Indications for an Anterior Approach

The spinal cord can be compressed by herniated discs, spondylotic bars, and uncovertebral osteophytes. Direct decompression of the cord and nerve roots from these degenerative changes can be accomplished with an anterior approach. An anterior approach also allows the surgeon to relieve directly any compression on the anterior spinal artery that has been shown to supply the ventral 75% to 80% of the spinal cord. For most patients with stenosis confined to only one or two levels, an anterior approach provides adequate decompression and is the procedure of choice for most surgeons.^43,44 Yonenobu and colleagues⁴⁴ recommended that an anterior procedure should be confined to the treatment of spondylosis involving no more than three levels, whereas a posterior procedure should be reserved for the treatment of spondylosis involving four levels or more.

The sagittal alignment of the spinal column is an important factor when deciding on an anterior versus a posterior approach. Cervical kyphosis and degenerative instability are clear indications for an anterior approach.^37,45 In patients who have lost the normal cervical lordotic curvature or who have developed a kyphotic deformity, a posterior decompression alone may destabilize the cervical spine and may lead to a progression of the deformity. Anterior surgery allows for direct decompression of the neural elements, fusion of the involved segments, and possibly reconstitution of the normal sagittal contours. An anterior approach may also be favored in patients who complain of preoperative neck pain. Two techniques described in anterior decompression and surgical treatment of cervical myelopathy include anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF).

Surgical Techniques

The surgical approach for ACDF and ACCF are identical. The patient is positioned supine on the operating table. The cervical spine is ideally placed in slight extension to facilitate exposure of the anterior neck. This position is accomplished by placing a longitudinally oriented bump under the patient’s upper thoracic spine, between the scapulae, and by placing a small thin pillow beneath the patient’s head. To avoid any neurologic deterioration, extreme caution must always be exercised in patients with myelopathy and significant canal stenosis during the positioning and intubation of the patient. Consideration should be given to performing an awake, fiberoptic intubation. After adequate general anesthesia, the arms are well padded and tucked at the patient’s side using arm sleds or a sheet placed under the patient’s torso. In addition, the shoulders are depressed caudally and held into place with adhesive tape to assist with proper visualization during the exposure and interpretation of intraoperative lateral radiographs. Excessive traction must be avoided because it may result in a traction injury to the brachial plexus.

The anterior cervical spine may be approached from either the right or the left side. This decision must be made by the individual surgeon and may be influenced by his or her training. Proponents of the right-sided approach suggest that it is technically easier for a right-handed surgeon. Proponents of the left-sided approach typically value the more consistent course of the left recurrent laryngeal nerve. The surgeon must have a comprehensive understanding of the anatomy of the region regardless of the side of the approach.

A transverse incision may be used for procedures involving one or two levels; an oblique, longitudinal incision along the course of the medial border of the sternocleidomastoid muscle may be needed for procedures involving three or more vertebral segments. The location of the transverse incision depends on what levels are involved in the surgical procedure (Fig. 41–1). Palpable landmarks of the anterior neck provide guidance as to the appropriate location for this incision. The C1-2 interspace is located at the angle of the mandible, whereas the hyoid bone usually lies anterior to the C3 level. The superior portion of the thyroid cartilage marks the position of the C4-5 interspace. The C6 level can be identified by palpation of the cricoid cartilage or by palpation of the carotid tubercle, which projects anteriorly from the transverse process of the C6 vertebral segment. Care should be taken to orient the transverse incision along the skin creases of the anterior neck to leave a cosmetic-appearing scar.

FIGURE 41–1 Palpable bony landmarks and their relationship to cervical spine.

(From Hoppenfeld S: Physical Examination of the Spine and Extremities. Norwalk, CT, Appleton & Lange, 1976, p 110.)

The skin and subcutaneous tissues are incised sharply with a scalpel. The platysma is divided in line with the skin incision with the transverse and longitudinal incisions. Superficial veins, especially the external jugular vein and its branches, must be protected or ligated if they cross the planes of dissection. Next, the medial border of the sternocleidomastoid is identified. Dissection is carried out through the superficial layers of the investing deep cervical fascia between the sternocleidomastoid and the medial visceral muscle column (Fig. 41–2).

FIGURE 41–2 Plane of surgical dissection through layers of deep cervical fascia medial to carotid sheath and lateral to trachea and esophagus.

(From Silber JS, Albert TS: Anterior and anterolateral, mid and lower cervical spine approaches: Transverse and longitudinal [C3 to C7]. In Herkowitz HN [ed]: The Cervical Spine Surgery Atlas, 2nd ed. Philadelphia, Lippincott Williams & Wilkins, 2004, p 91.)

After this plane is developed, the location of the carotid sheath must be identified by direct palpation. Blunt dissection is performed through the middle layers of the deep cervical fascia, between the esophagus and the carotid sheath. The surgeon must always be mindful of the location of the carotid sheath. With two blunt hand-held retractors in place, the prevertebral fascia is visualized directly anterior to the vertebral column. This fascia is incised sharply with scissors and bluntly dissected off of the anterior portion of the vertebral bodies using a dissector. The medial borders of the longus colli muscles are identified just off of the midline. A spinal needle or other locating device is inserted into a disc space to identify the level definitively. With larger patients, the spinal needle may need to be placed cephalad to the operative levels to assist with visualization on the lateral intraoperative radiograph. After the radiograph is completed, the localized disc space is permanently marked with electrocautery or a surgical marking pen.

When the operative levels have been identified, exposure of the disc spaces begins by releasing the medial border of the longus colli muscle starting at the disc space. Blunt, hand-held retractors are placed subperiosteally under the muscle bellies of the longus colli and used to retract these muscles laterally. Inadvertent dissection on the ventral surface of the longus colli muscles may result in injury to the sympathetic chain and a Horner syndrome. Continued lateral retraction and dissection of the longus colli muscles at each of the operative disc spaces exposes the most medial portions of the cranially projecting uncinate processes. The up-sloping portions of the uncinate processes serve as the most lateral extent of the dissection on both sides of the spine. Dissection lateral to the uncinate process can lead to injury to the vertebral artery as it ascends in the transverse foramen of the cervical vertebrae. Careful review of preoperative MRI or computed tomography (CT) myelography reveals any anomalies of the vertebral arteries. Exposure in the cranial-caudal direction can be enhanced by the use of blunt self-retaining retractors.

Discectomies are performed at the levels above and below the planned corpectomy. A scalpel blade is used to incise the anulus, and a combination of pituitary rongeurs and small curets is used to remove all disc material completely down to the level of the posterior longitudinal ligament. Identification of the midline throughout the discectomy and corpectomy is paramount. A Penfield elevator may be used to identify the transverse processes at the cranial aspect of the individual vertebral bodies. The junction of the transverse process and the vertebral body marks the lateral cortical wall of the vertebral body. The vertebral artery lies just lateral to this wall of cortical bone. Identification of these landmarks guides the actual bony resection and assists in keeping the trough centered and symmetrical.

A Leksell rongeur is used to create the most ventral portion of the corpectomy trough (Fig. 41–3). The use of a motorized bur without the creation of this initial trough is dangerous and could result in injury to the carotid vessels or the esophagus if the bur “jumps” off of the anterior vertebral body cortex. After the anterior cortex of the vertebral bodies has been removed, a 5-mm power bur is used to widen and deepen the through. Starting and stopping the bur within the bony trough avoids potential injury to the surrounding soft tissue structures. Resection is continued posteriorly until the posterior cortex of the vertebral bodies is encountered. Bleeding from the cancellous bone can be controlled with bone wax. A smaller bur may be used to thin the posterior cortex and to remove the osteophytes at the uncovertebral joints. The remaining thin shell of the posterior cortex can be removed with small angled curets by pulling the bone away from the posterior longitudinal ligament and the dura (Fig. 41–4).

FIGURE 41–3 Anterior two thirds of vertebral bodies to be removed can be safely excised using a rongeur after discectomies adjacent to and within area to be decompressed.

(From Whitecloud TS: Multilevel cervical vertebrectomy and stabilization using cortical bone. In Sherk H, Dunn EJ, Eismont FJ, et al [eds]: The Cervical Spine: An Atlas of Surgical Procedures. Philadelphia, JB Lippincott, 1994, p 202.)

FIGURE 41–4 After posterior cortex has been thinned, it can be safely removed with a small angled curet. All force must be directed anteriorly to avoid compression of dura and underlying spinal cord.

(Adapted from Smith MD: Cervical spondylosis. In Birdwell KH, DeWald RL [eds]: The Textbook of Spinal Surgery, 2nd ed. Philadelphia, Lippincott-Raven, 1997, p 1411.)

The posterior longitudinal ligament can be carefully removed with a nerve hook and a small Kerrison rongeur. One should use caution in the presence of ossification of the posterior longitudinal ligament (OPLL) because the ligament may be incorporated into the dura.⁴⁶ Removal of the ligament should not be attempted in this situation because it may create a dural tear. The cartilage endplates at the superior and inferior extent of the corpectomy are removed with the use of a curet or a bur. A safe and adequate decompression of the spinal cord requires approximately a 15- to 19-mm wide trough.^47,48 This trough can be measured directly with a caliper or estimated by comparing the width of the trough with the width of the surgeon’s finger. Foraminotomies may be performed at each of the decompressed levels if the patient’s pathology and symptoms warrant foraminal decompression.

After complete decompression of the neural elements has been accomplished, the endplates are prepared for insertion of the graft. A bone tamp and mallet are used to tap the graft gently in the appropriate position while traction is being applied to the head (Fig. 41–5). Heller¹ recommended a maximum of 25 lb of traction. Care must be taken to countersink the graft 1 to 2 mm behind the anterior cortex without forcing it into the canal posteriorly. A small nerve hook can be passed lateral to the graft in the trough to assess the space between the posterior longitudinal ligament and the posterior surface of the graft. The traction is released, and graft stability is assessed by manual flexion and rotation of the head by the anesthesiologist. If an anterior cervical plate is being used, it is placed at this time. The plate helps to prevent anterior migration of the graft and may provide graft compression to improve healing potential.

FIGURE 41–5 Graft is seated into cranial end of corpectomy defect. Traction is applied to the patient’s head, and distal end of graft is tamped into caudal end with a tamp. A Kocher clamp is used to hold graft to prevent displacement of graft into spinal canal while it is being impacted into place.

(Adapted from Smith MD: Cervical spondylosis. In Birdwell KH, DeWald RL [eds]: The Textbook of Spinal Surgery, 2nd ed. Philadelphia, Lippincott-Raven, 1997, p 1411.)

The wound is closed in layers over a suction drain, which is left in place for 1 to 2 days postoperatively to minimize the risk of postoperative airway compromise secondary to hematoma formation. The patient is placed into a cervical collar for additional immobilization. The choice of collar often depends on surgeon preference, number of levels fused, and presence or absence of instrumentation. After multilevel corpectomies with prolonged retractor times, many surgeons elect to keep the patient intubated overnight to minimize the possibility of respiratory distress from postoperative edema and swelling.⁴⁹

Anterior Cervical Discectomy and Fusion

The use of anterior cervical decompression and fusion for the treatment of ventral pathology has been consistently reported to be a safe and effective procedure.^50,51 Indications for ACDF in the treatment of cervical myelopathy include compression from any disk herniation or spondylotic degeneration that is confined to the disk level.

Although the removal of osteophytes has been reported to improve recovery in patients with CSM, controversy exists regarding the need for an osteophytectomy.⁵² Robinson and colleagues⁵³ and Connolly and colleagues⁵⁴ reported complete remodeling and resorption of osteophytes in the presence of a solid fusion. Bohlman²² reported excellent results in 16 of 17 patients who underwent ACDF and who were treated without any osteophyte removal. No patients experienced a loss of function, and all but one of the patients had improvement in functional status. Conversely, Stevens and colleagues⁵⁵ reviewed CT myelograms of 53 patients who underwent ACDF and reported that at 12 years of follow-up no patients showed any evidence of osteophyte resorption. These authors recommended the systematic removal of all osteophytes to decrease the incidence of persistent postoperative symptoms.

The removal of a thickened ligament or an OPLL may also allow for a more thorough decompression of the spinal cord and may be necessary for the safe exploration and removal of disc fragments that may have become sequestered behind the posterior longitudinal ligament. The surgeon must always be mindful that the removal of the posterior longitudinal ligament increases the risk of developing a cord contusion or a postoperative hematoma.⁵⁶ In the case of an OPLL, care must be exercised during the removal of the ligament because the dura of the spinal cord may also be ossified.⁴⁶

Using ACDF in the treatment of 121 patients with CSM, Zhang and colleagues⁵⁷ observed a 90% improvement in overall neurologic outcome. These authors noted an 85% fusion rate in association with the use of autogenous bone graft, whereas they noted a 50% fusion rate with the use of allograft. They also observed poorer clinical outcomes in patients who developed a pseudarthrosis. With an average number of 3.1 levels fused, Yang and colleagues⁵⁸ reported 214 patients who underwent ACDF for treatment of CSM. At last follow-up, improved functional status was noted in 90% of patients, despite a pseudarthrosis rate of 37%. With a mean follow-up of 10 years, Irvine and Strachan⁵⁹ retrospectively evaluated the long-term results of 46 patients who underwent ACDF for treatment of CSM. At last follow-up, 78% of the 46 patients had improved ability to ambulate, whereas 9% of patients experienced progression of their symptoms.

Certain disadvantages are encountered with every technique. During ACDF, there is decreased visualization of the spinal cord that increases the potential for an incomplete decompression or an inadvertent injury to the cord. ACDF is not suited for the treatment of patients with congenital cervical stenosis because it does not adequately decompress the overall diameter of the spinal canal. In a patient with this condition, a corpectomy and fusion would provide a more suitable option.

Anterior Cervical Corpectomy and Fusion

Subtotal corpectomy refers to the creation of a midline trough in the vertebral body with removal of the adjacent discs. It allows for removal of large osteophytes from the vertebral endplates and for complete decompression of the stenotic spinal canal. Indications for corpectomy in the treatment of cervical myelopathy include OPLL, migrated disc fragment behind the vertebral body beyond the disc space, and kyphotic cervical alignment. Essentially, any compression behind the vertebral body can be seen as an indication to perform a corpectomy.

Bernard and Whitecloud²⁹ evaluated multilevel cervical corpectomy. All 21 patients in this series had decompression of three or more vertebral levels with autograft. At an average of 32 months’ follow-up, these authors noted that 76% of patients had an improvement in functional outcome, and no patients developed pseudarthrosis. One patient in this series experienced graft dislodgment. In a study of 27 patients with CSM treated with multilevel corpectomy and fusion, Jamjoom and colleagues⁶⁰ noted a 96% fusion rate with clinical improvement in 80% to 88% of patients. Although no patients experienced postoperative neurologic deterioration, three patients developed dislodgment of the strut graft.

Emery and colleagues⁵⁰ reviewed their series of patients with CSM treated with different forms of anterior decompression and fusion procedures without the use of instrumentation. Of 108 patients, 58 were treated with ACCF using either fibular or iliac crest autograft without plate fixation. Six graft-related complications occurred in the corpectomy group, four of which occurred in patients who had been previously treated with cervical laminectomy. Of the patients who underwent corpectomy, a nonunion rate of 5% was observed, and the average improvement in Nurick grade ranged from 2.4 preoperatively to 1.2 at final follow-up.

Zdeblick and Bohlman⁶¹ reviewed their results of 14 patients with myelopathy and associated cervical kyphotic malalignment who were treated with anterior corpectomy and fusion using autograft without any plate fixation. The patients were stabilized postoperatively in a halo vest. At follow-up, 12 of the 14 patients had a solid arthrodesis. Nine patients had complete neurologic recovery, and only one patient failed to show any neurologic improvement. Correction of the kyphosis averaged 32 degrees. Zdeblick and Bohlman⁶¹ concluded that myelopathy in the setting of cervical kyphosis can be effectively and safely treated with multilevel corpectomy and strut graft reconstruction without instrumentation.

In 1998, Fessler and colleagues⁶² evaluated the outcomes of 93 patients with CSM who were treated with anterior corpectomy and fusion. Multisegmental involvement was noted in 31 of these patients. Fessler and colleagues⁶² reported that 86% of patients showed improvement in neurologic scores as measured by Nurick grade. In a more recent study published in 2005, Chibbaro and colleagues⁶³ documented their experience in management of CSM with anterior cervical corpectomy. Using autograft and plate fixation, 54 patients received a one-level corpectomy, 11 patients received a two-level corpectomy, and 5 patients received a three-level corpectomy. At 16 weeks’ follow-up, the authors observed no evidence of pseudarthrosis, and they documented a 94% improvement in functional status. Using the modified JOA scale, no patients experienced any decline in neurologic function compared with their preoperative status.

The combination of corpectomy and adjacent discectomy has also been performed as a technique that can be used in treatment of CSM (Fig. 41–6). This method has been described as a hybrid decompression. It is indicated when spinal cord compression is present at a disc space and a vertebral body at different levels. Ashkenazi and colleagues⁶⁴ published their series of 25 patients who underwent a hybrid decompression with anterior plate instrumentation for the treatment of multilevel CSM; 12 patients underwent a one-level corpectomy and adjacent one-level discectomy, and 13 patients underwent a two-level corpectomy with preservation of an intervening vertebral body. The investigators observed a 96% fusion rate, and 24 of the 25 patients reported either a neurologic improvement or an unchanged status.

FIGURE 41–6 A-C, Three-level compression may be treated with three-level discectomy (A), one-level corpectomy and one-level discectomy combined (B), or two-level corpectomy (C). Reconstruction after multilevel discectomy may allow for recreation of normal cervical lordosis.

(C, Courtesy of James D. Kang, MD, Pittsburgh, PA.)

Complications

Although an anterior cervical approach has been shown to be a safe and effective procedure in treating patients with myelopathy, suboptimal outcomes have been reported when this approach is used to treat three or more levels.^65–67 As more levels are involved in the attempted fusion, increased rates of nonunion have been noted in ACDF and ACCF procedures. Numerous studies have shown an inverse relationship between the fusion rate and the number of vertebral segments involved.^68–71 Nonunion is determined by the absence of bridging bone across the graft-host interface on static radiographs and by the presence of motion on dynamic films.

The arthrodesis rate after ACDF without instrumentation was compared in a series by Bohlman and colleagues.⁷² They reported a fusion rate of 89% of 62 patients after a one-level fusion, 73% of 42 patients after a two-level fusion, and 73% of 11 patients after a three-level fusion. An unsuccessful four-level ACDF was performed in one patient in their series. Bohlman and colleagues⁷² attributed the lower fusion rate to increased number of fusion interfaces and increased motion as more levels are involved. Emery and colleagues⁵⁰ reviewed their series of patients with CSM treated with different forms of anterior decompression and fusion procedures without the use of instrumentation. Of 108 patients, 45 were treated with anterior discectomy and fusion; the investigators reported 13 patients in the discectomy and fusion cohort who developed a nonunion. Similar to the observations made by Bohlman and colleagues,⁷² Emery and colleagues⁵⁰ observed increased rates of nonunion as the numbers of fused levels increased. Better clinical outcomes were noted in patients who went on to a solid fusion.

Vaccaro and colleagues⁶⁶ reported a series of patients who underwent an instrumented anterior corpectomy and fusion using a strut graft. They observed a 9% nonunion rate in two-level corpectomies, which increased to a 50% nonunion rate in three-level corpectomies. Sasso and colleagues⁷³ noted a similar trend in increasing nonunion rates in their series of patients who underwent ACCF. They reported a 6% failure rate in two-level corpectomies that increased to a 71% failure rate when three levels were involved. When compared with multiple discectomy and fusion, Hilibrand and colleagues⁷⁴ observed better fusion rates in patients treated with corpectomy and strut grafting. In their series, all reconstructions were performed with autograft and without anterior cervical plates. A 93% fusion rate was observed in the corpectomy cohort, whereas only a 66% fusion rate was noted in the ACDF cohort.

Although it is a more technically demanding surgery, corpectomy with fusion relies on an arthrodesis to occur at only two interfaces. Because a fusion is required between only two levels, the chance of developing a pseudarthrosis is decreased.⁶¹ Swank and colleagues⁷⁵ reported 38 patients who were treated with multilevel ACDF and 26 patients who were treated with subtotal corpectomy. Allograft and anterior plate fixation were used in all patients. Among patients with two-level disease, the patients treated with two-level discectomy had a 64% fusion rate, whereas the patients treated with one-level corpectomy had a 90% fusion rate. Similarly, among patients with three-level disease, the patients treated with three-level ACDF had a fusion rate of 46%, whereas the patients treated with two-level corpectomy had a fusion rate of 56%.

In noninstrumented ACCF, immediate stability of the graft depends on the graft-host bone interface. The sculpting of the graft and the vertebral endplates and the impaction of the graft into place while the head is in traction contribute to the initial stability of the graft.^29,76–78 Graft migration most commonly occurs at the inferior end of the construct. Wang and colleagues⁷⁹ reported their findings in a retrospective review of 249 patients who underwent corpectomy and fusion with the use of autograft and no plate fixation over a 25-year period. Graft migration was observed in 16 of 249 patients. None of the 16 patients experienced any respiratory or neurologic complications as a result of the graft displacement. Wang and colleagues⁷⁹ noted an increased rate of this complication occurring in patients undergoing longer fusions and in patients whose fusions ended at the C7 vertebral body.

To increase immediate postoperative stability, anterior plate instrumentation may be added. The addition of anterior plate fixation has been shown to improve the rate of fusion, reduce postoperative immobilization, reduce the incidence of segmental kyphosis, and reduce the prevalence of graft-related complications.^54,80,81 The plate may act as a buttress to block graft migration physically.^82–84 If plate fixation is performed, it is recommended that a minimum distance of 5 mm be maintained between the plate and the unaffected disc segment to minimize the potential of developing adjacent level disc ossification.⁸⁵

The use of anterior instrumentation does not absolutely prevent graft complications. Sasso and colleagues⁷³ noted that catastrophic construct failure occurred in five of seven patients who underwent a three-level corpectomy with autogenous iliac crest bone graft and anterior cervical locked plating. Most failures occurred with the graft cavitating into the vertebral body at the inferior end of the construct, which caused the graft to displace anteriorly. The biomechanical effects of long anterior cervical plates after three-level corpectomy and strut graft reconstruction were evaluated in two studies.^86,87 The authors of the studies believed that the failures typically seen with instrumented multilevel corpectomies treated with long anterior cervical plates were the result of pistoning of the inferior aspect of the graft. Vaccaro and colleagues⁶⁶ noted a 50% failure rate of the patients in their series who underwent three-level ACCF with anterior plate fixation. Based on their findings, they recommended the addition of a posterior stabilizing procedure to supplement multilevel ACCF.

Delayed fractures have been reported through fibular strut grafts after multilevel ACCF.^88,89 Some authors support the use of a titanium cage to achieve immediate construct rigidity.^90,91 The use of this construct may avoid the potential complication of late strut graft fracture. These cages are packed with bone and can be used in combination with anterior instrumentation after ACCF. Excellent fusion rates have been reported using this technique; however, caution must be exercised with the use of this construct in osteoporotic bone.^90,91

Although graft complications have been reported extensively in the literature, they are not the only problem. Injury to the vertebral arteries has also been reported during ACCF procedures.^61,74 In patients who underwent corpectomy, Eleraky and colleagues⁹² reported a prevalence of vertebral artery injury of 2% in 185 patients. It is imperative that a surgeon maintain a midline orientation during an anterior decompression to avoid any violation of the lateral wall and subsequent injury to the vertebral artery. This orientation is particularly important in patients who have tortuosity of the vertebral artery.⁹³ Anatomic landmarks that have been discussed include the medial margin of the uncovertebral joint, medial margin of the longus colli muscle, and natural curve of the vertebral endplate. Studies have shown that by leaving a margin of approximately 5 mm to the medial border of the foramen transversarium, a total central decompression of approximately 15 mm at C3 and 19 mm at C6 can be performed safely.^47,48

Individual patient characteristics or comorbidities may influence the surgeon’s decision to supplement an anterior decompression with allograft or autograft. Traditionally, the use of iliac crest autograft has been the “gold standard” in one-level and two-level anterior decompression and fusion procedures. For longer fusions, most surgeons prefer to use a structural fibula strut graft. The morbidity associated with the graft harvest is associated with an increased complication rate. Specific iliac crest donor site complications include neuroma formation, iliac crest fracture, cosmetic deformity, persistent pain, and infection.^94–96 In addition to infection, harvesting autogenous fibula has been associated with injury to the peroneal nerve, contracture of the flexor hallucis longus and flexor digitorum longus tendons, development of lower extremity deep venous thrombosis, stress fractures of the tibia, and chronic ankle pain.^97–100

To avoid the complications associated with the harvest of autograft, some authors advocate the use of allograft. The use of allograft in multilevel fusion has historically been associated with higher rates of nonunion.¹⁰¹ In a retrospective study of 126 multilevel discectomy and corpectomy cases, Fernyhough and colleagues¹⁰² compared the fusion rates between fibula strut autograft and fibula strut allograft. They noted a 27% nonunion rate in the autograft group versus a 41% nonunion rate in the allograft group. Conversely, MacDonald and colleagues¹⁰³ reported a 97% fusion rate in their series of patients who underwent a decompressive corpectomy with the use of fibula strut allograft. More recently, Samartzis and colleagues¹⁰⁴ published a series that showed equivalent rates of fusion between allograft and autograft in patients who underwent multilevel ACDF using cervical plates and current surgical techniques.

Adjacent segment degeneration in previously fused segments in the cervical spine has been reported in the literature. Based on a long-term follow-up study of 374 patients who underwent anterior cervical fusion, Hilibrand and colleagues¹⁰⁵ reported a 25% risk of development of adjacent segment disease within 10 years. In their published series, these authors noted that the C5-6 and C6-7 levels were the most frequently involved. They reported that the risk of developing adjacent segment disease was more likely a manifestation of the natural aging process rather than a consequence of the fusion. More recently, Rao and colleagues¹⁰⁶ reported that performing ACDF with plate fixation does not lead to the development of adjacent segment disease.

Postoperative radiculopathy is a well-recognized phenomenon that occurs after posterior decompression of the spinal cord.^23,107,108 This complication has also been reported in the treatment of CSM in anterior decompressive procedures. Saunders and colleagues⁶⁵ reported an incidence of C5 palsy of 20% in their series of 96 patients who underwent corpectomy to treat CSM. They recommended limiting the ventral trough to 14 or 15 mm. Yonenobu and colleagues¹⁰⁸ reported a prevalence of postoperative radiculopathy of 3.9% of 204 patients after anterior procedures. A proposed etiology for the development of the palsy is secondary to an impingement of the ventral aspect of the spinal cord against the edges of the corpectomy trough. The removal of osteophytes can increase the risk of inadvertent injury to the spinal cord itself. Yonenobu and colleagues¹⁰⁹ reported a single patient in their series of 75 patients who sustained an injury to the cord after the resection of posterior osteophytes during ACDF. Subsequently, these authors recommended that corpectomy be considered in patients with posterior osteophytes that are substantial enough to require removal.

Injuries to the soft tissue structures can occur during an anterior approach to the cervical spine. Swallowing difficulties are the most common postoperative problems encountered. Although a frequent complaint, the dysphagia most commonly follows a transient course.¹¹⁰ This problem seems to be related to esophageal dysmotility that can result from excessive retraction. Bazaz and colleagues¹¹⁰ reported a 50% prevalence of dysphagia at 1-month follow-up that was more frequently noted when multiple levels were involved in the fusion. At 1-year follow-up, of the 197 patients involved in this study, only 12.5% continued to complain of symptoms. Instrumentation has not been shown to increase the risk of dysphagia.^110,111 Esophageal injury can occur secondary to excessive retraction, electrocautery, or perforation from sharp instruments. The incidence of esophageal perforation has been reported by Newhouse and colleagues¹¹² to be approximately 0.25%.

Injuries to the recurrent laryngeal nerve have been reported among complications related to the dissection and mobilization of soft tissues in the neck. In a series of 650 patients who underwent an anterior cervical procedure, Frempong-Boadu and colleagues¹¹³ reported a 2% prevalence of injury to the recurrent laryngeal nerve. In contrast, Yue and colleagues¹¹⁴ reported a prevalence of recurrent laryngeal nerve injury of 11% in 85 patients. Injury to the laryngeal nerve is most commonly attributable to compression within the endolarynx.¹¹⁵ Apfelbaum and colleagues¹¹⁵ observed a significant decrease in the occurrence rate of this complication from 6.8% to 1.7% by deflating and reinflating the endotracheal cuff after the retractors were placed. After a review of the literature, Baron and colleagues¹¹⁶ reported an overall incidence of 4.9% for hoarseness and 1.4% for unilateral vocal cord paralysis. Other causes of nerve injury include direct trauma or an indirect pressure or stretch injury induced by a hematoma or by prolonged retractor placement.

Beutler and colleagues¹¹⁷ compared the rate of injury to the recurrent laryngeal nerve during right-sided and left-sided approaches. Although they found no difference in the rate of postoperative dysphonia between the two sides, they did observe a generally higher complication rate in the setting of revision surgery. For this reason, some surgeons advocate approaching the spine from the opposite side in a revision setting to avoid the frustration and dangers of operating through scar tissue. If a revision surgery is contemplated, a formal evaluation of vocal cord function must be done if the surgeon intends to approach the spine from the opposite side. In a situation in which the original surgery resulted in permanent unilateral vocal cord paralysis, an opposite-sided approach would be inadvisable because the potential for bilateral vocal cord paralysis would be catastrophic.

Prolonged retraction can also cause injury to the cervical sympathetic ganglion resulting in Horner syndrome, characterized by ipsilateral ptosis, miosis, and anhidrosis. This complication can also be seen in revision surgeries or in operations involving the cervicothoracic junction. Bertalanffy and Eggert⁵⁶ reported an incidence of 1.1% in their series of 450 patients who underwent an anterior cervical fusion. To prevent this complication, the longus colli muscles should be dissected of the anterior vertebral body in a subperiosteal fashion, and retractors should be placed deep to the longus colli muscles.

Indications for a Posterior Approach

Before the 1950s, the operative treatment of degenerative cervical disorders primarily occurred through a posterior approach. The posterior approach to the cervical spine has continued to be a safe and effective treatment option in the surgical management of CSM. Indications for a posterior approach to the cervical spine include congenital cervical stenosis, multilevel cervical spondylosis, OPLL, ossification of the yellow ligament, and posterior compression caused by infolding of the ligamentum flavum.^{37,45,118,119} A posterior approach to the cervical spine relieves spinal cord compression through two distinct mechanisms: direct and indirect decompression. When the pathology causing the myelopathy is primarily due to ventral structures, posterior procedures are indirect methods of decompression. With indirect decompression, expansion of the canal allows the spinal cord to shift posteriorly away from the anterior impinging structures. In situations in which the myelopathy is secondary to a congenital stenosis or a redundant ligamentum flavum, the decompressive effect of a posterior procedure is more direct. The removal or relocation of the posterior impinging structures acts to decompress the spinal cord and is a form of direct decompression. Laminectomy and laminoplasty are two techniques of decompressing the cervical spine from a posterior approach.

For an effective indirect spinal cord decompression to occur, certain prerequisites must exist. Posterior procedures are primarily indicated in the presence of a neutral or lordotic sagittal alignment to allow for the posterior translation of the spinal cord.¹²⁰ As spondylosis progresses, there is a general trend toward loss of lordosis.¹²¹ In a patient with a kyphotic cervical spine, the sagittal alignment of the bony elements does not allow for the posterior translation of the spinal cord (Fig. 41–7). Even after a posterior decompression, the cord remains draped over the anterior compressive pathology. A minimal lordotic curvature of 10 degrees should be present if posterior decompression is considered.¹²² Studies have shown that measured from C2 to C7, the average lordotic curvature in a normal cervical spine is 14.4 degrees.¹²³

FIGURE 41–7 Influence of cervical sagittal alignment on decompressive effect of laminoplasty. A, Multilevel cord compression arising from spondylosis of C3-7 in the presence of lordotic cervical alignment. B, Spinal canal expansion after laminoplasty with dorsal shift of spinal cord away from anterior impinging structures. C, Multilevel cord compression and kyphotic cervical alignment. D, Continued spinal cord impingement after laminoplasty. The presence of kyphotic alignment compromises indirect decompressive effect of laminoplasty.

Yamazaki and colleagues¹²⁴ observed continued ventral compression after posterior decompression in patients with anterior canal encroachment greater than 7 mm and with lordotic sagittal alignments of less than 10 degrees. When a posterior decompression is performed in patients with a kyphotic cervical alignment, modest improvements in neurologic outcome can be expected. The recovery achieved from a decompression in the presence of a cervical kyphosis tends to be inferior, however, when compared with a posterior decompression that is performed in the presence of a cervical lordosis.^37,125 These findings were echoed by Satomi and colleagues,¹²⁵ who found that patients with maintenance of preoperative lordosis exhibited a superior improvement in JOA score compared with patients in whom the lordosis decreased by 10 degrees or more.

In patients who underwent decompressive laminoplasty, Sodeyama and colleagues⁴⁵ showed that patients with lordotic spines had the greatest postoperative posterior translation of the spinal cord with an average shift of 3.1 mm. Patients who had a neutral alignment showed a peak posterior shift of less than 3 mm, and patients who had a kyphotic cervical alignment showed a peak posterior shift of less than 2 mm. In a study evaluating 114 patients with CSM after laminoplasty, Suda and colleagues³⁷ observed that a preoperative local kyphosis exceeding 13 degrees provided patients with the worst prognosis for neurologic recovery. They concluded that cervical kyphosis should be regarded as a relative contraindication for a posterior decompression.

As a second prerequisite, indirect spinal cord decompression also requires a sufficient length of canal expansion. Decompression of the posterior structures at levels beyond areas of focal stenosis may allow for greater translation of the cord. The degree of canal expansion that is achieved via a posterior approach has been shown to correlate with the success of postoperative recovery.^126–128 A statistically significant difference in recovery rate was reported by Hirabayashi and colleagues¹²⁶ when the anteroposterior diameter of the spinal canal increased greater than 5 mm versus an increase of less than 2 mm. Ishida and colleagues¹²⁷ observed better recovery rates in patients in whom posterior decompression increased the sagittal diameter of the canal to 15 mm or greater. Kohno and colleagues¹²⁸ showed that expansion of the anteroposterior canal diameter to 12.8 mm correlated with a good postoperative recovery after laminoplasty. Shaffrey and colleagues¹²⁹ reported an overall average increase in the spinal canal cross-sectional area of 55% after posterior decompression with an 88% increase at the most compressed level.

When adequately decompressed, the spinal cord has been reported to change in morphology from a flattened to a more natural oval shape. In a CT myelography study, Aita and colleagues¹²⁰ described changes in spinal cord morphology in 38 patients after open-door laminoplasty. Postoperatively, the largest increase in mean spinal cord cross-sectional area was improved by 12%. In addition, the mean sagittal cord diameter was enlarged by 1 mm, and the mean coronal diameter was decreased by 1 mm.

The longitudinal height of the cervical spine as a prognostic indicator for neurologic recovery has also been evaluated. Chiba and colleagues¹³⁰ noted that after extensive open-door laminoplasty, patients with CSM were more likely to have improved neurologic results compared with patients with OPLL. They observed a greater degree of preoperative cervical spine shortening owing to disc degeneration in patients with CSM. These authors attributed the improved recovery rate in these patients to the redundancy within the spinal cord after decompression.

Laminectomy and Laminectomy and Fusion

Laminectomy is indicated for multilevel decompression in elderly myelopathic patients with multiple medical comorbidities and preserved cervical lordosis. Decompressive laminectomy is typically performed at the junctions of the lateral masses and the laminae. If a patient also has concurrent radicular symptoms, a concomitant foraminotomy may be performed to decompress the associated foraminal stenosis. If a foraminotomy is performed, care must be taken not to remove much of the facet. Progressive removal of greater increments of the facet joint is correlated with greater degrees of instability.¹²³ To preserve stability, it is crucial to resect no more than 25% of the facet joint.¹³¹ In addition, any level with radiographic evidence of stenosis should be included in the decompression. Kato and colleagues¹³² observed increased rates of recurrent symptoms resulting from progression of disease at adjacent segments not involved in the decompression. Kaptain and colleagues¹³³ reported no added benefit in limiting the number of segments involved in the decompression because it did not influence the development of postlaminectomy kyphosis or instability.

Circumstances such as iatrogenic instability, flexible kyphosis, or focal instability require supplemental posterior cervical instrumentation. The goal of any fixation system is to provide structural support for a bony fusion mass to mature. The use of posterior instrumentation has been shown to maintain lordosis effectively after a posterior cervical laminectomy and fusion.^134,135 Before the introduction of lateral mass screws, wiring techniques were the mainstay of treatment when a fusion was performed. The wire would be passed between neighboring facets or tied to bone grafts or metallic rods. With these techniques, acceptable fusion rates were obtained.^136,137 With the introduction of lateral mass screws, wiring techniques have largely fallen out of favor.

Biomechanically, lateral mass screws have been proven to be a superior technique compared with wiring procedures. They produce a more rigid construct and show a better fusion potential.¹³⁸ The early screw-plate systems were difficult to use and very inflexible because they could not adapt well to variations in patient anatomy. The lack of versatility these early designs offered has been overcome with the evolution of multiaxial screw and rod constructs.¹³⁹ The newer systems are constrained and allow for more rigid fixation. Similarly, these new systems accommodate variations in the cervical anatomy without having to perform excessive rod contouring or having to compromise screw positioning.

A review of the literature reveals various lateral mass screw insertion techniques.^140–143 The biomechanical characteristics and anatomic relationships of each of these techniques have been studied.^144,145 Despite the various techniques described, clinically none have shown any difference in complication rate.¹⁴⁶ In a cadaveric study, Seybold and colleagues¹⁴⁷ showed no clear biomechanical advantage with bicortical placement of lateral mass screws versus unicortical placement of lateral mass screws. They showed an increased incidence of nerve root impingement and potential vertebral artery injury with the use of bicortical screws. These investigators reported no injuries using unicortical screws. Ultimately, an appropriate understanding and knowledge of anatomic relationships is needed when placing these screws.

Techniques for pedicle screw placement have also been described in the literature.¹⁴⁸ Pedicle screws have been shown to have a higher pullout strength compared with lateral mass screws.¹⁴⁹ Because of the small size and morphologic variation in the cervical pedicle, however, there is greater potential for injury with pedicle screw placement.¹⁵⁰ Pedicle screw placement is usually reserved for levels with larger pedicles, such as the C7 vertebra, or when crossing the cervicothoracic junction. The technique for pedicle screw placement is not discussed in this chapter.

Technique

As with any patient with myelopathy, care should be taken to avoid any extremes of neck motion during intubation. Mean arterial pressure should be monitored during positioning of the patient, and hypotension should be avoided throughout the entire operative procedure. A Mayfield tong or three-pin head holder is affixed to the patient’s head, and the patient is positioned prone on the operating table. The head should be fixed in neutral or in slight extension. The trunk should be supported by a four-poster frame or by padded chest rolls. If a padded headrest with a laminectomy frame is used, care must be taken to avoid any force on the eyes because this may increase intraocular pressure and create an ischemic optic neuropathy resulting in visual loss.¹⁵¹ All bony prominences should be padded. The arms should be tucked in and secured at the patient’s side using arm sleds or sheets under the patient’s torso. Legs should be flexed at the knees, and the patient should be secured to the table using the appropriate straps. The table should be positioned in a reverse Trendelenburg position to reduce any venous congestion. After the patient is positioned, the suboccipital region is shaved, and the surgical field is sterilely prepared and draped.

The spinous processes of C2 and C7 are usually palpable landmarks that are easy to distinguish and can be used to guide in planning of the surgical incision. A midline cervical incision is drawn out, and the skin is infiltrated with local anesthetic with epinephrine to aid in hemostasis. An incision through the skin is made using sharp dissection. The midline incision through the deep tissues is continued, maintaining strict hemostasis at all times with the use of monopolar electrocautery. Next, the ligamentum nuchae is divided, and the dissection is continued with a split through the splenius capitus fascia. It is imperative that care be taken to perform the dissection in the midline to prevent blood loss or any unnecessary intramuscular embarrassment.

Dissection is carried subperiosteally exposing the spinous processes and laminae of the appropriately selected cervical levels. Care should be exercised not to dissect the muscular attachments of C2 because its removal has been shown to create instability in the upper cervical spine.¹⁵² The extent of lateral dissection is minimized to just beyond the medial aspect of the facet joint, with care taken not to violate the facet capsules. A self-retainer is placed to mobilize the paraspinal musculature free from the surgical field. To avoid excessive damage to the paraspinal muscles, retractors should be intermittently released and repositioned. If an instrumentation and fusion is indicated, the exposure for lateral mass fixation requires the subperiosteal soft tissue dissection to extend to the far lateral margin of the facet. Care must be taken to avoid any compromise to the facet capsule of the most cranial and caudal aspects of the intended fusion.

It is essential that the landmarks of the lateral mass be clearly identified to ensure accurate placement of the screws. The cranial and caudal boundaries of the lateral mass are defined by the adjacent facet joints, and the medial boundary is defined by the lamina-facet junction. After adequate exposure of the lateral masses is achieved, entry sites for the lateral mass screws are marked using a high-speed bur. Screws are placed depending on the surgeon’s choice of technique. After the screws are adequately placed, the lamina can be resected. Laminectomies are performed after the insertion of the lateral mass screws to protect the cord with its neural elements. Care must be taken to preserve the bone for use as local autograft. Removal of the spinous processes with preservation of a small remnant facilitates visualization and removal of the laminae. Bilateral trough laminotomies are created with the aid of a bur at the lamina-facet junction just medial to the facet complex (Fig. 41–8). During the laminotomies, 1 to 2 mm of thinned ventral bony cortex or hypertrophied yellow ligament dorsal to the underlying thecal sac is preserved.

FIGURE 41–8 Bilateral trough laminotomies are created at lamina-facet junction medial to facet complex.

(From Komotar RJ, Mocco J, Kaiser MG: Surgical management of cervical myelopathy: Indications and techniques for laminectomy and fusion. Spine J 6:258S, 2006.)

Removal of the ventral cortex is accomplished with a low-speed 4-mm bur. The intraspinous ligament at the most cranial and caudal level is divided and resected. Following this, a towel clamp is placed on the most cranial and caudal spinous process, and the lamina and associated ligamentum flavum are gently lifted off the underlying dura (Fig. 41–9). The ligamentum flavum is divided, and the laminae are removed en bloc. Any residual osseous remnants are removed using a Kerrison punch, completing the laminectomy to the lateral edge of the thecal sac. In an extremely stenotic canal with no epidural fat and nearly no yellow ligament, there may be dense adhesions to the underlying dura. No instrument should be introduced in or near the midline to avoid cord contusion. In a patient with severe stenosis, the exclusive use of a high-speed bur may be advisable to minimize any further compression that may be caused by the footplate of a Kerrison punch.

FIGURE 41–9 Towel clamp is placed on most cranial and caudal spinous process. Lamina and associated ligamentum flavum are gently lifted en bloc with care taken not to lever one end into spinal cord.

(From Komotar RJ, Mocco J, Kaiser MG: Surgical management of cervical myelopathy: Indications and techniques for laminectomy and fusion. Spine J 6:259S, 2006.)

Undercutting and removal of the cephalad and caudal soft tissues is accomplished to avoid further extension of cord compression. A dome laminectomy under the surface of the C2 lamina may also be performed if further decompression is necessary. Foraminal decompression may be performed at this time if concomitant foraminal stenosis is noted. The visible expansion of the dural sac after removal of the laminae suggests adequate canal expansion. The expansion of the dural sac often adequately tamponades the epidural venous plexus as long as no cerebrospinal fluid leak has occurred. If lateral mass screws have been placed, malleable rods are cut and contoured and placed onto the screw construct. The locking mechanism is engaged securing the screw and rod construct. The facet joints and lateral masses are decorticated, and the autograft bone is impacted across the posterolateral aspect of the spine and into the facet joints.

If epidural venous bleeding is encountered, absorbable gelatin sponge (Gelfoam) with collagen strips may be placed in the lateral gutters over the thecal sac to aid in hemostasis. A drain may also be used if hemostasis is suboptimal. A routine layered watertight wound closure is performed, and the patient is taken from the operating table and brought to the postoperative recovery unit for continued monitoring. If a posterior fusion with instrumentation is performed, the patient is discharged home with a rigid cervical collar. A rigid cervical collar is worn postoperatively for a varying number of weeks depending on the bone quality, fixation adequacy, and fusion length.

Laminoplasty

Laminoplasty is well suited for management of cervical myelopathy resulting from multilevel stenosis. This procedure was designed to permit extensive decompression through posterior expansion of the canal, while continually maintaining cervical alignment and stability through the preservation of the posterior elements. Laminoplasty avoids the potential complications associated with an attempted fusion, such as donor site morbidity, graft displacement, nonunion, implant malposition or failure, and adjacent segment degeneration. Indications for the use of laminoplasty include congenital stenosis, spondylosis, multilevel disc herniations, and OPLL in a neutral or lordotic cervical spine. Although numerous laminoplasty techniques have been described, all share certain fundamental elements, which include the decompression of a stenotic spinal canal through the expansion of the posterior arch, the conservation of the posterior elements, and the preservation of segmental motion.

The preservation of the posterior elements of the cervical spine provides a biologic covering to the spinal canal and a reattachment site for paraspinal muscles. Pal and Cooper¹⁶⁸ tested load transmission in the anterior and posterior cervical column in cadavers. They showed that 36% of load transmission was through the anterior column, whereas 64% was through the posterior column. These findings highlight the importance of preserving the integrity of the posterior arch and facet complex. In addition, the posterior arch complex serves as an important static factor in the maintenance of cervical lordosis.^169–171 With preservation of the natural static and dynamic restraints of the posterior cervical spine, iatrogenic instability is rarely encountered after laminoplasty.^129,172 Of 171 patients treated with French-door laminoplasty, Shimamura and colleagues¹⁷² reported no cases of segmental instability at 5-year follow-up. Similarly, Kawakami and colleagues¹⁷³ observed no evidence of segmental instability on dynamic radiographs at 3.5-year follow-up in their series of 67 patients who underwent laminoplasty for the treatment of CSM.

The procedure was first described by Oyama and colleagues in 1973.¹⁷⁴ The technique involved a Z-plasty of each thinned lamina. Through the expansion of the modified lamina, a decompression of the spinal cord was performed, and the posterior arch was reconstructed. The original technique used a supplemental arthrodesis through the placement of bone graft over the expanded arch and facets. This technique never gained popularity owing to the prolonged time and painstaking detail required.

Two examples of laminoplasty techniques that are discussed in this chapter include the open-door laminoplasty technique described by Hirabayashi and colleagues¹⁷⁵ and the mid-sagittal laminoplasty or French-door laminoplasty technique described by Kurokawa and colleagues.¹⁷⁶ Comparative studies of these two procedures have failed to show a significant distinction with regard to neurologic outcomes.^177,178 Okada and colleagues¹⁷⁹ published a prospective randomized study comparing the clinical outcomes of open-door laminoplasty versus French-door laminoplasty. Although Okada and colleagues¹⁷⁹ observed higher rates of perioperative complications and added complaints of postoperative axial pain in the open-door laminoplasty group, no significant differences in postoperative JOA scores and recovery rates were noted between the two groups.

Open-Door Laminoplasty

In 1978, Hirabayashi¹⁸⁰ described the open-door laminoplasty technique. With this technique, the canal is expanded at consecutive levels by creating a bone hinge on one side of the canal while detaching the lamina at the opposite side. This technique enables the spinal cord to be adequately decompressed while maintaining stability of the spinal column. Advantages of the open-door procedure include a straightforward operative technique and shorter operative time. Advocates of this technique cite that entering the canal at its lateralmost extent, where spinal cord compression tends to be the least, protects the cord and provides for a greater margin of safety.

Disadvantages associated with the use of the open-door technique have been described. A greater degree of bleeding is encountered with this technique because of the vast plexus of epidural veins in the lateral portion of the cervical spinal canal. Cases have been documented in which the hinge prematurely closed resulting in radiologic and catastrophic neurologic deterioration. This complication was first described by Hirabayashi and colleagues¹⁷⁵ and termed the spring-back phenomenon. To safeguard against this complication, Hirabayashi advocated the use of stay sutures to secure the spinous process to the facet capsule on the hinge side.^175,181

The description of the spring-back phenomenon acted as a catalyst in the design of a newer generation of techniques to maintain a patent canal (Fig. 41–10). Itoh and Tsuji¹⁸² described the use of autograft spinous process bone blocks and stainless steel wiring to maintain canal patency. In 30 patients in their series, these authors reported no significant deterioration in 18 months of follow-up, and they observed an average of 4.1 mm of anteroposterior canal expansion. Various other strut materials have been employed, including contoured ceramic blocks, hydroxyapatite blocks, and allografts.^129,183,184

FIGURE 41–10 Methods of stabilizing expanded posterior arch with open-door laminoplasty. A, Tethering from hinge side with lateral mass suture anchor. B, Propping expanded arch open with contoured strut. C, Rigid intrasegment fixation with a plate and screw system.

The use of rigid internal fixation between the expanded laminae and the lateral masses has also been described as an alternative method of providing immediate stability. Specialized plates have been designed to maintain canal patency and to reduce the probability of hinge closure and restenosis. O’Brien and colleagues¹⁸⁵ showed a significant improvement in sagittal canal diameter with no hardware failure with the use of titanium plates to maintain patency in their series of patients who underwent an open-door laminoplasty. Similarly, through the use of plate fixation and allograft, Shaffrey and colleagues¹²⁹ reported an increase in sagittal canal diameter with an improvement in overall neurologic function in patients in their series. The long-term stability of these constructs is achieved with the eventual healing of the bone on the hinge side or the eventual healing of the host bone-strut graft interface on the open-door side, or both.

French-Door Laminoplasty

In 1978, Kurokawa and colleagues¹⁷⁶ described a spinous process splitting or French-door laminoplasty. This novel technique provided for symmetrical expansion of the stenotic canal by dividing the spinous processes in the midline before hinging open each hemilamina at the lamina–lateral mass junction. Bone or synthetic blocks were placed as a strut to maintain the patency of the hinged hemilaminae (Fig. 41–11). Advocates of the French-door technique reported decreased bleeding because of the paucity of veins encountered in the midline of the canal. They also reported a more symmetrical expansion of the canal compared with the open-door technique.^159,178 The French-door technique can be readily combined with lateral mass or pedicle screw fixation methods if a concurrent posterior fusion is necessary. Typically, the midline sagittal split in the spinous process is created with the use of a bur or a threadwire saw. Using the threadwire saw to perform the sagittal split in the spinous process, Tomita and colleagues¹⁸⁶ reported a mean decrease in operating room time of 63 minutes and a mean blood loss of 70 mL less than if a bur was used. No matter which instrument is used, the surgeon must always be mindful that the introduction of instruments into the central portion of a stenotic canal can increase the danger of creating a catastrophic neurologic injury.^176,186

FIGURE 41–11 Schematic showing spinous process splitting or French-door laminoplasty. Posterior arch is divided longitudinally at midline and expanded symmetrically off of bilateral partial-thickness gutters. Gap between expanded hemilamina is stabilized with interposition of spinous process or allograft strut.

Technique

Laminoplasty has proven to be a safe and reliable technique of decompressing the spinal cord. Although the described methods each have their own technical points, certain operative principles are applicable to all techniques. Patients are positioned prone, on the operative table. The use of a frame or rolls to support the trunk provides for decreased abdominal and chest pressure. Cranial tongs are used to secure the head, and the cervical spine is placed in a neutral or mildly flexed position. To minimize the bleeding from venous congestion and minimize facial or airway edema during surgery, the operative table is placed in 30 degrees of reverse Trendelenburg position.¹⁷⁵ Care must be taken to avoid any pressure on the eyes.

A posterior midline approach is made along the nuchal ligament to the spinous processes. The paraspinal muscles are dissected from the posterior elements. Care is taken to preserve the insertion of the paraspinal muscles to the spinous process of C2. If significant tension of the supraspinous and interspinous ligaments is noted during the expansion of an open-door laminoplasty, a partial osteotomy at the base of the spinous process just below the caudal end of the expanded construct may be performed.¹⁸⁷ The osteotomized spinous process is bent toward the hinge side to decrease the ligamentous tension. With an open-door laminoplasty from C3 to C7, significant ligamentous tension would be alleviated with an incomplete osteotomy through the base of the T1 spinous process. Other authors simply excise the spinous processes and their associated ligaments at the cranial and caudal ends to facilitate the opening of the spinal canal. The trough laminectomies are created at the lamina–lateral mass junction without disruption of the facet joints (Fig. 41–12).

FIGURE 41–12 Schematic images showing technique for open-door laminoplasty. A, Gutters are fashioned at junction between lamina and facet with high-speed bur. Care is taken to preserve ventral cortex on hinge side. B, On side to be opened, completion of gutter is performed with either a micro-Kerrison rongeur or a curet. C and D, Posterior arch of each level is expanded gently using a combination of digital manipulation and elevation with an instrument. When expanded, posterior arch is stabilized in its final position using one of various methods discussed in the text.

Preservation of the facet joints decreases the potential for subsequent instability and minimizes the probability of the facet joint acting as a pain generator. The posterior incision is closed in the usual fashion, described earlier in the laminectomy section. Postoperatively, patients are placed in a soft or rigid collar for comfort, and they are encouraged to begin isometric neck exercises while wearing the collar. Range of motion exercises are started at 2 weeks.

Complications

The most important role of any laminoplasty technique is to permit extensive decompression of the spinal canal through the expansion of the posterior arch. Early in the laminoplasty experience, cases of posterior arch closure were reported (Fig. 41–13).¹⁷⁵ Satomi and colleagues¹²⁵ observed postoperative lamina closure resulting in neurologic deterioration in 4% of 51 patients after open-door laminoplasty. Matsumoto and colleagues¹⁹³ identified the presence of preoperative cervical kyphosis as a significant risk factor for the development of lamina closure. In their series, recovery rates were not influenced by lamina closure; however, patients with lamina closure expressed a greater degree of dissatisfaction with the surgery.

FIGURE 41–13 Axial CT scan after open-door laminoplasty shows displaced strut producing spinal cord compression (arrowhead). Gutter on open-door side is also suboptimal, being too lateral with excessive facet joint resection.

Postoperative motor root palsy is a clinically significant complication of cervical laminoplasty and has received significant attention in the literature.^23,107,108 In most cases, the symptoms are not permanent, and complete to partial recovery can be expected. Obvious causes of neurologic deterioration include displacement of the posterior arch into the canal through strut graft or fixation failure, inadequate decompression, postoperative hematoma, and iatrogenic trauma to the cord. In cases in which no obvious abnormality is identified, the etiology of postoperative motor root palsy remains undetermined. Some authors believe that the mechanism of injury is associated with the tethering of the nerve roots secondary to the posterior migration of the spinal cord.¹⁰⁸ A posterior translation of the spinal cord may stress the ventrally exiting nerve roots, causing mechanical injury and ischemic insult to the nerve root and the adjoining spinal cord parenchyma. A posterior shift of the spinal cord could also produce focal pressure on the nerve root at its entry into the foramen.^194,195

Sasai and colleagues^196,197 suggested that preexisting subclinical C5 root compression is a cause of C5 palsy. They found that preexisting subclinical radiculopathy as determined by abnormal preoperative electrophysiologic studies was predictive for the development of postoperative motor deficits. Sasai and colleagues^196,197 also evaluated the role of prophylactic foraminotomies in decreasing the incidence of motor palsy. Based on their findings, they suggested that postoperative nerve palsy could be avoided if a selective foraminotomy was performed concurrently with the laminoplasty. The clinical presentation of most patients presenting with postoperative motor root palsy is often delayed hours to days after surgery and most commonly involves the C5 nerve root.^107,198 Uematsu and colleagues¹⁰⁷ reported on 20 of 365 patients who underwent laminoplasty and who developed postoperative motor palsy. They noted an 8% incidence of C5 root palsy, and most of their patients presented with symptoms within 1 week of surgery. Most of their patients presented with symptoms within 1 week of surgery. They recommended that expansion of the posterior arch be limited to prevent the development of anterior root tension.

Chiba and colleagues¹⁹⁸ reported 15 patients in their series who developed postoperative segmental motor paralysis after open-door laminoplasty. The symptoms developed an average of 4.6 days postoperatively. All 15 patients showed a high T2 signal intensity in the spinal cord on MRI. Of the 15 patients, 10 were observed to display signal changes that corresponded to the level at the paralyzed segment. At last follow-up, paralysis resolved completely in 11 patients. The remaining patients regained their strength to a motor grade of 4 out of 5. Based on their findings, Chiba and colleagues¹⁹⁸ concluded that impairments in the gray matter of the spinal cord might play an important role in the development of postoperative motor paralysis.

Laminoplasty has not been shown to be an effective procedure in the relief of axial neck pain in patients with myelopathy. In addition, patients who have undergone laminoplasty often complain of discomfort in the neck, the shoulders, and the intrascapular region in the postoperative period. The etiology of neck pain is undetermined, but it has been postulated to result secondary to posterior soft tissue dissection or to the inadvertent disruption of the facet joints.^199,200 Hosono and colleagues²⁰¹ noted that the prevalence of postoperative axial symptoms was significantly higher after laminoplasty than after anterior fusion. Axial symptoms were reported in 60% of patients after laminoplasty and 19% of patients after an anterior fusion. Similarly, in a study by Wada and colleagues²³ comparing subtotal corpectomy and laminoplasty, 15% of patients in the corpectomy group versus 40% of patients in the laminoplasty group complained of axial pain postoperatively. More recently, using a visual analog scale pain questionnaire, Takeuchi and Yasuhiro²⁰² reported the importance of preserving the C7 spinous process and the attached nuchal ligament to reduce postoperative axial symptoms after French-door laminoplasty.

Early in the development of the laminoplasty technique, most authors recommended a concomitant fusion to prevent the development of subsequent instability and recurrent stenosis.^182,203 The practice of applying bone graft to the posterior elements led to a reduced range of motion and a higher rate of postoperative axial discomfort than necessary. Studies over the years have shown that cervical lordosis and segmental stability are maintained after laminoplasty without the need of a simultaneous fusion. Based on these findings, most authors currently recommend that laminoplasty be performed without fusion except in cases of known instability or correction of deformity.^129,186,204

In the evaluation of long-term outcomes of laminoplasty, most authors have reported a significant loss of motion at final follow-up. Edwards and colleagues⁶⁷ reported a 38% loss of C2-7 sagittal motion after laminoplasty. Similarly, Kimura and colleagues²⁰³ noted a postoperative loss of motion of 62% in their series of patients who underwent an open-door laminoplasty. Kawaguchi and colleagues¹⁹¹ observed a similar reduction in range of motion in their long-term series of patients; 61% of patients in their series developed some decrease in range of motion. More recently, Hyun and colleagues²⁰⁵ observed a decrease in range of motion that was time dependent in patients who underwent an open-door laminoplasty. In their series of 23 patients, they noted a gradual decrease in cervical range of motion that continued for 18 months before stabilizing. To diminish the potential for spontaneous facet fusion and to preserve motion, some authors recommend the application of bone wax to the exposed cancellous hinge surfaces.⁶⁷ Many contemporary rehabilitation programs encourage early active range of motion with the goal of reducing postoperative neck stiffness and pain.²⁰⁶

The development of a kyphotic sagittal alignment after laminoplasty has been well reported.^189,191 Fewer reports exist documenting the potential neurologic decline that can accompany a loss of normal cervical lordosis. Over a 10-year follow-up, Iwasaki and colleagues¹⁸⁹ observed that 8% of 59 patients in their series developed a kyphotic sagittal alignment. No patients were reported to have developed any neurologic sequelae. Over the course of 10 years, Kawaguchi and colleagues¹⁹¹ observed 8 patients who developed a kyphotic deformity in a series of 126 patients who underwent laminoplasty for the treatment of CSM. They noted that the recovery rate in these eight patients was poor. Wada and colleagues²³ observed a loss of lordosis that occurred in three patients in their series after laminoplasty. They found no relationship, however, between loss of lordosis and final JOA score. Sasai and colleagues²⁰⁷ observed that diminished lordosis occurred most prominently at C2-3 and C6-7 after C3-7 French-door laminoplasty. In a retrospective analysis of 64 patients 6 years after laminoplasty, Matsunaga and colleagues²⁰⁸ noted that the expansion of C2 led to the development of segmental kyphosis in 20% of patients. In contrast, they noted that the preservation of C2 was protective because only 2% of patients developed a segmental kyphosis.

Postoperative dysfunction of the paraspinal musculature is reported by numerous authors to be a causative agent in the decrease in lordosis noted after laminoplasty.^209,210 Using MRI, Hayashi and colleagues²⁰⁹ found a significant postoperative reduction in the cross-sectional area of paraspinal musculature after laminoplasty. Matsuzaki and colleagues²¹¹ associated the paraspinal muscle dysfunction with the denervation of its nerve supply. They cautioned against dissection farther lateral than the medial third of the facet to prevent injury to the dorsal primary rami of the spinal nerves.