Indications for Use of Dynamic Four-dimensional Computed Tomography in Diagnosing Instability in Spinal Cervical Conditions
Authors: Lim Kai Zheong , Troupis John M. , Daly Christopher , Oehme David , Goldschlager Tony 
Published: April 2016

Introduction Cervical spinal instability is a pathological consequence of a variety of spine disorders such as trauma, malignancy and degenerative conditions. If left undiagnosed, cervical spinal instability can lead to compressive cervical myelopathy and devastating consequences such as quadriplegia and death. Although dynamic cervical X-ray is traditionally used to detect cervical instability, it provides only two static views and there is no gold standard in diagnosing such condition. Dynamic four-dimensional computed tomography (4DCT) is a non-invasive method that provides functional assessment of cervical motion in high resolution, throughout the entire range of motion. It has been previously shown to be clinically useful in assessing instability and impingement evaluation of the shoulder and finger joint. This is the first early case series utilizing dynamic 4DCT to assess cervical instability in various spinal pathologies. Material and Methods Six elderly patients who presented with neck pain and suspected instability in cervical spine from a major Australian academic hospital were included. In addition to routine imaging modalities, dynamic 4DCT of cervical spine was performed using a 320 × 0.5mm detector multislice-CT (Aquilion One, Toshiba Medical Systems, Japan) with consent. With gantry rotation speed of 275 milliseconds, scans were conducted without table motion with patients in the lateral-decubitus position, capturing approximately seven volume datasets per second. Patients were instructed to continuously move their necks between flexion and extension. Cine movie files were generated from the volume datasets. Results The mean age of the cohort was 69 years old. There was equal male:female ratio. All patients presented with neck pain. Two presented acutely after trauma: one with suspected ligamentous instability at C1/C2; the second presented after recurrent falls with suspected fracture of odontoid process. Four patients had neck pain of more than 6 months at presentation: one had severe rheumatoid arthritis with suspected C1/C2 instability; three patients had cervical spondylotic changes, with one having had a previous anterior cervical discectomy and fusion(ACDF). Before employing 4DCT, MRI and static CT of occipito-cervical regions were performed in five patients; dynamic X-ray of cervical spine at flexion and extension were performed in four patients. Interpretation of the imaging finding in all cases by neuroradiologist and neurosurgeon was found to be equivocal for stability. Dynamic 4DCT confidently ruled in or ruled out cervical spinal instability in all cases: one case was confirmed to have instability; five cases were confirmed to be stable. The one unstable case with severe cervical spondylosis was demonstrated on 4DCT to have instability at C3/C4 level and incomplete fusion from previous ACDF at C5/C6 level and a cervical stabilization procedure was offered. The remaining stable cases included all the trauma cases with a case of os odontoideum diagnosed on 4DCT. Conservative management was prescribed confidently Conclusion Dynamic 4DCT can be used to detect and confirm subtle cervical spinal instability (or lack thereof) with relative ease in various cervical spinal pathologies such as rheumatoid arthritis, cervical spondylosis, os odontoideum and trauma. We propose that dynamic 4DCT has an important role in detecting cervical spinal stability and further studies using this technique are warranted.