The Fullendoscopic Anterior Cervical Fusion: A New Horizone For The Selective Percutaneous Endoscopic Cervical Decompression

There is a high incidence of cervical discogenic pain symptoms in the population. It is estimated that one person in five in Germany who visits an orthopedic surgeon presents with the symptoms of a cervical disc syndrome. The treatment of cervical discogenic diseases makes high demands in terms of both diagnostics and therapy. Diagnostics has been made easier by improved imaging and the enhancement of neurological measuring methods. Consequently, there is now interdisciplinary consensus that the principal pathologic causes can be reliably identified.

The most common cause of cervical pain syndromes is a degenerative change in the intervertebral disc, where disc tissue is displaced, on the one hand, and damage occurs in the movement segment, on the other hand. Displacement of disc tissue to the epidural space may give rise to a biochemical lesion, vascular compression and mechanical compression of neural structures. This results in pain in the neck and head region, radiating into the arm, and also vegetative symptoms or even neurologic disorders. Other causes of disc-related pain are to be found in the dorsal anulus fibrosus, the posterior spinal ligament and the periosteum of the vertebral bodies, where there are active pain receptors.

With the aid of appropriate conservative therapy, approximately 80 percent of all cervical syndromes can be cured. Only once all the conservative and semi-invasive procedures have been exhausted should surgery be considered.

The development of surgical procedures for the treatment of intervertebral discs began in 1908 with the transdural removal of disc tissue with the aid of laminectomy by Oppenheimer and Krause. Extradural rectification of a herniated disc was prepared by Mixter and Barr in 1934. Later, Mixter and Barr also began looking at cervical intervertebral disc displacements. The intervention was developed on the lumbar spine, progressing from laminectomy to hemilaminectomy, and then to fenestrotomy and finally endoscopy (Hijikata 1975). The first operation on the cervical spine was performed by Elsberg in 1922, also transdurally. As from 1955, ventral methods of operation were introduced by Cloward, Smith and Robinson, and these are still standard procedures in the surgical treatment of discogenic diseases to this day. Both procedures has been combined with the fusion of the segment by a bone graft. This method continues to be accompanied by the problems of access morbidity (the incidence of recurrent laryngeal nerve lesions alone is put at 11%-15% (Apfelbaum)). The desire to reduce these problems led to continued development of the method. A discussion soon arose as to whether the fusion is necessary, and as early as 1960, Hirsch introduced the anterior cervical discectomy without fusion. In further studies, results comparable to fusion were obtained in many cases. The question regarding limited disc removal was also answered in favor of a selective procedure.

In recent years attempts have been made to preserve the physiologic mobility of the diseased movement segment by the use of intervertebral prostheses (artificial discs). This development will undoubtedly produce interesting results. The other focus of attention was on reducing surgical trauma and access morbidity. The first step was the introduction of the operating microscope by Hankinson and Wilson in 1966. Other innovations, such as high-speed burrs and bipolar electrocoagulation, produced a further reduction in surgical trauma.

With the aim of miniaturizing the treatment, non-endoscopic percutaneous procedures were soon being used on selected patients, and these also produced good results and a complication rate of less than 1 percent (Hellinger 2004). Thus, chemonucleolysis, which was introduced by Smith in 1964, was performed on the cervical spine. Similarly, automated discectomy (Onik 1985), percutaneous laser disc decompression and nucleotomy (Hellinger 1990) and the use of radiofrequency (Coblation 2003) broadened the percutaneous spectrum.

As a bridge between open and percutaneous therapy, endoscopy of the cervical Spine started to be used at the beginning of the 1990s (Lee, Chiu, Fontanella), following good experiences on the lumbar spine. The principle of microsurgery is combined with the minimally invasive principles by bringing the optical level to the forefront of pathology. Access morbidity has been significantly reduced by the percutaneous access technique. Furthermore, a large proportion of the intervertebral disc, in particular most of the anulus fibrosus, is preserved. The pathology is only removed selectively in the area of the nucleus pulposus and on the dorsal fibrous ring. This preserves the remaining biomechanical function of the degenerated intervertebral disc. By means of tried and tested minimally invasive methods under vision, such as the use of a laser to ablate and shrink tissue, the risk of complications has been further reduced, at the same time as enhancing efficiency. The advancement of the endoscopic technique with increased miniaturization of the endoscope and working options led to a restriction of use (e.g. LASE system).

Our objective was to create an adequate working space in front of the endoscope while preserving the minimally invasive approach. This was achieved by the use of dilation sheaths, which force the base plate and upper plate of the vertebras apart in the manner of a Cloward distractort and permit a working field of 5 mm or 6 mm. Here the visualization is sufficient to expose the ventral epidural space. A swiveling maneuver of the endoscope (fan sweep, Chiu) enables the dorsal section of the intervertebral disc to be visualized from one uncovertebral joint to the other as necessary. Removal of disc material is limited to the pathologic part, in a similar way to arthroscopic meniscus surgery. Equally, the surgeon has to become accustomed to the fact that limited viewing fields are lined up, rather as in joint arthroscopy. An irrigation system is used to rinse the ablated disc material out of the viewing field and to achieve partial hemostasis. Endosopic cervical discectomy can also be performed using a gas medium. In this case, it is advisable to use a familiar view, such as through a microscope, to facilitate differentiation of the individual structures.

While our primary aim has been to save the motion segment by an endoscopic procedure as well as possible, we get some times patients with a severe instability of a cervical motion segment, that requires a fusion or prostheses.

After the good experiences we got with our new endoscopic system build by Fa. Karl Storz in the treatment of cervical disc herniations with 85% success rate, comparable to the results of Chiu or Lee, we tried to develop a system and a procedure to do a fusion through a working sleeve. Meanwhile Lee got good results 2005 by using a WSHCervical B-Twin as a sole spacer without fusion in the cervical intervertebral space, we decided to modify the Cloward procedure for the endoscope. The intention has been by using a bone dowel to get an osseous fusion and to induce the resorption of spurs, like Cloward did.

After this we did the fullendoscopic fusion surgery in march 2006. It has been a 50 year old female with neck and head pain on VAS 8. Beside there has been a pain radiation into the left arm. The X-Ray has shown a mild spondylosis and in functional pictures there has been a movement between the vertebral bodies C4 and C5 to a quarter. In the MRI we found a disc extrusion left sided on this level.

The procedure was similar to the Selective Percutaneous Endoscopic Cervical Decompression. The level of the intervertebral disc that is to be operated on is marked using the C-arm. Then an approx. 5mm skin incision is made at this level on the right side, medially to the sternocleidomastoid muscle, and the platysma is exposed without cutting. Following lateralization of the carotid artery and the jugular vein, and medialization of the larynx, trachea, esophagus and thyroid gland by applying pressure with the index finger and middle finger, the anterior surface of the cervical spine can be touched. Under fluoroscopy, an 18G spinal needle is then inserted into the intervertebral disc, preferably in the midline, via the skin incision. The position of the needle is checked in at least two planes with the C-arm. Then a guidewire and various obturators can be placed on the intervertebral disc via the needle. A 6,5 mm working sleeve is inserted into the anterior fibrous ring via the last obturator. For this purpose, the dilation sleeve system has proved successful. The two narrow lips of the sleeve are tapped into the fibrous ring and, following removal of the fibrous ring inside the sleeve, the sleeve is rotated and the base plate and upper plate are spread apart. The working sleeve can now be advanced further into the disk space. The procedure is facilitated by using a trephine and a shaver. Under endoscopic vision, the intervertebral disc can be curetted in a wide channel as far as the posterior fibrous ring. The pathological region of the posterior fibrous ring, previously identified by imaging, determines the angle of entry into the intervertebral disc. This section of the disc is located and ablated together with the prolapsed disc tissue. When so doing, the working area can, if necessary, be extended as far as the uncovertebral joints by swiveling the endoscope. If required, the excision forceps can be used to carefully open the posterior spinal ligament and expose the epidural space. Similarly, relatively small osteophytes can be ablated under fluoroscopic vision using the ring curet. It is also possible, when working in the dorsal disc space, to change over to the gas medium. This gives a picture familiar from microscopy. A final check of the decompression is carried out with the palpation hook.

After the decompression we designed a bed for the bone graft in the midline with different burrs. The bone graft has removed from the iliac crest with a special gouge to create a compressed spongeous cylinder of 6mm diameter in the checked length. For safety we took more cylinder. Than the graft in combination with osteoinductive proteins (Coloss®) has been placed in the intervertebral bed through the working sleeve under endoscopic and flouroscopic view with various pushers. A last endoscopic view has shown the correct position of the graft. After removal of the scope the wound was closed like a band aid surgery.

After the surgery the pain of the patient diminished to VAS 1. The arm pain disappeared. The postoperative CT scans and X-rays show a correct positioning of the bone dowel with a good distraction. After six weeks a further CT scan has shown a beginning good fusion without any dislocation as well as a remaining good clinical outcome

Conclusion

The result of this method displays that a fullendoscopic fusion of the cervical spine with a bone dowel is possible. The clinical result seems to be comparable to the classical Cloward procedure. But the approach by 6,5 mm avoids a lot of complications, that are seen in open surgery. It entails less surgical trauma, and considerably reduces surgery-related stress for the patient, while also shortening the period of hospitalization.

To the best of my knowledge, this is the first report of a fullendoscopic osseous fusion on the cervical spine. Further investigations are necessary to determine the real outcome of this procedure. The future will show with the further development of new instruments and implants what real minimal invasive spine surgery will enable on cervical spine.

Figure 1: Flouroscopic control of the preparation of the endplates with a special burr

Figure 2: Endoscopic view of the intervertebral space after preparation and control with a hook

Figure 3: Inserting of bon cylinder in the working sleeve

Figure 4: Flouroscopic view of the endoscopic placed bone craft

Figure 5: Endoscopic control of the placed bone cylinder

Figure 6: Postoperative 3D CT scan of the fusion

Figure 7: Postoperative sagittal CT of the graft

Figure 8: The prepared bone graft