[Application of pedicle screw internal fixation for atlantoaxial instability of children].

OBJECTIVE: To investigate the effectiveness of pedicle screw internal fixation for the atlantoaxial instability of children.

METHODS: Between July 2005 and January 2012, 19 cases of atlantoaxial instability were treated, included 10 boys and 9 girls with an average age of 7.5 years (range, 4-15 years). The X-ray films, CT, and MRI examinations of the cervical spine showed craniocervical malformation in 9 cases, congenital os odontoideum in 3 cases, odontoid fracture (type II) in 1 case, disruption of transverse ligament in 2 cases, atlantoaxial fracture and dislocation in 4 cases; and spinal cord injury in 8 cases, according to the American Spinal Cord Injury Association (ASIA) impairment scale, 1 case was rated as grade B, 2 as grade C, and 5 as grade D. Preoperative skull traction was performed routinely on all cases, and complete reduction was achieved in 17 cases, no reduction in 2 cases. In 17 patients who achieved complete reduction, pedicle screw internal fixation was used through posterior approach, including occipitocervical fusion and fixation in 5 cases, and atlantoaxial fusion and fixation in 12 cases; in 2 patients with no reduction, pedicle screw internal fixation was used through posterior approach (atlantoaxial fusion and fixation) after release by transoral approach.

RESULTS: The operation was successfully performed in all patients. The mean operation time was 89 minutes; the mean intraoperative blood loss was 95 mL; the mean postoperative drainage volume was 73 mL; and the mean hospitalization days were 14 days. The patients were followed up 6-27 months (mean, 18.3 months). Satisfactory atlantoaxial fusion was obtained, and bone fusion was obtained at 3-7 months after operation (mean, 4.5 months). No breakage of screw or rods and re-dislocation occurred during follow-up. At last follow-up, the cervical range of motion (CROM) of the left and right rotation were (62.0 +/- 5.9) degrees and (63.9 +/- 3.8) degrees respectively in 5 patients receiving occipitocervical fusion and fixation, showing significant difference when compared with the values of normal children [(72.3 +/- 7.0) degrees and (74.1 +/- 7.6) degrees, respectively] at the same age (t = -3.915, P = 0.018; t = -5.954, P = 0.004). The CROM of the left and right rotation were (70.5 +/- 5.8) degrees and (72.7 +/- 4.9) degrees respectively in 14 patients receiving atlantoaxial fusion and fixation, showing no significant difference when compared with normal children at the same age (t = -1.417, P = 0.180; t = -1.021, P = 0.323). The visual analogue scale (VAS) score was significantly decreased from 7.8 +/- 1.1 at pre-operation to 3.5 +/- 0.8 at last follow-up (t = 17.267, P = 0.000). In 8 cases having spinal cord injury, 2 cases were rated as grade C, 1 case as grade D, and 5 cases as grade E according to ASIA impairment scale.

CONCLUSION: Technique of pedicle screw internal fixation has been proven to be an effective treatment for the atlantoaxial instability of children. It plays an important part in relieving pain and limitation of the cervical region.