Double-level myelopathy due to atlantoaxial dislocation (os odontoideum) and subaxial cervical spondylosis with angular kyphosis.

BACKGROUND: The surgical management of cervical spondylotic myelopathy (CSM) attributed to os odontoideum (OO with atlantoaxial instability atlantoaxial instability) and subaxial kyphosis together pose significant surgical challenges. CASE DESCRIPTION: An elderly male presented with CSM/myelopathy and severe quadriparesis attributed to an unstable OO and 87° fixed, subaxial cervical kyphosis. After performing a 540° spinal cord decompression with atlantoaxial fixation, the patient did well.
CONCLUSION: Double-level CSM due to an unstable OO and subaxial kyphosis is rare and typically requires combined 540° decompression and stabilization. Copyright:

INTRODUCTION

Unstable os odontoideum (OO) with atlantoaxial dislocation and subaxial “draping of the cervical spinal cord” over a kyphotic deformity contributed to dual-level significant cord compression and myelopathy in a 78-year-old male.[1-11]

Following a 540° anterior-posterior-anterior decompression and fusion, the patient improved.

CASE REPORT

A 78-year-old wheel chair bound male developed a severe spastic quadriparesis with sphincter disturbance over a 2-year period. His modified Japanese Orthopedic Association (mJOA) score was 8. Cervical X-rays, MR, and CT studies demonstrated OO instability with subaxial C4-C6 cord compression; there was an accompanying 87° fixed kyphosis [Figures 1-3].

Figure 1:

Lateral cervical radiographs, (a) lateral showing 87° subaxial kyphosis, (b) in flexion, kyphosis is aggravated with flexion, note atlantoaxial dislocation, (c) in extension, shows that the kyphosis is fixed.

Figure 3:

Computerized tomography scan sagittal reconstructed shows a posteriorly displaced os odontoideum.

Magnetic resonance imaging (a) demonstrates cervical myelopathy and posteriorly displaced os odontoideum (b) note two myelopathy patches one at upper and one at mid-cervical region.

Surgical intervention

The patient underwent a C2 to C7 laminectomy with C1 lateral mass screw placements and insertion of bilateral pedicle screws from C2 to C7 bilaterally [Figure 4]. After assembling a rod on one side from C2 to C7, multilevel Smith-Peterson osteotomies (SPOs) were performed on the contralateral side and vice versa [Figures 5 and 6]. An expandable cage was placed within the corpectomy site; when it became loose intraoperatively, the patient had to undergo anterior cage repositioning. Notably, all procedures were performed utilizing intraoperative neuromonitoring that demonstrated no changes.

Figure 4:

Intraoperative fluoroscopy shows inserting pedicle screws before posterior osteotomy.

Figure 5:

Smith-Peterson osteotomy from C2 to C7 along with pedicle screws, note at corpectomy site, short screws is used, note anterior osteotomy at corpectomy levels.

Figure 6:

Intraoperative fluoroscopy after assembling the rods, note an acceptable lordosis could be obtained.

The intraoperative cervical cross-table X-ray ultimately confirmed adequate C1 to C7 instrumentation with a 100° correction of the kyphosis [Figure 7a]. Three months later, the patient was able to eat and button his shirt without difficulty and ambulated with a walker (mJOA score: 11) [Figure 7b]. At 1 postoperative year, he demonstrated no further recovery, and the cervical X-ray showed no further changes in sagittal alignment [Figure 8].

Figure 7:

Cervical X-ray (a) lateral cross table. A week after surgery, lordosis is 13°, this means that 100° correction. (b) Lateral in sitting position.

Figure 8:

Plain cervical X-ray at 1-year FU (a) AP and (b) lateral X-ray at 1-year follow-up.

DISCUSSION

Management of OO with instability

The discovery of a symptomatic OO in an elderly patient is rare; we found only 12 such cases in the literature.[8,9] The management of symptomatic OO with reducible atlantoaxial instability has evolved to now using either a C1-2 screw rod fixation or the Harms technique.[4-8]

Treatment of subaxial CK

With an angular kyphosis from 30° to 90°, 540° surgery with a combination of anterior-posterior-anterior decompression/fusion may be warranted. In this case, while supine, the patient underwent a two-level corpectomy with three-level anterior osteotomy (C4-C6) (ATO).[2] Secondarily, while prone a C2 to C7 laminectomy with C1 lateral mass screw placements, and insertion of bilateral pedicle screws from C2 to C7 with multilevel SPOs were performed (C2-C7) [Figures 8 and 9].[10,11] In addition, a third anterior procedure was required to revise the “loose: anterior construct.”

Figure 9:

Schematic drawing, (a) front view the sites of foraminotomies and pedicle screw insertion, (b) lateral view shows the amount of lateral masses that should be drilled at each level with posterior osteotomy.

CONCLUSION

For patients displaying OO/instability and subaxial cervical kyphosis, combined anterior followed by posterior decompression/fusion surgery may be warranted.