Allograft versus autograft for pediatric posterior cervical and occipito-cervical fusion: a systematic review of factors affecting fusion rates

Abstract

<jats:sec> <jats:title>OBJECT</jats:title> <jats:p>Fusion rates are high for children undergoing posterior cervical fusion (PCF) and occipito-cervical fusion (OCF). Autologous bone has been widely used as the graft material of choice, despite the risk of donor-site morbidity associated with harvesting the bone, possibly because very low fusion rates were reported with posterior allograft cervical fusions in children several decades ago. Higher overall fusion rates using allograft in adults, associated with improvements in internal fixation techniques and the availability of osteoinductive substances such as bone morphogenetic protein (BMP), have led to heightened enthusiasm for the use of bank bone during pediatric PCF. A systematic review was performed to study factors associated with successful bone fusion, including the type of bone graft used.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>The authors performed a comprehensive PubMed search of English-language articles pertaining to PCF and OCF in patients less than 18 years old. Of the 561 abstracts selected, 148 articles were reviewed, resulting in 60 articles that had sufficient detail to be included in the analysis. A meta-regression analysis was performed to determine if and how age, fusion technique, levels fused, fusion substrate, BMP use, postoperative bracing, and radiographic fusion criteria were related to the pooled prevalence estimates. A systematic review of the literature was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>A total of 604 patients met the specific inclusion and exclusion criteria. The overall fusion rate was 93%, with a mean age of 9.3 years and mean follow-up of 38.7 months. A total of 539 patients had fusion with autograft (94% fusion rate) and 65 patients with allograft (80% fusion rate). Multivariate meta-regression analysis showed that higher fusion rates were associated with OCF compared with fusions that excluded the occiput (p &lt; 0.001), with the use of autograft instead of allograft (p &lt; 0.001), and with the use of CT to define fusion instead of plain radiography alone. The type of internal fixation, the use of BMP, patient age, and the duration of follow-up were not found to be associated with fusion rates in the multivariate analysis.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>Fusion rates for PCF are high, with higher rates of fusion seen when autograft is used as the bone substrate and when the occiput is included in the fusion construct. Further study of the use of allograft as a viable alternative to autograft bone fusion is warranted because limited data are available regarding the use of allograft in combination with more rigid internal fixation techniques and osteoinductive substances, both of which may enhance fusion rates with allograft.</jats:p></jats:sec>

Fusion rates support wired allograft combined with instrumented craniocervical fixation in the paediatric population

“…However, in a subgroup analysis for rigid internal fixation techniques including only 18 patients from 5 different studies where allograft was used, the differences were smaller (99% vs 94%, respectively). [19] In an adult population, Godzik and colleagues reported in adult population bony OC fusion in allograft group in 18 of 19 (95%) and 8 of 8 (100%) in the autograft group after a minimum of 12-month follow-up. [8] To overcome the lack of osteoinductive function of allograft, the use of bone marrow aspirate (BMA) [15] or bone morphogenetic proteins (BMP) are advocated.…”

“…Moreover, it is a challenge to harvest and craft a well-fitting bone block from a small costa or thin iliac crest in children. [8,19,21] Allografts are only osteoconductive, weakly osteoinductive, but not osteogenic like autografts; therefore, their use in posterior fixation is associated with a higher rate of nonunion. [4] An older publication by Koop et al (1984) noted that pseudoarthrosis occurred in one patient who received allograft instead of autograft in their pediatric OC fusion procedures, strengthening this author's view that autograft is superior in fusion.…”

“…However, in a recent meta-analysis, Reintjes et al did not find a statistically significant association of BMP with successful fusion in any of the univariate or multivariate analyses. [19] Sayama also concluded there is no need for routine use of recombinant BMP in the pediatric age group. [20] Based on our current findings and the literature, we do not consider application of BMP to be essential for fusion if rigid fixation is achieved.…”

Autogenic Rib Graft for Atlantoaxial and Occipitocervical Fixation in Pediatric Patients

“…Zhang et al [12] compared the fusion rate between autograft and allograft for pediatric patients with AAF, reporting that 94% of the fusion rates with allograft was comparable with 100% of the fusion rate with autograft. However, Reintjes et al [9] reported 80% rate of bony fusion with allograft and 94% bony fusion with autograft. The advantages of autogenic bone are the low cost and reduced potential risk of viral infection.…”

“…However, screw placement may be technically difficult in very young children because of small bone size, congenital variations, possible growth potential, and immature ossification [7,8]. With regard to bone grafts, autogenic iliac crest bone has long been considered the ‘gold standard’ bone source for posterior cervical fusion in pediatric patients [5,9,10]. However, there are some unsolved problems associated with donor-site morbidity and amount of bone grafting.…”