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204 Spine Core Knowledge in Orthopaedics

Figure 15–6: SAS in the rheumatoid spine typically involves the upper cervical region around C2 to C4 and often shows a stepladder type of subluxation.

presence of an advanced (IIIb) neurological deficit (Casey et al. 1996). Location of disease—SMO has a much worse prognosis than AAS and SAS. Preoperative PADI of 14 mm or greater predicts a potentially significant motor recovery after appropriate surgery. In contrast, PADI of less than 10 mm indicates a poor prognosis for neurologic recovery. A postoperative subaxial canal diameter less than 14 mm indicates poor prognosis for neurologic recovery.

Goals for Management

Recognize the problem early (before an irreversible neurologic deficit occurs) by a practical and reliable screening method for serial evaluation. Avoid sudden death because of unrecognized spinal cord compression.The reported incidence is 10%.

Avoid unnecessary surgery because 50% of AAS patients may never develop neurologic symptoms.

Indications for Surgical Stabilization

Definite indications for surgery are the following:

Intractable pain

Definite neurologic deficit Relative indications include the group of patients with radiological instability but with minimal symptoms and no neurodeficit.

Atlantoaxial Subluxation

PADI ≤14 mm indicates further investigation by MRI scan.

Space available for the cord ≤13 mm, a cervicomedullary angle ≤135 degrees, or a spinal cord diameter ≤6 mm indicates a need for surgery.

Superior Migration of the Odontoid

Any demonstrable SMO—on plain radiographs, CT scan, or MRI scan—is an indication for surgery because of high morbidity and poor prognosis with surgery in progressive basilar invagination.

Subaxial Subluxation

SAS exceeding 4 mm in plain radiographs indicates the need for an MRI scan. If the residual subaxial canal diameter is less than 14 mm, MRI scan is indicated. If MRI shows space available for the cord ≤13 mm or a notable dynamic instability, surgery is indicated. A flowchart for the treatment strategy is presented in Fig. 15–7.

CHAPTER 15

The Rheumatoid Spine 205

Surgical Stabilization

General Considerations

A posterior atlantoaxial fusion or craniocervical fusion is the preferred method of stabilization. Anterior surgery (transoral decompression, subaxial corpectomy, and stabilization) is infrequently indicated for specific problems. A period of preoperative cervical traction using halo is recommended to relieve pain, reduce subluxation, arrest or reverse neurologic deterioration, and correct deformity. If subluxation may be reduced, decompression may be avoided and a less aggressive surgical procedure may be adequate. Traction in the recumbent posture in bed may be hazardous, resulting in pressure sores and pneumonia; halo wheelchair traction for 2 or more days is preferable. Fiberoptic intubation without neck extension is often indicated.

Figure 15–7: Flowchart for the treatment of the rheumatoid spine. (F, female; M, male.)

206 Spine Core Knowledge in Orthopaedics

The need for bone grafting is controversial. It is often indicated in young, fit patients. However, many authors question the morbidity of harvesting bone graft in elderly patients with end-stage RA, because studies show little difference in instrumentation failure in the long-term follow-up with or without bone grafting (Crockard et al.

1990). It should be emphasized that many of the indications for surgery are essentially preventive, and patients are often debilitated, with fragile skin, poor wound healing secondary to the disease process and steroid medication, osteopenic bone, increased susceptibility to infection, and a high perioperative morbidity and mortality rate.

Types of Surgical Stabilization

Atlantoaxial Subluxation

AAS can be fixed by a posterior atlantoaxial fusion. When the subluxation is small or reducible, C1-C2 fusion may be performed by the Gallie wiring or Brooks wiring technique with an autologous bone graft. C1-C2 transarticular screw fixation, as described by Magerl in 1979, requires the reduction of subluxation but achieves better stabilization and may be performed when the C1 arch is thin or needs to be removed for decompression. When the subluxation is irreducible, C1-C2 lateral mass and pedicle screw fixation is an alternative method, but it is technically more difficult (Fig. 15–10).

Rarely, when notable subluxation is present and cannot be reduced, anterior decompression with corpectomy and reconstruction with strut bone grafting may be indicated. Graft resorption and progressive collapse is not uncommon. Usually, additional posterior stabilization is advised.

Combined Subluxation

In patients with combined upper and lower cervical instability, an occipitocervical fusion frequently may be performed, extending the fixation to all the anatomically involved segments in the subaxial cervical spine. There is a possibility of an accelerated progression of SAS following an occipitocervical fusion from the occiput to C2 level. Current data in the literature is inadequate to support this view.

Outcome and Complications

The clinical success rate for cervical fusions in patients with RA ranges from 60% to 90%. It is often difficult to define clinical success in the presence of progressive generalized disease. Complications include death (5% to 10%), infection, wound dehiscence, implant breakage or pullout, loss of reduction, nonunion (5% to 20%), and late subluxation below the fused segment. Not all nonunions are symptomatic, and their management must be individualized.

Superior Migration of the Odontoid

Posterior occipitocervical fusion is the mainstay of surgery. Because of the high morbidity and the poor potential for recovery, a more aggressive surgical approach is necessary. Isolated and fixed basilar invagination with no symptoms and no evidence of cord compression may be treated by observation. In the presence of cord compression, cervical traction is applied; if reduced, posterior occipitocervical fusion is indicated. If cord decompression is not achieved by traction, decompression by C1 laminectomy, in addition to occipitocervical fusion, may be performed. Anterior decompression by transoral resection of the odontoid is indicated when there is evidence of significant anterior pannus or marked vertical translocation of the odontoid (>5 mm).

Subaxial Subluxation

In most cases, posterior cervical fusion with lateral mass instrumentation is needed. When evidence of cord compression is present, decompression by laminectomy may be performed with fusion.

Surgical Technique

The Gallie wiring technique (1939) (Fig. 15–8) consists of an autologous bone graft fixed with a wire loop to the posterior arch of the atlas and the spinous process of C2. The advantage is the simplicity of the procedure.The disadvantage is inferior stability against anteroposterior translation of C1 on C2.The technique is not indicated unless the AAS is reduced and should always be supplemented with additional postoperative external support. The Brooks wiring technique (1978) involves two paramedial, wedge-shaped autologous bone grafts placed posteriorly between the arch of atlas and the lamina of the axis and secured by two wire loops.This technique provides superior rotational stability compared with the Gallie technique. However, it requires the wire loops to be passed under the C1 and C2 lamina in the spinal canal (Brooks et al. 1978). Transarticular fixation of C1-C2 (Magerl 1979) is a superior technique to wiring and can be performed even after laminectomy of the C1 arch.The fixation is achieved by one posterior screw crossing the atlantoaxial joints on each side; therefore it requires good reduction of the

Figure 15–8: Gallie wiring technique. A wire loop is first

passed under the C1 posterior arch upward. A corticocancellous graft from the iliac crest is then placed over the C1 arch and the C2 lamina. The closed end of the loop is then bent down superficial to the graft and hooked around the spinous process of C2, and the free ends are tied together over the graft.

CHAPTER 15

The Rheumatoid Spine 207

atlantoaxial joint.When performed with wiring, it provides three point fixation and therefore may eliminate the need for postoperative external support (Gebhard et al. 1998). However, the implants are small compared with the weight of the head, and additional external support may still be indicated to prevent implant failure (Fig. 15–9).

C1-C2 lateral mass and pedicle screw and rod fixation

provides superior stability (Harms et al. 2001).This is technically more difficult and carries a significant risk of injury to the vertebral artery. A three-dimensional CT reconstruction image using thin-slice CT axial images is an essential prerequisite.Theoretically, it may be performed even in the presence of an unreduced subluxation; however, that makes the procedure even more difficult (Fig. 15–10). Transoral odontoidectomy (Crockard et al. 1998) has an essential requirement: the ability to open the patient’s mouth more than 25 mm.Temporomandibular joint ankylosis or flexion deformity of the neck may prevent

adequate opening of the mouth. An alternative approach is a midline mandibular split retracting the tongue downward.The risk of sepsis is usually overestimated. But poor dental hygiene or sepsis, excessive damage to the pharyngeal mucosa, or dural tear may increase the risk of sepsis and meningitis. Postoperative intraoral swelling is common and may be avoided by application of topical steroid in the oral cavity. Division of palate is not usually required and may be retracted by a suture.

A midline 4-cm incision is preferred.The important

landmark is the anterior tubercle of atlas.The vertebral

artery lies 20 mm away from the midline. On either

side, 10 mm of the anterior arch may safely be

exposed.The arch of atlas and odontoid are removed

by a high-speed air drill to decompress the dura.The

pannus and the destroyed ligaments should be

removed, exposing a clear pulsatile dura, to ensure

satisfactory decompression.

208 Spine Core Knowledge in Orthopaedics

Figure 15–9: Magerl technique of C1-C2 transarticular screw fixation.With wiring, they provide a three-point fixation. Although

the technique provides a strong fixation and good rotational stability, the implants are too small and additional external protection with a cervical collar or a halo vest may be recommended to prevent early implant failure.

Usually anterior fixation is not indicated, and the segment is stabilized by posterior occipitocervical

fixation. Occipitocervical fixation uses rods or plates and screws to connect the occiput to the cervical spine. Solid internal fixation is the aim to avoid cumbersome postoperative external support. In the presence of osteopenic bone, internal fixation may be augmented by metal mesh with or without bone cement.

Summary

RA affects the cervical spine, causing instability in 50%80% of subjects, toward the end of the first decade of the disease process. Only a small percentage of cases progress to develop a neurological deficit. Once a neurodeficit starts, rapid deterioration is the rule with a mortality rate of nearly 50% within the first year. Three types of instability are seen:AAS is the most common (65%) followed by SMO (20%), also known as basilar invagination, and SAS, involving a stepladder pattern of subluxation of multiple segments commonly affecting the C2-C3 and C3-C4 segments.

Neurological deficit is most common with SMO, which also carries the poorest prognosis. Surgical stabilization is always indicated for instability with intractable pain or with any degree of neurological deficit. In the absence of significant pain or any neurodeficit, prophylactic surgical stabilization is indicated in cases with impending neurodeficit.

Impending neurodeficit is predicted when the PADI is less

than 14 mm, the space available for the cord is less than 13 mm, the cord diameter is less than 6 mm, the subaxial canal diameter is less than 14 mm, or there is any degree of SMO, as seen in radiographs, CT scans, or MRI scans. Posterior stabilization is usually indicated. Anterior decompression by transoral odontoidectomy or cervical corpectomy is rarely indicated for the decompression of anterior cord impingement. If the subluxation is reasonably reduced by traction, then AAS is stabilized by atlantoaxial fusion, SMO is stabilized by occipitocervical fusion, and SAS is stabilized by lateral mass instrumentation. Decompressive laminectomy of the subaxial cervical spine or removal of the posterior arch of atlas is indicated if persistent subluxation causes cord impingement.

CHAPTER 15 The Rheumatoid Spine 209

Figure 15–10: C1-C2 lateral mass and pedicle screw–rod instrumentation provides a strong fixation.Theoretically, it may be

performed even in the presence of persistent C1-C2 subluxation, unlike Magerl’s transarticular screw technique. However, persistent subluxation makes the procedure technically more difficult. In this particular case, additional Brooks wiring was performed to compress a graft between the C1-C2 posterior arch and the lamina.

Complications are common and include death, infection, wound dehiscence, the loosening of hardware, or implant failure because of osteopenic bone and nonunion.

References

Boden SD, Clark RC, Bohlman HH, Rechtine GR. (1998) Rheumatoid arthritis of the cervical spine. In: The Cervical Spine (Clark RC, ed.). Philadelphia: Lippincott-Raven Publishers, pp. 693-703.

The authors review the treatment strategy of cervical spine involvement in RA.They describe the radiological predictors of neurologic progression and outcome and outline a flowchart for the management of rheumatoid cervical spine.

Boden SD, Dodge LD, Bohlman HH et al. (1993) Rheumatoid arthritis of the cervical spine: A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am 75(9): 1282-1297.

For this landmark article, the authors analyzed 73 patients who were managed over 20 years for rheumatoid involvement of the

cervical spine and were followed for a minimum of 2 years.The average follow-up was 7 years.The authors found that the most important predictor of the potential for neurological recovery after the operation was the preoperative posterior atlanto-odontoid interval. PADI was a more reliable predictor than AADI.

Brooks AL, Jenkins EB. (1978) Atlantoaxial arthrodesis by the wedge compression method. J Bone Joint Surg Am 60(3): 279-284.

In this original article, the authors describe a new technique of atlantoaxial stabilization using two sublaminar wires, one on either side, compressing a wedge-shaped graft between the arch of the atlas and the axis.This method is popularly known as Brooks fusion.Although more difficult, this method provides superior rotational stability compared with Gallie fusion.

Bundschuh C, Modic MT, Kearney F et al. (1988) Rheumatoid arthritis of the cervical spine: Surface-coil MR imaging. AJR Am J Roentgenol 151(1): 181-187.

The authors describe the MRI changes in the rheumatoid cervical spine in 15 patients.They also analyzed the normal range of the cervicomedullary angle (135-175 degrees) in 50

210 Spine Core Knowledge in Orthopaedics

normal subjects. They note that a cervicomedullary angle below 135 degrees indicates a high probability of neurological damage and the need for surgical stabilization.

Casey AT, Crockard HA, Bland JM et al. (1996) Surgery on the rheumatoid cervical spine for the nonambulant myelopathic patient—Too much, too late? Lancet 347(9007): 1004-1007.

In this original article, the authors describe their experience with 134 patients treated surgically for rheumatoid involvement of the cervical spine after the development of objective signs of myelopathy.They found a strong likelihood of surgical complications, poor survival, and limited prospects for functional recovery in nonambulant patients and recommend a strong case for earlier surgical intervention. At a late stage of disease, most patients will have irreversible cord damage.

Crockard A, Grob D. (1998) Rheumatoid arthritis—Upper cervical involvement. In:The Cervical Spine (Clark RC, ed.). Philadelphia: Lippincott-Raven Publishers, pp. 705-713.

The authors review the literature and describe the indications and rationale for surgery and the management principles of upper cervical spine involvement in RA.They also describe the indications, methods, and complications of transoral odontoidectomy.

Crockard HA, Calder I, Ransford AO et al. (1990) One-stage transoral decompression and posterior fixation in rheumatoid atlantoaxial subluxation. J Bone Joint Surg Br 72(4): 682-685.

In this original article, the authors describe their experience with combined anterior transoral decompression with posterior occipitocervical fixation in 68 rheumatoid patients with irreducible anterior neuraxial compression at the craniocervical junction.They found that use of bone graft may be justified in young subjects but question the morbidity of harvesting bone graft in elderly patients with end-stage RA, because studies show little difference in instrumentation failure in the longterm follow-up with or without bone grafting.

Dvorak J, Grob D, Baumgartner H et al. (1989) Functional evaluation of the spinal cord by magnetic resonance imaging in patients with rheumatoid arthritis and instability of upper cervical spine. Spine 14(10): 1057-1064.

In this article, 34 patients with atlantoaxial instability caused by RA were examined with plain x-ray views and functional MRI and were neurologically evaluated.The authors observe that the spinal canal diameter was significantly decreased in the flexed position and emphasize the need for a functional evaluation of the spinal cord by MRI.

Gebhard JS, Schimmer RC, Jeanneret B et al. (1998) Safety and accuracy of transarticular screw fixation C1-C2 using an aiming device:An anatomic study. Spine 23(20): 2185-2189.

In this anatomic study, the safety and accuracy of C1-C2 transarticular screw placement was tested in a normal anatomic situation in cadaver specimens using a specially designed aiming device. Five frozen human cadaveric specimens were thawed and instrumented with 10 C1-C2 transarticular screws according to the technique described by Magerl but using a specially designed aiming device described by the senior author (Jeanneret).The structure at the greatest risk was the atlantooccipital joint, with one screw found to be damaging the joint.

Vertebral artery or spinal canal penetration was not observed in any of the specimens.

Harms J, Melcher RP. (2001) Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine 26(22): 2467-2471.

In this article, a novel technique of atlantoaxial stabilization using individual fixation of the C1 lateral mass and the C2 pedicle with minipolyaxial screws and rods is described. In addition, the initial results of this technique on 37 patients are described.

Lipson SJ. (1989) Rheumatoid arthritis in the cervical spine. Clin Orthop (239): 121-127.

In this literature review, the author describes the risk factors for the progression of cervical disease.They found that male gender, severe peripheral disease, and the use of corticosteroids indicate a rapid progression and poor outcome.

Magerl F, Seeman PS. (1986) Stable posterior fusion of the atlas and axis by transarticular screw fixation. In Cervical Spine (Kehr P, Weidner A, eds.). Berlin: Springer-Verlag, pp. 322-327.

The authors described the technique of C

transarticular

1-C2

screw fixation originally developed by Magerl in 1979.

Mikulowski P,Wollheim FA, Rotmil P et al. (1975) Sudden death in rheumatoid arthritis with atlantoaxial dislocation. Acta Med Scand 198(6): 445-451.

In this study, postmortem material of 11 consecutive cases of severe atlantoaxial dislocation with cord compression is reported.The total number of deaths from RA during 5 years was 104, and all were autopsied.They observed sudden death in 7 of the cases. Only 2 cases obtained a correct diagnosis intra vitam.

Pellicci PM, Ranawat CS,Tsairis P et al. (1981) A prospective study of the progression of rheumatoid arthritis of the cervical spine. J Bone Joint Surg Am 63(3): 342-350.

In this prospective study with long-term follow-up, the authors review the incidence of cervical spine involvement in RA and describe the natural history.

Ranawat CS, O’Leary P, Pellicci P et al. (1979) Cervical spine fusion in rheumatoid arthritis. J Bone Joint Surg Am 61(7): 1003-1010.

In this landmark article, the authors describe a new system for the classification of pain and the neural involvement in rheumatoid patients.They also describe a new method of measuring superior odontoid migration.

Redlund-Johnell I, Pettersson H. (1984) Vertical dislocation of the C1 and C2 vertebrae in rheumatoid arthritis. Acta Radiol Diagn (Stockh) 25(2): 133-141.

In a retrospective analysis of 450 patients with RA, the cervical films were reviewed to detect vertical dislocation of the C1 and C2 vertebrae.A frequency of 10% was found among all patients and one of 24% was found among those with cervical arthritis. The authors’ method of measuring vertical dislocation using conventional radiography turned out to be superior to the method of McGregor, especially sin cases with severe dislocation.The vertical dislocation was shown to be preceded by a horizontal dislocation, and the appearance of the vertical dislocation diminished or abolished the radiographic appearance of the horizontal dislocation.

CHAPTER 15 The Rheumatoid Spine 211

Riew KD, Hilibrand AS, Palumbo MA et al. (2001) Diagnosing basilar invagination in the rheumatoid patient:The reliability of radiographic criteria. J Bone Joint Surg Am 83-A(2): 194-200.

The authors studied cervical radiographs of 67 cases of rheumatoid patients (of which 29 had basilar invagination and 38 did not) who had tomograms, MRI, sagittally reconstructed computed tomography scans, or a combination of these to detect the presence of basilar invagination. Three observers, who were

blinded to the diagnosis, independently scored each radiograph as positive, negative, or indeterminate according to the criteria for invagination established by various methods. No single diagnostic test had sensitivity above 90%, but a combination of Clark station, Ranawat criterion, and Redlund-Johnell criterion could increase the sensitivity to 94%. However, these combined criteria would result in a 44% false-positive diagnosis.

CHAPTER

Vertebral Discitis

and Osteomyelitis

Rafael Levin*, Christopher M. Bono §, and Steven R. Garfin †

*M.D., M.Sc., Comprehensive Spine Care, Emerson, NJ

§M.D., Attending Orthopaedic Surgeon, Boston University Medical Center; Assistant Professor of Orthopaedic Surgery, Boston University School of Medicine, Boston, MA †M.D., Professor and Chair, Department of Orthopaedics, University of California San Diego, San Diego, CA

Introduction

Anatomy

●

The vertebral body is composed primarily of cancellous bone, which is highly vascular.

●

The posterior arch (lamina, facets, and pedicles) is mostly dense cortical bone.

●

The intervertebral disk is made up of the anulus fibrosis (outer with some vascularity) and the nucleus pulposus (inner and avascular).

Classification

●

See Table 16–1 for classifications of spinal infections.

Vertebral Pyogenic Osteomyelitis

Epidemiology

●

2%-7% of all cases of osteomyelitis, 1%-2% of osteomyelitis cases in children

●

Concomitant involvement of bone and disk (i.e., spondylodiscitis) is the “rule”

●

Isolated bone or joint involvement (each represents around 1% of adult cases)

●

Isolated discitis more common in younger children but still rare

●

Can occur at any age (50% of cases in patients older than 50 years) (Sapico et al. 1979, Emery et al. 1989)

●

Incidence increasing, especially in young intravenous (IV) drug abusers

●

2:1 to 3:1 male/female ratio (Currier et al. 1999, Hadjipavlou et al. 2000)

●

Cephalad levels more prone to developing secondary epidural abscesses and thus more likely to develop neurologic deficits (Table 16–2)

●

Mortality rate below 5% (Sapico et al. 1979)

Etiology (in Order of Frequency)

●

Hematogenous spread from any condition causing bacteremia (Perronne et al. 1994)

●

Urinary tract infections and transient bacteremia from genitourinary procedures are the most common sources, followed by soft tissue infections and respiratory tract infections.

●

Frequency increases in association with IV drug abuse.

●

Unidentified source (42% in one series—Emery et al. 1989)

●

Direct inoculation (e.g., penetrating trauma or invasive spine procedures)

Risk Factors

●

Immunocompromised hosts (e.g., diabetes, chronic disease, HIV, malnutrition, or steroids)

212

CHAPTER 16 Vertebral Discitis and Osteomyelitis 213

Table 16–1: Classification of Spinal Infections

FACTOR DESCRIPTION

Organism Bacterial

Mycobacterial Fungal Parasitic

Anatomic location Spondylitis—Confined to bony elements (common

with TB) Discitis—Confined to disk space Spondylodiscitis—Involving bone and disk Epidural abscess Septic arthritis—Confined to synovial joint (e.g.,

rare facet joint arthropathy) Paraspinal abscess—Outside the vertebral column (e.g., psoas muscle abscess) and may eventually seed or extend to the spine Describe by region—Cervical, thoracic, thoracolum

bar junction, lumbar, sacral

Route Hematogenous (most common)

Direct inoculation (including iatrogenic, e.g., after

discography) Contiguous spread (e.g., psoas abscess)

Chronicity Acute (<6 weeks)

Subacute (6 weeks to 3 months) Chronic (>3 months)

Host age Pediatric or adult

●

Elderly males

●

IV drug abuse (Currier et al. 1999, Hadjipavlou et al. 2000, Sapico et al. 1979, Perronne et al. 1994)

Causative Bacteria

Gram-positive Aerobic Cocci

●

Most common (>80% of all isolates in one series) (Hadjipavlou et al. 2000)

●

Staphylococcus aureus isolated in more than 50% of all infections (Currier et al. 1999, Hadjipavlou et al. 2000, Sapico et al. 1979)

●

Recent increase in methicillin-resistant S. aureus is a growing concern (6.8% of all isolated bacteria in one series) (Hadjipavlou et al. 2000)

●

Streptococcus is the second most common followed by coagulase-negative staphylococcus (20% and 15% of

Table 16–2: Location of Vertebral Pyogenic

Osteomyelitis and Secondary Epidural Abscesses

REGION LUMBAR THORACIC CERVICAL

Spondylodiscitis 50% 35% <10% Secondary epidural abscess 40% 33% 27%

(% of total cases)

Secondary epidural abscess 24% 33% 90%

(% of cases within a specific spinal region)

isolates in one series, respectively) (Hadjipavlou et al.

2000)

Gram-negative Aerobic Cocci

●

15%-20% of isolates in one series (Hadjipavlou et al.

2000)

●

Organisms responsible for urinary tract infections are the most common

●

Escherichia coli

●

Pseudomonas aeruginosa (also frequent in IV drug abusers)

●

Proteus species

Gastrointestinal Tract Organisms

●

Salmonella is rare, but the following is true:

●

Has been reported following acute gastroenteritis or cholecystitis

●

Has a tendency to localize in preexisting diseased tissue

●

Is associated with sickle cell disease