Atlanto occipital dissociation should be treated surgically as soon as possible. If immediate surgery is not possible, the dissociation may be reduced by gentle traction while awaiting surgery.
2. Preliminary remark
The halo ring can be placed under local anesthesia in conscious patients. The patient is in a supine position on a stable surface.
3. Halo ring installation
The circumference of the patients head is measured and an appropriately sized halo ring is selected.
The ring should allow 1-2 cm clearance from the skull.
Temporary halo fixation
The appropriate halo ring is placed with temporary stabilization pins.
Anterior screws are inserted 1 cm superior to the lateral 1/3 of the eyebrows.
The eyelids should be kept closed.
The posterior screws are placed approximately 5 cm posterior to the ear.
Ideally any posterior screw should be directed towards its contralateral anterior screw, and vice versa.
Care should be taken to prevent contact between the halo ring and the ears.
For adults at least four screws are necessary. For children, 6-8 screws are recommended. The halo ring should be placed inferior to the equator of the skull.
The pin sites are cleaned with a disinfectant and the skin and periosteum is infiltrated with local anaesthesia.
During insertion of the screws, the eyelids of the patient should be kept closed. Screws are inserted into the supraorbital rim with the eyelids open, the patent may not be able to close the eyelids postoperatively.
Initially the permanent screws are tightened by hand, followed by the use of a torque screw driver. Opposing screws are tightened sequentially 1, 2, 3, and 4.
For adults the maximum torque should be set to 0.56 kg/cm3 and 0.28 kg/cm3 for children.
Reduction is made by gentle maneuvers not to injure the spinal cord.