Chapter 223 Management of Cervical Disc Herniation
Dorsal Laminoforaminotomy plus Discectomy
Cervical spondylosis is one of the most common pathologies seen by spine surgeons.1,2 Patients with cervical spondylosis can present with pure mechanical neck pain, arm pain that can be traced back to a specific nerve root distribution, signs of spinal cord dysfunction, or often a combination of these factors. On the basis of the location of the degenerative process, the clinical diagnosis accompanying cervical disc disease can be broadly categorized as arthritic neck pain, radiculopathy, myelopathy, or myeloradiculopathy. It is imperative to classify the patient into one of these four diagnoses before selecting the appropriate nonoperative and operative treatment.3 The sole focus for this chapter is the diagnosis and treatment of cervical radiculopathy.
The diagnosis of isolated cervical radiculopathy is established when a patient complains of arm pain that surpasses neck pain. This may or may not be accompanied by motor loss, sensory dysfunction, or an alteration of the reflex arc associated with a particular nerve root. This symptom complex can be caused by a dorsal and lateral disc herniation or a degenerative cascade that results in uncovertebral spurring, ligamentum hypertrophy, and facet arthrosis, leading to cervical neural foraminal stenosis. The natural history of cervical radiculopathy is distinctly separate and different from cervical spondylotic myelopathy.4 Lees and Turner performed a long-term follow-up on patients with cervical spondylosis and reported that 30% of these individuals experienced intermittent radiculitis, whereas about a quarter had persistent radiculopathy.5 As a general principle, conservative care can quell symptoms of cervical radiculopathy in the short term, but in the long run, symptoms frequently recur. Gore et al. conducted a long-term retrospective review on patients with cervical radiculopathy and reported that with conservative care, 79% had a significant decrease in pain, and 43% were free of pain. However, they noted that 50% continued to have persistent symptoms, and approximately 32% had moderate or severe residual pain at 15-year follow-up.6
Unyielding radiculopathy that is recalcitrant to nonoperative management such as nonsteroidal anti-inflammatory drugs, physical therapy, and epidural steroids can be treated surgically. Patients with isolated radiculopathy can be treated with either a ventral or a dorsal decompression as dictated by their pathology. The approach of choice has been a subject of debate for the last 70 years. Semmes and Murphy first described this pathology in 1943. They delineated the compression of the seventh cervical nerve root at the foramen by a unilateral rupture of the C6-7 disc.7 Around the same time, Spurling and Scoville8,9 and separately Frykholm10 pioneered the technique of dorsal foraminal decompression. Within 10 years, Smith and Robinson described the ventral cervical discectomy and interbody fusion using autograft.11 This procedure was revised by Cloward in 1958, with disc excision, removal of compressive structures, and bone dowel grafts for fusion.12 Bailey and Badgley,13 along with Cloward12 and Smith and Robinson,11 helped to establish the ventral cervical discectomy and fusion as the gold standard for degenerative cervical disc disease. Although the ventral approach is associated with high patient satisfaction rates and short recovery times, it does have a greater potential for serious complications.14 Conversely, the dorsal approach completely sidesteps major complications such as recurrent laryngeal nerve injuries and esophageal, tracheal, or vascular injuries. Furthermore, it avoids graft- and fusion-related issues.15
The problem of adjacent-segment degeneration and disease following spine procedures remains a controversial topic. In a large retrospective series, Henderson et al. reported an overall prevalence of 9% with annual incidence of 3% for the development of adjacent-level degeneration in their patients undergoing dorsal cervical foraminotomy.16 Hilibrand et al., in their analysis of 383 patients with ventral surgery, showed that 25.6% of the patients who had a ventral arthrodesis would have new disease at an adjacent level within 10 years after the operation with a relatively constant incidence of 2.9%.17 However, Clarke et al. analyzed 303 patients, using a survivorship analysis similar to that used by Hilibrand, and showed that 6.7% of patients who had a dorsal cervical foraminotomy would have new disease at an adjacent level within 10 years after the operation with a constant incidence of 0.7%.18 These clinical observations suggest that dorsal cervical foraminotomy has a reduced rate of adjacent-segment degeneration compared with anterior cervical discectomy and fusion. Dorsal cervical foraminotomy is a motion-preserving operation. It may avoid increasing loads on the adjacent levels, unlike cervical fusion surgery.
The current spine literature supports the dorsal laminoforaminotomy approach to the cervical spine for several disorders. The most common indication is persistent and recalcitrant shoulder and arm pain or numbness with or without focal weakness. The ideal candidate should exhibit a specific dermatomal pattern that is correlated and confirmed with radiographic analysis. The typical pathology includes dorsolateral disc herniations and single-level or multilevel spondylotic foraminal stenosis without central canal compromise. Unremitting cervical radiculopathy after ventral cervical discectomy and fusion is another indication.19 The efficacy of dorsal laminoforaminotomy with or without discectomy for lateral recess or foraminal stenosis has been well documented over the last several decades.10,16,20,21 Most studies show that outcomes for axial neck pain are inferior to those for radiculopathy. The success for radicular symptoms is 90% to 95% improvement versus the 70% to 85% for axial neck pain.
The high rate of clinical success can be truly appreciated by analyzing the anatomic constraints of the intervertebral foramina. The neuroforamen is a funnel-shaped structure that is bordered by the uncovertebral joint ventrally and dorsally by the facet joint, specifically the superior articular process. The nerve root can be compressed ventrally by the disc or the osteophytes at the uncovertebral joints of Luschka. In contrast, dorsally the superior articular process or hypertrophic ligamentum flavum causes nerve root compression. Raynor et al. defined this anatomic relationship and delineated that a dorsal decompression allows 3 to 5 mm of the cervical nerve root to be visualized, whereas only 1 to 2 mm of the root can be freed up ventrally.22,23
However, dorsal cervical foraminotomy must be used discreetly, the primary indications being a unilateral dorsolateral disc herniation, facet arthritis with compression, uncovertebral osteophytes, or ligamentum flavum thickening. This procedure would be contraindicated for cases of myelopathy due to central or paracentral stenosis and for cases of deformity or instability.24 Spondylosis with a kyphotic deformity or instability, bilateral symptoms or a broad-based central disc bulge should be managed directly with a ventral decompression and fusion or a dorsal decompression (laminectomy or laminoplasty) with or without a fusion. In certain instances, a combined ventral and dorsal procedure may be the most appropriate.21,25
Begin with a deliberate and detailed history and physical exam. Identify the affected nerve root(s) via sensory, motor, and reflex testing. A through neurologic exam is essential to identify the level of radiculopathy as well as to rule out myelopathy and pathology that would require a different surgical treatment. The dermatomal distribution of pain, parasthesias, and weakness in the arm and hand can pinpoint the predominant nerve root involvement. The upper cervical nerve roots typically produce pain in their region of innervations; however, owing to a lack of motor deficit, they are tougher to identify. The most common levels involved are the C6 and the C7 nerve roots and they are easier to identify based on biceps or triceps weakness, respectively. Despite an attentive neurologic examination, there may be some confusion in localizing one level as some variation and overlap of innervations can occur. Therefore, clinical examination should be followed with a radiographic correlation of the pathology. Start with an anteroposterior and lateral radiograph of the cervical spine to assess for deformity and instability. Myelography and postmyelography CAT scan can be obtained, but MRI remains the study of choice. It is noninvasive, now readily available, and highly specific.
Frykholm was the first to describe the dorsal foraminotomy in 1951.26 The surgical techniques for this procedure have evolved tremendously over the last several decades. Initially, this surgery was performed as part of a multilevel laminectomy in the seated position.25 With surgical innovation and microscopic techniques, a less invasive keyhole foraminotomy was developed, and most recently, a microendoscopic laminoforaminotomy through a minimally invasive approach has been described.27
The prone position, the sitting position, and the Concord position have all been described, and they all demonstrate comparable results. All patients should have placement of thromboembolic stockings or sequential compression devices and prophylactic antibiotics administered within an hour of incision. A Foley catheter is not routinely used, and neurophysiologic monitoring in the form of SSEP can be utilized if there is concern about spinal cord function, but it is not usually needed. The essential steps of the surgery are the same in either position and will be detailed later for the more common prone position.
After endotracheal intubation, the patient’s head is placed in a three-point Mayfield pinion, and the patient is turned prone onto gel-filled rolls for chest bolsters on a standard operating room table. The patient’s arms are tucked at the patient’s side, and any pressure points around the elbow, wrist, and hand are padded. Gentle inferior traction applied on the shoulders will allow visualization of the lower vertebrae in the cervical spine with lateral fluoroscopy or radiographs. Using a shoulder harness, taping the shoulders downward, using long Kerlex gauze wrapped around each wrist for traction, or alternatively pushing each shoulder downward with an empty suction canister is a useful and viable method for inferior traction on the shoulders for improved intraoperative radiographic localization. Excessive or prolonged force on the shoulders can cause injury to the brachial plexus and should be avoided. The knees are flexed, a foot rest is slid to position under the knees, and pillows are used to pad this pressure point. A buttock strap is placed behind the patient, and then the bed can be brought into a reverse Trendelenburg position. The buttock strap and foot rest under the knees prevent the patient from sliding down as the table is tilted. Tilting the table will obtain a parallel relationship of the neck to the floor, improve venous return, and minimize bleeding (Fig. 223-1).
FIGURE 223-1 A, Lateral positioning in reverse Trendelenburg with a foot board and buttock strap (black) to prevent sliding of patient. Gel rolls allow for neck flexion. The shoulder harness strap (white) provides gentle downward traction, improving lateral imaging of the lower cervical vertebrae. B, The head is held securely in Mayfield pinions, and the shoulder harness is placed under the gel rolls.
After the bed has been tilted, it is helpful to recheck the positioning of the neck and place the cervical spine in a small amount of flexion with two to three finger breadths between the chin and the chest in most patients. The neck is then clipped where needed, prepped, and draped in the usual sterile manner. Using fluoroscopy or a lateral radiograph will confirm the correct operative level and minimize the length of the skin incision. Typically, a 3- to 4-cm skin incision is marked in the midline centered on the disc space. After cutting through the skin, the dissection is carried down the midline or slightly ipsilateral to the side of the planned exposure to the level of the spinous process. Staying within the nuchal ligament will avoid any unnecessary muscle trauma and minimize bleeding. The deep dissection after identification of the spinous process is then performed unilaterally and subperiosteally, the paraspinal muscles being stripped only on the symptomatic side. The paraspinal muscles insert on the inferior edge of the hemilamina, and division of the muscle at this location will allow the subperiosteal dissection to show the area of interest. The inferior aspect of the superior lamina and superior aspect of the inferior lamina are exposed by this process. After the spinous process and the lamina are exposed, another localizing radiograph is preformed to ensure the appropriate level. The exposure is carried laterally to expose the medial aspect of the facet joint, and a self-retaining retractor is placed. Removal of the medial 20% to 30% of the facet capsule will expose the lateral limit of the foraminotomy. Take heed that removal of more than 50% of the facet capsule can destabilize the spine.
Under microscopic or loop magnification, a high-speed burr is used to perform the foraminotomy. A 3- to 4-mm diamond burr will minimize bleeding during this step, although a small round- or acorn-tipped cutting burr on a long bit such as the Midas Rex AM-8 bit is also appropriate. A long bit and a small cutting or diamond burr will optimize visualization during the drilling process. The keyhole foraminotomy begins at the lamina-facet junction, with careful consideration of the amount of facet resection. Typically, only the medial one third is drilled. Then a 1- or 2-mm Kerrison punch can be carefully placed over the nerve root and then used to undercut the facet, ensuring that the spine is not destabilized by the foraminotomy. The amount of facet resection must not exceed 50% in order to preserve spine stability.28
After the laminotomy is completed, the ligamentum flavum is identified and removed. Careful attention is needed to protect and coagulate the venous plexus surrounding the nerve root. Bipolar cautery along with the use of hemostatic agents will prevent injury to the nerve root during this process. If the compression is from an osteophyte without suspected disc herniation, then the procedure is completed when a small ball tip probe can easily be passed out through the neural foramen dorsal and inferior to the nerve root. Using a probe with a 45- to 90-degree angle or a Woodson elevator may be helpful in examining the neural foramina. The superior aspect of the pedicle below the nerve root should be easily palpable as well. Disc exploration beneath the nerve root is important if a disc herniation is suspected clinically or radiographically as a contributor to the radiculopathy.
To gain access to the disc, the nerve root must be identified, and only gentle manipulation of the root can be performed rostrally and minimally in the caudal direction. The inferior edge of the laminotomy should be limited by the pedicle of the inferior level, which is a useful landmark during exploration to the level of the disc. Start by inspecting the axilla of the nerve root with a micro nerve hook; the disc fragment is usually located caudal to the root. If no free disc fragment is found, the posterior longitudinal ligament can be opened sharply with a no. 11 or a Beaver blade (Beaver Visitec International, Waltham, MA). Before incision of the disc space ensure that the nerve root is protected and the disc space is clearly identified. The micropituitary or a small nerve hook can be used to deliver and remove the fragment through the annulotomy. Thorough exploration is conducted around the nerve root to ensure that all fragments have been removed. The decompression is again complete when a small ball tip probe or a Woodson elevator can be easily passed through the foramen.
Surgical hemostasis should be achieved prior to removal of the microscope. The wound is then copiously irrigated with antibiotic solution. The fascia is reapproximated with an interrupted absorbable suture, often a #0-vicryl. Subcutaneous closure is performed with an interrupted or running stitch, such as a #2-0 vicryl. Subcuticular closure is performed with a fine running suture such as a #4-0 monocryl or vicryl or staples. Dermabond may be used to seal the wound if desired. There is no need for postoperative cervical orthosis, and often the patient can be discharged the same day or the next morning.
The same standard setup is utilized to position the patient as was described in the section on open foraminotomy. Lateral fluoroscopy is brought into the field for this procedure, and it is often helpful to utilize gentle traction on the shoulders to visualize the lower cervical vertebra radiographically. The image should be matched to the anatomic position of the patient. A Steinman pin maybe used lateral to the neck to give a true dorsal and ventral reference and to help determine the angle of the lamina and disc space (see Fig. 223-1). The neck is then clipped where needed, prepped, and draped in the usual sterile manner.
After fluoroscopic confirmation of the correct operative level, a 2-cm incision is made 1 to 2 cm lateral to the spinous process. Avoid using a K-wire or a Steinman pin, as it may pass between the lamina and injure the dura, spinal cord, or nerve root. The fascia may be opened by a pair of Metzenbaum scissors or Bovie electrocautery so that dilators can be easily passed to the desired location. The smallest dilator can be used to palpate the inferior and superior lamina to identify this necessary landmark. This step also allows the dissection of the paraspinal muscles at the surgical field without resecting them (Fig. 223-2). Avoid excessive downward force in the interlaminar window with the dilator, as it could cause injury to the spinal cord or nerve root. After the smallest dilator is positioned over the appropriate disc space, serial dilation is performed to widen the opening and allow the tubular retraction system to be docked into place on the facet complex. A 14- to 18-mm-diameter tube is adequate for a single-level foraminotomy. Using the smallest beveled tube will allow strategic retractor placement on the lamina to avoid excessive muscle creep into the operative field. The tube is held in place by a retractor arm attached to the contralateral side of the bed, allowing the assistant to tighten the retractor arm while the surgeon holds the tube in position. The final retractor location should be verified via fluoroscopy to ensure the correct level.
The operative microscope or an endoscope can be utilized to provide adequate visualization of the operative field through the tubular retractor. If muscle encroachment continues to be an issue, a redilation of the muscles through the final retractor system may be performed, and a smaller tubular retractor may be utilized. Once again, this process can avoid the need for muscle resection for optimal visualization (Fig. 223-3). However, a small circular cuff of muscle may sometimes be removed to identify the lamina-facet junction. The foraminotomy is performed following the same principles and steps as detailed previously with the help of specialized bayoneted long instruments that allow the surgeon to work within the confines of a long, narrow working portal.19,24,27,29 By using these techniques, a soft lateral disc herniation can also be removed with a small incision and minimal exposure, reducing the length of hospital stay, narcotic requirements, and blood loss from the procedure (Fig. 223-4).
The seated position is labor intensive for the operating room staff, and most hospitals are not equipped for or familiar with the setup. More important, additional monitoring is required during the entire length of the procedure for rapid detection and treatment of venous air embolism. The reported incidence of air emboli varies throughout the anesthesia literature depending on the monitoring device utilized. A rate of 7% to 76% has been described in the literature. The incidence is about 7% to 25% for cervical laminectomies and 76% for posterior fossa surgery.30–32 The typical monitoring methods include precordial Doppler and the measurement of end-expired carbon dioxide and nitrogen with a mass spectrometer. Transesophageal echocardiography is a more sensitive monitor and may be utilized for higher-risk cases. A central venous catheter is also placed with its tip in the upper right atrium so that any air entering the venous system can be aspirated promptly.
If air embolism is detected, the surgeon should immediately attempt to locate and eliminate the site of air embolism. Flooding the field with saline and/or packing the wound with wet sponges may eliminate air embolism. Bone wax should be placed over any cut bleeding bone. Jugular venous pressure will minimize air entry and may aid the surgeon in localizing open veins at the site of increased bleeding. In addition to aspiration of air via a central venous catheter, the anesthesiologist should stop nitrous oxide, and the patient should be placed on 100% oxygen. Nitrous oxide may increase the size of the air embolus.33 In the event of cardiovascular collapse, the operative site should immediately be lowered below the level of the heart. Furthermore, the left lateral decubitus (Durant) position may be utilized to release an air lock in the right side of the heart.34
One distinct advantage to the seated position is radiographic localization of the levels. Even the C7 spinous process can be easily identified without shoulder obstruction in the majority of patients. Caudal traction of the shoulder is not necessary in the seated position. In addition, the seated position can minimize operative site bleeding.
Dorsal cervical foraminotomy, with or without discectomy, is a safe procedure associated with a very low complication rate (0–10%).35 However, potential complications can range from a simple stitch abscess to a life-threatening air embolism or severe spinal cord injury. Excessive bleeding is noted more commonly in the prone position, while air emboli, pneumocephaly, and cord and brain ischemia are cited in the sitting position.
Intraoperative air embolism can be a lethal event.36 It is essential for a surgeon using the seated position to be well versed in the prevention as well as rapid detection and management of air emboli. Lower-extremity compression stockings and adequate preoperative hydration will increase right atrial pressure and reduce the negative pressure gradient of the surgical field. The key step in preventing air embolism is prompt surgical hemostasis, minimizing the exposure of the open venous system to the atmospheric pressure.
Another possible complication is a dural tear. Incidental durotomies are noted with this procedure at a rate of 1% to 3% with the open procedure, which is no different than the ventral approach. However, the rate of durotomy with the minimally invasive endoscopic approach has been reported to be as high as 8% in the early surgical experience and then levels out to a rate less than 3%.27 Wound infections are much lower compared to other dorsal cervical surgeries, likely due to the limited incision and minimal muscle retraction and ischemia.
The most common neurologic complication is a transient nerve root palsy, the majority of which resolve within a week.20 The most common nerve root affected is at the C5 level. The mechanism of action is thought to be a revascularization-related transitory ischemia and a traction injury after decompression of an inflamed nerve root. Transient nerve root palsy may be more common when two or more levels are preformed. Nerve root and spinal cord injury are reported but very rare. Recurrence of symptoms are reported in a small number of cases and are more common with long-term follow-up of patients with significant spondylosis.37–39
Finally, instability of the cervical spine can result from excessive resection of the facet joint. Several studies suggest that instability results only if more than 50% of the facet or facet capsule is resected,40–42 and that is usually unnecessary for an adequate decompression.
The effectiveness of dorsal cervical foraminotomy with or without discectomy is consistently documented favorably with the appropriately selected patients. In general, the outcomes are reported to be successful in more than 90% of the cases with a 70% to 100% range of success.43,44 Henderson et al. reported their experience of 846 cervical foraminotomies for hard and soft disc disease in 736 patients. They documented a 96% incidence of relief in regard to arm pain and parasthesias and a 98% improvement of the preoperative motor weakness.16 They delineated similar results for soft and hard disc protrusions, including purely spondylotic radiculopathy. Krupp et al. reported a good to excellent result in 98% of the 161 patients analyzed after dorsal cervical foraminotomies. They determined a slight difference between hard and soft disc pathology, with favorable outcomes of 98%, 84%, and 91% for soft, mixed, and hard discs, respectively. However, this study had a large loss to follow-up with an initial population of 230 patients.45 Herkowitz et al. prospectively compared the ventral and the dorsal approaches to address the soft disc radiculopathy and demonstrated a 75% good or excellent outcome in 16 patients randomized for the dorsal cervical foraminotomy.39 Silveri et al., in a retrospective study of 84 patients at a mean follow-up of 6 years, reported a 98% good to excellent result.46 Jodicke et al. report a 94% good to excellent result at 6 weeks post dorsal foraminotomy and an 85% good or excellent outcome at a mean of 33 months. According to their study, soft disc pathology had a higher ratio of good outcomes as compared to hard disc disease at early follow-up; however, at long term, there was no statistical difference between the two. A 15% recurrence rate was reported.47 More recently, Jagannathan et al. performed a retrospective review on 162 cases of a single-level unilateral dorsal foraminotomy by a single surgeon with a 5-year minimum follow-up. They reported a significant neck disability index improvement in 93% of the patients and a resolution of radiculopathy in 95% of the patients. They also reported no statistically significant change in focal or segmental kyphosis in their cohort. However, they did delineate certain risk factors associated with worsening sagittal alignment: age greater than 60 years, preoperative cervical lordosis less than10 degrees, and a previous dorsal surgery.48
Postoperative cervical muscular pain and spasms resulting from ischemia during subperiosteal dissection of the paraspinal muscles are the major disadvantages of the standard open approach. This has resulted in the advent of minimally invasive microendoscopic approaches to dorsal nerve root decompression. Roh et al., through a cadaveric study, showed that the average vertical and transverse diameters of the laminoforaminotomy defects were similar between the open and minimally invasive techniques. Furthermore, the length of the nerve root that was decompressed and the average portion of the facet that was removed were not statistically different in the two groups.19 Fessler and Khoo reported their clinical data on minimally invasive cervical microendoscopic foraminotomy (MEF). They performed a traditional open dorsal foraminotomy on 26 patients and compared it to the MEF technique in 25 patients. They reported that the MEF group had a lower operative time (115 minutes vs. 171 minutes), decreased blood loss (138 mL vs. 246 mL), shorter hospitalization (20 hours vs. 68 hours), and less narcotic use when compared with patients who underwent the open procedure. Both the open and MEF groups had greater than 90% improvement of symptoms and were statistically similar in outcome.24
Adamson reported the results of 100 consecutive cases of microendoscopic laminoforaminotomy for the treatment of unilateral cervical radiculopathy secondary to disc herniation or foraminal stenosis. In this study, 97% of the patients had good or excellent results, and 100% returned to their preoperative occupation at baseline activity between 1 day and 4 weeks postoperatively. Ninety percent were done as same-day procedures, and 10% of patients were discharged on postoperative day 1.27
Although criteria defining good outcome after dorsal laminoforaminotomy differ markedly in the literature, certain variables were commonly cited as positive prognosticators. The length of preoperative symptoms had an inverse relationship with improved outcomes. The patients with a shorter duration of symptoms tended to do better with the decompression. Additionally, patients with far lateral disc herniations and soft disc disease did better than the cohort with central disc pathology or those with hard discs. Moreover, patients with a specifically identifiable dermatomal pattern of pain or parasthesias did better than those who had overlapping symptoms even when more than one level was decompressed. Finally, legal disputes and disability claims did not have a positive effect on outcome.
Multiple procedures allow access to the spinal canal and/or neural foramen. Each procedure has distinct advantages and disadvantages. The dorsal laminoforaminotomy with or without discectomy is historically a very successful surgery. It avoids potentially serious complications such as esophageal and vascular injuries, as well as fusion problems associated with ventral surgery. The dorsal approach provides the simplest and the most direct exposure to single-level or multilevel nerve root pathology without requiring instrumentation and fusion, and it does not accelerate spondylotic degeneration of adjacent levels.18 The decompression does not require significant facet resection to affect the spine stability, and there is no postoperative immobilization. Careful patient selection with good surgical technique results in 95% improvement of preoperative symptoms. The optimal surgical candidate has a lateral soft disc or focal osteophyte pathology causing a unilateral medically refractory radiculopathy in the absence of kyphosis or spine instability.
Henderson C.M., Hennessy R.G., Shuey H.M.Jr., et al. Posterior-lateral foraminotomy as an exclusive operative technique for cervical radiculopathy: a review of 846 consecutively operated cases. Neurosurgery. 1983;13:504-512.
Jagannathan J., Sherman J.H., Szabo T., et al. The posterior cervical foraminotomy in the treatment of cervical disc/osteophyte disease: a single-surgeon experience with a minimum of 5 years’ clinical and radiographic follow-up. J Neurosurg Spine. 2009;10:347-356.
1. Adams C.B., Logue V. Studies in cervical spondylotic myelopathy. I. movement of the cervical roots, dura and cord, and their relation to the course of the extrathecal roots. Brain. 1971;94:557-568.
14. Graham J.J. Complications of cervical spine surgery. A five-year report on a survey of the membership of the cervical spine research society by the morbidity and mortality committee. Spine (Phila Pa 1976). 1989;14:1046-1050.
16. Henderson C.M., Hennessy R.G., Shuey H.M.Jr., et al. Posterior-lateral foraminotomy as an exclusive operative technique for cervical radiculopathy: a review of 846 consecutively operated cases. Neurosurgery. 1983;13:504-512.
17. Hilibrand A.S., Carlson G.D., Palumbo M.A., et al. Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis. J Bone Joint Surg [Am]. 1999;81:519-528.
30. Papadopoulos G., Kuhly P., Brock M., et al. Venous and paradoxical air embolism in the sitting position. A prospective study with transoesophageal echocardiography. Acta Neurochir (Wien). 1994;126:140-143.
37. Woertgen C., Holzschuh M., Rothoerl R.D., et al. Prognostic factors of posterior cervical disc surgery: a prospective, consecutive study of 54 patients. Neurosurgery. 1997;40:724-728. discussion 728–729
48. Jagannathan J., Sherman J.H., Szabo T., et al. The posterior cervical foraminotomy in the treatment of cervical disc/osteophyte disease: a single-surgeon experience with a minimum of 5 years’ clinical and radiographic follow-up. J Neurosurg Spine. 2009;10:347-356.
Ventral Cervical Discectomy and Fusion with Allograft or Bone Morphogenetic Protein and Plating
Since the introduction of the ventral cervical discectomy and fusion for the treatment of cervical disc disease by Cloward, Smith, and Robinson1–3 the technique has undergone continual refinement, incorporating the advances in plating and allografts and the recent developments in osteobiologics. Anterior cervical approaches remain one of the most popular and successful operative approaches to treat cervical spine disorders. Because of the simplicity and elegance of the procedure and its overall versatility and success in treating ventral cervical pathologies, every spine surgeon should be comfortable with the surgical anatomy and operative techniques of this operation. With the vast array of plating systems, the numerous allograft alternatives, and the introduction of bone morphogenetic proteins, a sophisticated understanding of these options by the surgeons facilitates their selection and safe implementation. This chapter provides a description of operative techniques for ventral cervical discectomy and then reviews the alternatives to autograft, including the various options for allograft and the use of bone morphogenetic protein. Finally, the principles of cervical plating are reviewed.
The surgeon should determine the graft type before surgery. This decision depends on patient preference, nature of the pathology, patient compliance, and risk factors for pseudarthrosis. Radiographs should be examined to confirm the level of pathology, the extent of spinal cord compression, the presence or absence of kyphosis, bone quality, presence of spondylolisthesis, or instability. The surgeon should preoperatively select the most appropriate bone graft and plating system for the patient. Most implant systems are user friendly, and there do not appear to be significant differences in single-level fusion rates between the older plating systems and the newer dynamic systems.4 For single-level fusions, rigid or hybrid screw-plate systems suffice for most purposes. While a variety of plating systems are currently available, the basic principles of graft loading and screw-plate interface are the same in all of them. These principles are reviewed in the following sections.
Patients are brought into the operating room and placed supine on the operating table. After induction of general anesthesia, a bag of intravenous fluid wrapped in a surgical towel is placed under the neck to restore lordosis (Fig. 223-5). The head may be placed on a doughnut. Esophageal stethoscopes and nasogastric tubes are avoided, since they can aggravate esophageal injury by retracting against rigid objects. Various anatomic landmarks may be palpated to estimate the level of the disc space. The hyoid bone is generally at C3, the thyroid cartilage is at C5, and the cricoid cartilage is at C6. The carotid tubercle, the most reliable landmark, can be palpated at C6. In the absence of reliable anatomic landmarks, a preoperative lateral cervical radiograph may be used to determine location of the incision. Once the incision has been planned, the ventral neck region is prepped and draped in the usual sterile fashion.
The incision for a single- or two-level discectomy generally follows one of the neck creases. The incision should extend from midline to the medial border of the sternocleidomastoid muscle (SCM) (Fig. 223-6). Oblique incisions along the medial border of the SCM may be used if access to three or more levels is desired. The right side is generally preferred for a right-handed surgeon. There is not an increased incidence of recurrent laryngeal nerve palsies with a right-sided approach compared with a left-sided approach.5
FIGURE 223-6 Typical incision for a single- or two-level discectomy. The thyroid cartilage can be palpated at C5; the cricoid cartilage can be palpated at C6. The most reliable anatomic landmark is the carotid tubercle, which can be palpated at C6.
After the incision is made with a no. 10 blade, Bovie electrocautery or Metzenbaum scissors can be used to traverse the subcutaneous tissues to access the platysma muscle. Undermining the platysma muscle is critical to aid in retraction. After the platysma muscle has been divided and undermined, the medial border of the SCM is identified. A plane is gently developed along the medial border of the SCM using superficial and sharp dissection. The carotid sheath is identified, and its contents are retracted laterally as the spine is bluntly palpated. The omohyoid muscle at C5-6 may be divided if necessary to improve access and exposure. The prevertebral fascia is divided in the middle of the vertebral body and swept off the spine by using a Kittner (Sheavor). Once the level has been reached, a localizing radiograph is obtained to confirm the operative disc space level. The use of a spine needle in the disc space may be helpful for this. The surgeon also may place an initial vertebral distraction pin into a body to aid with screw length determination. Once the level has been determined, optimal exposure is obtained by cauterizing the edges of the longus colli muscle to gain access to the uncovertebral joints (Fig. 223-7). This also aids in the identification of midline.
FIGURE 223-7 Cauterizing the edges of the longus colli muscle to gain access to uncovertebral joints. Clear identification of the uncovertebral joints allows midline identification and facilitates foraminal decompression.
The longus colli muscle can be released with the Bovie or bipolar electrocautery. Bovie electrocautery should be used judiciously below C6 to avoid inadvertent thermal injury to the recurrent laryngeal nerve. No attempt during the exposure is made to visualize the recurrent laryngeal nerve. Self-retaining retractors are placed, with small teeth under the medial longus colli muscle (Fig. 223-8). Larger-toothed retractors can be used, but care should be taken to ensure that the teeth insert well under the longus colli. Once the self-retaining retractors have been placed beneath the longus colli, the surgeon may request the cuff of the endotracheal tube to be deflated completely and reinflated only to prevent an air leak. If further exposure is desired, longitudinal blunt self-retaining retractors can be placed in a rostrocaudal fashion, as shown in Fig. 223-9.
A Cushing rongeur and a quarter-inch key elevator can be used to remove ventral osteophytes and to “garden” the vertebral bodies of interest (Fig. 223-10; see also Fig. 223-9). Vertebral body gardening further exposes the ventral disc and prepares the vertebrae for plating. Next, distraction posts (Caspar pins) are placed into the vertebral body, which will allow the graft to be placed under distraction. These posts may be angled to reduce a kyphosis (Fig. 223-11). If radiographs are taken, the length of the distraction pins can be used as a guide to select the appropriate screw length. A no. 15 or no. 11 blade is used to incise the annulus and anterior disc (Fig. 223-12).
FIGURE 223-10 “Gardening” with quarter-inch key elevator to expose bone. Note that the edges of the longus colli muscle were cauterized to allow access to uncovertebral joints and lateral disc, staying away from adjacent disc joints.
FIGURE 223-11 Placement of distraction pins. Pins are placed in midline of the vertebral bodies and may be angled to reduce a kyphosis. Distracting the pins allows access to interspace and allows graft to be placed under the distraction. In addition if a radiographic or fluoroscopy image is obtained, the pin length can be used as guide for the depth of vertebral body to choose anterior screw length.
The disc is then removed to the level of the posterior longitudinal ligament (PLL) using curettes. The spine segment is expanded by applying distraction across the disc space as the disc is removed (Fig. 223-13). The PLL and disc space are usually obscured by ventral and dorsal osteophytes (Figs. 223-14 and 223-15). As the inferior aspect of the vertebral bodies are naturally scalloped, the ventral lip of the superior vertebral body may be drilled to improve visualization of the disc space and prepare for graft insertion (Fig. 223-16). Dorsal osteophytes and end plates may be drilled to access the PLL (Fig. 223-17). The drilling of the end plates widens the disc space and increases access to the PLL (Fig. 223-18). Further drilling of the dorsal edge of the caudal vertebra and undercutting with 3-mm thin-lipped cervical Kerrison rongeurs may be performed to remove osteophytes and further widen the interspace (Figs. 223-19 and 223-20).
FIGURE 223-13 Release of the spine by simultaneous distraction and disc removal. This opens up the disc space and facilitates disc curettage. A few clicks of distraction are applied after each stage of disc curettage and the process is continued until the disc space is sufficiently widened.
FIGURE 223-16 Drilling the ventral lip of the rostral vertebral body. The ventral lip of the rostral vertebral body is drilled to gain access to the disc space. This helps to create parallel end plates, improves visualization, and prepares for graft insertion.
FIGURE 223-18 Preparing end plates to gain access to the posterior longitudinal ligament (PLL). It is important to go wide and expose the uncovertebral joints. Drilling the end plates widens the disc space and increases access to the PLL.