Introduction: The purpose of this study is to determine the fusion rate in posterior instrumented fusions of the craniocervical junction in a pediatric population. Older studies have reported a 98-100% fusion rate on flexion extension x-rays, however more recent studies have demonstrated much lower than anticipated fusion rates from 84-89% on computed tomography (CT). We now report our fusion rates with a minimum of 3 month radiographic follow-up.

Methods: A retrospective review of 21 consecutive pediatric patients (25 procedures) who underwent posterior occipitocervical or atlantoaxial instrumented fusion from April 2004 to January 2015 at Doernbecher Children’s Hospital was performed. 5 patients were excluded from further analysis because of insufficient follow-up data. Fusion was defined as no motion noted on post-operative flexion-extension x-rays (XR) obtained any time after 3 months. Other factors, such as patient age, body mass index (BMI), diagnosis, number of vertebral levels fused, graft material, and use of postoperative orthosis, were recorded. Half of the patients underwent CT scans as well and thus XR and CT were compared in this cohort.

Results: 16 patients (20 procedures) had postoperative flexion and extension x-rays obtained at least 3 months after surgery. The average patient age was 10 years, 3 months (range: 2 years, 6 months to 17 years). The mean radiographic follow-up per procedure was 17 months (range: 3 – 118 months; median 8.5 months). Radiographic fusion was achieved in 81% of patients. 4 revision procedures were required in 3 patients (19%). CT-confirmed rates of fusion were even lower; 11 patients with X-ray documented fusion also underwent CT and only 7 of the 11 (64%) had documented CT fusion (grade 4- or 4) .

Conclusions: Our outcomes of spinal fusion in the pediatric population suggest that rates of fusion in occipitocervical and atlantoaxial instrumented fusions are lower than predicted compared to historical studies and on par with more current studies. Flexion extension x-rays as a means to evaluate fusion may overcall the true bony fusion rate, as depicted by lower fusion rates on CT in those with no instability on x-ray.

Patient Care: This research will improve patient care by helping to elucidate current problems that may lead to lower fusion rates in OC and C1-C2 fusions in children and to help identify possible ways to improve fusion rates in the future

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of recognizing higher fusion failure rates in OC and C1-C2 fusions of the pediatric spine, 2) Discuss in small groups the possible reasons why fusion rates are so much lower than expected, 3) Identify risk factors for lower fusion rates and ways to increase fusion rates

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