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C1 Lateral Mass and C2 Pedicle Screw Fixation


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  • Chapter Synopsis

  • Although many different fixation techniques have been developed to manage atlantoaxial instability, C1 lateral mass–C2 pedicle screw fixation has emerged as a preferred treatment, based on its comparative biomechanical strength and modest risk of neurologic or vascular injury, as well as the ability to perform intraoperative reduction.

  • Important Points

  • Surgical indications include atlantoaxial instability caused by trauma, tumors, infection or inflammatory disease, or congenital abnormalities.

  • Alternative fixation techniques include halo vest immobilization, Brooks or Gallie wiring procedures, and Magerl transarticular screw fixation.

  • The C1 lateral mass–C2 pedicle screw technique is typically used for “stand-alone” fixation, but it may be supplemented by rigid cervical collar immobilization in the early postoperative period.

  • Clinical and Surgical Pearls

  • Reduction of the C1-C2 joint is not required before screw placement and can be subsequently achieved through repositioning of the patient’s head or direct manipulation of the C1 and C2 instrumentation before rod placement.

  • C1 lateral mass screws typically have a 10-mm proximal smooth shank, which increases mechanical strength and theoretically decreases the risk of C2 nerve root neuralgia.

  • C1 lateral mass and C2 pedicle screws are placed with the use of both direct visualization and fluoroscopic guidance.

  • Because of its modularity, C1 lateral mass–C2 pedicle screw fixation can be extended cranially to the occiput or caudally to the subaxial spine, if needed.

  • Clinical and Surgical Pitfalls

  • Preoperative evaluation of atlantoaxial bony anatomy with advanced imaging (computed tomography or magnetic resonance imaging, or both) is crucial to ensure that the C1 lateral masses and C2 pedicles can safely accommodate screw placement.

  • Bleeding from the epidural venous plexus near the C1-C2 joint is common, but it can be controlled with bipolar cautery, FLOSEAL, and cottonoid patties.

  • C2 pedicle screw placement poses the greatest risk of vertebral artery injury, but a superior and medial trajectory decreases this risk.

Atlantoaxial instability can result from multiple disorders, including trauma, tumors, infection and inflammatory conditions, and congenital abnormalities. Regardless of the pathologic process, surgical treatment is often indicated. Surgeons have tended away from halo vest immobilization, which has been associated with significant morbidity and poor patient tolerance, and toward internal fixation techniques performed through a posterior approach. Multiple techniques have been described, including two different posterior wiring procedures described by Brooks and Gallie and C1-C2 transarticular screw fixation described by Magerl.

Although posterior wiring techniques are, in some ways, technically less difficult, they do involve insertion of wires or cables into the spinal canal, a maneuver that poses a risk of spinal cord injury. These techniques also require the use of structural allograft to improve stability and achieve fusion. Even with the addition of halo vest immobilization, however, the rate of pseudarthrosis is up to 30%, as a result of the inferior biomechanical properties of this construct.

The transarticular screw technique provides more stability, based on biomechanical studies, and is also associated with a very high rate of fusion. However, this technique requires reduction of the C1-C2 facet joints bilaterally before screw placement. Additionally, anomalous vertebral artery anatomy, seen in up to 20% of patients, increases the risk of vascular injury and may even preclude the use of this technique.

The most contemporary technique for atlantoaxial fixation was first described by Dr. Jürgen Harms. This technique involves individual screws placed in the lateral masses of C1 and the pedicles of C2 bilaterally connected with rods. The advantages of this technique, also known as the Harms technique, include ability to perform intraoperative reduction and fixation of C1-C2, increased biomechanical strength, and minimized risk of injury to the spinal cord and vertebral artery compared with other fixation techniques. Since its first description in 2001, the Harms technique has been extensively validated in the spinal literature and is now widely used for atlantoaxial fixation.

Preoperative Considerations

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