Autologous rib graft augmentation for occipitocervical fusion in pediatric patients and a novel radiographic grading scale.

Objective: Occipitocervical fusion (OCF) in children fails at a rate of up to 20% despite multiple technical advances; while the literature reports multiple grading scales of radiographic fusion, none function independently of the surgical technique or type of osseous graft used. In this study, the authors sought to establish 1) a novel reproducible surgical technique with low failure rates and 2) a new, easily applied radiological scoring system to objectively evaluate arthrodesis.

Methods: The authors conducted a single-institution retrospective cohort study of 21 patients who underwent OCF with and without rib autograft fixation from January 2015 to May 2022. OCF includes any fusion from the occiput to the cervical spine. Cohort 1 patients underwent OCF with standard instrumentation and allograft/bone morphogenetic protein (BMP) onlay from January 2015 to July 2016. Cohort 2 patients underwent OCF with standard instrumentation and rib autograft screw fixation from August 2016 to May 2022. Primary evaluation of arthrodesis with CT at ≥ 3 months postoperatively was performed by two blinded board-certified neuroradiologists. Radiological criteria utilized a 0- to 2-point scale: nonfused graft resorption, pseudarthrosis, or hardware failure (grade 0); unilateral fusion (grade 1); or bilateral fusion (grade 2).

Results: From cohort 1, 7 cases underwent OCF, with 42.9% requiring revision surgery for complete/significant bony resorption. In cohort 2, 17 cases underwent OCF (including 3 revisions from cohort 1) with standard instrumentation and rib autograft using the new arthrodesis technique. One case was excluded because CT imaging was not available. Using a novel arthrodesis radiographic grading system, the authors found that 16 cases (100%) achieved a solid bony fusion. OCF augmented by rib autograft screw fixation significantly increased fusion rates (p = 0.0066). No significant differences were observed in arthrodesis rates by use of BMP (p = 0.2880), presence of congenital syndromes (p = 0.3639), or halo use (p = 0.2329).

Conclusions: Rib autograft augmentation using screw fixation as the primary grafting technique for standard OCF significantly improved the rate of arthrodesis at 3 months, without any observed fusion failure in a > 5-year period. This novel objective neuroradiology fusion score standardizes the classification of arthrodesis regardless of instrumentation or bone graft material, improving assessment and objective generalizability of future fusion research.