Accuracy Assessment of Using Rapid Prototyping Drill Templates for Atlantoaxial Screw Placement: A Cadaver Study

Figure 3

The C1-LMS and C2-PS entry points and directions. (a) The C1-LMS entry point was in the middle of the junction of the C1 posterior arch and the midpoint of the posterior inferior part of the C1 lateral mass (red). The C2-PS entry point was the midpoint between the superior and inferior articular processes (yellow). (b) The C1-LMS was placed in a slightly medial trajectory in the axial plane (red arrows). (c) The C1-LMS was placed parallel to the plane of the posterior arch of the C1 in the sagittal plane (red arrow), and the C2-PS was placed 15–30° cephalad (yellow arrow). (d) The C2-PS was placed 20–25° medially in the axial plane.

(a)

(b)

(c)

(d)