Книга_6030_Библиотеки_им_академика_М_И_Перельмана

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Kazumasa Ueyama, M.D.

Vice-Director Department of Orthopedics Hirosaki Memorial Hospital Hirosaki City, Japan

Alexander R. Vaccaro, M.D.

Co-Chief, Spinal Surgery Co-Director of the Spine Fellowship Program Co-Director, Delaware Valley Regional

Spinal Cord Injury Center Thomas Jefferson University and The Rothman Institute Philadelphia, Pennsylvania

Kurt W. Von Rueden, M.D.

Texas Scoliosis & Spine Austin, Texas

Archibald H. von Strempel, M.D., D.Eng.

Chief Surgeon Professor of Orthopaedic Surgery Department of Orthopaedic Surgery Landeskrankenhaus Feldkirch, Austria

Mark Weidenbaum, M.D.

Associate Professor Department of Orthopaedic Surgery Columbia University New York, New York

Thomas S. Whitecloud III, M.D.

Department of Orthopaedic Surgery Tulane University Medical Center New Orleans, Louisiana

Jeffrey J. Wise, M.D.

Attending Surgeon Department of Orthopaedic Surgery The Fauquier Hospital Warrenton, Virginia

Douglas C. Wong, M.D.

Orthopaedic Spine Surgeon Panorama Orthopedics St. Anthony Central Golden, Colorado

Kirkham B. Wood, M.D.

St. Croix Orthopaedics Stillwater, Minnesota

Hansen A. Yuan, M.D.

Professor of Neurological and Orthopaedic Surgery Department of Orthopaedic Surgery SUNY-Upstate Medical University Syracuse, New York

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Section

The Cervical Spine

1 OCCIPITOCERVICAL JUNCTION

SECTION I THE CERVICAL SPINE

Occipitocervical Junction

Decompression and Fusion

Michael F. O’Brien

Goals of Surgical Treatment

1. To treat pathology at the craniocervical junction (CCJ), the degree of in-

stability present, and the type and extent of the neurologic involvement must be considered before conservative or surgical intervention is proposed (Fig. 1–1).

2. The specific goals for surgery vary depending on the pathology to be

addressed. In general, surgery is performed to alleviate pain, correct deformities, stabilize instabilities, and decompress the neuraxis.

3. The final surgical outcome must result in near anatomic alignment,

decompression of the neuraxis, and effective CCJ stabilization to counteract the tendency for craniocervical kyphosis, and it must promote a solid fusion (Fig. 1–2).

Diagnosis

The pathologic entities that may affect the craniocervical junction are numerous (Table 1–1). Often attention is drawn to the craniocervical junction only after the onset of CCJ instability, which results in pain or neurologic deficits. Neurologic deficits typically involve either myelopathy or lower cranial nerve deficits or both. Radiographic investigation begins

with plain x-rays for evaluation of standard radiographic landmarks. These studies are supplemented with magnetic resonance imaging (MRI), computed tomography (CT), and CT myelograms and myelographic studies as needed.

Indications for Surgery

1. Treat established or impending neurologic injury to the brainstem or

spinal cord.

2. Reduction and stabilization of instability [atlantoaxial subluxation

(AAS), rheumatoid arthritis (RA)].

3. Correction of deformity [atlantoaxial rotatory subluxation (AARS) and

fixed CCJ kyphosis].

4. Alleviate pain [osteoarthritis (OA), tumors].

5. Debridement (infection, tumors).

Relative Contraindications

1. Severe osteopenia (difficult to stabilize postop, halo may be required).

2. Chronic, severe myelopathy or paralysis (neurology unlikely to be re-

versible).

3. Nonambulatory: Ranawat III B (unlikely to regain ambulatory status if

long-standing, 50% morbidity and mortality rate in RA).

4. Insufficient subspecialty experience on surgical team.

5. Inability of patient to cooperate with postoperative regime.

Figure 1−1

Cranial cervical junction algorithm.

Table 1−1. Pathologic Processes that May Involve the Craniocervical Junction (CCJ)

Rheumatoid arthritis Infection Trauma Down syndrome Congenital anomalies Osteoarthritis Osteogenesis imperfecta Achondroplasia Tumor Morquio’s disease Iatrogenic instability Dwarfing syndromes

Advantages/Disadvantages

Anterior Approaches: Advantages

1. Transoral approach allows simple direct access to CCJ from mid-clivus

to C2–C3.

2. Open-door maxillotomy allows access from upper clivus to C3.

Anterior Approaches: Disadvantages

1. Risk of infection (probably no higher than in posterior approach).

2. Difficult to close durotomies.

3. May be difficult to achieve stable instrumentation and may not be sui-

table as a stand-alone procedure.

4. Open-door maxillotomy requires oral surgeon or skull base surgeon as

an additional team member.

Posterior Approaches: Advantages

1. Quick.

2. Does not require manipulation of anterior cervical visceral structures.

3. Can visualize entire CCJ and is extensile.

4. CCJ and extensile constructs possible, good visualization of osseous

fixation points.

5. Extensive bed for occipital, cervical, and thoracic fusion is available.

6. Anterior decompression may be achieved indirectly via reduction of

mobile CCJ kyphosis.

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Posterior Approaches: Disadvantages

1. CCJ pathology usually has significant anterior component.

2. Neuroaxial decompression in fixed kyphosis must be performed anteriorly.

3. CCJ deformity, typically kyphosis, may be difficult to treat via a posterior only approach.

4. Lack of anterior column support may contribute to failure of posterior instrumentation.

Procedure

Transoral Approach

The transoral approach is the preferred method to directly access the anterior craniocervical junction. Access can be gained from the inferior third of the clivus to the superior aspect of C3. Proximal extension can be achieved by splitting the soft palate in the midline with retraction of the uvula superiorly. Additional superior extension can be achieved by osteotomy of the hard palate. Caudal extension can be achieved by splitting the tongue either in the midline without mandibular osteotomy or in the midline with osteotomy of the mandible, and caudal retraction of the tongue. In this way, surgical exposure can be achieved from the mid-clivus to C3.

1 OCCIPITOCERVICAL JUNCTION

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ABC

D E

Figure 1−2

(A–G) Illustrative case. (See text for complete

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SECTION I THE CERVICAL SPINE

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discussion.)

Figure 1−3

Transoral retractor positioning (anterior). 1, Armored nasotracheal tube; 2, soft palate retractors; 3, perioral ring; 4, tongue retractor. (See Color Plate 1–3.)

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Figure 1−4

Transoral retractor positioning (lateral). 1, Red rubber catheter; 2,

armored nasotracheal tube; 3, soft palate retractor; 4, tongue retractor. (See Color Plate 1–4.)

Figure 1–5

Retropharyngeal anatomy and retractor. 1, anterior atlanto-occipital membrane; 2, armored nasotracheal tube; 3, longus colli muscle; 4, anterior longitudinal ligament; 5, clivus; 6, longus capitis muscle; 7, rectus capitis anterior muscle; 8, anterior tubercle of C1; 9, lateral atlantoaxial joint capsule; 10, retropharyngeal soft tissue retractor. (See Color Plate 1–5.)

1 OCCIPITOCERVICAL JUNCTION

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Figure 1–6

Open-door maxillotomy (lateral). 1, Maxillotomy retractor; 2, armored nasotracheal tube; 3, tongue retractor. (See Color Plate 1–6.)

Figure 1–7

Posterior dissection. 1, Intracranial vertebral artery; 2, extracranial vertebral artery. (See Color Plate 1–7.)

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Figure 1–8

Posterior instrumentation. 1, Drill; 2, screw tap; 3, screw driver. (See Color Plate 1–8.)

SECTION I THE CERVICAL SPINE

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Preparation and Preoperative Assessment for Transoral Surgery

Careful preoperative evaluation of the oral cavity is mandatory to identify sepsis. If necessary, cultures and sensitivities may be performed. The condition of the teeth must be evaluated. In those patients with significant dental problems or in the edentulous patients, special protective dental guards may be necessary. Soft dental molds may be useful to protect the teeth and gums from the rostral and caudal retractors. If the interdental distance is less than 25 mm with the patient’s mouth maximally opened, it is unlikely that a conventional transoral procedure will be possible. Patients

with large, thick tongues (Down syndrome) may also present a challenge to retractor positioning.

Anesthesia

For most transoral procedures, tracheostomy is not necessary. Either an oral endotracheal or an armored nasal tracheal tube may be used. The armored nasal tracheal tube is preferred. It enters nasally,out of the operative field, and is easily retracted laterally intraorally by the transoral retractor system CODMAN. Patients remain intubated for several days postsurgery to allow retropharyngeal swelling to subside. Nasotracheal tubes are more comfortable during this period than oral tracheal tube. Awake intubation may be necessary for those patients with an unstable CCJ or tenuous neurologic function.

The decision to extubate postoperatively depends on the degree of residual soft tissue swelling. When the majority of the dissection is above the soft and the hard palate, that is, in the clivus, early postoperative extubation is acceptable. When the incisions and/or surgical dissections is car-

ried to the superior margin of C3, retropharyngeal swelling is more likely and may cause mechanical compression of the airway. In this case intubation for at least 24 to 48 hours, or until lateral x-rays document normal pre-

vertebral soft tissue shadows on lateral cervical radiograph, is recommended.

A nasogastric tube is passed prior to surgery. This allows the stomach contents to be emptied, preventing any regurgitation or gastric soiling of the operative site. The nasogastric tube also allows for fluid replacement and enteral alimentation postoperatively. It may be removed at 5 to 7 days.

Once intubated and prior to placing the retractors, a throat gag may be placed. The oral cavity is then irrigated with antimicrobial agents. Finally, the oral mucosa, tongue, and retropharynx are liberally coated with 1% hydrocortisone cream to prevent intra- and postoperative swelling of the lips, tongue, and oral mucosa. Topical hydrocortisone treatment may be continued every 6 hours for the next 48 hours.

Patient Positioning

The patient is placed supine, and the head is fixed in a Mayfield clamp for stable head and neck positioning. The pins should be approximately 1 to 2 cm above the tip of the ear, preferably below the occipital equator. The single pin should be directly rostral to the external auditory meatus. The dual pin side should be evenly spaced anteroposterior of the external auditory meatus. The tip of the ear should not touch the Mayfield clamp.

Retraction

The transoral retracting systems consist of a perioral frame to which is attached a tongue, retropharyngeal, and soft palate retractors (Figs. 1–3, 1–4, and 1–5). Care must be taken to protect the gums and dental structures. In the edentulous, gum guards may be necessary to prevent soft tissue damage. The tongue must be positioned to prevent entrapment between the tongue blade and the teeth. During the course of surgery, as lingual swelling increases, this must be rechecked. Improved visualization of the posterior oral pharynx can be achieved by mobilizing the uvula superiorly. This is simply accomplished by placing a red rubber catheter transnasally and suturing the tip of the catheter to the uvula. The catheter is gently

withdrawn from the nose until the uvula is pulled superiorly into the retronasal cavity (Fig. 1–4). When placing and adjusting the retropharyngeal soft tissue retractors (Fig. 1–5), the soft tissues must be handled gently to ensure an acceptable layered closure at the end of the procedure. This is necessary to prevent infection and to provide a barrier against intraoral leakage of cerebrospinal fluid (CSF) in the event of a planned or incidental durotomy.

Incision

Care must be taken to identify the anterior tubercle on C1, especially in the case of rotatory subluxations either mobile or fixed. With rotatory subluxations of C1, the tip of the C1 transverse process may be mistaken for the anterior tubercle. Failure to clearly identify the anterior tubercle can lead the surgeon into the path of the vertebral artery with dire consequences.

Once the anterior tubercle has been identified, a safe path to the anterior aspect of the neuraxis is identified. The vertebral arteries will be approximately 15 to 20 mm on either side of midline. Prior to making the incision, the posterior oral mucosa is infiltrated with local anesthetic and epinephrine in a 1:200,000 concentration. In addition to controlling mucosal bleeding, the injection creates a cleavage plane between the oral pharynx and the prevertebral tissue. A midline incision from above the tubercle of C1 to the base of C2 is performed. On entering the prevertebral space, positive identification of the arch of C1 can be achieved by tracing the converging longus coli muscles to the anterior tubercle of C1 (Fig. 1–5). Next, the dens and the body of C2 are identified and dissected free of soft tissue. Once these two landmarks are positively identified, lateral dissection can be carried to the right and the left to expose the anterior aspect of the lateral atlantoaxial joint (Fig. 1–5). In the case of significant subluxation, capsular release and manual reduction can be achieved via this approach. When decompression is necessary (odontoidectomy), either a high-speed bur is used to transect the dens at its base followed by extraction, or decancellation of the dens is carried out followed by piecemeal resection of the posterior cortex. When possible, it is advantageous to maintain an intact anterior arch of C1 to prevent splaying of the lateral masses of C1 over time, particularly when stabilizing instrumentation is not anticipated. Splaying of C1 may result in painful C0-C2 motion or cranial settling. However, when dealing with significant rostral settling of C2 into the cranial vault, and basilar invagination, complete resection of the anterior arch of C1 will be necessary to access the invaginated aspect of C2. When removing the posterior cortex of C2, care must be taken to avoid durotomies, because the neuraxis will be tented anteriorly over the posteriorly displaced dens. If durotomy occurs, direct closure is difficult but should be attempted. Cryoprecipitate or hemocele may then be used to additionally seal the dura along with fascial or dural grafts as needed. Other hemostatic agents such as Surgicel may be necessary. If during the course of a transoral procedure durotomy is anticipated, a diverting lumbar CSF drain is suggested.

Adequate decompression of the craniocervical junction is visualized by free pulsation of the dura through the corpectomy. The osseous decompression must be carried sufficiently inferior to prevent the development of a sharp inferior bony ridge distally. This bony ridge may replace the dens as the anterior osseous compressive structure. This is particularly a problem in patients with severe or fixed occipital kyphosis when reduction of the kyphosis is either impossible or minimal. If there is any question about the efficacy of the decompression, the corpectomy site can be filled with a radiopaque dye and lateral x-ray taken to ascertain the adequacy of the anterior decompression. Adequate lateral decompression is assured by visualizing the right and left side of the dura.

When the decompression is complete, closure is achieved in a layered fashion. The retropharyngeal muscle and mucosal layer are closed separately with interrupted 3–0 Vicryl sutures. If a soft or hard palate extension has been performed, these must be repaired. The soft palate should also be closed in two layers: muscular and mucosal.

Open-Door Maxillotomy Approach

Although ideal for most approaches to the craniocervical junction, the surgical field provided by the standard transoral approach is limited in its upward and lateral extension by the maxilla. Performing a LaForte maxillotomy can provide good exposure to the upper clivus but will not allow adequate exposure to the lower craniocervical junction. For this reason, the open-door maxillotomy modification of the transoral procedure was proposed by Crockard and James. It allows a midline maxillotomy to be added to the LaForte osteotomy. This allows the two halves of the maxilla to be hinged out of the oral cavity and thus provides full exposure of the clivus and the craniocervical junction to C3 (Fig. 1–6). This is an intricate approach requiring a surgeon skilled in oral surgery and/or skull base surgery. It requires modification of the transoral technique and the retractor system. The patient is intubated orally.

Posterior Approach

For a posterior approach to the craniocervical junction, the patient is placed in a Mayfield clamp. This allows optimal positioning of the head and neck with the ability to flex and extend the occiput on the cervical spine and distract and manipulate the patient intraoperatively. It is important to ensure that the face and nose do not impinge on the Mayfield frame.

A standard posterior incision is performed from the inion to the mid- or lower cervical spine depending on the number of subaxial levels that need to be exposed (Fig. 1–7). Upon reaching the fascia, the midline avascular plane between the converging symmetrical postcervical muscles is identified. Dissection is carried down to the spinous processes. The occiput is exposed to thewidthofthelateralmasses of the subaxial cervical spine. The posterior prominence of C1 is identified by palpation but initially not dis-

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1 OCCIPITOCERVICAL JUNCTION

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sected. The spinous process of C2 is identified, and dissection is carried down along the spinous process to the lateral aspect of C2 just above the C2–3 joint. Thus, having identified the depth of the dissection, the posterior

ring of C1 is dissected in the midline and then carried laterally on both sides. Approximately 15 mm from the midline, an indentation in the superior edge of the posterior arch of C1 identifies the extracranial course of the vertebral artery and its accompanying veins. Inferior to this, between the arch of C1 and the pars of C2 is the exiting C2 nerve root. It is accompanied by a significant venous plexus, which if entered will bleed vigorously. Attempts at coagulation are often futile, and it is often most expeditious to pack with hemostatic agents and continue the dissection on the contralateral side. Between the occiput-C1 and C1–C2, the posterior occipital and atlantoaxial membranes, respectively, become invested in the posterior dura, and incidental durotomy can occur during exposure. If subaxial extension of the operative site is necessary, standard posterior cervical dissection is continued caudally. If desired, the posterior aspect of the atlantoaxial joint can

be exposed by mobilizing the soft tissue over it (C2 nerve root with accompanying vascular plexus). After exposure of the C1–C2 joint, manual reduction of a C1 anterior subluxation can be achieved by placing smooth, thin elevators (Freer or Penfield No. 4) into the C1–C2 joint bilaterally and levering C1 back onto C2. This can be monitoredvia lateral fluoroscopy.Posterior CCJ decompression is achieved as either a suboccipital craniotomy for a foramen magnum decompression or a cervical laminectomy or both.

Because of the limited space for bone grafting the fusion must be planned. Prior to placing instrumentation the facet joints should be cleaned of all cartilage and soft tissue and then decorticated. Autograft is then packed into the facet joints. Once the instrumentation is in place all available exposed osseous surfaces are decorticated and covered with autologous bone. Additional struts or blocks of bone may be wired between the occiput and cervical spine (C1 and C2).

Numerous techniques have been described for posterior occipitocervical fixation. My preferred technique at this time is to use plate/rod and screws (Fig. 1–8). Plate and rod constructs each have their advantages and disadvantages. Long plate constructs require careful planning for screw placement but, depending on the system, may be more rigid than available

rod systems. Long rod constructs using currently available systems are typically not as rigid as plate constructs and are often complicated by tedious rod contouring and difficulty with rod-screw engagement. However, they allow optimal screw placement and offer top loading, post-screwplacement connection to the rod. Practice and experience with both techniques will result in biomechanically sound constructs capable of counteracting CCJ movements. The advantage of these systems over other techniques is reliable, versatile, and rigid fixation utilizing a variety of fixation points on the occiput and cervical spine in a manner that allows triangulation of fixation points to maximally stabilize the CCJ. Placing the instrumentation requires careful planning and meticulous application because the margin for error is much less then in the thoracic or lumbar spine. In the cervical spine, pedicle screws and C1–C2 transarticular screws are placed first because their location and trajectory is determined and constrained by the anatomy. The lateral mass fixation is achieved next. Once the construct is attached to the cervical spine, the precontoured plate/rod is fixed to the occiput. Prior to occipital fixation the alignment of the CCJ should be checked in the lateral projection via x-ray and in the anteroposterior (AP) projection by visual inspection within the operative field. For long plate constructs, the same sequence of fixation is followed, except that short Steinmann pins are temporarily placed in the prepared screw holes to facilitate relocalization and alignment of the plate to the cervical fixation points. The plates are then placed over the pins. The pins are then sequentially removed and replaced with screws. Careful sequential tightening of the screws will prevent malalignment of the plates/rods, screw pullout, or malalignment of the CCJ. The posterior instrumentation typically functions as a neutralization device rather than as a mechanical reduction device as is often the case in the thoracic and lumbar spine. However, careful precontouring and sequential reduction to the cervical spine can be used to increase cervical lordosis. Because of the tenuous fixation, in-situ reduction via plate/rod bending is impractical and dangerous. Closure is achieved in a layered fashion. The surgeon should attempt to close the fascia to the spinous processes that remain, especially reattaching the musculoligamentous connections to C2.

Pitfalls

1. Failure to appreciate rotatory subluxation of C1 on C2, which causes

the vertebral artery to approach the midline.

2. Rough handling of the retropharyngeal soft tissue, which compromises

its viability and hence the surgical closure.

3. Failure to achieve a complete decompression: missing superior invaginated fragments of the dens or more commonly by not carrying the decompression far enough inferiorly, creating a sharp bony ridge on caudal posterior aspect of C2.

4. Failure to achieve adequate lateral decompression (insufficient midline corpectomy).

5. Incision through the uvula may cause swallowing difficulties.

6. Resection of the hard palate may cause swallowing difficulties.

Posterior

1. Failure to achieve adequate fixation to stabilize the craniocervical junction.

2. Excessive manipulation and dissection between C1 and C2 causing significant blood loss around the C2 nerve root.

3. Failure to perform a detailed dissection around C1 and C2 to allow for safe placement of C1 and C2 instrumentation, particularly transarticular screws.

4. Failure to assess the C2 pars preoperatively with sagittal reconstructed CT scans if C1–C2 transarticular screws are planned.

5. Vertebral artery laceration as a result of dissection or instrumentation.

Complications

1. Infection (infrequent)

2. Swallowing difficulties

3. Persistent neurologic deficits secondary to inadequate anterior decompressions

4. Respiratory embarrassment due to premature extubation, requiring reintubation

Posterior

1. Infection (more common posteriorly than anteriorly).

2. Hardware failure (requires early intervention if the stability of the construct is in jeopardy).

3. Pseudarthrosis is a common problem, in the elderly, nutritionally depleted, and patients with systemic diseases such as rheumatoid arthritis. It is much less of a problem in the pediatric population.

Postoperative Care

1. Continue intubation for 24 to 48 hours.

2. Nasogastric tube for parenteral alimentation and fluids, and to prevent gastric regurgitation onto the operative site.

3. Topical steroids administered to the oral mucosa.

4. Intravenous antibiotics until all lines and tubes are removed.

Posterior

1. Sterile wound dressing for 3 days.

2. Intravenous antibiotics until all drains and tubes have been removed.

3. External orthosis: Halos are used only for patients who are at high risk for hardware failure postoperatively (severe osteopenia, uncooperative patients, inadequate CCJ constructs, posterior reduction of severe kyphosis). An occipito-cervical-thoracic external orthosis in all others for 6 to 8 weeks while out of bed. The orthosis may be removed while the patient is reclining, sleeping, or eating.

4. Out of bed ambulating if neurologically appropriate as soon as possible.

5. Postoperative evaluation in the office at 7 to 10 days (wound check), 6 weeks, 3 months, 6 months, 1 year, and yearly for 5 years. AP and lateral x-rays are obtained at each visit and flexion-extension views are obtained at 3 months and thereafter as required.

Illustrative Case

A 42-year-old man was treated with a posterior CCJ decompression (suboccipital craniotomy and cervical laminectomy) for "stenosis" at the ages of 4 and 9. The patient recovered "uneventfully" from these surgeries. Over the ensuing 30 years, he developed CCJ kyphosis. Because of the patient’s large size and short, thick neck, this was not clinically obvious. The patient presented with slowly progressing lower extremities weakness of 2 years’ duration. At presentation he was essentially wheelchair-bound. Bowel and bladder control was intact, and he had only mild upper-extremity weakness with clumsiness of his hands. He had no respiratory complaints. Plain x-rays (Fig. 1–2A) taken on admission show CCJ kyphosis and intrusion of the dens into the foramen magnum. MRI (Fig. 1–2B) on admission shows severe compression of the brainstem and spinal cord (arrows) as a result of anterior translation of the occiput (0) and C1 (1) and the upward and poste-

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rior migration of C2 (2) into the cranial vault. The preoperative CT-myelogram sagittal reconstruction (Fig. 1–2C) clearly shows the basilar invagination of C2 into the foramen magnum and the deformation of the brainstem (arrows). The axial image (Fig. 1–2D) shows C0, C1, and C2 all in the same plane with posterior subluxation of C2 and severe compression on the

brainstem (arrow). The patient was treated with a standard transoral procedure without soft palate splitting to decompress the CCJ. Complete decompression of the neuraxis is documented on the axial (Fig. 1–2E) and sagittal (Fig. 1–2F, large arrow) MRI. Residual plastic deformation of the neuraxis is clearly demonstrated (Fig. 1–2F, small arrow). Reduction of the CCJ kyphosis was achieved posteriorly after anterior mobilization of the lateral atlantoaxial joints. Posterior stabilization was achieved with plates and screws (Fig. 1–2G). The fusion was solid at 2 years postoperatively (Fig. 1–2G). The patient regained independent ambulation and full use of his upper extremities.