 250 cervical fusions. Acta Neurochir 1994; 129:54 - 7. [37] Sonntag VKH, Klara P. Controversy in spine care. Is fusion necessary after anterior cervical discectomy? Spine 1996;21:1111 - 3. [38] Smith GW, Robinson RA. The treatment of certain cervical spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg Am 1958;42:607 - 23. [39] Snyder GM, Bernhardt AM. Anterior cervical fractional interspace decompression for treatment of cervical radiculopathy. A review of the first 66 cases. Clin Orthop 1989;246:92 - 9. [40] Tascioglu AO, Attar A, Tascioglu B. Microsurgical anterior cervical foraminotomy (uncinatectomy) for cervical disc herniation. J Neurosurg Spine 2001;94:121 - 5. [41] Tew JM, Mayfield FH. Surgery of the anterior cervical spine: prevention of complications. In: Dunsker SB, editor. Cervical spondylosis. New York7 Raven Press; 1981. p. 191 - 208. [42] Verbiest H. A lateral approach to cervical spine: technique and indications. J Neurosurg 1968;28:191 - 203. [43] Watters WC, Levinthal R. Anterior cervical discectomy with and without fusion. Results, complications, and long-term follow-up. Spine 1994;19:2343 - 7. [44] Williams RW. Microcervical foraminotomy. A surgical alternative to intractable radicular pain. Spine 1983;8:708 - 16. [45] Wirth FP, Dowd GC, Sanders HF, Wirth C. A prospective analysis of three operative techniques. Surg Neurol 2000;53:340 - 8. [46] Yamamato I, Ikeda A, Shibuya N, Tsugane R, Sato O. Clinical longterm results of anterior discectomy without interbody fusion for cervical disc disease. Spine 1991;16(3):272 - 9.
Commentary Professor Aydin et al have presented another minimally invasive anterior approach to the cervical spine for treatment of cervical radiculitis and cervical myelopathy. The paper demonstrates that adequate decompression of the appropriate nerve root exit zone will relieve neck and arm pain complaints related to nerve root impingement syndrome. The paper seems to confirm the literature premise that post-surgical non-rigid, non-fused cervical spine does not lead to progressive adjacent segmental deterioration but still provides for adequate decompression of the nerve root for pain relief and for improvement in neurological function. The paper, however, suggests that this procedure provides for less than adequate decompression for spinal cord myelopathic disease. Perhaps the minimal anterior decompression with the persistent posterior telescoping soft tissues on motion continue to traumatize the spinal cord. A larger decompression and fusion is probably needed to treat this entity of myelopathy better. My preference still remains the posterior cervical laminoforaminotomy to treat neck and arm pain complaints secondary to nerve root impingement syndrome. The trading of relief of neck and arm pain for the not infrequent side effects of hoarseness, swallowing dysfunction, droopy eye, problems breathing, etc., much less pseudofusion, progressive adjacent joint disease, seems to be a less desirable choice than just non-improvement of the post-operative symptoms of neck and arm pain. Another point the paper makes is that early neural decompression does better than late. In this paper, about half the patients are operated on under the 3-month time period of onset of symptoms, and those patients did significantly better than patients who had longer sustained disease. This is in contrast to the changing of attitudes here in America where long, conservative, non-operative care is often extended beyond 6 months in the face of overt disease and is associated with neurologic deficits. They then have a poorer result than if they were done early in the course of their disease history. These findings will correlate well with the lumbar disk natural history that has been demonstrated by the European studies. Henry M. Shuey Jr., MD Baltimore, Maryland 21229, USA Aydin et al present a series of 216 patients operated upon for cervical disk herniation by a more minimally invasive anterior approach. The technique involves a small incision, hand retraction of the trachea and esophagus and a channel through the disc from the side contralateral to the lesion. The disc space is not spread, and the cartilaginous plates are left undisturbed. The patients were followed up for 18 months. The results are roughly equivalent to that seen with other techniques except that a 1% infection rate
Minimally invasive anterior contralateral approach for the treatment of cervical disc herniation Yunus Aydin, MDa, R. Alper Kaya, MDa,*, S. Meltem Can, MDa, Osman Tqrkmenog˘lu, MDa, Halit Cavusoglu, MDa, Ibrahim M. Ziyal, MDb b
Abstract
a Clinic of Neurosurgery, Sisli Etfal State Hospital, Istanbul 34077, Turkey Department of Neurosurgery, Hacettepe University Faculty of Medicine, Ankara 06100 Received 15 January 2004; accepted 22 March 2004
Background: During the practice of ipsilateral approach to the offending lesion in anterior simple discectomy, the authors realized that it achieves better surgical exposure of the opposite foraminal area. In addition, it was also realized that routine procedures for better visualization of the foraminal area, such as stripping longus colli muscles, further excising of the anterior longitudinal ligament, or using a spreader, which cause more invasive surgery during the standard anterior approach, are not necessary because the contralateral approach already achieves sufficient exposure of the target foraminal area. Objective: Evaluation of the results and effectiveness of this minimal invasive technique in patients with either soft or hard disc herniations. Methods: Between January 1994 and April 2002, 216 patients underwent anterior contralateral microdiscectomy without fusion for cervical disc herniation at 1 or 2 adjacent levels. Anterior contralateral microdiscectomy is a less invasive technique than standard anterior simple discectomy in which longus colli muscles are not stripped, and the lateral part of annulus fibrosis at the side of intervention and ventrolateral part of it at the opposite side are not removed. In addition, a mini Zenker handheld retractor is used for retraction of paravertebral soft tissues and a spreader is not used during the discectomy procedure. There were 182 patients diagnosed with radiculopathy and 34 patients with myelopathy. Assessments of the neurological status of patients with radiculopathy were done by physical examinations, and of those with myelopathy according to the modified Japanese Orthopaedic Association cervical spine functional assessment scale. These neurological assessments were repeated in the 18th month after surgery. In the follow-up period, the outcomes of surgery were also assessed for all patients in 4 categories, from failure to excellent. Results: Surgery outcomes generally have been good to excellent and none of the patients were made worse by the procedure. The outcomes were significantly better in the radiculopathy and soft disc herniation groups. Other positive outcome factors were short duration and sudden onset of symptoms, normal cervical curvature, and single-level disease. Follow-up radiological studies revealed fibrous healing with normal or slight loss of disc height in 199 (92.1%) patients and total obliteration of the involved disc space representing radiological fusion signs in 13 (6%) patients. The overall complications observed in this study were 2 spontaneous and 2 postinfection collapses of disc level, 1 excessive fibrosis of disc level, and 2 adjacent-level diseases. Conclusion: Anterior contralateral microdiscectomy without fusion achieves better exposure for resection of the offending foraminal or far lateral lesions, ventral osteophytes, or a disc fragment
* Corresponding author. Gokturk Cad. No: 46/14, Samat Apt. Gokturk/Kemerburgaz, Istanbul, Turkey. Tel.: +90 212 2343338; fax: +90 212 2416012. E-mail address: [email protected] (R.A. Kaya). 0090-3019/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2004.07.001
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under direct microscopic visualization. Collapse and instability of the involved disc level can also be avoided via this less invasive technique. D 2005 Elsevier Inc. All rights reserved. Keywords:
Anterior cervical discectomy; Contralateral approach
1. Introduction The surgical approach to cervical disc disease has gone through an evolution over several decades. There is now an extensive body of literature on the surgical treatment of this clinical entity. Recently, anterior approaches with or without interbody grafting have become customary in the surgical management of diseased intervertebral discs in the cervical spine. Although most clinical results are satisfactory, some probable complications with regard to graft and graft site after a fusion procedure, collapse or instability of the level involved after simple discectomy, and adjacent-level disease after both procedures have led surgeons to seek some variations in anterior approaches [15,20,23,34,39,40,42]. More recently, some studies have reported the application of cervical disc prosthesis for maintaining the functioning motion segment of the affected level after anterior cervical discectomy [2,12]. Although its early results are encouraging, comprehensive clinical studies describing long-term results are necessary for routine surgical use of this device. During the practice of anterior cervical discectomy the senior author recognized that the standard right-side exposure allowed much better visualization of the left foramina than the right one. Since 1994, we have used the anterior contralateral approach as a standard procedure at the opposite site of brachialgia in all cases. We started this study in 1994 to determine the results of our less invasive anterior cervical discectomy technique without fusion through contralateral approach.
2. Clinical materials and methods Between January 1994 and April 2002, 216 patients with cervical paramedian disc herniation who met the criteria of this study underwent anterior contralateral microdiscectomy without fusion. All patients who had one or more of the following criteria were included in this study: (1) the existence of radicular motor weakness, (2) the existence of long tract signs, (3) the persistence of radicular pain refractory to at least 3 weeks of conservative treatment, and (4) concordance between the patient’s signs and symptoms and magnetic resonance imaging (MRI) findings. Patients with advanced cervical spondylosis and/or 3-level disc herniations and those referred to our clinic for a second operation were not included in this study. Of these 216 patients, 133 were male and 83 were female, with ages ranging from 28 to 69 years (average, 42.6). The duration of the symptoms ranged from 1 week to 2 years, less than 3 months in 102 patients (47.2%), 3 to 12
months in 53 patients (24.5%), and more than 12 months in 61 patients (28.2%). There were 182 patients diagnosed with radiculopathy and 34 patients with myelopathy. The assessments of the neurological status of patients with radiculopathy were evaluated by physical examinations and of those with myelopathy according to the Japanese Orthopaedic Association (JOA) cervical spine functional assessment scale modified by Benzel et al [3] (Table 1). Table 1 JOA cervical spine myelopathy functional assessment scale, modified by Benzel et al [3] Score
Definition
Motor dysfunction score of the upper extremities 0 Inability to move hands 1 Inability to eat with a spoon but able to move hands 2 Inability to button shirt but able to eat with a spoon 3 Able to button shirt with great difficulty 4 Able to button shirt with slight difficulty 5 No dysfunction Motor dysfunction score of the lower extremities 0 Complete loss of motor and sensory function 1 Sensory preservation without ability to move legs 2 Able to move legs but unable to work 3 Able to walk on flat floor with a walking aid (ie, cane or crutch) 4 Able to walk up and/or down stairs with handrail 5 Moderate to significant lack of stability but able to walk up and/or down stairs without handrail 6 Mild lack of stability but able to walk with smooth reciprocation unaided 7 No dysfunction Sensory dysfunction score of the upper extremities 0 Complete loss of hand sensation 1 Severe sensory loss or pain 2 Mild sensory loss 3 No sensory loss Sphincter dysfunction score 0 1 2 3
Inability to micturate voluntarily Marked difficulty with micturation Mild to moderate difficulty with micturation Normal micturation
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Fig. 1. Illustrative drawing of anterior contralateral approach for cervical microdiscectomy. LCM indicates longus colli muscle; C, curette; PD, protruded disc; and *, remaining part of annulus fibrosis.
These were repeated at the 18th month postoperatively to determine the final neurological status of the patients. Preoperative radiological investigations were made with plain roentgenograms and MRI for all patients. The affected side was the right side in 83 patients (38.4%) and the left in 133 patients (61.5%). Single-level disc herniation was present in 162 (75%) patients and double level in 54 (25%) patients. The operative findings in a total of 270 discs removed were a ruptured disc in 109 (40.3%) segments, a soft protrusion in 58 (21.4%) segments, and a hard disc protrusion in 103 (38.1%) segments. The number of operated levels were as follows: C3-4, 7 patients (3.2%); C4-5, 28 patients (12.9%); C5-6, 129 patients (59.7%); C67, 102 patients (47.2%); and C7-T1, 4 patients (1.85%). 3. Surgical technique The operation is made in a similar fashion to anterior simple discectomy that has been previously described [5,7], but the approach is performed at the contralateral side of the radiculopathy with some modifications. The head is placed in a neutral position with a towel roll under the neck, thus preserving the cervical lordosis. The entire operation is performed with an operating microscope. A 2-cm transverse skin incision is made medial to the medial border of the sternocleidomastoid muscle. After splitting the platysma muscle longitudinally, the areolar tissue between the carotid sheath and the tracheoesophageal bundle is separated by finger dissection down to the anterior surface of the vertebral bodies. Since the automatic retractors are too wide
to work with the small incision, a 15-mm-wide mini Zenker handheld retractor is used to retract the skin, trachea, and esophagus medially. The proper level is verified by a C-arm scope. As opposed to the conventional technique, the longus colli muscles are not stripped. The anterior longitudinal ligament between the longus colli muscles is incised in a rectangular shape just next to the medial border of the ipsilateral muscle with a scalpel. The disc material is removed with microcurettes and punches down to the posterior longitudinal ligament (PLL) without using a spreader, and care is taken not to remove cartilaginous end plates. However, all the lateral border of the annulus fibrosus at the side of the intervention and the ventrolateral part at the opposite side are left intact (Fig. 1). If there are accompanying posterior osteophytes to the disc herniation, these are removed with microcurettes and/or an air drill to decompress the spinal canal, taking care not to remove cartilaginous end plates. The epidural space, foramen, and nerve root are controlled for free sequester after excision of the PLL. In cases of foraminal osteophytes or far lateral extruded disc fragments, partial uncinate joint excision is performed. The contralateral approach provides an additional advantage with direct microscopic visualization of the target area during this procedure. When decompression is confirmed with direct inspection under surgical microscope, the operation is completed. The operation takes about 40 minutes in soft protrusions and extends to 60 to 90 minutes per level in hard disc cases. The patient is allowed out of bed without a cervical collar 5 hours after surgery and is discharged within 24 hours. An exercise program is started after 3 weeks to strengthen the paracervical muscles. Patients are advised to return to their daily activities after 2 weeks. 4. Follow-up All patients were followed up regularly at 4 weeks and at 3-, 6-, 12-, and 18-month intervals. The mean follow-up time was 26.9 months, ranging from 6 to 108 months. The outcomes of surgery in the long-term follow-up examinations were categorized for all patients according to the criteria used by Hadley and Sonntag [14] (Table 2).
Table 2 Outcome criteria after anterior cervical discectomy without fusion according to Hadley and Sonntag [14] Excellent Good
Improved
Failed
Patient’s preoperative symptoms and signs completely resolved Patient has complete pain relief and return of motor power and muscle bulk but with residual sensory or reflex abnormality Patient with some residual motor, sensory, or reflex abnormality and residual pain (typically neck pain) but improved compared with preoperative symptoms and signs Patient unimproved (or worse) after surgery
Y. Aydin et al. / Surgical Neurology 63 (2005) 210 –219 Table 3 Relief of symptoms and signs in 182 patients with radiculopathy Symptoms and signs
Neck/interscapular pain Severe Slight or moderate Brachialgia Radicular motor deficit Radicular sensory deficit Reflex changes Muscle atrophy
No. of patients Preoperative
Postoperative (at the 18th month)
59 123 182 146 134 167 22
– 17 – 13 21 44 10
(32.4%) (67.5%) (100%) (80.2%) (73.6%) (91.7%) (12%)
(9.3%) (7.1%) (11.5%) (24.1%) (5.4%)
Conventional radiographs including flexion/extension views at the 3rd, 6th, 12th, and 18th month were taken routinely, and MRI and/or CT scans were taken according to the decision of the attending surgeon when needed. The routine radiological investigations at these time intervals were taken in 158 of 216 patients, and the remaining 18 after 6 months and 40 after 12 months refused to have control radiological investigations. The features studied on these imaging data included (1) the presence of a reduction in height of the interspace and spontaneous osseous union at the discectomy level, (2) the presence of abnormal motion at dynamic roentgenograms, (3) the presence of straight curvature or anterior angulation of the cervical spine, and (4) the relationship between the radiological investigations and neurological status of the patient. 5. Results All of the 216 patients recovered immediately after the operation, being free from radicular pain and having a normal range of motion of the neck. Hoarseness was not observed in any of the patients, and 9 (4.1%) complained of minimal temporary dysphagia immediately after the operation. The preoperative and late postoperative symptoms and signs at 18 months after operation of 182 patients with radiculopathy are summarized in Table 3. Of the 146
213
patients with radicular motor weakness, 98 improved to normal within 4 weeks after discharge. For the other 48 patients for whom the duration of neurological deficit was longer than 6 months, the weakness of the concerned muscles did not necessarily improve within that time and they needed physical therapy. Nevertheless, there was still slight motor weakness in 13 patients even 1 year after the operation. The preoperative and postoperative modified JOA scores of the patients with myelopathy are shown in Fig. 2. Neurological deterioration was not observed after the operation in this group and there was a statistically significant difference between the pre and postoperative JOA scores ( P = .0001, Student t test=12.61). Follow-up radiological studies revealed fibrous healing with a slight loss of disc height in 199 (92.1%) patients (Fig. 3) and total obliteration of the involved disc space representing radiological fusion signs in 13 (6%) patients (Fig. 4). All patients except 3 showing spontaneous radiological fusion signs at the involved disc were in the hard disc lesion group. In this study, no fusion procedure was performed in any of the patients, but only 4 patients— 2 after discitis and 2 spontaneously—developed postdiscectomy collapse and kyphosis, causing recurrent brachialgia. They underwent a second operation for Smith-Robinson– type [38] fusion and plate-screw fixation. All of these second operations resulted in entire resolution of brachialgia and osseous union at their follow-ups. A functional instability of the cervical spine was not determined in any of the patients at follow-up dynamic roentgenograms. There was normal cervical lordosis in 149 patients (68.9%) and abnormal cervical curvature (ie, straightened cervical spine or slight kyphosis) in 67 patients (31%) preoperatively. Of the 149 patients with preoperative normal cervical curvature, 8 showed a slightly straightened cervical spine at initial controls but improved to normal at later follow-up; 34 patients with preoperative abnormal cervical curvature also improved to normal at follow-up, but the remaining 29 patients maintained their preoperative condition. On the other hand, there was no patient with
Fig. 2. The preoperative and follow-up (at the 18th month) JOA scores of patients with myelopathy (n = 34). ( P b .05)
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Fig. 3. A, The preoperative T2-weighted sagittal MRI showing disc herniation at C4-C5 and C5-C6 levels in a 56 year old patient. B, The preoperative lateral cervical roentgenogram. C, The postoperative lateral cervical roentgenogram shows a slight loss of the disc height with fibrous healing after 2-level microdiscectomy (78 months after the operation).
additional kyphosis postoperatively except 4 who developed collapse of the involved level. All 4 patients who received a second operation for fusion either because of spontaneous or postinfectious collapse of the level were in the group of abnormal cervical curvature preoperatively and had a hard disc disease. The total number of patients with normal cervical curvature or improving their preoperative cervical curvature was 183 (84.7%) at final follow-up. The results
generally have been good to excellent, and none of the patients were made worse by the procedure. Aside from the 4 patients representing collapse of the level, there were also 2 patients who showed failed outcome. One, who was a drug user, was reoperated on because the preoperative symptoms were not resolved. Although his postoperative magnetic resonance images did not show significant findings corresponding with his symptoms, a significant
Fig. 4. A, The preoperative T2-weighted sagittal MRI showing an extruded disc fragment at the C5-C6 level in a 35-year-old patient. B, The axial T2weighted MRI at the herniation level. C, The postoperative lateral cervical roentgenogram shows spontaneous fusion and normal cervical curvature 36 months after operation.
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215
Fig. 5. Outcomes of surgery according to symptoms and type of lesion.
interspace fibrotic tissue also covering the foraminal area was detected at his second operation. In this study, 2 patients represented adjacent-level disease at the late postoperative period. One with relapse of symptoms was reoperated on, and the other asymptomatic patient underwent additional follow-up and was not operated on. Thus, all of the complications observed were as follows: 2 spontaneous and 2 postinfection collapses of the level, 1 excessive fibrosis of the level, and 2 adjacentlevel disease (1 of them symptomatic). The clinical longterm results according to symptoms and types of lesions are shown in Fig. 5. The results were better in the radiculopathy and soft disc groups than those in the myelopathy and hard disc groups ( P = .0001, v 2 = 36.21, and P = .0001, v 2=26.84, respectively). The correlations between the long-term outcome and age, sex, duration, and onset of symptoms were also studied (Table 4). The number of patients with good or excellent outcome was higher in the group of patients younger than 50 and it was statistically significant ( P = .0001, v 2=22.61). There was
also a statistically significantly better outcome in patients with short duration and sudden onset of symptoms ( P = .0001, v 2=105.9 and P = .0001, v 2=41.97). On the other hand, the statistical analysis of the effect of the postoperative cervical curvature and the number of segments operated on (double or single) revealed that there was a significantly better results in patients with normal cervical curvature and single-level disease (Table 5). 6. Discussion There are several effective surgical options for the treatment of patients with symptomatic disc herniation of a cervical spine segment [1,5,7,15,17,20,23,38,39]. The posterior approach provided considerable success and was described in the treatment of cervical disc herniation by many early surgeons [1,17,22,28,44]. While generally satisfactory results were achieved in the management of lateral perforated discs, the results were often disastrous because of the need to retract the spinal cord to remove
Table 4 Correlation between the outcome and age, sex, and duration and onset of symptoms Groups
Age Sex Duration of symptoms Onset of symptoms
Excellent
N50 b50 Female Male b 3 mo N 3 mo Sudden Gradual
Good
Improved
Failed
Total
P
n
%
n
%
n
%
n
%
n
%
14 70 28 56 75 9 72 12
23.0 45.2 33.7 42.1 73.5 7.9 53.7 14.6
33 63 45 51 27 69 52 44
54.1 40.6 54.2 38.3 26.5 60.5 38.8 53.7
8 22 9 24 – 30 7 23
13.1 14.2 10.8 15.8 – 26.3 5.2 28.0
6 – 1 5 – 6 3 3
9.8 – 1.2 3.8 – 5.3 2.2 3.7
61 155 83 133 102 114 134 82
100 100 100 100 100 100 100 100
.0001 .116 .0001 .0001
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Table 5 Outcome according to follow-up cervical curvature and number of involved levels Excellent Normal curvature Abnormal curvature Single level Double level
Good
Improved
Failed
Total
P
n
%
n
%
n
%
n
%
n
%
84 – 70 14
46.9 – 43.2 29.8
84 12 78 18
46.9 36.4 48.1 38.3
11 15 12 11
6.1 45.5 7.4 23.4
– 6 2 4
– 18.2 1.2 8.5
179 33 162 47
100 100 100 100
midline disc herniations. However, the anterior surgical approach allows a thorough decompression of the ventral aspect of the cervical spinal cord and cervical nerve roots. Besides, the PLL can be opened via this approach to remove sequestered disc fragments or osteophytes that cause ventral or ventrolateral cord/root encroachment. Although the anterior approach has become customary as a preferred surgical choice for cervical disc disease because of its efficiency and simplicity, it has brought about a new controversy concerning the anterior discectomy with or without fusion [35,37,45]. The advocates of the anterior approach with interbody fusion propose that bone grafts are necessary to maintain biomechanical stability, to facilitate fusion, to promote the resorption of osteophytes, and to widen the neural foramina. However, the rate of graft and graft-site complications, reaching 18% in larger series [6,25,36], prompted several surgeons to perform discectomy without fusion. In particular, after the introduction of the operating microscope into anterior cervical procedures, many surgeons using the simple discectomy technique reported favorable results that were comparable to those obtained by the fusion technique [16,21,25,30,33]. It is asserted that anterior simple discectomy subsequently leads to bone fusion; thus, a bone graft is not necessary after such a procedure [19,29,31,35,41,46]. However, such a result can only be expected if all disc material and both end plates are thoroughly removed, which may result in the subsequent deterioration of preoperative cervical curvature leading to neck pain and/or stretch-mediated recurrent radiculopathy due to collapse of disc level. On the other hand, fusion formation at discectomy levels either spontaneously or via a graft results in the loss of a motion segment, leading to increased strain-induced mechanical stress on the adjacent segments. According to an experimental biomechanical in vitro study by Pospiech et al [32], the increased intradisc pressure may be one mediator for the acceleration of the degenerative changes. In 1997, Hilibrand et al [18] postulated that up to 25% of the patients who undergo cervical fusion might require treatment of adjacent-level disease within 10 years. DePalma et al [9], reported a series of 229 patients who underwent anterior cervical interbody fusion, describing a rate of 81% of adjacent-level disease. During the surgical technique used in this study both lateral borders of annulus fibrosis and end plates are preserved to maintain the height of disc level to avoid subsequent development of morbidities such as collapse of disc level and/or adjacent-level disease. According to the
.0001 .001
results of this study, the rate of the radiologically confirmed spontaneous fusion formation is 6% and postdiscectomy collapse is 1.8% (2 of them due to infection). The published incidence of complete bone fusion ranges from 28% to 100% [19,21,24,29,31,41,46] and collapse of the involved disc space from 1.5% to 43% [14,24] after anterior cervical discectomy without fusion. Comparing the results of our technique with those of the classical technique without bone graft application, the rate of the postdiscectomy collapse and spontaneous fusion formation is very low. Moreover, there was no patient having additional kyphosis postoperatively except 4 patients who developed collapse of the involved level. We observed adjacent-level disease in 2 patients, a figure that is also low in comparison to the published figures. During the classical ipsilateral anterior approach, usually an excessive dissection of anterior longitudinal ligament, more removal of both end plates and sometimes bone structures, and distraction of level with a spreader are necessary for the decompression of foraminal lesions. All of these procedures are factors creating subsequent problems such as collapse of the level or instability as mentioned earlier. To accomplish decompression of more limited anterior foraminal compressive lesions, anterolateral and transuncodiscal approaches have been introduced by Verbiest [42], Hakuba [15], and Lesoin et al [23]. In 1989, Snyder and Bernhardt [39] reported anterior fractional interspace decompression by performing lateral one-third discectomy and leaving the remainder of the disc untouched. More recently, a surgical technique to the same area was introduced: removing the buncovertebral jointQ— the uncinate process, the lateral portion of the cephalad end plate and lateral portion of the intervertebral disc—by Jho [20] and later by Tascioglu et al [40], and modification of this technique by Saringer et al [34]. All these modifications of the anterior approach to the cervical disc disease propose to achieve more foraminal exposure and to preserve the mobility of the involved cervical segment. Nevertheless, these approaches are useless in cases of ventral compression and may cause recurrent disc herniations. However, the contralateral anterior approach used in this study, while achieving more exposure to the foraminal area, also allows decompression of ventral compressions less invasively and at the same time prevents settling of the involved disc. Because our surgical approach attacks and eradicates the causative lesion where it grows, we did not encounter a recurrent disc prolapse in any of our patients.
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Contrary to some authors [8,29,43], we think it is essential to remove all of the posterior and lateral osteophytes. With contralateral anterior microsurgical technique, it is possible to eradicate them without causing settling of the level and injury to the neural structures. As mentioned in most of the relevant literature [13,19, 27,37,45,46], we insist on the routine resection of the PLL and direct visualization of the dura and the foramen to avoid postoperative deterioration due to missed free fragments, and probable swelling or calcification of the PLL in the postoperative long term as pointed out previously [4,5]. In agreement with the literature [5,11], in our series, patients with radiculopathy achieved a significantly better outcome than patients with myelopathy. Seventy-eight percent of patients with radiculopathy had ruptured disc or soft protrusion and 85.2% percent of patients with myelopathy had hard disc protrusion. In addition, patients with ruptured disc or soft protrusion had a significantly better outcome than the ones with hard disc protrusion. In concurrence with O’Laoire and Thomas [30] and Bertalanffy and Eggert [5], our results also support that compression due to prolapsed intervertebral disc carries better prognosis than compression due to a chronic degenerative disc disease. The results of the present study showed that patients with a sudden onset and a short duration of symptoms (less than 3 months) had a statistically significantly better outcome than those with a gradual onset and duration of symptoms (more than 3 months). Thus, we fully agree with the previous reports emphasizing an early operation to achieve a better outcome [5,10]. Vocal cord paresis has been reported in most references as transient, varying from 1.1% (4) up to 16% [26] that may occasionally be permanent (1%-2%) [8]. However, we did not observe such a complication in our series, and it seems to be the result of our minimally invasive microsurgical technique dealing with the intermittent application of a mini Zenker handheld retractor instead of an automatic large retractor.
7. Conclusions Anterior contralateral microdiscectomy accomplishes direct visualization and resection of the offending foraminal lesions, ventral osteophytes, or a disc fragment, and prevents settling of the involved disc. Because the surgical procedure does not necessitate a fusion procedure, fusionrelated complications with regard to graft and graft site are avoided. In addition, preserving the end plates and both lateral parts of annulus fibrosis during this surgical procedure prevent early spontaneous fusion, thus minimizing the adjacent-level disease. This minimally invasive technique achieves better postoperative comfort with a quite low complication rate and allows patients to resume full activity immediately after surgery.
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Commentary Professor Aydin et al have presented another minimally invasive anterior approach to the cervical spine for treatment of cervical radiculitis and cervical myelopathy. The paper demonstrates that adequate decompression of the appropriate nerve root exit zone will relieve neck and arm pain complaints related to nerve root impingement syndrome. The paper seems to confirm the literature premise that post-surgical non-rigid, non-fused cervical spine does not lead to progressive adjacent segmental deterioration but still provides for adequate decompression of the nerve root for pain relief and for improvement in neurological function. The paper, however, suggests that this procedure provides for less than adequate decompression for spinal cord myelopathic disease. Perhaps the minimal anterior decompression with the persistent posterior telescoping soft tissues on motion continue to traumatize the spinal cord. A larger decompression and fusion is probably needed to treat this entity of myelopathy better. My preference still remains the posterior cervical laminoforaminotomy to treat neck and arm pain complaints secondary to nerve root impingement syndrome. The trading of relief of neck and arm pain for the not infrequent side effects of hoarseness, swallowing dysfunction, droopy eye, problems breathing, etc., much less pseudofusion, progressive adjacent joint disease, seems to be a less desirable choice than just non-improvement of the post-operative symptoms of neck and arm pain. Another point the paper makes is that early neural decompression does better than late. In this paper, about half the patients are operated on under the 3-month time period of onset of symptoms, and those patients did significantly better than patients who had longer sustained disease. This is in contrast to the changing of attitudes here in America where long, conservative, non-operative care is often extended beyond 6 months in the face of overt disease and is associated with neurologic deficits. They then have a poorer result than if they were done early in the course of their disease history. These findings will correlate well with the lumbar disk natural history that has been demonstrated by the European studies. Henry M. Shuey Jr., MD Baltimore, Maryland 21229, USA Aydin et al present a series of 216 patients operated upon for cervical disk herniation by a more minimally invasive anterior approach. The technique involves a small incision, hand retraction of the trachea and esophagus and a channel through the disc from the side contralateral to the lesion. The disc space is not spread, and the cartilaginous plates are left undisturbed. The patients were followed up for 18 months. The results are roughly equivalent to that seen with other techniques except that a 1% infection rate