Effect of Osteogenic Progenitor Cell Concentration on the Incidence of Foot and Ankle Fusion

The use of biologics, namely demineralized bone matrix, bone marrow aspirate (BMA), and other growth factors, has gained popularity in foot and ankle surgery for use in compromised hosts or high-risk situations. Our research has shown the concentration of these pluripotent cells was greatest in the iliac crest. A medical record and radiographic review was performed to compare the effect of BMA harvest site osteogenic progenitor cells on the incidence of fusion. Radiographs were reviewed for radiographic evidence of trabecular bridging in 2 or more views. If fusion occurred, the number of osteogenic progenitor cells found in the combined BMA at surgery was recorded. A total of 33 patients were included in the present study. Of the 33 patients, 32 (97.0%) had radiographic fusion at a mean of 13 ± 6 (range 8 to 30) weeks, and 1 (3.0%) experienced nonunion and required revision. The patient procedures were as follows: 18 (54.5%) hindfoot arthrodeses, 8 (24.2%) forefoot arthrodeses, 4 (12.1%) fractures, and 3 (9.1%) isolated ankle fusions. The mean colony-forming units for the patients with fusion was 20.3 ± 23.5 (range 0.0 to 107.0). In the patient with nonunion, it was 0.20 colony-forming unit. Our comparison of the incidence of fusion with the use of osteogenic progenitor cells from 3 anatomic sites showed a low incidence of complications and a high incidence of fusion. No association was found between the BMA concentration and the incidence of fusion, suggesting a minimum concentration and biologic potential of pluripotent cells is necessary to achieve the clinical effect of fusion.