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CERVICAL DEFORMITY
Rationale for Selecting the Appropriate Fusion Technique
(Anterior, Posterior, and 360 Degree)
Susan M. Liew, MD, MB, BS(Hon), and Edward D. Simmons, MD, BSc, CM, MR, FACS, FRCS(C)

IATROGENIC DEFORMITY
Post-Anterior Discectorny Without Fusion

Patients who have multiple-level anterior discectomy without fusion can present with pain and progressive kyphotic deformity and collapse.^{11, 31} Treatment of a patient who presents with kyphotic deformity secondary to anterior discectomy without fusion is usually managed with an anterior approach. The authors prefer the keystone method with anterior iliac crest or fibular graft contoured into a slightly trapezoidal shape and keystoned into position. For a longer construct of three or more disc spaces, an anterior plate may be added. The patient is usually managed with a four-poster or Miami-J brace postoperatively when out of the house or in a car. The authors do not believe that there is any advantage to anterior plating for one-level or two-level fusions. ¹¹ There are several types of plates on the market ^{16, 34} and the authors have found, as have others, that unicortical screws are usually sufficient.¹⁰ The authors' experience with the keystone technique has indicated a high fusion rate with low incidence of graft dislodgment or other complications.²⁴ Others have found similar results with appropriate placement of structural bone graft and careful postoperative care.²⁹ Autogenous bone graft is preferred but has the disadvantages of graft site morbidity.³¹ In the authors' experience, however, this is usually a shortlived problem with most patients having no long-term sequelae from the bone graft donor site .² Other treatment options include bone substitutes, such as hydroxyapatite, titanium mesh cages, and other materials such as carbon fiber.

Postlaminectomy
Postlaminectomy deformity is becoming increasingly uncommon. It is occasionally seen in patients who may have been treated for a cervical tumor or Arnold-Chiari malformation with or without syringomyelia⁴ in childhood or in adults treated for multilevel cervical stenosis. In cases of fully correctable flexible deformities, the authors prefer posterior fusion with lateral mass screw plates and iliac crest graft with a Minerva/SOMI brace. In cases of flexible deformities that are not fully correctable, the authors recommend preoperative correction in a halo-thoracic vest or halo-dependent traction, then posterior fusion as previously, remaining in a halo-thoracic vest. Finally, in cases of rigid deformity, the authors recommend one-stage anterior release and fusion with iliac crest graft, then posterior fusion as previously, remaining in a halo-thoracic vest. Interval traction with two-stage surgery in the rigid deformity may be necessary, although others have had good results with anterior surgery alone ¹⁸ and in combination with anterior plating.³⁶ Other treatment options include anterior strut grafting with autograft or allograft fibula or cage, anterior plating, and posterior lateral mass segmental fixation.

POSTTRAUMATIC DEFORMITY
Most burst fractures with or without neurologic signs are treated with anterior stabilization with or without decompression, so posttraumatic deformity is rare. Posterior fractures in patients with normal bone (contrast to those with ankylosing spondylitis; see later) also generally heal without deformity. A patient with a residual kyphotic deformity usually presents with pain, probably as a result of a combination of disc pathology and posterior incompetence with imbalance.

For surgical management, the authors prefer anterior corpectomy and keystone fusion with iliac crest graft and a four-poster brace. For a long construct, meaning more than two vertebral bodies, an anterior plate may be added. The same considerations as for post-anterior discectomy without fusion also apply here. The authors have found high fusion rates in smokers and nonsmokers. The advantages are low cost and no instrumentation-related complications, and the disadvantages are graft site morbidity and brace compliance. Other treatment options include allograft, bone substitute, cages, and anterior plating.

ANKYLOSING SPONDYLITIS
The patient with ankylosing spondylitis commonly presents with a progressive deformity after neck trauma with a delayed or missed diagnosis of fracture, particularly at the cervicothoracic junction.¹⁴ Other causes can be a lesion of spondylodiscitis or a myopathy in a spine that is not fully ankylosed by the disease.

Treatment . In cases of acute fractures, particularly in the cervicothoracic region, the patient should be placed and held with a halo-thoracic vest or internal fixation, in the prefracture alignment and not corrected. Any straightening at this time can induce neurologic compromise. For rigid deformities not related to acute fracture, the authors recommend resection-extension osteotomy at C7-T1 (with anterior osteoclasis), and local bone graft done under local anesthesia in the upright position followed by halo-body cast. In cases of flexible deformity, if not ankylosed and easily fully correctable, the authors recommend supportive therapy with exercises and bracing until the spine ankyloses in an acceptable position. Surgical treatment consists of preoperative halo-dependent traction or halothoracic vest for correction of deformity, followed by posterior fusion with lateral mass plates and iliac crest graft, remaining in a halothoracic brace. Open reduction and internal fixation of fractures in ankylosing spondylitis may be necessary if the patient has a neurologic deficit or develops one during nonoperative treatment. In acute fractures, if internal fixation is used, an anteroposterior approach may be necessary for adequate stability. Once the sagittal balance has been restored, the authors have not found it necessary to perform anterior fusion, although others have,¹³ and some advocate a formal opening wedge osteotomy in any rigid inflammatory deformity.⁵

There may be some residual movement present at the occipitocervical and atlantoaxial joints, which must be considered when planning the amount of correction. The spine is stiff and cannot compensate for overcorrection. Therefore it is important to evaluate the amount of correction carefully. For an elective osteotomy, the authors have not used internal fixation, finding a halo-cast adequate, although others advocate fixation as biomechanically advantageous.^20,27 The fusion rate of the osteotomy is extremely high without internal fixation and to carry out internal fixation is technically difficult, with landmarks obscured by the postinflammatory ossification changes. Other treatment options included posterior wire/cable techniques, posterior clamps, posterior lateral mass segmental fixation, sequential anterior fusion, and allograft.

RHEUMATOID ARTHRITIS
Atlantoaxial subluxation and basilar invagination commonly present as myelopathy without deformity, but the so-called staircase spine with subaxial subluxations may be present along with a flexion /kyphotic deformity, which is usually flexible.

Treatment. The authors prefer correction with halo-traction followed by posterior fusion with lateral mass plates and iliac crest graft. Because of poor bone stock, sequential anterior fusion may be needed, but consideration should be given to the patient's general condition. If fusion needs to be extended to the occiput, the authors prefer to use a plate, ¹⁷ although rod and Steinmann pin techniques have been described.^3,19 Other treatment options included posterior wiring techniques, other posterior lateral mass segmental fixation, sequential anterior fusion, and allograft.


DEGENERATIVE SUBAXIAL SPONDYLOLISTHESIS
Degenerative subaxial spondylolisthesis is less commonly seen than the rheumatoid type discussed previously. In this group, it is common for the patient to present with radiculopathy along with a mild deformity. Myelopathic changes may also be present.
Figure 1. A, Dewar fixation-fusion technique. B, AP radiograph of 39-year-old man with posttraumatic instability treated with Dewar technique. C, Lateral radiograph of same patient.
Figure 2. A and B, Lateral radiographs of 22-year-old woman with Down's syndrome, presenting with progressive quadriparesis secondary to basilar invagination. C and D, Sagittal and axial MRI scans showing extreme upper cervical cord impingement. E and F, Patient developed respiratory deficiency as well as progressive quadriparesis and had emergent surgery with posterior decompression and stabilization, followed immediately with anterior decompression with transoral oclontoid resection. Postoperative AP and lateral radiographs. Gand H, Postoperative CT scans showing areas of decompression and internal fixation. 1, Postoperative sagittal CT scan showing area of odontoid resection.

Treatment. In cases of myelopathy, the authors prefer laminectomy, posterior fusion with lateral mass plates, and iliac crest graft, followed by a Miami-J brace.⁷ In cases without myelopathy, the authors recommend posterior decompression and fusion with lateral mass plates and iliac crest graft. Wiring techniques can also be satisfactory, and the authors use the Dewar technique ³² rather than interspinous or tension band ²⁵ techniques (Fig. 1).^{7, 13} For cases of myelopathy with primary anterior encroachment, it is best to carry out anterior decompression and stabilization, if the involvement is over three or four levels. For more than three-level involvement, a laminoplasty along with posterior stabilization is often preferred. Other circumstances, such as amount of deformity, rigidity of the deformity, and bone quality, may also influence which is the best approach for any given patient. Combined anteroposterior stabilization may be necessary occasionally for unstable condiiions and biologic factors, such as bone quality (Fig. 2).

MYOPATHY
Myopathv is most commonly seen in elderly women with generally poor muscle tone and general poor health. It usually is passively correctable to some extent. It can also contribute to the deformity in ankylosing spondylitis, discussed previously. Rarely does it require surgical treatment.

Treatment. The authors prefer extensor muscle strengthening with isometric exercises. For failure of conservative therapy, the authors recommend posterior fusion with lateral mass plates and iliac crest graft, followed by a Minerva/SOMI brace or Luque rectangle fixation with fusion (Capicotto and Simmons, personal communication, 1994) (Fig. 3). Anterior stabilization and fusion can be done in more rigid and severe deformities.
Figure 3. A, Lateral radiograph of 83-year-old man with myopathic flexion deformity of cervical spine, presenting with "chin on chest" deformity. Band C, Postoperative AP and lateral radiographs. Deformity was passively correctable; patient was treated with posterior Luclue rectangle instrumentation.

INFECTIOUS SPONDYLITIS
Infectious spondylitis is rarely seen in the cervical spine, and the mainstay stay of treatment remains chemotherapy.

Treatment. A full discussion of the treatment of infections is beyond the scope of this article, but generally the surgical management is reserved for infections refractory to chemotherapy, deformity secondary to collapse, or neurologic instability. In cases with deformity secondary to vertebral body collapse, anterior discectomy / corpectomy with iliac crest grafting is used, preferably after the infection has been treated. The success of this approach is well documented, especially in the treatment of tuberculosis.⁶ For those who require debridement of the infection, the same approach is used with the principle of trying to use minimal instrumentation in the infected area while still leaving a stable construct. The authors do not think it routinely necessary to add additional posterior instrumentation after anterior debridement and grafting.

TUMORS
Metastatic tumors are the most common tumors and usually are found in the vertebral body rather than the posterior elements. Kyphotic collapse in addition to pain or neurologic instability is fairly common. Surgical intervention can be necessary for problems of instability and neurologic deterioration or to prevent neurologic problems prophylactically as well as for pain control. Neurofibromatosis also can produce a rapidly progressive kyphotic deformity.³⁷

Treatment . For anterior collapse alone, the authors recommend anterior corpectomy surgery with iliac crest or fibular strut graft, anterior plate fixation, followed by a soft collar. In cases with posterior destruction, the authors recommend posterior decompression as necessary, along with posterior lateral mass plates and iliac crest graft, followed by a soft collar. In certain cases involving anterior and posterior structures or evidence of concomitant instability, both procedures may be necessary and are performed as previously in single-stage surgery. Prophylactic anterior and posterior instrumentation and fusion in the treatment of anterior pathology is often necessary in the case of neurofibromatosis.²³

CONGENITAL SCOLIOSIS AND KYPHOSIS
The most common presentation of congenital deformity is an incidental finding on investigation or other pathologies, such as a chest infection. Many of these are (and remain) blanched, requiring prudent observation, especially through the growth period. Congenital kyphoses are more common in the thoracolumbar spine.

Treatment. A detailed discussion of congenital deformities is beyond the scope of this article, but the age of the patient, remaining growth, type of anomaly, and other anomalies (including the spinal cord) need to be taken into account.³³ In children who require fusion to prevent progression, a posterior fusion without instrumentation is usually adequate²¹ and if done early enough allows some correction with growth. To obtain correction of the deformity, anterior and posterior procedures⁸ with an instrumented fusion are generally needed. Autologous iliac graft is preferred; however, other grafts can be used, including autogenous or allograft fibula, allograft iliac crest, and bone graft substitutes.⁹

TORTICOLLIS AND ROTATORY ATLANTOAXIAL SUBLUXATION
Torticollis and rotatory atlantoaxial subluxation is rarely seen except in children and usually as a result of trauma or reaction to an infectious insult. When diagnosed early,²⁶ it is readily amenable to reduction in traction. When presenting later, sometimes years, it is usually painful and irreducible.

Treatment . The authors prefer preoperative halo-dependent traction and, if necessary, posterior C12 Gallie/wire fusion with iliac crest graft, followed by Minerva/SOMI brace. Reduction maneuvers, through the mouth, under general anesthesia have been described but are dangerous. An adequate amount of realignment, although not necessarily with 100% correction, can be obtained with a period of preoperative halo traction. An in situ fusion relieves the pain but does not affect the deformity. In young children, torticollis may also be caused by ophthalmic or ocular problems. Internal fixation options include various posterior wire/cable techniques, posterior C12 transarticular screws, and lateral atlantoaxial fixation.

References
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Address reprint requests to
Edward D. Simmons, MD Associate Clinical Professor State University of New York at Buffalo 235 North Street Buffalo, NY 14201

From The Royal Children's Hospital, Parkville, Victoria, Australia (SML); and the Department of Orthopaeclic Surgery, State University of New York at Buffalo, Buffalo, New York (EDS)