To investigate the clinical outcomes of pedicle screw fixation assisted with the 3D printing positioning guide template for treatment of unstable atlas fractures.

A retrospective case series review was made on 10 patients with unstable atlas fractures undergone direct posterior C₁ pedicle screw fixation assisted with the 3D printing drill guide template from September 2012 to May 2015. There were 7 males and 3 females, with a mean age of 52.6 years (range, 23-75 years). All patients complained of neck pain, stiffness and decreased range of motion without neurologic deficit. Preoperative skull traction was used routinely. After the three-dimension reconstruction of cervical vertebrae, ideal trajectory for C₁ pedicle screws was designed with a complementary basal template for posterior surface of atlas corresponding anatomical structure. Then the drill guide template was materialized in a rapid prototyping machine and used during operation. Start point and direction of the ideal and actual trajectories were measured after matching the position of the pre- and post-operative patients’ cervical spine. Safety of pedicle screw fixation was assessed in the transverse and sagittal planes of CT scan. Operation time and blood loss were recorded. Visual Analogue Scale (VAS) of neck pain was recorded before operation and 3 months after operation. Clinical efficacy, fracture reduction, stability and surgical complications were reviewed at the follow-up.

A total of 20 screws were inserted safely. No significant differences existed in deviation of entry point and direction between ideal and actual trajectories (P>0.05). Operation time was 60-90 min (mean, 75 min) and intraoperative blood loss was 110-300 ml (mean, 160 ml). No spinal cord or vertebral artery injury was noted during operation. All patients were followed up for 12-36 months (mean, 20.5 months). VAS was improved from preoperative 7.3(6.3-9.5)points to 1.4(0.3-2.5) points 3 months after operation (P<0.05). All patients had normal range of motion of the cervical spine 3 months after operation. Bony fusion was achieved 6 months after operation. At the follow-up, good cervical alignment was maintained with no instrument failure and C_1-2 instability.

For treatment of unstable atlas fractures, direct posterior C₁ pedicle screw fixation assisted with the 3D printing drill guide template can improve the precision of screw placement, reduce complications, and preserve the function of the occipital-atlanto-axial junction.

Atlas; Fracture fixation, internal; Rapid prototyping