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Anterior C1-C2 pannus


Introduction

C1-C2 pannus most commonly results from both chronic instability of the atlanto-axial segment and an inflammatory process of the atlanto-axial joint (AAJ). These degenerative processes are typically associated with rheumatoid arthritis (RA) and cause ligamentous structural destruction. RA affects an estimated 1% to 2% of the adult population. Although RA spares the axial skeleton, the cervical spine is an important exception, being involved in up to 86% of all patients with this condition. Cervical inflammatory disease usually manifests as atlanto-axial subluxation (AAS), cranial settling (CS), and subaxial subluxation (SAS). Interestingly, spinal involvement is commonly described as a late manifestation of the condition. Moreover, 50% of the patients who suffered from RA for at least 7 years may develop craniocervical complications. Neurological symptoms are reported in 7% to 34% of all the patients, where neck pain is the most common symptom. Other notable symptoms radiculopathy, myelopathy, and cranial nerve dysfunction, where the presence of multiple cranial neuropathies strongly suggests the presence of a cervical pannus. Pannus develops from the inflamed synovial lining surrounding the odontoid and is typically located between the dens and the anterior arch of C1. Pannus involving the AAJ leads to further instability and may cause progressive compression of the cervico-medullary junction. The prevalence of a C1-C2 pannus ranges from 32% to 93%. Standard radiography is considered the first-line imaging method of choice and is indicated as a routine evaluation for patients with RA. Magnetic resonance imaging (MRI) is the best modality to assess the C1-C2 pannus, dens erosions, and neurological impact of the rheumatoid lesions. Patients with persistent neck or suboccipital pain and neurological impairment should undergo surgical treatment. Arthrodesis and posterior stabilization of the atlanto-axial segment remain the preferred techniques in cases of RA with cervical articular degeneration and pannus. Direct mass removal is not advocated as retrodental pannus significantly diminishes after immobilization.

Example Case

  • Chief complaint: neck pain, upper limb weakness

  • History of present illness: An 81-year-old male patient presents with progressive neck pain for a year, and he has a 6-month history of difficulty using his hands and lifting his arms. The patient underwent a computed tomography (CT) scan and x-rays as part of his evaluation ( Fig. 12.1 ).

    Fig. 12.1, Preoperative imaging. (A) Sagittal T2-weighted imaging and (B) sagittal computed tomography scan demonstrating severe C1-C2 central canal stenosis resulting from hypertrophic synovial tissue from the atlanto-odontoid joint (pannus). There is severe compression of the spinal cord with increased cord signal. The odontoid process appears irregular due to the presence of erosion. The atlanto-dental distance shows mild widening. There is also C2-C7 ankylosis secondary to diffuse idiopathic skeletal hyperostosis. (C) Lateral x-rays demonstrating osteopenia with prominent osteophytes along the upper cervical spine with slightly milder changes inferiorly. The motion was limited but there was no dynamic instability.

  • Medications: warfarin, oxycodone

  • Allergies: no known drug allergies

  • Past medical and surgical history: atrial fibrillation, coronary artery disease, deep vein thrombosis

  • Family history: none

  • Social history: smoking, occasional alcohol

  • Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/triceps/biceps 5/5; right interossei 4/5; left interossei 5/5; iliopsoas/knee, flexion/knee extension/dorsi, and plantar flexion 5/5

  • Reflexes: 3+ in bilateral biceps/triceps/brachioradialis with positive Hoffman; 3+ in bilateral patella/ankle; three beats of ankle clonus and positive Babinski; sensation intact to light touch

  • James S. Harrop, MD

  • Neurosurgery

  • Jefferson University

  • Philadelphia, Pennsylvania, United States

  • John G. Heller, MD

  • Orthopaedic Surgery

  • Emory University

  • Atlanta, Georgia, United States

  • Manoj Phalak, MCh

  • Neurosurgery

  • All India Institute of Medical Sciences

  • New Delhi, India

  • Mohamed A.R. Soliman, MD, MSc, PhD

  • Neurosurgery

  • Cairo University

  • Cairo, Egypt

Preoperative
Additional tests requested

  • C-spine flexion-extension x-rays

  • CT C-spine

  • C-spine lateral flexion-extension x-rays

  • Standing full-length AP/lateral spine x-rays

  • CTA C-spine

  • Urine nicotine test

  • Medicine evaluation

  • MRI complete spine and craniovertebral junction

  • Standing full-length AP/lateral spine x-rays

  • PET

  • Cardiology evaluation

  • Anesthesia evaluation

  • CT head and C-spine spine

  • CTA head and C-spine spine

  • MRI C-spine with flexion-extension

  • DEXA

  • Lower extremity Dopplers

  • Medicine, anesthesia, rheumatology evaluation

Surgical approach selected C1–4 laminectomy and C1–5 posterior fusion C1 laminectomy, C1–2 instrumented fusion, with possible extension to the occiput Confirm no malignancy, C1–2 laminectomy C1 and foramen magnum decompression and C1–2 posterior fusion
Goal of surgery Decompress spinal cord, stabilize C1–2 Decompress spinal cord, stabilize C1–2, reduce C1–2 subluxation Decompress spinal cord Decompress medulla and spinal cord, stabilize C1–2
Perioperative
Positioning Prone with neck neutral and Mayfield pins Prone with Mayfield pins Prone on horseshoe headrest Prone with Mayfield pins on Jackson table
Surgical equipment

  • Fluoroscopy

  • IOM (MEP/SSEP, BAERs)

  • Fluoroscopy

  • IOM (MEP/SSEP)

  • Fluoroscopy

  • Ultrasonic bone scalpel

  • Fluoroscopy

  • IOM

  • Surgical navigation

  • Ultrasound

  • Surgical microscope

Medications Steroids Maintain MAP None Steroids, maintain MAP
Anatomical considerations Occipital bone, vertebral arteries C2 nerve roots, venous plexus, spinal cord, vertebral arteries Dura, vertebral artery Vertebral artery, neural structures, C1–2 bony anatomy
Complications feared with approach chosen Spinal cord injury, CSF leak, vertebral artery injury Spinal cord injury, vertebral artery injury, nonunion, pseudoarthrosis Spinal instability, vertebral artery injury, medical complications Vertebral artery injury, stroke, brainstem and spinal cord injury
Intraoperative
Anesthesia General General General General
Exposure C1–5 C1–2 C1–2 Occiput-C2
Levels decompressed C1–4 C1 C1–2 Occiput-C1
Levels fused C1–4/5 C1–2 None C1–2
Surgical narrative Intubated with fiberoptic, head fixed in Mayfield pins, baseline IOM, prone position with neutral neck, stable IOM, midline incision, expose C1–5, C-arm to identify levels, bilateral C1 lateral mass/C2 pars screws, C3–5 lateral mass screws, drill off C1 and C2 lamina, en bloc laminectomy of C3–5, subfascial drain Intubated with head/neck in neutral position, preflip IOM, position prone adjusting brow-chin angle to desired position, lateral x-ray document C1–2 relationship and brow-chin angle, postflip IOM, standard midline posterior exposure of C1 and C2, detach extensor insertions into the spinous processes and lamina of C2, C1 laminectomy avoiding ventral manipulation of lamina, section C2 nerve proximal to dorsal root ganglia on one or both sides in order to provide more bony surface for fusion/venous control of plexus/removal of some pseudopannus, screws in C1 articular mass and C2 pars or pedicle depending on local anatomy, pack cancellous iliac crest autograft into decorticated C1–2 joint posteriorly and filling void between exposed remaining portions of C1 arch and C2 pars, add BMP inside the joints before bone graft, bur hole in C2 spinous process and repair muscle attachments with nonabsorbable suture, layered closure Fiberoptic intubation avoiding neck manipulation, position prone on horseshoe headrest with collar, avoid IOM and monopolar cautery because of pacemaker, midline incision, subperiosteal dissection exposing C1 posterior arch up to 1.5 cm from midline on either side, maintain C2 attachments, confirm level with x-ray, C1 laminectomy using bone scalpel or high-speed drill with partial drilling of superior C2 lamina, look for posterior displacement of thecal sac and pulsation, layered closure Intubated with fiberoptic intubation avoiding neck extension and/or manipulation, baseline IOM check, patient positioned prone with head in neutral position, intraoperative fluoroscopy to confirm good alignment, attach surgical navigation, incision made from inion to 3 cm below C2, dissect in avascular plane of ligamentum nuchae, subperiosteal dissection of neck muscles from spinous process of C2/lamina of C1, expose lateral mass of C1 and C2, register navigation, identify boundaries of C1 lateral mass, retract C2 nerve root downward, place C1 lateral mass with Goel technique and place C2 pedicle screw, use preoperative CT to estimate length and width of screws, another intraoperative spin to confirm screw position, decorticate lateral mass and joints, place slightly lordotic rod, decompress foramen magnum using high-speed drill and C1 laminectomy with Kerrison rongeurs, confirm decompression with ultrasound, place autograft on decorticated bone, closure in layers
Complication avoidance Avoid occipital screws, baseline IOM Pre- and postflip IOM, section C2 nerve root to facilitate fusion/hemostasis/pseudopanns removal, iliac crest bone graft and BMP, repair muscle attachments to C2 spinous process through bur hole Avoid IOM and monopolar cautery because of pacemaker, expose C1 posterior arch up to 1.5 cm from midline on either side, maintain C2 attachments, look for posterior displacement of spinal cord and normal pulsations to assess adequacy of decompression Baseline IOM, surgical navigation, ultrasound to assess decompression
Postoperative
Admission Spine unit ICU ICU Floor
Postoperative complications feared Dysphagia, spinal cord injury, CSF leak Hematoma, stroke, loss of fixation, nonunion, malpositioning of head Spinal instability, vertebral artery injury, medical complications Worsening neurological function, CSF leak, pseudoarthrosis
Anticipated length of stay 2–3 days then rehab 5–7 days 5–7 days 3–4 days
Follow-up testing Standing x-ray

  • C-spine x-rays 6 weeks, 3 months, 6 months, 12 months after surgery

  • CT C-spine 6 or 12 months after surgery

C-spine flexion-extension x-rays prior to discharge and 3 months after surgery

  • CT head and cervical spine within 24 hours of surgery and 6 months after surgery

  • MRI brain and cervical spine within 3 days of surgery

Bracing 6 weeks Rigid collar for 12 weeks when out of bed Philadelphia collar for 6 weeks None
Follow-up visits 2 weeks with APP, 6 weeks 6 weeks, 3 months, 6 months, 12 months after surgery 10 days and 3 months after surgery 10–14 days, 4 weeks, 3 months, 6 months, 1 year after surgery
APP , Advanced practice provider; BAERs , brainstem auditory evoked responses; BMP , bone morphogenic protein; CSF , cerebrospinal fluid; CT , computed tomography; CTA , computed tomography angiography; DEXA , dual-energy x-ray absorptiometry; ICU , intensive care unit; IOM , intraoperative monitoring; MAP , mean arterial pressure; MEP , motor evoked potentials; MRI , magnetic resonance imaging; SSEP , somatosensory evoked potentials.

Differential diagnosis

  • ▪

    Cervicomedullary junction tumor

  • ▪

    Retro-odontoid synovial cyst

  • ▪

    Epidural hematoma

  • ▪

    Calcium pyrophosphate arthropathy

  • ▪

    Basilar invagination

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