Posterior Occipitocervical Instrumentation and Fusion for Ventral Compression in Rheumatoid Arthritis: Case Report

Rheumatoid arthritis (RA) is the commonest inflammatory disorder to affect the cervical spine, with a predilection for the atlantoaxial joint complex.(21) Characteristic changes occur in various organs and tissues throughout the body as a result of a chronic systemic autoimmune inflammatory response. The precise mechanisms behind the pathogenesis of RA are not fully defined, however, it is commonly held that in patients with RA the synovium of joints express an antigen that triggers the production of rheumatoid factor, an IgM immunoglobulin which is directed against autologous IgG. This interaction, mediated by polymorphonuclear leukocyte infiltration, complement activation and immune complex formation, leads to the propagation of a chronic inflammatory response. Rheumatoid pannus, is the term used to describe the granulation tissue that forms within the synovium by proliferating fibroblasts and inflammatory cells. It has been suggested that this pannus may also represent fibrous tissue that occurs as a result of instability, as well as occurring as a consequence of the inflammatory response.(21)

Stethoscope over a medical reportIn patients suffering from RA, involvement of thoracic or lumbar spine is quite rare, in comparison to the frequency of involvement of the cervical spine. Most commonly, anterior atlantoaxial subluxation, vertical atlantoaxial subluxation with basilar invagination/cranial settling, subaxial subluxation, or a combination of the aforementioned ocurrs.(16) The subaxial changes can occur in a stepladder fashion.(20) The cause of these instabilities is probably as a result of destruction of the synovial joints and their supporting capsules and ligamentous structures. The incidence of cervical findings correlates to the duration of rheumatic disease.(16) In more than half of patients with polyarticular RA, the radiological changes in the cervical spine are due to instability.(1) Half of these patients may show clinical signs of instability or medullary compression.(19) Typical symptoms can include headache or neck pain, neck stiffness or more peripheral neurological symptoms. The changes in the cervical spine are typically mirrored by the changes in peripheral joints.(24)The deterioration in cervical spine lesions, can be correlated to serum levels of C–reactive protein, as well as to the number of joints that have marked erosive changes in the systemically. (9) Male sex, seropositivity, and a history of corticosteroid therapy have also been correlated with more extensive cervical involvement.(21)

When medullary compression occurs, it does because of several possible mechanisms that can occur in isolation or in concert. Subluxation at the atlantoaxial level can lead to canal narrowing. Impingement of inflammatory periodontoid pannus onto the perimedullary subarachnoid space and neural structures can also occur. Finally, vertical migration of the odontoid into the foramen magnum can cause direct compression.

The management of cervical disease in patients with RA typically involves decompression and fusion, despite potentially poor bone quality, when patients become symptomatic, or when neurological signs develop.(1),(14) Some authors have suggested decompression alone may play a role without fusion, particularly in the management of subaxial disease,(4) although this view is not widely embraced.(15),(22) For atlantoaxial instability, surgical stabilization is generally recommended.(5),(6),(13) When there is direct cord and brainstem compression by inflammatory pannus, direct anterior decompression via a transoral approach has been advocated,(2),(6),(7),(23) particularly if the compression does not reduce with traction. Alternatively, a reduction in the inflammatory retrodental pannus can be facilitated by posterior occipitocervical fusion alone, with posterior decompression, as required.(11),(25) This case report describes a patient with multiple cervical complications of RA and describes the management of brainstem compression due to periodontoid pannus by a standalone posterior instrumented approach.

Mrs J.B. was a 70 year–old right–handed white female with a 32 year history of polyarticular RA, first reviewed in January, 2000. She initially presented with a 2 year history of progressive parasthesiae and numbness with associated weakness, in both hands, progressing proximally to involve her arms. These symptoms had been slowly progressive. She also described loss of sensation on her finger tips and difficulty in fine motor skills with her right hand for everyday tasks. Over the 3 preceding months prior to being initially reviewed, she also noted that she had increasing unsteadiness of gait. There was no neck pain or headache and her bladder and bowel function was unaffected. J.B. had a significant past medical history of RA, which was still active and quite severe. The RA affected a spectrum of joints, particularly her hands and feet, with an absence of extra–articular features. Typically she would have an hour of morning stiffness, and in the past, because of the severity of her erosive arthropathy, had undergone several joint replacements, including both knees, and left hip. Her past medical history was also significant for essential hypertension, which was reasonably well controlled on medication. She had no allergies. Her current medications included aspirin, fosamax, non–steroidal anti–inflammatory medications (NSAID), prednisone (10 mg daily), gold injections (monthly), hormone replacement therapy and metoprolol. She had been on various doses of prednisone for the past 15 years. Her family history was not significant. She had a 15 pack year history of smoking, having ceased 15 years previously. She also had a 20–30 gram intake of alcohol per day.

Her general physical examination was significant for the typical RA changes in her hands and feet. The remainder of the general physical examination was unremarkable. There was no cervical tenderness, but rotation and flexion/extension in the neck were reduced by 50%. Her cranial nerve examination was unremarkable. There was hypertonia in her right arm. Strength assessment revealed 4+/5 weakness of her proximal right arm and leg, with greater weakness distally (4/5) in these limbs. Power on her left side was unaffected. There was hyperreflexia of her right upper limb deep tendon reflexes, but those in her lower limbs were symmetrical and not pathologically brisk. Hoffman’s sign could not be elicited in either upper extremity. Babinski reflexes were equivocal bilaterally and her gait was not grossly spastic, although tandem gait was poor.

Baseline routine investigations, including routine blood tests, electrocardiogram and a chest x–ray were unremarkable. A two–dimensional echocardiogram, performed the year previously, revealed grade 1 out of 4 left ventricular function with no segmental wall motion abnormalities. Spirometry showed an FEV1 of 107% of predicted with an FEV1/FEVC ratio of 101%.

Routine cervical spine x–rays showed marked degenerative changes in the cervical spine (see Figure 1) with cranial settling and basilar invagination confirmed by a Ranawat index19 of 10 mm. The odontoid process was poorly defined. There was extensive subaxial disease with degenerative spondylolisthesis at C4–5 and C5–6. There was no movement on flexion/extension. In view of the progressive nature of the myelopathy, MRI and CT scanning of the cervical spine were ordered. The MRI scan (see figure 2) showed that at the level of the foramen magnum, marked ventral compression of the brainstem and upper cervical spine was occurring, secondary to inflammatory periodontoid pannus. The medulla and pons were kinked over this ventral mass. In the subaxial spine, compression of the spinal cord occurred at several levels from C3 to C7, with associated T2–weighted high signal changes in the adjacent spinal cord. This was due to a combination of both ventral and dorsal compression. Hyperlordosis with Grade I C4–5 and C5–6 spondylolistheses were also noted, with markedly degenerative discs at several levels in the cervical spine. CT scanning was performed primarily to assess the bony anatomy and functional state of the occipitocervical joints as well as the atlantoaxial joint complex (see Fig 3 and 5). Figure 3 shows sequential axial 1mm fine cut CT scans from the tip of the odontoid process to the base of the C2 body. The erosive changes in the C1/C2 joints are defined. The transverse atlantal ligament appears intact. Figure 5 shows CT reconstructions in the sagittal and coronal plane of the cervical spine, to illustrate the markedly degenerative changes occurring in both the occipitoatlantal joints, as well as the atlantoaxial joints. Subaxial facet joint changes are also noted.

J.B. is a 70 year–old female with severe RA and clinically a progressive myelopathy with MRI and CT evidence of compression of upper cervical spinal cord and medulla/pons by a combination of retro–odontoid pannus and cranial settling (Ranawat measure 10 mm), as well as destructive changes in her C0–C2 joint complexes. Coupled with this, J.B. has extensive subaxial degenerative disease with cervical stenosis from C3–C7, as well as multilevel spondylolistheses at several levels in her lower cervical spine.

Initial Management
Because of the progressive myelopathy observed clinically, coupled with the marked degree of compression and kinking of neural structures at the level of the foramen magnum, surgical intervention was offered to the patient and her family. The patient gave informed consent, and gold therapy was ceased for 1 month prior to the planned surgical date, with aspirin and NSAID medication ceased 2 weeks after this date. J.B. was admitted to hospital 1 week prior to the planned surgical date and a halo ring was applied with cervical traction instituted, commencing at 0.5 kg. Over the next 72–96 hours, the weight applied to the traction apparatus was increased, to achieve a total weight of 10 kg. With each incremental increase in weight, repeat x–rays of her cervical spine were taken and serial neurological assessments were performed. She remained stable throughout. Once 10 kg of traction had been achieved, a halo vest was applied in this position. X–rays of her cervical spine taken at this time showed no change in the degree of cranial settling, but some realignment of her subaxial spine (see figure 4). Repeat fine cut CT scanning of her cervical spine was performed using an image–guided protocol in preparation for surgery (see Figure 5).

Operative Procedure
On February 3, 2000 J.B. was brought to the operating room and intubated using an awake fiberoptic technique. Somatosensory evoked potential (SSEP) recording was utilized throughout the induction of anesthesia and operative procedure, particularly during positioning in the prone position. These recordings were stable throughout. A combination of real time digital fluoroscopy, as well as CT image–guidance using a frameless stereotactic apparatus (Surgical Navigation Network, Mississauga, Ontario, Canada) were utilized (see Figure 6). The trajectory for the transarticular screws had been planned preoperatively, and no vertebral artery anomalies were noted. The pars interarticularis on the left, however, was deemed to be too narrow to accept a suitable screw safely, and as a result only a right transarticular screw was planned. A standard exposure via a posterior midline incision was effected, with subperiosteal dissection to expose from the occiput to T2 (see figure 7). A laminectomy with bilateral foraminotomies from C3–C6 was performed in a standard fashion. Dural compression was most marked at the C4/5 level. Using image guidance and real time digital flouroscopy, a 45 mm self–tapping (3.5 mm diameter) screw was placed transarticularly through the right C1/C2 joint. (see figure 8). In a similar fashion, 24 mm (3.5 mm diameter) T1 pedicle screws were also placed bilaterally. Finally, lateral mass screws (14 mm length, 3.5 mm diameter) were placed from C3–C7 (excluding the right C3 lateral mass, as the bone quality was poor in this area). The entry point for these was 1 mm medial to the midpoint of the lateral mass, with cranial angulation of 15–20° and lateral angulation of 25–30°. After decortication and placement of left iliac crest allograft, two Cervifix® rod/plate constructs (SYNTHES Spine, Paoli, PA) were then contoured and secured to the occiput using a combination of 10–16 mm bicorticate occipital screws. The transarticular, lateral mass and pedicle screws were then secured to this construct and C1/C2 Songer cerclage sublaminar titanium cables (De Puy AcroMed, Raynham, MA) completed the construct. (see Figure 9). After hemostasis was achieved, the wound was thoroughly irrigated with saline solution and a standard multilayered wound closure was effected.

Postoperative Course
Immediately after surgery, J.B. awoke and moving all four extremities well. There was no worsening of her preoperative neurological state and she was mobilized satisfactorily in a rigid cervical orthosis. Plane x–rays of her cervical spine showed satisfactory placement of the hardware (see figure 10). MRI scanning performed on February 14, 2000, approximately 10 days after surgery, showed restoration of sagittal balance in her cervical spine, with improvement in the degree of basilar invagination and ventral cervicopontomedullary compression (see Figure 11). The patient had a protracted hospital course, primarily because of general medical complications related to her RA, but was eventually discharged home. At last follow up 3 months after surgery, there was no progression in her myelopathy and her plain cervical spine x–rays were satisfactory.

This case report describes a patient with cervicomedullary compression/kinking, secondary to periodontoid RA pannus, managed by one stage posterior decompression and instrumented fusion. In this example, use of preoperative traction allowed for the correction of subaxial instability and despite anterior compressive pathology, posterior instrumentation led to relief of this compression. Typically, in the management of degenerative disease of the cervical spine, the approach is usually dictated by the site of compression. The pathophysiology of cervical spine disease in RA is, however, unique in comparison to seronegative degenerative arthropathies and consequently this dictum does not necessarily apply.

Grob et al11 reported on 22 patients with atlantoaxial instability and verified periodontoid pannus on MRI. All patients underwent posterior cervical instrumented fusion. Follow–up consisted of clinical, radiologic and MRI scanning for 12– 75 months after surgery. In all patients the retrodental pannus significantly decreased in size postoperatively, or disappeared. If significant cranial migration of the dens was present, anterior decompression was performed. Symptomatic reduction in neck pain was also achieved. No patient had neurological deterioration.

It is difficult to correlate standard measures of atlantoaxial instability with the clinical manifestations of myelopathy.(3),(8) This may be because the presence or absence of periodontoid pannus is not considered in relying on these measures alone.(11),(18) Similarly, it is unclear what time course regression of pannus takes. In this example, changes were seen as early as 10 days after surgery, although reestablishment of normal craniocervical anatomy contributed to the improvement in the degree of compression. Marked changes have been noted radiologically in terms of pannus reduction by 4–6 months after surgery.(11)

The precise technique of posterior instrumented occipitocervical fusion can involve different permutations of screws, rods, plates, metal loops, mesh and wires.(12),(25) It has been shown that a better reduction is achieved using plating and screws as opposed to wiring, with lower pseudoarthrosis rates and higher rates of neurological improvement.(5),(10)

RA is a difficult management problem for the spinal surgeon. Treatment is complicated by the patient’s general debility, with poor tissue quality and impaired wound healing being compounded by the concomitant negative effects of rheumatoid medications. Perioperative mortality in modern series still stands at 5–10%.(17) This case illustrates that combined 360 degree decompression/fusion at the craniocervical junction may not be required if cervicomedullary compression is occurring as a result of periodontoid pannus, and confirms previous reports suggesting similar results. With careful preoperative assessment, use of “drug holidays”, the application of cervical traction to ensure optimal preoperative reduction, intraoperative CT–guided navigation and meticulous postoperative nursing care and attention to wound healing and nutrition, a one stage posterior occipitocervical decompression and instrumented fusion may suffice as definitive therapy for brainstem distortion and kinking due to periodontoid pannus, as well as allowing potential atlantoaxial and subaxial instability to be addressed. It is vital to ensure careful clinical and radiologic follow up is instituted to ensure that pannus absorption occurs and neurological decline is halted.


x-ray of c-spine

(Above) Figure 1: Lateral c–spine xray taken in the neutral position. The Ranawat index is shown, measured from the center of the sclerotic C2 pedicle to the midpoint of a line joining the anterior to the posterior arch of the atlas. A value below 13 mm is suggestive of cranial settling. In this case, the measure was calculated to be 10 mm. The odontoid was poorly defined. Spondylotic changes in the subaxial spine are marked and there is an exaggerated cervical lordosis.

scans of cervical spine

(Above) Figure 2: T1–weighted (left) and T2– weighted MRI scans of the cervical spine and craniocervical junction elegantly demonstrate the pathology at this level. At the level of the foramen magnum marked ventral compression of the brainstem and upper cervical spine is occurring secondary to periodontoid pannus. There is 4 mm of superior migration of the odontoid above the level of foramen magnum. In the subaxial spine, compression of the spinal cord is occurring at several levels from C3 to C5 with associated T2–weighted high signal intensity in the spinal cord. Hyperlordosis with Grade I C4–5 and C5–6 subluxation is also present, with markedly degenerative disc spaces.

sequential axial fine cut CT scans

(Above) Figure 3: Sequential axial fine cut CT scans from the tip of the odontoid process to the base of the C2 body. There are erosive changes in the C1/C2 joint complex. The transverse atlantal ligament appears intact.

lateral c-spine x-rays taken before and after the application of cervical traction

(Above) Figure 4: Lateral c–spine x–rays taken before and after the application of cervical traction. The halo ring was applied, and 10 kg of skull traction was applied with serial radiological and clinical assessments. Once this goal had been achieved, the halo vest was applied in this position. It is notable that although some restoration of sagittal alignment did occur in the subaxial spine, the degree of cranial settling was unaffected.

CT reconstructions in the sagittal spine
CT reconscrutions of coronal plane

(Above) Figure 5: CT reconstructions in the sagittal (top row) and coronal (bottom row) planes to illustrate the degenerative changes occurring in both the occipitoatlantal joints, as well as the atlantoaxial joints. Because of the extent of disease involving the C0/C1 joints, instrumentation was extended to the occiput.

operating room setup for posterior C1/C2 instrumentation

(Above) Figure 6: Typical operating room setup for posterior C1/C2 instrumentation. In addition to real–time fluoroscopy, image–guidance is also utilized to facilitate the optimal planning of trajectories for transarticular screw placement.

Standard exposure using subperiosteal dissection

(Above) Figure 7: Standard exposure using subperiosteal dissection from the occiput to T2.

placement of transarticular screws

(Above) Figure 8: The placement of transarticular screws was facilitated through the use of CT guided frameless stereotaxy, as well as real time intraoperative fluoroscopy.

C3-6 laminectomy

(Above) Figure 9: The final construct, demonstrating the C3–6 laminectomy, with the Cervifix® plate/rod construct attached to occipital screws, a right C1/C2 transarticular screw, lateral mass screws from C3–7, and bilateral T1 pedicle screws. Sublaminar wires are also seen at the C1/C2 levels.

postoperative instrumentation
postoperative instrumentation

(Above) Figure 10: Postoperative AP and lateral cervical spine x–rays demonstrating adequate placement of the instrumentation and restoration of some sagittal alignment.

pre and post op scans

(Above) Figure 11: Comparative T2– weighted sagittal MRI scans of the cervical spine, showing the preoperative study and that performed 10 days after surgery. Note that the subaxial spine deformity has been corrected, with improvement in the degree of ventral compression of the brainstem and upper cervical spine in the vicinity of the odontoid process.

Updated on: 11/02/16
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