Percutaneous Cervical Discectomy

 

Daniel Gastambide, M.D, orth. surg., Peyrou P.L., M.D., orth. surg *

Sang- Ho Lee, M.D.,Ph.D., neurosurg. **

Introduction

Percutaneous cervical discectomy (PCD) is a surgical method for treating cervical disc diseases. D. Gastambide introduced it in Europe in 1989 with Tajima, and performed the first European procedure in 1990 [21]. The first Korean procedure was performed in 1992. The goal is decompression of the spinal nerve root by percutaneous removal and shrinkage of the nucleus pulposus and the herniated mass under local or general anesthesia. Most of the patients requiring surgery for cervical disc herniations can be successfully treated by this method.

For soft cervical disc herniation with a normal lordosis, simple anterior open discectomy is generally considered [27] .The open anteromedial discectomy without fusion is briefer and there are no complications from either allograft or autograft. However, the operation could be followed by segmental instability, loss of the physiological lordosis, collapse of the disc space, or a posterior narrowing of the intervertebral foramen.[9,11,12,23]

The open anteromedial discectomy with fusion requires usually to enter into the spinal canal with the risk of complications such as an epidural bleeding, peri-radicular fibrosis, transient or permanent myelopathy, bone graft related problems (donor site morbidity, painful pseudarthrosis, graft extrusion or angular collapse, kyphotic deformity, impacting of the graft into the body, dysphasia, and hoarseness (temporary or permanent vocal cord paresis) [6, 8, 18, 29]

The PCD with minimal invasive techniques under local anesthesia can possibly avoid those complications, and offers an alternative to the open therapeutic methods in cervicobrachial neuralgia or radiculopathy alone due to protruded soft cervical hernia. In case of failure, this operation does not impede the further conventional surgical approaches and it offers numerous advantages in addition to the absence of the complications described above, the stability of the intervertebral mobile segment is maintained, and the risk of recurrence is reduced in performing an anterior discal window. Finally, the time spent in operating room is reduced as well as the duration of hospitalization and the patient can perform again his or her usual activities more rapidly.

The open microsurgical anterior cervical foraminotomy [17] or the posterior foraminotomy [24] with only partial discectomy maintains disc space height, but could approach only lateral or foraminal herniation and they have big difficulty to treat paramedian, central hernia and diffuse hernia.

The PCD with preservation of disc space could approach and treat foraminal or lateral, paramedian, central, and diffuse herniations.

 

1         Indications and contraindications

The indication of PCD is radicular pain not responding to conservative treatment or sustained radiculopathy over three months. The best indication seems to be a patient of less than 50 years old, with a provocation test positive, without bony spur ≥ 2 mm, regardless hernia size, location (median, paramedian or foraminal) and epidural leakage.

The contraindications of PCD are extruded disc with myelopathy and severe spondylosis (< 3 mm intervertebral height or ≥ 3 mm bone spur). The success rate for the myelopathies is too low and the aggravation of neurologic signs may be developed.

 

2         Preoperative preparation

One has to check patient's clinical and neurological status the day before surgery, to review critically CT and MRI for the precise disc location, and to confirm the level on a lateral radiograph. CT or MRI  have to be of less than 3 months, because of the possibility of  sequester resorption by enzymes or macrophagic cells and that the radicular pain become independent  of the inflammation caused by the disc fragment.

 

3         Prerequisites, imaging and planning

3.1        The instruments

required for percutaneous cervical discectomy comprise a guide needle adjusted with the first 1 mm dilation tube  (fig 1, A and B) or a 18G spinal needle, a thin guide wire (fig 2), several dilators, working tubes, an annulus trephine, various forceps with or without an irrigation hole (fig 2 and 3), and a washing canula. The procedure should be performed only with a clear view of the entire operative disc under lateral and A P fluoroscopic projection has been obtained. The operating table must be radiolucent (fig 4).

Fig 1a

Fig 1b

Fig. 1B Kit cervical

Fig l A and B
A: needle, drift, first dilation tube, separated (up) and fitted (down). See the beveled guide needle and the first beveled dilation tube with its notch allowing the adjustment to the guide needle edge, so that the both bevel edges, at the tip, are in continuity, adjusted altogether like an unique bevel
B: Complete set: see the second dilation tube; the working tube; the trephine with its inverted interior thread with aspiration effect, allowing automatic extraction of the disc; the cutting dissecting forceps; the toothed dissecting forceps, and the washing canula. (ACO France)
Advantage of these tools is the few number of operating times, without using Kirschner wire; and trephine particular efficiency which makes the forceps practically useless
Bigger working tubes for endoscopic laser are optional.
Disadvantages are: the absence of incorporated suction system in the dissecting forceps and possibility of leakage during discography if both needle and first dilation tube are not strictly fitted during manufacturing

Fig 2

Fig 2
The cutting dissecting forceps is presenting a suction system; one and two millimeters dilation tubes , three, four and five millimeters working tubes allowing endoscopic laser; annulus trepan. Disadvantages are the absence of trephine with inverted interior thread and necessity of using a Kischner wire after discography (Medsys, Belgium)
Fig 3

Fig 3
Complete set: there is no trephine , which is made useless by the laser (Wooridul Spine Hospital kit, Storz)

Fig 4

Fig.4 Patient's position

3.2        Preparation and Anesthesia

Preoperative antibiotics (usually cefazoline 1 gram) should be given the day before operation, for antibiotics impregnation of the poorly vascularized disc to decrease the risk of infection. Preoperative sedatives are recommended. Anterior neck skin preparation and showers with iodized antiseptics are usual.

The PCD must be performed in operating room with a strict asepsis. The PCD is performed in supine position of the patient with the neck mildly extended on a radiolucent table. The anesthesiologist has to be told to put the perfusion on the surgeon opposite side. The forehead is fixed by an Elastoplast on midline. A 7 cm thickness short rolled drape is put under the neck.  The shoulders are sloped down with an Elastoplast fixed on the table. For strict patient immobilization, anterior knee right and left knee supports are associated with plantar distal fixed supports. The two arms lie along patient’s trunk. Fluoroscopic C-arm, lying on surgeon opposite side, is put in antero-posterior, then in lateral view, and the area to operate is carefully marked on the skin with a felt-pen using a metal instrument on front and profile. The lesion site is marked in counting the cervical vertebra cephalad then “caudalad”. For a better visualization of the disc C6-C7, a slight slope of the fluoroscope can be necessary. The felt-pen marks the internal edge of the sternocleidomastoid muscle, the median axis of neck, the upper edge of the sternum and marks the periphery of the cutaneous area to asepticize. The skin is distempered with an antiseptic. The fluoroscope is covered with a sterile field, then the face is surrounded with a plastic field which will be hold up only on the head of the patient in order for anesthesiologist to observe the patient and speaks with him (Fig 4), or a normal sterile drape will be hanged on the opposite side of the operator (the surgeon has to be able of going cephalad and caudal around the C-arm when in lateral position).

If local anesthesia with neuroleptanalgesia is chosen, the conversation of the operator with the patient is possible during the PCD. Then the changes of the patient's symptoms and signs can be immediately noted, particularly if the discography with provoked pain test is necessary. If general anesthesia is chosen, the patient is intubated.

Usually, a solution of xylocaine 2% with adrenaline is used to infiltrate the skin and subcutaneous tissues.  In order to minimize the thickening of underlying tissues and to allow a minute palpation of the spinal axis, we prefer to not infiltrate more deeply with xylocaine.

 

4         Surgical Anatomy of the Neck

All the operation is based on the fact that all the prevertebral content is very mobile due to compartmentalization of the neck by direct reach for the herniated portion. The visceral axis (thyroid, trachea, Pharynx, larynx, and esophagus) is easily displaced on the opposite side of the operator from the lesion with one or two fingers (fig. 5 A and B), and it is removed from critical neural structure. The cervical spine can even be palpated with the index and/or middle finger while the vascular axis (carotid artery, internal jugular vein) is displaced outside.

Fig 5a

Fig 5b

Fig 5 A and B: Imaging approach simulations: A: MRI simulation of approach with a small ball pen pushing trachea, showing a clear way toward cervical discs. B: Simulation of cervical anatomy by CT scan with operator finger in touch with disc anterior border. The right carotid artery is surrounded with red

Because the esophagus lies slightly to the left of the spine at C7 in most patients, we prefer anterior approach to the disc from right side at an acute angle to the midline, on the skin incision. Tools penetrate middle of the disc, in strict avascular zone. If paramedian approach, 2 to 5 mm from anterior border disc midline, is preferred, one has to know that the way to homolateral foraminal zone can be blocked by the homolateral uncus. Consequently, a paramedian approach on the opposite side of a foraminal hernia can be preferred in the goal to pass diagonally better behind the controlateral uncus, as far as possible of medullar axis. A  left anterior approach can be chosen  in case of right foraminal or posterolateral herniation although the risk of esophageal puncture might be slightly increased, but usually visceral axis is enough “mobilizable” to authorize anterior border disk penetration on the middle with right side skin incision.

On the cadaver dissection there is about 2mm of safe zone which consist of epidural subdural subarachnoïdal space before reaching the spinal cord parenchyme.

 

5         Surgical Technique

When the forefinger of the operator pushes the trachea or the larynx toward opposite side to clear a way which opens the vasculo-visceral axis on the patient, he perceives perfectly the beats of the carotid artery outside. The carotid artery can be protected under the other fingers. The index and long fingers are used to palpate the anterior aspect of the vertebra in the cleavage between trachea and carotid artery (fig. 5 A and B)

The pulp of index finger of the operator then slips inside towards the front of vertebral body and perceives the prominence of the anterior edge of the disc to be treated, between two depressions corresponding to the concavity of adjacent vertebral bodies.

The entry point is usually 1.5 cm lateral to the lateral margin of the visceral axis.  After a short skin incision, the operator passes the guide needle together with the first dilation tube or an 18 gauge spinal needle at the edge of the forefinger. The guide needle penetrates the disc just in the middle, controlled by the AP view, oriented at about 25 ° to the opposite side. After a last check of the front scopy, a slight pressure makes the needle enter the anterior wall of the disc. C-arm of the fluoroscope is placed in profile, the good level is checked and the needle is entered on around 5mm to the midline under lateral radiographic view.

The discography and the provocation test may be performed in order to differentiate the type or presence of the soft disc hernia and know the origin of pain [1, 25]. 0.5 ml to 1ml of contrast media can be injected to opacify the posterior part of the disc (fig. 6). If the provocation test shows positive response, it is a very good indication of PCD. The guide needle is pulled alone, leaving in place the first 1 mm dilation tube which has been introduced altogether with the needle (fig 1A) or a Kirschner wire is pushed through the 18 G needle and the needle is pulled. If you have used a single use needle, you can cut its distal part and use it like a Kirschner wire.

Fig 6: Discography allows showing hernia exact contour on lateral C-arm fluoroscopic view :

The operator may have confirmed the pulsation of carotid artery far out of the working tube or wire

The second 2-mm dilation tube and/or third 3-mm dilation tube then are introduced against the annulus for progressive dilation under guidance of fluoroscopy in the lateral projection. Small movements of axial rotation and some pressure applied on the first 1-mm metallic tube allow a passage through the anterior wall of the disc on 1 or 2 mm. An intradiscal hyperpressure can drive back and make leave out from the disk the instruments if a firm pressure is not applied. The working tube or sheath is introduced over the dilation tube. Sometimes anterior bony spur impedes the insertion of instrument, so that we must use a hammer with attention to hit the tube. A 1.7 mm rigid endoscope with saline irrigation may be used to see and confirm no other tissue except the disc.

Fig 7 A, B, and C: Discal hernia fragments taken only with the trephine; 7A: trephine tip with teeth and inside threading; 7B: white disc fragments in saline; 7C: discal substance cores of another disk, aligned in order from left to right ; the last are reddish, near the vascularized disk edge .

A core of discal substance is pulled using the inside threading trephine (fig 7A) entered through the working tube to cut the annulus. The internal spire of trephine with interior thread allows automatic extraction of several "carrots" of disc [23]. You try to take five cores of 5 (fig 7B) to 15 mm long (fig 7C), and stop when the discal substance seems too reddish, meaning that we are on the uncus or near the epidural space.

Verify with the small forceps that all free discal fragments are taken off.

Try to extract the tail of the hernia mass, which is more fibrotic and collagenous.

Do not try to remove the anterior part of disc in order to avoid the localized kyphosis. We rinse the intradiscal space with saline fluid mixed with cefazoline.

If discography is done the contrast image of protruded disc beyond the posterior body line become visible on the C-arm monitor, so, it is good indicator of depth for small disc forceps to remove herniated fragment of the disc close to the posterior longitudinal ligament

If the patient is not intubated, we ask him directly and confirm if the abnormal pain disappears or decreases. Mostly, the cervicobrachial neuralgia decreases or disappears simultaneously with PCD. The amount of removed disc is 200 to 1590mg (920mg in average), but success rate is not proportional to removed disc weight.

At the end of the operation, an abundant rinsing is performed in using a washing canula or a needle. After the instrument is removed, a slight compression can be applied with fingers on the surgical area for a few time to prevent hematoma. The skin closure can be made with stitch or adhesives. The average duration of the PCD is about 45 min. Cervical brace such as Miami collar is attached around neck in the operating room.

 

 

6 Optional Holmium-YAG laser associated with endoscopy in the same fiber (fig 8)

Fig 8 Endoscope with one way for optical fibers for associated light, vision and laser, and two ways for saline irrigation (Storz)

A working scope with passage of the laser probe or thin instruments can be used : laser is more delicate, works precisely with 0.3-0.5 mm cutting depth in the continuous saline irrigation and safely ablates the tissue near or inside the hernia mass close to posterior longitudinal ligament so that it can protect spinal cord or nerve root from energy transmission.  In order to ablate the tissue near or inside the hernia mass instead of endplate and posterior longitudinal ligament you should see inside disc with small endoscope.

You shoot the laser beam as posteriorly as possible to ablate and shrink directly the herniated part of the discs against the posterior longitudinal ligament in the set of 0.5-0.8 Joule of 10Hz under control of 1.7 mm endoscope with saline irrigation and fluoroscopy. You decompress and partially vaporize large contained subligamentous fragments (fig 9A). In A-P x-ray projection the laser probe should be correctly positioned toward herniated portion. Total energy of laser is about 5000 Joule. You may see inside the disc, the ablated defect of the posterior disc and annulus under the pumping irrigation of the normal saline 1000 cc mixed with cefazoline 2 grams. When the endoscopic laser does not meet any resistance in the posterior part of the disc or can not see the hernia mass anymore under posterior longitudinal ligament, the intervention is finished.

   Fig 9a Fig 9b

Fig 9 A and B Before PCD sagittal MRI of a C6C7 hernia: A:; B:control 3 months after PCD showing hernia complete disappearing; note disk height minimal lessening

 

6         Postoperative Management

The patient is observed for 3 to 24 hours in the clinic for seeing if he or she is developing any complications. The patients can be permitted to go home on the same day. The patients do not need bed rest more than one night.

Postoperative antibiotics and analgesics are recommended per oral for three to ten days. Cervical collar is recommended for 3 to 14 days according to patient improvement. Physical therapy such as head traction in mildly flexed neck and TENS might be helpful to recover faster within two weeks postoperatively if the cervicobrachialgia did not disappear completely.

Rehabilitation exercise for neck muscle strengthening and improvement of neck motion range is recommended two times a week for three months after four to six weeks postoperatively.

Fig 10: Roentgenographic evidence of spontaneous fusion and marked collapse of the interspace at operated level 1 year after open surgery, facilitating emergence of hernias below and above the C5C6 level.

 

7         Errors and potential hazards

-         Incision

One has to be able of making a new short incision if the first incision is not appropriate for needle course

-         Complications (21) (table 1)

The complications of PCD were mainly potential.

Immediate complications to be postulated were:

1)      vascular injury (1 case)- right carotid artery perforation due to inability to detect carotid pulsation through the patient‘s thick and short neck. The artery was sutured after conversion to open discectomy-,

2)      prevertebral hematoma, laryngeal edema,

3)      esophageal perforation,

4)      lesion of recurrent nerve (1 case)(transient hoarseness due to deep Xylocaine infiltration around laryngeal nerve which became normal after several hours), or lesion of superior laryngeal nerve or of large hypoglossal nerve.

5)      cervical cord compression with neurological disorders (1 case: transient pyramidal symptoms due to compressing the cord from passing the pituitary forceps beyond the posterior vertebral body lines. He recovered immediately after conversion to open discectomy with fusion)

Secondary complications could be postulated;

1)      worsening of the initial symptoms: delayed aggravation of herniation  which needed open discectomy one month after PCD (1 case)

2)      subacute discitis and epidural abscess with neurological disorders.

Late complications is worsening of osteoarthritis, accelerated by disc height diminution (mean 15%) (21)

8         Special problems: recurrence

If the patient has been already operated for cervical discal hernia at the same side or the other side, at the same level or at an other level, either with percutaneous (2 personal cases) or open surgery (3 personal cases), there is no special risk of operative complication if the visceral axis has a normal mobility.

 

9         Results

On one series of more than 170 patients, the mean preoperative duration of symptoms was 22 months (range 1-240 months).

There were 76% of cervicobrachial neuralgias (dominant radiculalgia 55%, dominant cervicalgia 21%), 18% of isolated radiculalgia, 6% of isolated cervicalgia.

The vertebral levels of soft cervical disc herniations ranged from the C3-C4 level to the C6-C7 level. 127 patients had 1 level operated (5 C3C4, 13 C4C5, 83 C5C6, 25 C6C7, 1 C7D1), 42 patients had 2 levels operated (5 C3C4 + C4C5, 15 C4C5 + C5C5C6, 17 C5C6+C6C7, 5 C4C5+ C6C7), 1 had 3 levels operated (C3C4 + C4C5 + C6C7).

The mean duration of the operation was 45 min.

Provocating pain test by injecting 1/2cc of non ionic dye is very significant for a good result if positive (reproduction of the same topography of pain). Epidural leakage, initial size and location of the hernia, presence of bony spurs ≤ 2 mm do not modify significantly the results. An important size lessening of the hernia improves significantly the results (21)

The mean follow-up was 37 months (1 to 13 years)

The rate of success is 92% (81% excellent and good, 11% fair. Among the 14 poor results (8%), 4 were reoperated by fusion after 3 to 24 months.

10   Comparison with open surgery

The clinical success rate is the same in open and percutaneous procedures. Complication rate seems to be quite different, favoring PCD in table 1. PCD complications occurred in four patients of our series (1 carotid wound, 1 reversible recurrent nerve impairment, 1 transient pyramidal syndrome, 1 secondary symptoms worsening). There were no infection, no pulmonary embolism, no thromboplebitis, no perforation of esophagus and no death.

Another advantage of PCD is avoidance of disc space collapse after discectomy.(fig 8)

In open surgery, there are the same complications (4 recurrent nerve impairments, 3 transient pyramidal syndromes, 2 secondary symptoms worsening), and 3 other types of complications (Claude Bernard Horner syndrome: 2, superficial complications on cervical incision or on donor site: 17, graft mobilizations: 12, graft collapse: 18). The ratio of complications between open surgery and percutaneous procedures is 9,44. In other words, there are near ten times more complications in open surgery.

11   Discussion

The advantages of this cervical percutaneous surgical procedure are numerous:

-           Performed either under neuroleptanalgesia associated with local anesthesia, or under general anesthesia,

-           confirmation of symptomatic level during the same operation time  if performed under local anesthesia.

-           Reduced operation time

-           No epidural bleeding

-           No post-operative periradicular fibrosis

-           No risk of instability, nor postoperative kyphosis, nor complications of donor site, graft migration or collapse

-           Reduced risk of discal hernia relapse on anterior percutaneous surgical window

-           ablation of hernia mass with inverted trephine, forceps,  and eventually with the endoscopic Ho:YAG laser,

-           No difficulty if further open approach

-           Complications rate high reduction compared with open surgery (table 1)

-           Hospital staying shortened to 24 hours or less

-           Faster return to work

-           Better cost/efficiency ratio

Per-operative complications fears, particularly oesophagal lesions or hematoma, are not confirmed in our series of 227 surgeries. This percutaneous cervical discectomy widens and broadens indication of percutaneous cervical approach and might become the treatment of choice in future because of possibility of direct ablation of the hernia mass with less serious complication.

 

In the treatment of soft cervical hernias, when the surgeon chooses a simple discectomy procedure, without graft nor arthrodesis, the first choice is the minimal invasive approach of percutaneous cervical discectomy, followed, in case of failure, by open anterolateral approach.


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