Endoscopic partial corpectomy using anterior decompression for cervical myelopathy
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.227270
Source of Support: None, Conflict of Interest: None
Keywords: Cervical spinal cord, cervical spondylosis, cervical vertebrae, compressive myelopathy, endoscopic surgical procedure
Symptomatic ventral cervical spinal cord compressions have been treated by anterior discectomy with fusion, anterior corpectomy and fusion, discectomy with an artificial disc, as well as by various minimally invasive techniques. There are advantages and limitations of these procedures. Complications related to the fusion technique such as non-fusion, pseudo-arthrosis, and adjacent segment degeneration, have been reported. Significantly increased morbidity in the form of dysphagia, postoperative neck pain, and more postoperative narcotic usage has been seen in patients who undergo a four vertebral-level fusion compared to a three-vertebral level fusion.
Various decompressive techniques have been described that avoid fusion such as an oblique corpectomy,,,,,,,,,, anterior percutaneous discectomy,,,, microforaminotomy, transcorporeal discectomy,,,,,,,,, and medial corpectomy. These techniques have their own advantages and limitations. Partial removal of the vertebral body while leaving most of the body and disc intact can be used to effectively decompress the spinal cord and root. It has the advantages of avoiding fusion and its associated complications. Removal of only the compressing part of the disc while leaving most of the disc intact could help in preserving motion between vertebral bodies, and also in preventing adjacent segment degeneration. We are describing the surgical technique, early results, advantages, and limitations of endoscopic partial corpectomy. To the best of authors' knowledge, the endoscopic technique of partial corpectomy for decompression of the spinal cord and nerve roots lying opposite the vertebral body and disc has not been described.
Pre- and postoperative workup
A detailed clinical evaluation should be done for patients with cervical myelopathy with or without radiculopathy. Computed tomography (CT) scan or magnetic resonance imaging scans are performed to define the extent of the compression. Details of patient demography, i.e., age, sex, duration of symptoms, etc., are recorded. Pre- and postoperative visual analog scale (VAS) for neck and arm pain, and the functional outcome using the Nurick grading system, are assessed. Any change in the disc height or change in the range of movement is assessed at 3 months and at later dates after surgery.
Indications and exclusion
The main indication for this minimally invasive endoscopic decompressive procedure is in patients with significant anterior compression at single or multiple levels, not responding to conservative therapy. An unstable spine, or the presence of an infective or a traumatic lesion are conditions unsuitable for this procedure.
The patient is placed in a supine position on an operating table, without the requirement of a cervical traction, and surgery is performed under general anesthesia. The neck is kept in a slightly extended position. Fluoroscopic guidance is used to mark the site of incision. A transverse skin incision, about two-third medial and one-third lateral to the medial border of sternocleidomastoid, is given. When there is symmetrical compression, the symptomatic or the more symptomatic side, or the right sided approach is used. The trachea and esophagus are retracted medially and carotid sheath laterally. The pretracheal and prevertebral fascial layers are dissected. The correct level is again confirmed using a C-arm image intensifier. Tagged gauze pieces are placed cranially, caudally, medially, and laterally to prevent soft tissue migration into the surgical field [Figure 1]. The Destandau set (Karl Storz GmbH and Co KG Tuttlingen) is placed in the surgical field created. A small part (at the lateral position) of the two adjacent discs (at the pathological level) is removed. These two points are connected by drilling of the intervening lateral part of the vertebral body using a high-speed drill [Figure 2]. We removed this lateral part of the vertebral body in patients included in our study because of the natural medial angle of the working channel in the Destandau system [Video 1]. A midline corridor can also be used in other systems such as the “Easy Go” system (Karl Storz GmbH and Co KG Tuttlingen), where there is no angulation of the working channel. Any bleeding from the bone can be controlled by bone wax [Figure 3] or by dry drilling using a diamod burr. The surgical technique should allow a bimanual dissection. Small diameter instruments should be used to allow for a bimanual dissection through a small bony opening [Figure 4]. Drilling is done by angulating the drill to the right, left, cranial, and caudal direction so that more of the compressing bony elements lying adjacent to the cord or root can be removed with excision of only a small portion of the anterior vertebra. Drilling of the vertebra should be done by keeping the endoscope as much away as possible to prevent lens soiling [Figure 5]. The posterior part of the vertebra in close proximity to the cord should be drilled by careful medial, lateral, cranial, and caudal movement with gentle paint brush technique [Figure 6]. Drilling in the direction of cord and with any force should be avoided. The finally remaining, thin portion of the vertebrae and the posterior longitudinal ligament are removed by a 1 mm Kerrison punch [Figure 7] or by using a fine curette [Figure 8]. Good cord pulsations and visualization of the lateral margin of the thecal sac are indications of a good decompression [Figure 9]. An illustration of the surgical technique is shown in [Figure 10]. A good posterior decompression can be achieved with a small amount of bony removal of the anterior and middle portion of the vertebral body. Angulation of instruments can better decompress the posterior part of vertebral body [Figure 10]c. Removal of a few millimeters of the anterior part of the body can further improve angulation towards the compressing part on the cord [Figure 10]c. Use of angled instruments (angled drill or angled curette) can further reduce the extent of vertebral body removal [Figure 10]d. Use of small diameter instruments can permit decompression through small openings using even the bimanual technique.
This procedure was performed in 15 patients. The patients' age ranged from 22 to 69 years (their mean age being 46 years). There were 9 male patients. There were one vertebral and two disc-level, two vertebral and three disc-level, and three vertebral and four disc-level pathology in 4, 6, and 5 patients, respectively [Table 1].
The preoperative mean VAS scores for arm and neck pain were 7.6 and 3.2, which improved to 1.9 and 1.1, respectively, at the 3-month follow up assessment. The various Nurick grades of patients constituting the study cohort included the grades 0, 1, 2, 3, and 4; and, the preoperative number of patients in each of these groups were 1, 2, 2, 8, and 2 patients, respectively. The mean preoperative Nurick grade was 2.5. The postoperative Nurick grade 0, 1, and 2 had 6, 5, and 4 patients, respectively, with the mean postoperative Nurick grade improving to 0.8. All patients improved after surgery, including the 1 patient in grade 0 with only radiculopathy. Improvement in 1, 2, and 3 grades were seen in 4, 9, and 1 patients, respectively. Postoperative imaging showed a good decompression with minimal removal of the vertebral body [Figure 11].
The duration of surgery for a one vertebral and two disc-level pathology ranged from 90 to 150 min (average: 105 min). The blood loss during surgery ranged from 30 to 380 ml (average 90 ml). There was no infection, deterioration, or nerve palsy encountered. The loss in disc height ranged from 1.1 to 1.4 mm (mean, 1.2 mm). The follow-up ranged from 3 to 5 months. The average hospital stay was for 3.5 days.
Various surgical techniques for anterior decompression without fusion
A short summary of the various surgical techniques for anterior decompression which do not require fusion have been described in [Table 2]. Oblique corpectomies without fusion have been used in multiple level compressions and in tumors.,, A multilevel oblique corpectomy has been found to be a safe and an effective procedure with a long-term spinal stability. It also allows permits a wide anterior decompression of the spinal cord and complete unilateral nerve root decompression. It can be done to remove the vertebral bony compression that is associated with an ossified posterior longitudinal ligament. There are also disadvantages associated with the procedure. A progressive decrease in the range of movements, though without clinical worsening; difficulty in approaching pathology at the C1-C2 level; the occurrence of Horner's syndrome (5.9%), postoperative C5 radiculopathy (3.3%), dural tear with cerebrospinal fluid leak (0.7%), vertebral artery injury (0.7%), asymptomatic kyphosis (4.3%), and preoperative lordosis progressing to straightening of the spine (25.6%), have been observed., In a summary statement by Traynelis et al., this technique was not considered as a first-line treatment strategy for anterior vertebral body and disc compression.
Anterior percutaneous approach has been proven to be safe and and an efficient surgical option in the presence of symptomatic cervical disk herniations with or without concomitant spondylosis and/or foraminal stenosis.,, Anterior transdiscal endoscopic technique has been found to be effective with the additional advantages of a lower cost, a smaller incision, no requirement of a bony fusion, preservation of motion segments, a faster recovery, less postoperative pain, no postoperative dysphagia, and no increased risk of adjacent segment disease. Anterior microforaminotomy can be used in the presence of disc disease or in a tumor. Transcorporeal approach has been used for radiculopathy.,,,,,,, It is a decompression procedure through the cervical vertebral body to decompress areas of central or foraminal stenosis while preserving the native disc. Transcorporeal approach has been found to be a better technique than the transuncal approach due to the preservation of disc height, stability of the spine, a shorter length of hospital stay, a higher degree of patient satisfaction, and its association with less complications. The additional advantages of decreased damage to the anterior annulus fibrosis and nucleus pulposus, which can cause less settling of the disc height, and its use in the case of a migrated disc behind the vertebral body have been reported. It has the advantage of preservation of most of the disc tissue, avoiding the utilization of a corpectomy for migrated disc, avoiding injury to the longus colli muscles, and the lack of requirement of a vertebral body spreader for performing the discectomy procedure. It preserves motion at the operated and adjacent segments without causing any significant decrease in the disc and vertebral height. The minimally invasive central corpectomy, using only the upper- or lower-half central corpectomy of the involved cervical spine, has been used to decompress the adjacent disc, and for removal of the ossified posterior longitudinal ligament. Fusion with cylindrical titanium cages, if needed, can be done. Our technique of partial corpectomy is just an extension of the transcorporeal approach, although the transcorporeal approach was used for removal of the disc only. In our procedure, we not only utilized the partial corpectomy for disc removal but also for compressions lying behind the vertebral body.
Advantages and limitation of the present technique
Endoscopic techniques have been frequently used now for various cranial ,, and spinal , conditions with a wide variety of indications such as an endoscopic third ventriculostomy,, as well as endoscopy for a brain abscess, arachnoid cyst, hematomas  and anterior C1-2 fixation.
Partial corpectomy without fusion has been found to be a safe and effective technique in our experience. It is effective in removing a compression lying behind the vertebral body and also in the region of the disc. There was no significant complication associated with the procedure in our patients. Fusion is not required as there is only limited removal of the vertebral body. Only a limited part of the vertebral body is removed anteriorly and in the middle portion of the involved vertebrae, while the wider part of the culprit bone or disc which is compressing the cord or root can be effectively removed, as shown in [Figure 10] and [Figure 11]. The amount of bleeding that occurs during the procedure, and the amount of surgical time required to complete surgery is comparable to that needed during the open technique.
There is preservation of most of the vertebral body and disc. Stability of the spine is maintained without the need for an additional procedure of spinal fusion. There is a shorter length of hospital stay due to the conduction of the minimally invasive technique. The procedure can be used for a migrated disc or any other bony compression behind the vertebral body. It avoids injury to the longus colli muscles and to most of the annulus fibrosis. It preserves motion in the operated and adjacent segments without any significant decrease in the disc and vertebral height. Although we did not use any interposing graft or implant for fusion in our patients, a titanium implant or a bone graft can be used to fill the gap created due to the bony drilling, if at all it is needed.
A short follow-up and a steep learning curve, both while using the endoscope and in performing the bone and disc preserving corpectomy are the limitations of this technique. The technique should be used with caution in the presence of a long segment anterior bony compression as well as when significant asymmetrical bony compression is encountered, as is often seen in the cases of ossified posterior longitudinal ligament.
The results of this technique are comparable to that of the commonly available surgical techniques, such as oblique corpectomy, microforaminotomy, transdiscal discectomy, transcorporeal discectomy and an open corpectomy with fusion.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]
[Table 1], [Table 2]