The purpose of this study focusing on fusion rate was to determine the efficacy of recombinant human bone morphogenetic protein–2 (rhBMP-2) use in posterior instrumented fusions of the craniocervical junction in the pediatric population. The authors previously reported the short-term (mean follow-up 11 months) safety and efficacy of rhBMP-2 use in the pediatric age group. The present study reports on their long-term results (minimum of 12 months' follow-up) and focuses on efficacy.
The authors performed a retrospective review of 83 consecutive pediatric patients who had undergone posterior occipitocervical or atlantoaxial spine fusion at Texas Children's Hospital or Riley Children's Hospital during the period from October 2007 to October 2012. Forty-nine patients were excluded from further analysis because of death, loss to follow-up, or lack of CT evaluation of fusion at 12 or more months after surgery. Fusion was determined by postoperative CT scan at a minimum of 12 months after surgery. The fusion was graded and classified by a board-certified fellowship-trained pediatric neuroradiologist. Other factors, such as patient age, diagnosis, number of vertebral levels fused, use of allograft or autograft, dosage of bone morphogenetic protein (BMP), and use of postoperative orthosis, were recorded.
Thirty-four patients had a CT scan at least 12 months after surgery. The average age of the patients at surgery was 8 years, 1 month (range 10 months–17 years). The mean follow-up was 27.7 months (range 12–81 months). There were 37 fusion procedures in 34 patients. Solid fusion (CT Grade 4 or 4−) was achieved in 89.2% of attempts (33 of 37), while incomplete fusion or failure of fusion was seen in 10.8%. Based on logistic regression analysis, there was no significant association between solid fusion and age, sex, BMP dose, type of graft material, use of postoperative orthosis, or number of levels fused. Three of 34 patients (8.8%) required revision surgery.
Despite the large number of adult studies reporting positive effects of BMP on bone fusion, our long-term outcomes using rhBMP-2 in the pediatric population suggest that rates of fusion failure are higher than observed in contemporary adult and pediatric reports of occipitocervical and atlantoaxial spine fusions.