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Fall, 2011 Volume 7

Issue 3

Neurosurgery Views

www.buffaloneuro.com

Buffalo Neurosurgery Group

Cervical Disc Replacement By P. Jeffrey Lewis, MD

Anterior

Prodisc-C Cervical Disc Replacement

CERVICAL DISC REPLACEMENT AT A GLANCE Instead of fusing and eliminating movement in the joint space, the joint is replaced allowing for continued movement (Fig. 1) Eliminates pseudoarthrosis (failure to obtain a bony fusion) Intended to reduce progression of adjacent level disease

cervical discectomy and fusion (ACDF) remains the gold standard procedure for the surgical treatment of cervical disc herniation and cervical spondylosis that produce intractable neck and or radicular arm pain that is unresponsive to conservative methods of treatment. It is also used in cases of cervical disc herniations and cervical spondylosis causing nerve root and spinal cord compression that result in radiculopathies and myelopathies with motor and sensory deficits. The use of the operating microscope has resulted in a safer and more complete decompression of the spinal canal and exiting nerve roots. High speed pneumatic drills and the development of fine microsurgical drilling technique, for example, skull base egg shell drilling, have advanced the art of removing the offending anterior compressive osteophytes and herniated disc from the dura and nerve roots. In the majority of cases, osteophytes must first be drilled out and removed before the disc herniation can be adequately identified and removed. The decompression has become wider and

Figure 1. Implanted PRESTIGE® Artificial Cervical Disc at C5-6. Note normal function at replaced joint.

P. Jeffrey Lewis, MD

more complete with the development of this microsurgical technique. I attribute a large part of the success of this procedure to the proper decompression of the dura and nerve roots. The reported success rate for relief of pain is around 78% for ACDF1. The procedure takes 1-1.5 hrs to perform for a single level and in the majority of cases, patients go home the same day. Given the high rate of success for this procedure, why is there interest in a revolutionary change from fusion to artificial disc replacement? The answer lies in the “fusion” aspect of the procedure. Pseudoarthrosis, or the failure of the bone to fuse with the adjacent vertebral body, can occur following the ACDF procedure. This can cause foraminal stenosis and recurrence of symptoms. Another reason for interest in artificial disc replacement is something called adjacent segment disc disease. Following ACDF, once fusion takes place there is no movement in the joint. The joint can no longer do what it was originally intended to do, that is, to perform its share of work as a member of the array of joints that allow a full range of motion in the neck. The fusion of one level is felt to create greater stress on the remaining “movable” joints leading to their early failure. Both of these problems can result in the need for another operation. (Continued on page 2)


Neurosurgery Views

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Dr. Lewis is currently performing Cervical Disc Replacement on an outpatient basis at the Center for Ambulatory Surgery at the Western New York Medical Park in West Seneca.

Pseudoarthrosis In the conventional ACDF procedure, failure of the bone to heal (fuse with the adjacent vertebral bodies) results in a pseudoarthrosis (fibrous union rather than a bony one) (Fig.2). The potential resulting bone graft subsidence and graft collapse result in disc interspace subsidence, osteophyte formation, and secondary foraminal stenosis. In other words, the failure to obtain a solid bony union results in the development of a severe spondylitic segment with resultant stenosis producing recurrent neck pain and radiculopathy. Upon reoperating on these pseudoarthrosis segments, I routinely remove the osteophytes and decompress the dura out to the exiting nerve roots (decompression width 20-25 mm) before placing a new graft. Kyphosis and instability are potentially further results of pseudoarthrosis.

The risk of pseudoarthrosis is highest in cigarette smokers whose time to heal is delayed well beyond the already slow rate of 3 to 6 months. The multitude of fusion implants attests to the continued struggle to find a better way. Unfortunately, no one method is unequivocally superior to another. Surgeon preference most often dictates the method of fusion. My approach is to use an interbody PEEK cage with synthetic bone graft and an anterior titanium plate in order to avoid the morbidity of iliac graft site complications. A high rate of bone fusion occurs with this technique even in smokers. Smokers, of course are strongly encouraged to stop smoking. The complication of pseudoarthrosis, including the need to re-operate, the prolonged time to heal a bone fusion, and the morbidity of the iliac graft site when autogenous bone is used, all represent limitations of this procedure.

With conventional Anterior Cervical Discectomy with Fusion (ACDF) the complication of pseudoarthrosis may result in: The need to re-operate Prolonged time to heal a bone fusion Morbidity of the iliac graft site when autogenous bone is used.

Figure 2. CT sagittal reconstruction image. Good bony fusion is present at C4-5 and C5-6. At C6-7 a pseudoarthrosis (failed bone fusion) is present. Adjacent level disease is also present at C3-4 with cervical subluxation.

(Continued on page 3)


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Neurosurgery Views In adjacent segment disease there is accelerated adjacent segment disc degeneration, osteophyte formation (spondylosis), herniation and or stenosis. Recurrent severe symptomatology may result in the need for further surgery at the adjacent segment.

(From page 2)

Adjacent Segment Disc Disease In adjacent segment disease the discs above and below a fusion are placed under greater stress because of the fusion. This can result in accelerated adjacent segment disc degeneration, osteophyte formation (spondylosis), herniation and or stenosis (Fig. 3). Recurrent severe symptomatology may result in the need for further surgery at the adjacent segment. Preserving motion while still achieving the necessary important decompression of the offending disc, theoretically can greatly reduce healing time (especially in smokers) and reduce the need for re-operation by avoiding pseudoarthrosis and reducing the effect of adjacent segment disc disease. Preserving motion of the operated disc segment may also improve the success of pain relief by restoring the segment to it’s more natural function of motion and reduce the excess strain on the other segments of the cervical spine. Artificial Cervical Disc

Figure 3. Sagittal MRI image showing Adjacent Segment Disease below the operative levels.

The disc is placed under radiographic control with various sizing available to allow a secure press fit with an optimal posterior center of rotation for preservation of normal motion. Early stability of the implant occurs by the secure press fit and superior and inferior rails secured into the vertebral endplates (figure 4). Preservation of cortical endplates after the discectomy minimizes the risk of subsidence, implant loosening and malfunction. Bone growth fixation surfaces on the implant superiorly and inferiorly are present for long term stability. The low profile design allows for multi-level use (Fig. 5). Case Report

Figure 4. PRESTIGEÂŽ Artificial Cervical Disc

A 42 year old male presented to our Buffalo office by self-referral after being diagnosed with a large disc herniation on MRI scan. He thoroughly researched the condition on

the internet prior to his arrival and decided that he wanted the artificial disc. He had a history of several years of neck pain but over the past 6 months had become much more disabled. While presenting at the office in a hard cervical collar, it was obvious that he was having severe neck pain and stiffness. He was barely able to move his neck and now finds working at his place of employment as impossible. He was also a very active, competitive athlete and now could not play at all. He described symptoms of myelopathy, bilateral hand numbness, weakness and stiffness with intermittent upper extremity spasms. There were no symptoms in the lower extremities and there were no definite physical findings of myelopathy. Figure 6 shows the large C6-7 disc herniation producing spinal cord compression. The C5-6 disc shows degeneration with spondylosis but without any spinal compression. The disabling symptomatology and the MRI scan, along with failure of a long trial of conservative therapy including physical therapy and antiinflammatory medication, clearly identified this patient as a candidate for an anterior cervical microdiscectomy with fusion at C6-7. He was a heavy smoker. The patient was also a very good candidate for an artificial cervical disc due to his severe compressive pathology. Additionally, he has a history of heavy cigarette smoking and is a poorer candidate for a bone fusion. The degenerative disc above at C5-6 does not require surgery at this time, however it could undergo accelerated degeneration if a fusion were performed at the level below it. The artificial disc should place less strain on this C5-6 disc than a fusion by maintaining motion at the operative level, C6-7. His recovery would be expected to be much quicker than if he had a fusion, especially since harvesting bone from the patient for an autogenous iliac grafting will be avoided. (Continued on page 4)


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Figure 5. Intraoperative PRESTIGE速 LP Artificial Cervical Disc at two levels with post-operative AP and Lateral X-rays.

(From page 3)

Surgery was performed without complication. A very large disc herniation was removed and the dura well decompressed with a height of decompression measuring 7 mm and a width of decompression measuring about 24 mm. A 7mm X 18mm PRESTIGE速 LP Artificial Cervical Disc was implanted (Fig. 7) precisely under AP and LAT fluoroscopy. Surgical time was about 1.5 hours and the patient was discharged on the 2nd postoperative day. His preoperative neck and arm pain and paresthesia resolved completely. Figure 7 shows the dural decompression and the implanted disc. Figure 8 shows the postoperative lateral flexion/extension x-rays, illustrating movement at the interspace and normal disc space kinematics as well as the precise midline placement just posterior to the center of rotation. CONCLUSION

Figure 6. Sagittal MRI showing a huge C6-7 disc herniation with spinal cord compression where the artificial disc will be implanted. The level above, C5-6 has disc degeneration and spondylosis. This level does not require surgery at this time, however, a fusion at the level below it could accelerate its degeneration.

The etiology of pain from spinal disc disease is complex, and multifactorial. An underlying pre-existing degenerative disc disease is most often present, as the majority of the population harbor degenerative discs with advancing age. This spinal osteoarthritis is more severe in genetically predisposed patients, smokers, and a particular body habitus (overweight patients with relatively small spines). Spinal trauma is the most common inciting event for these

predisposed but asymptomatic discs to become painful. Trauma producing disc herniation and spinal compression is most often obvious, however other injuries to the discs occur such as annular tears, ligamentous disruption, and segmental instability. Secondary gain issues (disability benefits, litigation, and psychological factors) may complicate the pain syndrome, however they are difficult to sort out from the objective clinical and radiographic findings. Practitioners need to be very careful about denying a patient the benefit of treatment because of presumed secondary gain issues. Iatrogenic factors are the most relevant concern to any cervical disc procedure. Obviously a safe, effective discectomy is an absolute requirement for the best chance of a successful outcome. Operative injury to the spinal cord, or nerve roots will have a disastrous outcome. Incomplete discectomy will result in failure of pain relief even with a well placed bone graft or artificial disc. The use of the operating microscope and microsurgical techniques add greatly to the safety and success of these procedures. As mentioned above, failure of a bone fusion to heal, often results in recurrent or persistent pain from secondary foraminal stenosis and instability. Adjacent segment disc disease may occur after a fusion. (Continued on page 5)


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Neurosurgery Views (From page 4)

Preserving motion while still achieving the necessary important decompression of the offending disc, theoretically can greatly reduce healing time (especially in smokers) and reduce the need for re-operation by avoiding pseudoarthrosis and reducing the effect of adjacent segment disc disease.

Re-operation for these problems is not uncommon. The artificial cervical disc has been developed and is being studied in clinical trials with the hope of reducing iatrogenic problems associated with fusion including the often long duration of healing as well as iliac graft donor site complications. Further, an overall better patient outcome is being sought by maintaining motion after discectomy and reproducing normal disc space kinematics. Dr. Lewis is currently performing Cervical Disc Replacement on an out-patient basis at the Center for Ambulatory Surgery at the Western New York Medical Park in West Seneca.

Figure 7. Intra-operative photo showing the disc space after removal of the herniated disc (left) and the implanted PRESTIGE速 LP Artificial Cervical Disc (right).

References: 1. Silvers, HR, Lewis PJ et al. Day Surgery for Cervical Microdiscectomy: Is It Safe and Effective? Journal of Spinal Disorders. 9(4): 287293, 1996 2. Gore DR. Sepic SB. Anterior discectomy and fusion for painful cervical disc disease. A report of 50 patients with an average follow-up of 21 years. Spine. 23(19):2047-51, 1998

Figure 8. Post operative Flexion (Left) and Extension (Right) x-rays of the above patient showing optimal placement and preserved motion in the C6-7 space.


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For an appointment with Dr. Lewis to see if Cervical Disc Replacement is right for you, please call:

P. Jeffrey Lewis M.D. – (716) 677-6000

Buffalo Neurosurgery Group www.buffaloneuro.com

Comprehensive adult neurosurgical care Operating at hospitals in the Catholic Health System and Kaleida as well as at Niagara Falls Memorial Hospital and ECMC. Immediate appointments available at your request for patients requiring expedited care Neurosurgical consultation with any of our surgeons can be arranged at these locations by calling the number listed:

West Seneca – WNY Medical Park 550 Orchard Park Road West Seneca, NY 14224

Olean Olean Medical Group Building Second Floor - Area B 535 Main Street Olean, NY 14760

P. Jeffrey Lewis, MD – (716) 677-6000 James G. Egnatchik, MD – (716) 677-5005

Lee R. Guterman, PhD, MD – (716) 803-1504

Williamsville – Park Center 180 Park Club Lane Williamsville, NY 14221

Amherst 4050 Harlem Road Amherst, NY 14226

Douglas B. Moreland, MD – (716) 839-9402 Gregory J. Castiglia, MD – (716) 839-9402 John Pollina, Jr., MD – (716) 839-9402

Lee R. Guterman, PhD, MD – (716) 803-1504

Dunkirk 3898 Vineyard Drive Dunkirk, NY 14048 John Pollina, Jr., MD – (716) 839-9402


Cervical Disc Replacement