Lateral mass screws safe and effective for subaxial cervical fusion
Despite the many techniques used to place lateral mass screws, the overall goal for these devices is to obtain solid bony fixation while avoiding neurovascular structures, according to a study that discussed the Magerl, Anderson and An techniques for placing lateral mass screws in the subaxial spine.
Researchers noted indications for lateral mass fixation in the cervical spine are the same as those for posterior cervical fixation, such as when increased stability is needed after complex anterior spine procedures and when fusion success is required after anterior cervical discectomy pseudarthrosis.
The investigators noted they prefer the An technique to the Magerl and Anderson techniques. It involves a starting point 1 mm medial to the midpoint of the lateral mass. They noted the angle should be 30° to 33° lateral and 15° to 17° cephalad.
The surgeon needs to ensure the borders of the lateral mass can be readily seen and can be palpitated during the procedure, the researchers noted.
If the C7 lateral mass is small, they suggested using a C7 pedicle screw. However, the muscle attachments to the C2 and C7 spinous processes must not be disrupted, according to the abstract.
In addition, the lateral mass screws need to be angled laterally and superiorly to obtain solid bony fixation. Avoiding the vertebral artery and exiting nerve root is also important, according to the investigators.
The researchers noted the nursing and anesthesia staff should be aware that patients who undergo posterior cervical fusion may experience significant spinal cord compression. Therefore, care should be taken during positioning and intubation to prevent a spinal cord injury during those maneuvers. – by Robert Linnehan
Disclosures: The researchers report no relevant financial disclosures.