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Rheumatoid Arthritis in the Cervical Spine Abstract The cervical spine often becomes involved early in the course of rheumatoid arthritis, leading to three different patterns of instability: atlantoaxial subluxation, atlantoaxial impaction, and subaxial subluxation. Although radiographic changes are common, the prevalence of neurologic injury is relatively low. The primary goal of treatment is to prevent permanent neurologic injury while avoiding potentially dangerous and unnecessary surgery. Strategies include patient education, lifestyle modification, regular radiographic follow-up, and early surgical intervention, when indicated. Magnetic resonance imaging is indicated when neurologic deficit (myelopathy) occurs or when plain radiographs show atlantoaxial subluxation with a posterior atlantodental interval ≤14 mm, any degree of atlantoaxial impaction, or subaxial stenosis with a canal diameter ≤14 mm. Surgery should be considered promptly for any of the following: progressive neurologic deficit, chronic neck pain in the setting of radiographic instability that does not respond to nonnarcotic pain medication, any degree of atlantoaxial impaction or cord stenosis, a posterior atlantodental interval ≤14 mm, atlantoaxial impaction represented by odontoid migration ≥5 mm rostral to McGregor’s line, sagittal canal diameter <14 mm, or a cervicomedullary angle <135°. R heumatoid arthritis (RA) is a chronic inflammatory autoim- mune disorder characterized by poly- arthritic disturbance of peripheral joints and early involvement of the cervical spine. RA is relatively com- mon, affecting 0.5% to 1.5% of the US population and twice as many women as men. 1 The etiology of the disease is unknown but is likely to be multifactorial, with a relatively strong genetic component. RA re- duces life expectancy, and half of all afflicted patients become disabled within 10 years of diagnosis. 2 The course of the disease in any given pa- tient, however, is unpredictable and may be relentlessly progressive or characterized by intermittent flares and remissions. Current medical treatment involves early and aggres- sive use of disease-modifying anti- rheumatic drugs, such as methotrex- ate, antimalarial drugs, sulfasalazine, and gold. Early clinical studies sug- gest that pharmacologic blockade of tumor necrosis factor-α with etaner- cept or infliximab can preserve joint function and favorably affect the nat- ural history of the disease. 3 Chronic synovial inflammation leads to progressive destruction of the joints, ligaments, and bone, par- ticularly in the atlantoaxial region. Eventually, this process leads to clinical manifestations of pain, de- David H. Kim, MD, and Alan S. Hilibrand, MD Dr. Kim is Assistant Clinical Professor of Orthopaedic Surgery, Department of Orthopaedic Surgery, Tufts University School of Medicine, Boston, MA, and The Boston Spine Group, New England Baptist Hospital, Boston. Dr. Hilibrand is Associate Professor, Departments of Orthopaedic Surgery and Neurosurgery, and Director of Medical Education for the Department of Orthopaedic Surgery, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA, and The Rothman Institute, Philadelphia. None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Kim and Dr. Hilibrand. Reprint requests: Dr. Hilibrand, The Rothman Institute, 925 Chestnut Street, Philadelphia, PA 19107-4216. JAmAcadOrthopSurg2005;13:463- 47 4 Copyright 2005 by the American Academy of Orthopaedic Surgeons. Volume 13, Number 7, November 2005 463 formity, instability, and neurologic deficits. Three characteristic pat- terns of instability resulting from rheumatoid involvement of the cer- vical spine have been described; each may occur in isolation or in combi- nation: atlantoaxial subluxation, at- lantoaxial impaction, and subaxial subluxation. Each form of instabili- ty can lead to compression of or in- jury to the spinal cord or brainstem and can progress to paralysis or death. Treatment strategies for the rheumatoid cervical spine include patient education and lifestyle mod- ification, periodic assessment for ra- diographic signs of increased risk of neurologic injury, and early surgical intervention to prevent permanent neurologic injury. Epidemiology After the hands and feet, the cervical spine is the most common site of disease involvement in RA. 4 De- pending on the population and diag- nostic criteria, between 17% and 86% of patients with RA have evi- dence of cervical spine disease. 5 Sev- eral studies of patients with RA sug- gest that the cervical spine becomes involved early in the course of the disease, often within the first 2 years following diagnosis. 6 A prospective study of 103 Finnish patients with rheumatoid factor–positive RA re- vealed a 20-year incidence of atlan- toaxial subluxation of 23%, atlanto- axial impaction of 26%, and subaxial subluxation of 19%. 7 Pathophysiology The cervical spine is composed of 22 separate synovial joints, all potential targets of rheumatoid disease. 5 The synovial joints between the trans- verse atlantal ligament and the odon- toid process, as well as those between the anterior atlas arch and the odon- toid, are frequently involved. The oc- cipitoatlantal and atlantoaxial artic- ulations are the only segments in the spine without intervertebral disks, which may account for the high prev- alence of disease in the upper cervi- cal spine in patients with RA. Atlantoaxial Subluxation Rheumatoid involvement of the synovial joints in the cervical spine is characterized by formation of pan- nus, an inflammatory tissue with variable fibrous content. Synovitis and pannus formation can weaken the transverse, alar, and apical liga- ments. The weight of the head, par- ticularly with neck flexion, contrib- utes to the repetitive strain of these ligaments, leading to stretching or rupture and the onset of atlantoaxi- al subluxation. Transverse ligament weakening and rupture occur most commonly at the site of a synovial bursa separating the ligament from the posterior surface of the odontoid. Inflammation also leads to decalcifi- cation and occasional rupture of the ligamentous insertion sites on the atlas. Erosion of the odontoid process, a hallmark of RA, may occur anterior- ly at its synovial joint with the arch of C1, posteriorly at its synovial joint with the transverse ligament, and at the tip of the odontoid in re- lation to the apical ligament inser- tion. Asymmetric patterns of ero- sion can lead to various radiographic instability patterns, including an- teroposterior, rotatory, or lateral sub- luxations (Table 1). Both rotatory and lateral subluxation patterns can result in torticollis. Atlantoaxial subluxation may oc- cur in up to 49% of RA patients and usually manifests as anterior sub- luxation of the atlas (C1) on the ax- is (C2). 8 This increased anterior at- lantodental interval and decreased posterior atlantodental interval is apparent on lateral cervical spine ra- diographs, particularly with the neck in flexion (Figure 1). As sublux- ation increases with time, the space available for the spinal cord decreas- es, which may compress or injure the spinal cord. However, in patients with a large spinal canal, an anterior atlantodental interval >10 mm may be seen without any apparent neuro- logic sequelae. The reducibility of atlantoaxial subluxation, either with extension positioning or external traction, is important in planning treatment. Initially, subluxation may be purely dynamic, appearing only on flexion views. Eventually, pannus may be- come interposed between the anteri- or atlas arch and the odontoid, con- verting a dynamic subluxation into a fixed one. Atlantoaxial Impaction Involvement of the atlanto- occipital and atlantoaxial joints can lead to weakening and collapse of the lateral masses, with rostral mi- gration of the odontoid process and atlantoaxial impaction. Atlantoaxial impaction also has been referred to as superior migration of the odon- toid, cranial settling, and basilar in- vagination. The prevalence of atlan- toaxial impaction is reportedly between 5% and 32% and generally is thought to follow the appearance of atlantoaxial subluxation. 5 Com- pared with other instability patterns, atlantoaxial impaction appears to carry the worst prognosis and a much higher risk of myelopathy. The symptomatology of atlanto- axial impaction is highly variable. Compression of the C1 and C2 nerve roots leads to occipitocervical pain. Ventral pressure on the medulla ob- longata can injure local cranial nerve nuclei or cause sudden death by Table 1 Patterns of Rheumatoid Arthritis in the Cervical Spine Atlantoaxial subluxation Anterior Posterior Lateral Rotatory Atlantoaxial impaction Subaxial subluxation Rheumatoid Arthritis in the Cervical Spine 464 Journal of the American Academy of Orthopaedic Surgeons compressing the respiratory center. The anterior spinal artery and verte- bral arteries also can be compro- mised, leading to neurologic deficits, vertebrobasilar insufficiency, or tran- sient ischemic attacks. 9,10 With pro- gression of atlantoaxial impaction and greater penetration of the odon- toid process into the foramen mag- num, the degree of atlantoaxial sub- luxation may decrease in a process referred to as “pseudostabilization.” 5 However, any reduction in atlan- toaxial subluxation with the pro- gression of atlantoaxial impaction actually carries a worse prognosis because of the increased risk of brainstem injury and sudden death. 11 Subaxial Subluxation Destabilization of the facet joints as a result of weakening of the facet capsules and interspinous ligament results in anterior subaxial sublux- ation. Although marked degenera- tive disk changes are consistently present, synovitis has not been ob- served in disk or annular tissue. Therefore, anterior spinal disease does not appear to contribute direct- ly to the development of subaxial subluxation. This instability pattern is a relatively late manifestation of cervical spine disease and is ob- served in 20% to 25% of patients with RA. 5 It is also the most fre- quently observed new instability pattern following upper cervical fu- sion in RA patients. Subaxial sub- luxation occurs most frequently at the C2-3 and C3-4 levels and typical- ly affects multiple adjacent levels, yielding a characteristic “staircase” deformity and associated kypho- sis. 6,12 Spinal cord compression oc- curs anteriorly from the proximal edge of the vertebral body distal to the slip or posteriorly from the neu- ral arch of the slipped vertebrae. Sub- axial subluxation may not be appar- ent on radiographs with the patient in neutral position but should be- come apparent, when present, on flexion or extension views. Clinical Presentation Rheumatoid involvement of the cer- vical spine is often asymptomatic. Neck pain, the most frequent com- plaint, may be present in 40% to 80% of patients. 5 Characteristically, pa- tients describe the pain as a deep ache radiating into the occipital, retro- orbital, or temporal areas. The tem- poral pattern is typically mechanical and readily distinguishable from the typical pain of r heumatoid s ynovitis. Pain referred to the face, ear, or sub- occiput originates from irritation of the C2 nerve root supply to, respec- tively, the nucleus of the spinal trigeminal tract, greater auricular nerve, or greater occipital nerve. 13 Some patients with atlantoaxial subluxation report the sensation of the head falling forward during neck flexion. 14 A clunking sensation also can occur during neck extension with spontaneous reduction of atlan- toaxial subluxation; this has been la- beled a positive Sharp-Purser test. 15 Stiffness, crepitus, and painful range of motion also are common com- plaints. Sleep apnea may be caused by brainstem compression associat- ed with atlantoaxial impaction. 16 Objective neurologic signs are present less frequently than pain but may be found in 7% to 34% of pa- tients. 17,18 In contrast to radiograph- ic changes, which appear early in the course of RA, neurologic deficits usually appear later, most common- ly in late middle-age patients. They may be difficult to elicit in patients with more advanced disease. Ex- tremity weakness is thought to re- sult from advancing joint involve- ment with neurologic symptoms. Signs of cervical myelopathy, the clinical manifestation of spinal cord Figure 1 A 65-year-old woman with rheumatoid arthritis and progressive cervical myelopathy. A, Lateral radiograph of the cervical spine reveals atlantoaxial subluxation. The anterior atlantodental interval measures 4 mm and the posterior atlantodental interval measures 14 mm. Sagittal (B) and axial (C) T2-weighted MRI scans reveal significant additional reduction in space available for the cord to 7 mm because of a large soft-tissue pannus posterior to the odontoid process. David H. Kim, MD, and Alan S. Hilibrand, MD Volume 13, Number 7, November 2005 465 compression, should be sought, in- cluding a wide-based spastic gait, clumsy hands, a visible change in handwriting, or difficulty manipu- lating buttons or handling coins. Other classic physical findings asso- ciated with myelopathy include hy- perreflexia, a positive Babinski test, and a positive Hoffmann sign. Mild motor and reflex deficits may be im- possible to identify in patients with significant pain and deformity of ex- tremity joints. Lhermitte’s sign, the sensation of electric shocks traveling down the torso or upper extremities on neck flexion, suggests myelopa- thy. Urinary retention, followed by overflow incontinence, is a symp- tom of severe myelopathy. Occa- sionally, injury to the pyramidal tract decussation can manifest as a “cruciate paralysis,” with varying degrees of upper extremity weakness that may be symmetric or asymmet- ric. 10 This injury pattern is often dif- ficult to distinguish from central cord syndrome. Radiographic Evaluation Plain Radiography Appropriate preoperative screen- ing for cervical spine disease in pa- tients with RA is a controversial subject. No radiographic screening protocol is universally accepted. Nevertheless, certain groups of pa- tients should be considered strong candidates for preoperative radio- graphic screening (Table 2). All pa- tients with RA should undergo an initial series of cervical spine radio- graphs, including an anteroposterior view and lateral views with the pa- tient in the neutral position as well as in flexion and extension. These radiographs are recommended before any surgical procedure requiring in- tubation. One study of 113 RA pa- tients undergoing elective hip or knee arthroplasty found that 61% demonstrated evidence of instabili- ty, defined by at least 3 mm of dy- namic atlantoaxial subluxation, by atlantoaxial impaction (according to Ranawat’s method), or by subaxial subluxation, although only 50% of patients were symptomatic. 19 Atlantoaxial Subluxation Traditionally, an anterior atlanto- dental interval >5 mm was consid- ered diagnostic of atlantoaxial sub- luxation. However, several studies have demonstrated that the anterior atlantodental interval does not cor- relate with the risk of neurologic injury. 19-21 Boden et al 20 showed that measurement of the posterior atlan- todental interval appears to be a more reliable predictor of neurolog- ic deficit in patients with atlantoax- ial subluxation; a value ≤14 mm has been suggested as an indication for surgical stabilization (Figure 2). The posterior atlantodental interval also may be used to predict neurologic re- covery after surgery. Atlantoaxial Impaction Several radiographic measure- ment techniques have been suggest- ed as means to gauge the severity of atlantoaxial impaction. The original definition of atlantoaxial impaction was protrusion of the odontoid above the margins of the foramen magnum, also known as McRae’s line. Because identifying the mar- gins of the foramen magnum on plain radiographs is difficult, alter- native landmarks have been estab- lished (Figure 3). McGregor’s line is defined on a l ateral radiograph by the hard palate and the base of the oc- ciput (opisthion). Protrusion of the tip of the odontoid above McGre- Table 2 Indications for Anteroposterior and Lateral Radiographs of the Cervical Spine* in Patients With Rheumatoid Arthritis Prolonged cervical symptoms >6 months Neurologic signs or symptoms Scheduled procedures requiring endotracheal intubation in patients who have not had cervical radiographs in the last 2 to 3 years Rapidly progressive carpal or tarsal bone destruction Rapid overall functional deterioration * Neutral, flexion, and extension Figure 2 Diagrammatic representation of atlantoaxial subluxation typically seen in patients with rheumatoid arthritis. The posterior atlantodental interval (PADI) is measured from the posterior margin of the odontoid process to the anterior margin of the posterior arch of C1. (Reproduced with permission from Boden SD, Dodge LD, Bohlman HH, Rechtine GR: Rheumatoid arthritis of the cervical spine: A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am 1993;75:1282-1297.) Rheumatoid Arthritis in the Cervical Spine 466 Journal of the American Academy of Orthopaedic Surgeons gor’s line >4.5 mm is considered diagnostic of atlantoaxial impac- tion. 20 The presence of odontoid erosion can make all of these radiographic measurements inaccurate. For this reason, other techniques have been developed to diagnose atlantoaxial impaction on plain radiographs, even with significant odontoid ero- sion. 22 These include the Ranawat method, designed to assess the ex- tent of collapse at the atlantoax- ial articulation, and the Redlund- Johnell method, which uses the dis- tance between the anterior axis base and McGregor’s line 22 (Figure 4). Subaxial Subluxation The radiographic appearance of subaxial subluxation is characteris- tic and includes not only sagittal plane listhesis of sequential verte- bral bodies but also posterior ele- ment changes, including facet joint erosions and widening, whittling, or spindling of the spinous processes (Figure 5). There are multiple def- initions of subaxial subluxation. Figure 3 Radiographic landmarks for assessing atlantoaxial impaction in patients with rheumatoid arthritis. On a lateral radiograph, atlantoaxial impaction is diagnosed by protrusion of the odontoid tip proximal to McRae’s line or 4.5 mm above McGregor’s line. (Adapted with permission from Riew KD, Hilibrand AS, Palumbo MA, Sethi N, Bohlman HH: Diagnosing basilar invagination in the rheumatoid patient: The reliability of radiographic criteria. J Bone Joint Surg Am 2001;83:194-200.) Figure 4 Methods to assess atlantoaxial impaction on plain radiographs. A, Ranawat method. A line (a) is drawn across the transverse axis of the atlas, and a connecting line (b) is drawn through the vertical axis of the odontoid from the center of the C2 pedicle radiographic shadow. Values (x)<15 mm in men and <13 mm in women are diagnostic for atlantoaxial impaction. B, Redlund- Johnell method. A line (a) is drawn between McGregor’s line (b) and the midpoint of the inferior end plate of C2 (c). A value (x)<34 mm in men and <29 mm in women is diagnostic for atlantoaxial impaction. (Adapted with permission from Riew KD, Hilibrand AS, Palumbo MA, Sethi N, Bohlman HH: Diagnosing basilar invagination in the rheumatoid patient: The reliability of radiographic criteria. J Bone Joint Surg Am 2001;83:194-200.) David H. Kim, MD, and Alan S. Hilibrand, MD Volume 13, Number 7, November 2005 467 Yonezawa et al 12 described subaxial subluxation as >4 m m o r 20% listhe- sis of vertebral body diameter. Magnetic Resonance Imaging Although plaintomography,cine- radiography, computed tomography (CT), and CT myelography have been used to follow the rheumatoid cervical spine, these studies have been supplanted by the use of mag- netic resonance imaging (MRI). MRI provides the most detailed defini- tion of the craniocervical junction, including the size of rheumatoid pannus. The finding of odontoid ero- sion on MRI is considered highly specific for RA and may clarify the diagnosis in otherwise nonspecific cases. 23 The space-occupying effect of the periodontoid pannus can be visual- ized clearly on MRI. Both T1- and T2-weighted images provide excel- lent visualization of brainstem or spinal cord contour. Increased signal intensity within the spinal cord on T2-weighted images may represent edema, gliosis, or myelomalacia and has been associated with poor neuro- logic recovery following surgery. 24 The cervicomedullary angle can be measured on MRI by drawing a line along the anterior aspect of the cervical spinal cord and the medulla. This angle normally is between 135° and 175° (Figure 6). With progressive craniocervical disease, the brain- stem angulates ventrally over the displaced odontoid process, leading to increased obliquity of the cervi- comedullary angle. One study re- ported a 100% correlation between a cervicomedullary angle <135° and neurologic signs of cervicomedullary compression, myelopathy, or C2 ra- diculopathy. 25 The utility of flexion-extension or so-called dynamic MRI evaluation has been debated. 26 A theoretic ad- vantage is the ability to identify, when the patient is in the neutral position, potentially significant dy- namic cord compression before sta- tic compression is apparent. One study suggested that cord diameter in cervical flexion <6 mm is a risk factor for neurologic deficit. 27 How- ever, a theoretic risk of sudden death exists as a result of prolonged cervi- cal flexion in a patient with severe instability; therefore, the recommen- dation for routine dynamic MRI in these patients may need to change. Natural History Understanding of the natural histo- ry of the rheumatoid cervical spine is limited. Most studies have been handicapped by small sample size or retrospective design. Oda et al 28 re- viewed the records of 49 patients fol- lowed radiographically for a mini- mum of 5 years and identified a progressive pattern of cervical sub- luxations. The earliest instability pattern is most often a reducible at- lantoaxial subluxation. 6 Transition from reducible subluxation to an ir- reducible subluxation often ac- companies atlantoaxial impaction, which appears, on average, 6 years after atlantoaxial subluxation. 11 Sub- axial subluxation occurs less fre- quently than do the other two pat- terns and generally develops after atlantoaxial impaction. 29 Forty percent to 80% of patients with rheumatoid subluxations dem- onstrate radiographic progression. 17 Neurologic deficits occur much less frequently and do not correlate well with radiographic progression. 17 Rana 30 retrospectively reviewed the records of 41 patients with atlanto- axial subluxation who were followed for 10 years; 61% of patients had no change, 27% had progressive sublux- ation, and 12% had improvement at final follow-up. Boden et al 20 retro- spectively reviewed the records of 73 patients followed for an average of 7 years. In 31 patients, all treated non- surgically, no significant neurologic deficit developed during the observa- tion period. Of the 42 patients (58%) in whom paralysis developed, 7 were managed nonsurgically. Six of the Figure 5 Lateral radiograph demonstrating subaxial subluxation across the C3 through C5 segments, with associated facet joint erosions and spinous process changes. Figure 6 Midsagittal T-2-weighted MRI scan of the craniocervical junction in a patient with atlantoaxial impaction. The cervicomedullary angle (CMA) is defined by the angle subtended between a line parallel to the long axis of the brainstem (a) and a line parallel to the cervical spinal cord (b). Rheumatoid Arthritis in the Cervical Spine 468 Journal of the American Academy of Orthopaedic Surgeons seven patients treated nonsurgically experienced progressive neurologic deterioration, and all seven died within 4 years of the onset of paral- ysis, five from cord compression. Of the 35 patients who underwent sur- gery, 25 (71%) experienced marked neurologic improvement. Despite the general impression that rheumatoid involvement of the cervical spine does not contribute to increased mortality in this patient population, the high rate of sudden death observed in patients with un- treated myelopathy argues against this conclusion. 31 When myelopathy appears, the mortality rate increases dramatically; without surgery, most patients die within 1 year. 32 An au- topsy study of 104 patients with RA identified 11 with atlantoaxial sub- luxation and notable spinal cord compression; most had experienced sudden death. 33 This finding sug- gests that the mortality rate from cervical spine instability in patients with RA may be as high as 10%. Grading systems have been devel- oped to assess disease severity as well as treatment outcomes. The Ranawat grading system is widely used in clinical studies but has been criticized for lacking the ability to discriminate mild degrees of myel- opathy 34 (Table 3). The Zeidman and Ducker modification of the Nurick myelopathy scale provides more dif- ferentiation, with an assessment of gait and hand function, and may be more useful 10 (Table 4). However , its failure to account for severity of ra- diculopathic complaints significant- ly limits this system for guiding sur- gical decision making. Risk Factors and Predictors of Recovery Several risk factors for progression of atlantoaxial subluxation have been suggested, including male sex, rheu- matoid factor seropositivity, higher initial C-reactive protein level, presence of subcutaneous nodules, and advanced peripheral joint dis- ease, specifically rapid loss of carpal height. 6,18,28,36,37 HLA-DR4 and B-27 seropositive antibodies do not ap- pear to be significant risk factors. 6 Whether corticosteroid treatment represents an independent risk fac- tor remains controversial. 38 Patients with any degree of atlantoaxial im- paction or cord compression on MRI are at significant risk of neurologic injury and should be considered strong candidates for prophylactic decompression and/or stabiliza- tion. 37,39 Plain radiography is an efficient and inexpensive means of monitor- ing disease progression. Boden et al 20 found that the posterior atlanto- dental interval and subaxial sagittal canal diameter correlated with the presence and severity of paralysis, whereas the anterior atlantodental interval did not. Using a standard tube distance of 6 feet (1.8 m), 96% of patients with atlantoaxial sublux- ation and paralysis demonstrated a posterior atlantodental interval ≤13 mm. In contrast, 60% of the same patients had an anterior atlantoden- tal interval <9 mm. All patients with subaxial subluxation and paralysis demonstrated a subaxial sagittal ca- nal diameter ≤13 mm. Boden et al 20 found the posterior atlantodental interval to be a predic- tor of surgical outcome. Postopera- tively, no patient experienced signif- icant neurologic recovery when the preoperative posterior atlantodental interval measured <10 mm. In pa- tients with isolated atlantoaxial sub- luxation, a posterior atlantodental interval of at least 10 mm predicted improvement of at least one Rana- wat class. In the setting of atlanto- axial subluxation and atlantoaxial impaction, recovery required a pre- operative posterior atlantodental in- terval ≥13 mm. All patients with a preoperative posterior atlantodental interval and subaxial sagittal canal diameter measuring at least 14 mm experienced complete motor recov- ery. Multiple studies have suggested that the degree of preoperative neu- Table 4 Zeidman and Ducker Modification of Nurick Grading Scale for Myelopathy 10 Grade Radiculopathy Myelopathy Gait Hand Function 0 Present Absent Normal Normal I Present Present Normal Slight II Present Present Mildly abnormal Functional III Present Present Severely abnormal Unable to button IV Present Present With assistance only Severely limited V Present Present Nonambulatory Useless Table 3 Ranawat Grading Scale for Myelopathy 35 Grade Severity I Normal II Weakness, hyperreflexia, altered sensation IIIA Paresis and long-tract signs, ambulatory IIIB Quadriparesis, nonambulatory David H. Kim, MD, and Alan S. Hilibrand, MD Volume 13, Number 7, November 2005 469 rologic deficit is also a strong predic- tor of postoperative neurologic re- covery. 40,41 Factors with no apparent predictive value in terms of recovery include age, sex, duration of paraly- sis, and preoperative anterior atlan- todental interval. 42 Nonsurgical Treatment Patients with rheumatoid involve- ment of the cervical spine benefit from early, aggressive medical inter- vention as well as regular follow-up. Because of the prevalence and early appearance of cervical spine involve- ment, screening cervical spine radio- graphs should be considered in all patients with RA. Regular follow-up radiography should then be per- formed in patients with any evi- dence of cervical spine involvement, especially when they have advanced peripheral joint disease. At least one study has demonstrated that early, aggressive combination disease- modifying antirheumatic drug ther- apy can prevent or delay develop- ment of atlantoaxial subluxation. 43 Soft cervical collars are appropri- ate treatment of symptomatic pa- tients with relatively minor occipi- tocervical pain and may occasionally represent the treatment of choice in elderly or debilitated patients who are poor surgical candidates. 44 Unfor- tunately, orthoses may be problem- atic in patients with temporoman- dibular joint involvement. Although they offer excellent relief of symp- tomatic neck pain, soft cervical col- lars do not provide much limitation of motion and probably do not alter the natural history of cervical spine disease. 5 Progressive neurologic de- terioration has been observed in pa- tients with spinal cord myelopathy treated with a soft collar. 20 A comprehensive program of pa- tient education, physical therapy, collars, practical aids, symptomatic treatment, and disease-modifying antirheumatic drugs achieves signif- icant (P < 0.001) lasting pain relief in most patients. 45 Patients should be taught to avoid cervical flexion. Physical therapy should focus on isometric strengthening of neck muscles and overall postural train- ing. Narcotic medication may be ap- propriate for short-term relief of acute pain, but when chronic narcot- ic use is required for pain relief, then surgical treatment should be consid- ered. Surgical Management The goals of surgical treatment of rheumatoid disease of the cervical spine are to achieve spinal stability through a solid fusion and to decom- press involved neural structures. The most commonly accepted indi- cations for surgical treatment of RA in the cervical spine include neuro- logic deterioration and intractable pain with spinal instability (Table 5). In addition, Boden et al 20 proposed surgery, even without neurologic findings, when patients demonstrate one of three radiographic risk fac- tors: (1) atlantoaxial subluxation with a posterior atlantodental inter- val ≤14 mm; (2) atlantoaxial impact represented by odontoid migration ≥5 mm rostral to McGregors’s line; or (3) subaxial subluxation with sag- ittal canal diameter ≤14 mm. Patients with RA are a challenging surgical population. Those requiring surgery suffer from a systemic illness and may be significantly malnour- ished and debilitated. In addition to cervical spine disease, micrognathia and temporal mandibular disease make standard intubation difficult and anesthesia hazardous. Excessive trauma caused by standard intuba- tion has been associated with a 14% incidence of upper-airway obstruc- tion following extubation. 46 This rate can be reduced to 1% with fiberoptic assistance. Skin lesions and corticos- teroid use notably increase the rate of wound complications and infections. Poor structural bone quality may ren- der standard surgical fixation tenu- ous and unreliable. Atlantoaxial Subluxation When atlantoaxial subluxation is reducible, a variety of posterior fu- sion techniques are possible, includ- ing Gallie or Brooks wiring, Magerl transarticular screws, or Harms C1-2 lateral mass fixation. 4 Fixa- tion strategies incorporating Magerl screws appear to provide particular- ly stable fixation; a fusion rate of 95% has been reported with use of transarticular screws. 47 The need for postoperative halo-vest stabilization depends on the quality of surgical fixation. When atlantoaxial subluxation is nonreducible, transar ticular screw Table 5 Indications for Surgery in Patients With Rheumatoid Arthritis With Cervical Spine Involvement Progressive neurologic deficit (eg, weakness, gait disturbance, loss of fine motor coordination) Mechanical neck pain unresponsive to nonnarcotic pain medication (in the setting of radiographic evidence of AAS, AAI, or SAS) Radiographic risk factors of impending neurologic injury PADI ≤14 mm in the setting of AAS AAI represented by odontoid migration ≥5 mm rostral to McGregor’s line Sagittal canal diameter ≤14 mm in patients with SAS Any degree of AAI or cord stenosis A cervicomedullary angle <135° AAI = atlantoaxial impaction, AAS = atlantoaxial subluxation, PADI = posterior atlantodental interval, SAS = subaxial subluxation Rheumatoid Arthritis in the Cervical Spine 470 Journal of the American Academy of Orthopaedic Surgeons fixation in combination with C1 laminectomy should be considered, especially when the patient has pos- terior cord compression. An occipi- tocervical fusion is an alternative. MRI studies revealing significant pannus resorption after spinal stabi- lization indicate that, if bone is not impinging anteriorly on the cord, then odontoid resection may be un- necessary. 48 Sublaminar wire fixa- tion is contraindicated when atlan- toaxial subluxation cannot be reduced. Atlantoaxial Impaction Because the risk of neurologic in- jury is high with atlantoaxial impac- tion, early surgery following identi- fication of this condition has been recommended. 41 Neurologic deficit or evidence by MRI of cord compres- sion is a strong indication for sur- gery. 13 The use of preoperative halo traction has been recommended to reduce the degree of atlantoaxial im- paction and obviate foramen mag- num decompression or odontoid re- section. An occipitocervical fusion can be performed using wires or screws attached to the occiput below the superior nuchal line and con- nected to fixation in the subaxial spine (Figure 7). When traction is un- successful, symptomatic decompres- sion with a transoral odontoid resec- tion or C1 laminectomy, along with posterior stabilization, is required. 4 An alternative technique for multi- level instability including atlantoax- ial impaction is a long rod loop fixed with occipital and cervical laminar wires without attempted fusion. Subaxial Subluxation Evidence from clinical studies suggests that patients with subaxial subluxation and neurologic deficits, or asymptomatic patients with a subaxial canal diameter ≤14 mm, should be considered for surgical sta- bilization. 20 Preoperative halo-vest immobilization can provide tempo- rary stabilization and reduction of displacement, often with immediate improvement in neurologic defi- cits. 49 Reducible subluxations can be fused anteriorly or posteriorly, but optimal treatment of irreducible subluxations is anterior decompres- sion and fusion. 23,34 Posterior fusion should be strongly considered fol- lowing any laminectomy 50 (Figure 8). The extent of fusion required is often not apparent but is a critical decision because RA is progressive. Instability patterns can occur in combination at multiple levels of the cervical spine. When atlantoax- ial subluxation and subaxial sublux- ation occur concurrently, fusion should be extended to the lowest in- volved level to minimize the risk of junctional degeneration. 51 Some in- vestigators recommend more exten- sive fusions, at times including the entire cervical spine and extending caudally to T1 or T2. 52,53 The extent of postoperative im- mobilization depends on the type of surgical fixation used. Wiring tech- niques typically require rigid immo- bilization in a halo-vest or four- poster orthosis for 8 to 12 weeks. 5 Following plate and screw fixation, a cervical orthosis may be sufficient. New plate, rod, and screw instru- mentation techniques with less rig- id fixation appear to have improved fusion rates and maintenance of alignment but may increase the risk of neurovascular injury. Outcomes of Surgery Over the past 10 years, outcomes of surgery on the rheumatoid cervical spine have improved markedly, largely because of e arlier diagnosis of myelopathy and surgical referral. 54 More aggressive medical manage- ment of RA and a decrease in corti- costeroid use may be additional con- tributing factors. Most studies favor surgery over nonsurgical management for pa- tients with neurologic deficits. 55,56 One of the strongest predictors of postoperative neurologic recovery Figure 7 A 56-year-old woman with rheumatoid arthritis and atlantoaxial impaction. A, Preoperative midsagittal T2-weighted MRI scan demonstrating penetration of the odontoid through the foramen magnum with impingement on the brainstem. B, Postoperative radiograph demonstrating reduction of the occipitoatlantoaxial relationship and occipitocervical instrumented fusion using a plate-and-screw system. David H. Kim, MD, and Alan S. Hilibrand, MD Volume 13, Number 7, November 2005 471 appears to be preoperative neurolog- ic status. Nonambulatory patients demonstrate higher complication rates and lower overall survival. 57 Boden et al 20 reported a retrospective review of the records of 35 patients and found that all Ranawat class II patients had notable neurologic im- provement after surgery compared with 62% of class III patients. Casey et al 58 reported results from their prospective study of 116 pa- tients with atlantoaxial impaction. Transoral odontoid resection was performed for anterior bony com- pression; otherwise, laminectomy and instrumented fusion were done. A higher revision surgery rate was noted in patients without fusion to the occiput. Occipitocervical fusions failed because subaxial instability below the level of fusion progressed. Satisfactory results were more like- ly in patients with better preopera- tive neurologic function. Overall, marked neurologic improvement oc- curred in 45% and significant pain relief in 97% of patients. A high rate of perioperative complications was attributed to the general debility of the patient population; the perioper- ative mortality rate was 10%. Surgical results for subaxial sub- luxation may be less favorable. Olerud et al 52 reported a small retro- spective study of 16 patients with subaxial subluxation and varying de- grees of myelopathy who underwent anterior and/or posterior decompres- sion and fusion. Although neck pain was typically relieved, arm pain im- proved less reliably. Patients with myelopathy had the worst prognosis, and four of five with severe myelop- athy died within 3 months of surgery. The authors recommend early sur- gery for subaxial subluxation, before significant myelopathy develops. The overall complication rate is markedly increased in patients with RA. Wound complications, includ- ing infection, may occur in up to 25% of patients. Generalized os- teopenia correlates with systemic disease activity and compromises fixation strength, leading to in- creased rates of instrumentation f ail- ure. 52 Successful outcomes are pred- icated on achieving solid fusions, and pseudarthrosis has been associ- ated with a less favorable clinical re- sult because of persistent instabili- ty. 20 Recurrent instability in the form of subaxial subluxation at more caudal levels may occur either as a result of the natural progression of the disease or as a result of in- creased stress from an adjacent fu- sion. Current perioperative mortali- ty rates have been reported to be between 5% and 10%, with in- creased rates in patients having coin- cident cardiovascular disease or at- lantoaxial impaction. 34,41,58,59 Summary In most patients with RA, neck pain occurs without significant neurolog- ic deficit. Multimodality therapy, in- cluding patient education, physical therapy, and active medical treat- ment, can be very effective in con- trolling symptoms and limiting dis- Figure 8 A, Preoperative lateral cervical radiograph of a 46-year-old woman with RA myelopathy and subaxial subluxation of C4 on C5. B, Preoperative sagittal T1-weighted MRI scan revealing cervical cord compression at level of subluxation. C, Postoperative radiograph following laminectomy and instrumented fusion using C1-2 transarticular screws and lateral mass screws from C3 to C5. Rheumatoid Arthritis in the Cervical Spine 472 Journal of the American Academy of Orthopaedic Surgeons