Occipitocervical Instability

Posted bythespinebookadminPosted inTopics, Trauma

Background 

  • Aka atlanto occipital dissociation 
  • Degen or trauma 
    • Down’s – most frequently, asymptomatic, identified in screening for surgery or special olympics prep 
  • 15-30% of injuries at OC junction 

Pediatric 

  • Don’t do halo 

Mechanism 

  • High energy 
  • Translation or distraction 

Associated 

  • AA instability (Down’s) 
  • Neuro deficit 
  • Vertebral artery injury 

Anatomy 

  • Occipito Atlanto Axial Complex 
    • 6 articulation 
    • A and P medial Atlanto Odontoid joints 
    • Paired occipttoatloid joints 
    • Paired atlantoaxial jointts 
  • Ligaments 
    • TL 
      • Bony tubercles on atlas anterior arch 
    • Paired alar 
      • Odontoid to occip condyles 
    • Apical 
      • Odontoid to foramen 
    • Tectorial membrane 
      • Cephalad continuation of PLL 
      • Very strong 
      • If this is torn very bad (Dr. Ahn) 

Classification  

  • Traynelis 
    • Anterior occiput 
    • Longitudinal 
    • Posterior 
  • Harborview 
    • Stage 1 – minimal or non displaced, unilateral ligament damage 
    • Stage 2 – minimal displaced but MRI shows ++ soft tissue (stable or unstable) 
    • Stage 3 – Gross unstable 

Imaging 

  • XRs 
    • Powers ratio 
      • AB/CD (I don’t know why they chose the letter to stupid) 
      • AB – basion (front of foramen) to posterior arch 
      • CD – opsthion (bask of forramen) to anterior arch 
      • 1 – normal 
      • > 1 anterior dislocation 
      • <1 posterior dislocation (or ring fractures or odontoid fracture) 
    • Harris rule of 12 
      • Basion-dens or basion posterior axial interval 
        • BDI 
        • BPAI 
      • >12 is occipitocervical dissociation 
  • CT gold standard 
  • CT angio (vertebral arteries, preop) 
  • MRI – neuro deficits, occult injury, suspected type 2 

Management 

***DO NOT DISTRACT PATIENTS 

  • Stage 1 – Halo 
  • Stage 2 – MRI shows ligament injury 
    • Traction test for CCJ Instability (OAA Instability) 
      • 5 then 10 pounds traction 
      • Lateral XR 
      • Positive if: fracture displacement >2mm, AO distraction >2mm, At Ax >3mm 
    • Stable – Halo 
    • Unstable – OC fusion 
  • Stage 3 – OC fusion 

Complications 

  • Internal carotid 
  • Vertebral artery