Association between structural rib autograft and the rate of arthrodesis in children undergoing occiput–C2 instrumentation and fusion

OBJECTIVE The purpose of this study was to identify factors associated with fusion success among pediatric patients undergoing occiput–C2 rigid instrumentation and fusion. METHODS The Pediatric Spine Study Group registry was queried to identify patients ≤ 21 years of age who underwent occiput–C2 posterior spinal rigid instrumentation and fusion and had a 2-year minimum clinical and radiographic (postoperative lateral cervical radiograph or CT scan) follow-up. Fusion failure was defined clinically if a patient underwent hardware revision surgery > 30 days after the index procedure or radiographically by the presence of hardware failure or screw haloing on the most recent follow-up imaging study. Univariate comparisons and multivariable logistic regression analyses were subsequently performed. RESULTS Seventy-six patients met inclusion criteria. The median age at surgery was 9 years (range 1.5–17.2 years), and 51% of the cohort was male. Overall, 75% of patients had syndromic (n = 41) or congenital (n = 15) etiologies, with the most frequent diagnoses of Down syndrome (28%), Chiari malformation (13%), and Klippel-Feil syndrome (12%). Data were available to determine if there was a fusion failure in 97% (74/76) of patients. Overall, 38% (28/74) of patients had fusion failure (95% CI 27%–50%). Univariate analysis demonstrated that use of a rigid cervical collar postoperatively (p = 0.04) and structural rib autograft (p = 0.02) were associated with successful fusion. Multivariable logistic regression analysis determined that patients who had rib autograft used in surgery had a 73% decrease in the odds of fusion failure (OR 0.27, 95% CI 0.09–0.82; p = 0.02). Age, etiology including Down syndrome, instrumentation type, unilateral instrumentation, use of recombinant human bone morphogenetic protein, and other variables did not influence the risk for fusion failure. CONCLUSIONS In this multicenter, multidisciplinary, international registry of children undergoing occiput–C2 instrumentation and fusion, fusion failure was seen in 38% of patients, a higher rate than previously reported in the literature. The authors’ data suggest that postoperative immobilization in a rigid cervical collar may be beneficial, and the use of structural rib autograft should be considered, as rib autograft was associated with a 75% higher chance of successful fusion.