Extension of prior idiopathic scoliosis fusions to the sacrum: A matched cohort analysis of sixty patients with minimum two-year follow-up

Study Design. Comparative study. Objective. To compare the radiographic and clinical outcomes of patients undergoing extension of a previous idiopathic scoliosis fusion to the sacrum using either autogenous bone graft or recombinant human bone morphogenetic protein-2 (rhBMP-2). Summary of Background Data. Extension of an existing idiopathic scoliosis fusion to the sacrum for distal degeneration or sagittal imbalance has been associated with a high rate of pseudarthrosis. We hypothesized that rhBMP-2 could be successfully used as a substitute for distant autograft in this challenging population. Methods. Consecutive patients were identified from a single institution prospective database. The control group (autogenous harvesting without rhBMP-2, 1998-2002) included 24 of 25 patients with minimum 2-year follow-up while the study group (rhBMP-2 without distant autograft, 2002-2006) included 36 of 39 patients with minimum 2-year follow-up. Radiographs were measured using standard adult deformity criteria. Fusions were evaluated by independent observers using a published 4-point scale. Clinical outcomes were evaluated using Scoliosis Research Society and Oswestry Disability Index Questionnaires. Results. Groups were well matched with respect to demographic, radiographic, and surgical data with the following exceptions: the control group (autogenous graft, no BMP) was younger (43.5 vs. 49.8 years; P = 0.04), had more anterior levels fused (3.3 vs. 1.7; P = 0.01), more thoracoabdominal approaches (25% vs. 2.7%; P = 0.01), and greater estimated blood loss (1938 vs. 1221 mL; P = 0.01). There was 1 wound complication (deep infection) in each group. Rates of radiographic pseudarthrosis (11.1% vs. 20.8%) and revision for pseudarthrosis (5.6% vs. 12.5%) were lower in the rhBMP-2 group, although this did not reach statistical significance. Preoperative, postoperative, and improvements in Scoliosis Research Society and Oswestry Disability Index scores were similar between groups. We did not observe any increase in adverse events with the use of rhBMP-2. Conclusion. BMP-2 is a safe and effective alternative to iliac or rib harvesting when extending an existing idiopathic scoliosis fusion to the sacrum.