History

Patients may give a history of past trauma, sometimes associated with an intercurrent illness of ankylosing spondylitis or rheumatoid arthritis, as well as previous cervical spine surgery or degenerative and neoplastic disorders.

Signs and Symptoms

Symptoms may include suboccipital headache and neck stiffness, occipital neuralgia, symptoms of myelopathy, or progressive deformity leading to functional impairment, such as difficulty with looking forward or with eating and drinking. Patients may report low back pain and standing fatigue resulting from use of compensatory muscles to elevate pelvic tilt to alter gaze angle.

Physical Examination

Assessment of the patient with cervical kyphotic deformity should include a comprehensive neurologic examination. Signs of myelopathy may be evident because of past injury, compression, or spinal cord tension secondary to stretch induced by kyphosis. In addition to a complete neurologic examination, the surgeon should assess the patient’s regional and overall global alignment. Assessment of the location of the kyphotic deformity should include evaluation of not only the craniocervical relationship, but also the thoracolumbar spine and lumbopelvic relationships. The angle from the brow to chin relation to the vertical line with the hips and knees extended and the neck in its fixed or neutral position (chin-brow to vertical angle) can be used to measure the degree of flexion deformity.

Clinical and radiographic assessments should be performed with the patient’s hips and knees in the extended position to obtain a better understanding of the sagittal alignment and the location of the deformity. This is important because occasionally the focus of the deformity lies within the thoracolumbar spine or lumbar pelvis. In addition, examination of the pelvis may reveal hip flexion contractures. Occasionally, lumbar sagittal deformities must be corrected first. Correction of lumbar imbalance alters head position substantially, especially in rigid deformities such as ankylosing spondylitis. However, all corrective lumbar osteotomies change the T1 slope angle to some extent and therefore change cervical alignment and often cervical C2 sagittal vertical axis.

Imaging

The deformity should be evaluated by anteroposterior and lateral cervical radiographs along with dynamic lateral flexion and extension views. The deformity is then accurately measured (i.e., sagittal angle determination), and any other abnormalities are noted (e.g., subluxation and pseudarthrosis). The surgeon should obtain full-length posteroanterior and lateral 36-inch scoliosis radiographs to examine overall sagittal and coronal balance in these patients. The authors assess cervical, thoracic, and lumbar sagittal alignment individually and globally, define the effect of regional imbalance on cervical balance, and determine whether it is a primary, secondary, or compensatory cervical deformity. The degree of required correction depends on the angle of the cervical deformity (the chin-brow to vertical angle), the C2 plumb line, and the desired final lordosis.

The goals of treatment are to obtain balance, horizontal gaze, and spinal cord decompression and to normalize spinal cord tension. Dynamic (i.e., flexion and extension) radiographs permit assessment of the overall flexibility of the cervical spine that is paramount when designing a treatment strategy. Computed tomography (CT) scans of the cervical spine are also useful in determining the presence of fusion or ankylosis of the facet joints and disks and allow assessment of fixation points such as C2 and upper thoracic pedicles.

All patients should be evaluated with preoperative magnetic resonance imaging or CT myelography. These image modalities permit the evaluation of compressive disease. If significant ventral compressive disease (disk, osteophyte) is present, a ventral decompressive procedure may first be performed before correction of the deformity.

Indications and Contraindications

Osteotomy is indicated when the deformity is irreducible (possibly following a trial of traction) and sufficient to result in severe pain and functional or neurologic impairment that cannot be relieved with a surgical decompression or stabilization procedure alone. The procedure is contraindicated in the presence of significant osteoporosis or debilitating comorbidities.

Figure 37-2 is a case example of craniocervical junction osteotomy. Plain radiographs at the atlantoaxial level reveal substantial kyphotic deformity, possibly in the presence of an old odontoid fracture, with subluxation or dislocation of the C1-C2 joints (see Fig. 37-2 , A to C ). The patient may have bony union across the subluxed joints or involving other elements of the atlantoaxial complex.

A 59-year-old woman with a history of rheumatoid arthritis and severe suboccipital neck pain and early signs of myelopathy 6 months after a motor vehicle accident resulting in a type III odontoid fracture that was managed conservatively in a SOMI brace. Plain radiograph, computed tomography, and magnetic resonance imaging show development of fixed 27 degree kyphotic deformity ( A to C ), bilateral facet joint dislocations ( D ), and spinal cord compression ( E ).

Surgical Techniques

• 1.
  

  The ease of surgical access to the ventral aspect of C2 is an important consideration when choosing between an anterior-posterior approach and a posterior-only approach. Grundy and Gill described a posterior-only approach in cases in which the anticipated anterior access may be difficult. Preoperative planning of the intended osteotomy orientation is also important when considering the type of anterior approach. An osteotomy, which is oriented obliquely backward and upward from the base of C2 ( Fig. 37-3 , A ), enables satisfactory exposure through a high anterior retropharyngeal approach. This approach is described later.

  
  

  
  

  
  

  

  
  

  
  

  Computed tomography sagittal and coronal reconstructions showing the orientation of the planned osteotomy ( A ) and the bilateral extent of the base of the osteotomy ( B ).

  
  
  
  
• 2.
  

  Anesthesia and positioning: The patient usually requires awake endoscopic intubation and is positioned supine for the first (anterior) stage of the surgical procedure. It is preferable to use an operating table such as the Jackson table (Mizuho OSI, Union City, Calif.), which permits rotation of the patient to the prone position for the second surgical stage, and to secure the patient’s head in a Mayfield three-point head holder. Access for adjustment of the head and neck position should be maintained throughout the procedure. Intraoperative image-guided surgical navigation, such as with an O-Arm/Stealth (Medtronic, Dallas, Tex.), Iso-C (Siemens, Erlangen, Germany), or similar system may facilitate the surgeon’s orientation and placement of the osteotomy. Intraoperative neuromonitoring may be helpful during deformity reduction.

  
  
• 3.
  

  A high anterolateral skin incision is made for a retropharyngeal approach to the C2 vertebral body.

  
  
  
  
  • a.
    

    A retropharyngeal approach to the ventral aspect of the C2 vertebral body is used, with fluoroscopic confirmation of position.

    
    
  • b.
    

    The longus colli muscles are mobilized bilaterally.

    
    
  • c.
    

    The old fracture line is identified (when present). The bilateral extents of the fracture line are defined, and the surgeon endeavors to dissect upward to define the lateral aspects of the odontoid process bilaterally ( Fig. 37-3 , B ). This maneuver is important to mobilize the odontoid with the osteotomy completely and to avoid injury to the vertebral arteries.

    
    
  • d.
    

    The osteotomy is made through the old fracture line by using a high-speed drill with a small cutting burr. Frequent position and orientation checks are made with fluoroscopic or image guidance. The osteotomy is extended through to the back of the odontoid and bilaterally. The surgeon should take care not to venture too widely, to avoid injury to the vertebral arteries. If necessary, navigation may be used.

    
    
  • e.
    

    Depending on whether bony union of the posterior elements of the C1-C2 complex is present, an attempt may be made at this stage to open up the fracture line and correct the deformity by using intervertebral spreaders.

    
    
  • f.
    

    The anterior wound is then closed over a suction drain before the patient is turned to the prone position.

    
    
  • g.
    

    Through a midline suboccipital incision, subperiosteal dissection of the posterior elements of C1 to C3 is performed with identification of the C2 nerve roots.

    
    
  • h.
    

    While controlling any hemorrhage from the venous plexus around the C2 nerve roots, the superior articular surfaces of C2 are exposed, and the posterior edges of the C1 lateral masses, adjacent to the inferior joint surfaces, are defined on each side. If any bony union has occurred between the C1 and C2 joints, this is divided with the high-speed drill or osteotome ( Fig. 37-4 ). Dissectors are then carefully inserted into the dislocated C1-C2 joints and are used to lever back the C1 lateral masses gently onto C2 while the surgical assistant and anesthesiologist adjust the patient’s head position in the Mayfield headholder.

    
    

    
    

    
    

    

    
    

    
    

    An osteotome may be used to mobilize the C1-C2 joint space from the anterior or posterior approach in cases of fixed atlantoaxial deformity.

    
    
    
    
  • i.
    

    It is helpful to remove the articular cartilage from the C2 joint surfaces before reducing the dislocation. Subsequently, the articular cartilage is removed with a small, angled curet from the inferior surface of the C1 lateral masses. Cancellous bone graft is then placed into the C1-C2 joint spaces.

    
    
  • j.
    

    Depending on the surgeon’s preference and the vertebral artery anatomy, the C1-C2 segment is then stabilized using either transarticular screws (with additional posterior wiring) or a C1 lateral mass and C2 pars screw construct.

    
    
  • k.
    

    Further bone graft is placed over the decorticated posterolateral elements before posterior wound closure, in layers, over a vacuum drain.

  
  
  
  
• 4.
  

  Depending on how the patient is tolerating the procedure and the time available, the patient may be repositioned supine immediately or later, as a delayed procedure, for placement of bone graft into the anterior osteotomy site. This will have opened up into a wedge-shaped defect following the posterior deformity correction ( Fig. 37-5 , A ). Suitably fashioned allograft or iliac crest autograft is inserted into the wedge-shaped osteotomy site and secured with a small locking plate ( Fig. 37-5 , B ). Subsequent, standard postoperative care is given following segmental atlantoaxial stabilization and fusion ( Fig. 37-6 ).

  
  

  
  

  
  

  

  
  

  
  

  Intraoperative fluoroscopic images showing an anterior wedge defect resulting from posterior relocation of dislocated facet joints and transarticular screw fixation ( A ) and following anterior bone grafting and plate fixation ( B ).

  
  

  
  

  
  

  

  
  

  
  

  Six-month postoperative lateral ( A ) and anteroposterior ( B ) plain radiographs.

  
  
  
  
• 5.
  

  The patient is then returned, ventilated, to the intensive care unit.

Semirigid Deformity (e.g., Spondylitic Joints and Disks but No Segmental Bridging Bone in a Patient with Good Bone Quality)

The Smith-Petersen extension osteotomy technique, described in 1945, has been used extensively and was previously considered the prototype procedure for reconstruction of sagittal imbalance in patients with deformity above the thoracolumbar junction. Inspired by the lumbar osteotomy performed by Smith-Petersen, Urist in 1958 first reported his experience of cervical osteotomy on one patient with severe flexion deformity of ankylosing spondylitis. It is important to distinguish between opening wedge osteotomy (the classic Smith-Petersen osteotomy used for patients with ankylosing spondylitis at C7) and the procedure involving complete facet removal and posterior closure over a mobile disk space that is more commonly used for semirigid cervical deformity and is sometimes more appropriately called the cervical Ponte osteotomy.

If the deformity is partially correctable with traction or posture (i.e., neck extension), a dorsal-alone Smith-Petersen osteotomy/Ponte strategy may be used. Traction may be used to reduce the deformity and then may be continued into the operating room. Because this osteotomy uses some cantilever force on the prebent rod to achieve lordosis and segmental osteotomy closure, a stiffer cobalt chromium rod is recommended over a 3.5 titanium rod. Usually, these cases involve fusion from C2 to T2 or T3 (see the case example in Figs. 37-7 and 37-8 ).

Case example of semirigid deformity treated with Smith-Petersen osteotomy and cobalt chromium rods (see Fig. 37-8 ). Preoperative lateral radiograph showing cervical kyphosis ( A ) and preoperative sagittal magnetic resonance imaging showing spinal stenosis ( B ).

Case example of semirigid deformity treated with Smith-Petersen osteotomy (SPO). Intraoperative photograph displaying the cervical kyphotic correction using multiple SPOs ( A ) and a postoperative lateral radiograph showing correction of the cervical kyphosis and the use of a cobalt chromium rod ( B ).

Ankylosing spondylitis may produce an extreme fixed flexion deformity at the cervicothoracic junction. This extreme deformity may place the chin in close proximity to the chest and thus may interfere with eating and respiration. Some investigators have advocated treating this deformity by using Smith-Petersen osteotomy with anterior osteoclasis and gentle extension of neck intraoperatively that results in the classic opening wedge.

Indications and Contraindications

Severe flexion deformities of the cervical spine, in which patients have loss of horizontal gaze, difficulty with personal hygiene and function, and dysphagia, are corrected by traction or neck extension. Ankylosing spondylitis with fixed deformity is treated with Smith-Petersen osteotomy with anterior osteoclasis. Standing 36-inch radiographs are critical in determining whether lumbar or thoracic kyphosis also exists. If so, and if global imbalance is present, the thoracolumbar deformity usually should be corrected first because this procedure by itself may restore horizontal gaze. If lumbar sagittal deformity is present and cervical osteotomy is performed first, then secondary lumbar correction may lead to an unacceptably high (gaze on the ceiling) issue, and flexion osteotomy may then be needed.

Surgical Techniques (C7 Smith-Petersen Osteotomy with Anterior Osteoclasis for Fixed Low Cervical Deformity in Ankylosing Spondylitis)

• 1.
  

  Classically, the patient is positioned sitting. However, at the authors’ institution, patients are positioned prone in a halo ring. The kyphotic head position is accommodated by additional rolls and pads as needed to elevate the patient’s thorax. Transcortical motor-evoked potentials (MEPs), somatosensory-evoked potentials (SSEPs), and electromyography (EMG) are used.

  
  
• 2.
  

  An incision is made posteriorly, and the paraspinous muscles are dissected in a subperiosteal fashion, thus exposing the spinous processes, laminar facets, and lateral processes of C4 to T2. If the bone is very soft, fixation is extended to bicortical C2 screws. Preoperative standing films allow determination of the apex of the upper thoracic kyphosis, and the fixation is extended below this apex as needed.

  
  
• 3.
  

  After exposure, the osteotomy is performed. A complete C7 laminectomy and partial C6 and T1 laminectomies are performed. The resection is carried laterally to include the removal of the C7 pedicle with rongeurs. All resected bone is saved for reuse later to create the bone graft.

  
  
• 4.
  

  The residual portions of the C6 and T1 laminae must be carefully bevelled and undercut to avoid any impingement or kinking of the spinal cord on closure of the osteotomy. Furthermore, the area near the C8 nerve root is curved to provide ample room for the nerve root on closure.

  
  
• 5.
  

  The surgeon grasps the halo and extends the patient’s neck gradually with closure of the osteotomy posteriorly as the osteoclasis across C7 to T1 occurs anteriorly. An audible snap and sensation of the osteoclasis are usually heard. Also at this time, rotation malalignment and lateral tilt are corrected.

  
  
• 6.
  

  A prebent rod is placed and locked down. The C8 foramen is inspected to make sure the nerve is free after complete closure. At the C7-T1 area, the posterior aspects of the spine may then be decorticated. The autologous bone graft from the resection is packed bilaterally onto the decorticated areas.