BACKGROUND CONTEXT: Cervical disc arthroplasty (CDA) is an innovative procedure launched in the early 2000s. Compared with anterior cervical discectomy and fusion, many studies show that CDA offers equivalent clinical outcomes while reducing secondary procedures and total cost. PURPOSE: We sought to determine the incidence of anterior bone loss after CDA and the related biomechanical effects. STUDY DESIGN/ SETTING: Retrospective chart review. PATIENT SAMPLE: Patients who underwent CDA with one level Bryan Disc (Medtronic Sofa-morDanek, Memphis, TN, USA) at one institution. OUTCOME MEASURES: Radiological measurements, including the extent of anterior bone loss, global alignment angle, shell angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global range of motion (ROM) and ROM of the index level were recorded. The grading of anterior bone loss of the index level was defined as Grade 0, no remodeling; Grade 1, spur disappearance or mild change in body contour; Grade 2, obvious bone regression with Bryan Disc exposure.

AimAn estimated 88% of rheumatoid arthritis (RA) patients experience various degrees of cervical spine involvement. The excessive movement of the atlantoaxial joint, which connects the occiput to the upper cervical spine, results in atlantoaxial instability (AAI). AAI stabilization is usually achieved by C1 lateral mass‐to‐C2 pedicle screw‐rod fixation (LC1–PC2 fixation), which is technically challenging in RA patients who often show destructive changes in anatomical structures. This study aimed to analyze the clinical results and operative experiences of C1–C2 surgery, with emphasis on the advancement of image‐guided surgery and augmented reality (AR) assisted navigation.MethodsWe presented our two decades of experience in the surgical management of AAI from April 2004 to November 2022.ResultsWe have performed surgery on 67 patients with AAI, including 21 traumatic odontoid fractures, 20 degenerative osteoarthritis, 11 inflammatory diseases of RA, 5 congenital anomalies of the os odontoideum, 2 unknown etiologies, 2 movement disorders, 2 previous implant failures, 2 osteomyelitis, 1 ankylosing spondylitis, and 1 tumor. Beginning in 2007, we performed LC1–PC2 fixation under C‐arm fluoroscopy. As part of the progress in spinal surgery, since 2011 we used surgical navigation from presurgical planning to intraoperative navigation, using the preoperative computed tomography (CT) ‐based image‐guided BrainLab navigation system. In 2021, we began using intraoperative CT scan and microscope‐based AR navigation.ConclusionThe technical complexities of C1–C2 surgery can be mitigated by CT‐based image‐guided surgery and microscope‐based AR navigation, to improve accuracy in screw placement and overall clinical outcomes, particularly in RA patients with AAI.

BACKGROUND Ossification of the posterior longitudinal ligament (OPLL) is a rare but potentially devastating cause of severe spinal cord compression and degenerative cervical myelopathy. Because OPLL is rarely accompanied by prominent syringomyelia, when both are observed, other causes of syringomyelia should be considered. Simultaneous presentation of OPLL and hemangioblastoma of the cervical spine is a rare encounter and has never been reported in the English-language literature. OBSERVATIONS The authors present a case of a 64-year-old man with muscle weakness of the right upper limb and worsening dysesthesia of the right thumb and index finger. Noncontrast magnetic resonance imaging (MRI) of the cervical spine from another institution revealed OPLL from the C2 to C6 levels with severe spinal cord compression and prominent syringomyelia. Repeated MRI with contrast showed an intramedullary tumor, about 11 mm in diameter, at the right posterior aspect of the C4 level. The authors performed laminectomies from C1 to C6 with posterolateral fusion and removed the C4 tumor. Pathohistological examination of the tumor demonstrated hemangioblastoma. LESSONS Careful evaluation of the preoperative imaging study is extremely important in surgical decision making. Although rare, concomitant cervical hemangioblastoma should be listed in the differential diagnosis when OPLL is accompanied with prominent syringomyelia.