C-1 lateral mass screw fixation in children with atlantoaxial instability: case series and technical report.

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To evaluate the feasibility, safety, and efficacy of incorporating C-1 lateral mass screws into fusion constructs in children with atlantoaxial instability.

SUMMARY OF BACKGROUND DATA

The operative treatment of atlantoaxial instability varies widely based on anatomy, patient age, and surgeon preference. The modified Harms construct, consisting of polyaxial C-1 lateral mass screws together with C-2 pedicle or pars screws and rods, has shown satisfactory fusion rates and minimal incidence of complications in adult patients. However, its utility in the pediatric population remains unproven, largely because of the technical challenges and risks inherent in placing C-1 lateral mass screws in children with immature bone quality, extensive anatomical variability, and smaller osseous structures.

METHODS

We retrospectively reviewed the records of all pediatric patients with atlantoaxial instability treated surgically, with a fusion construct incorporating C-1 lateral mass screws, at our institution between July 1, 2005 and June 30, 2008. Eight patients were identified and their relevant clinical data were abstracted from the medical record.

RESULTS

All patients had C-1 lateral mass screws placed as part of a fixation construct. Six cases used C-2 pedicle screws and 2 cases used C-3 lateral mass screw fixation for the inferior portion of the construct. There were 6 female and 2 male patients. Age at the time of the surgery ranged from 5 to 13 years (mean 9 y), and follow-up ranged from 11 to 38 months (mean 23 mo). No C-2 nerve root was sacrificed in any patient. There were no intraoperative or postoperative complications, including neurological injury, vascular injury, or hardware-related complications. Successful fusion was documented with dynamic cervical spine radiography in all cases.

CONCLUSIONS

C-1 lateral mass screw placement is generally feasible and safe in pediatric patients. With a nearly 2-year average follow-up, C1-2 rigid screw/rod fixation has proven to be an effective treatment modality for pediatric atlantoaxial instability in our series.