The Influence of Aspiration Volume on the Number of Osteoblastic Progenitors Obtained From Bone Marrow in Children.

Background: Autologous bone marrow aspirates are utilized to treat various conditions in children. The biological value of bone marrow aspirate depends on the concentration of competent osteoblastic progenitors present in the aspirate. It has been shown in adults that increasing bone marrow aspiration volume beyond 2 mL decreases the concentration of osteoblast progenitor cells because of dilution of the sample with peripheral blood. The effect of varying bone marrow aspiration volumes on the osteoblast cell content has not been determined in children. Methods: In total, 21 children (3 male and 18 female patients, age range 8 mo to 14 y) scheduled for pelvic osteotomy were included in the study. Three separate bone marrow aspirates of 1, 5, and 10 mL were obtained from the anterior superior iliac crest. Total number of nucleated cells was counted per aspirate and the prevalence of alkaline phosphatase-positive colony-forming units was determined per million nucleated cells. Results: We measured a significant, proportional increase in the total number of nucleated bone marrow precursor cells between the 1 and 5 mL samples (mean +/- SD, 27 +/- 13 and 152 +/- 78 million nucleated cells, respectively; P<0.0001). When the aspiration volume doubled from 5 to 10 mL the total number of nucleated cells was 178 +/- 76 million (P=0.17). A proportional increase from 2214 alkaline phosphatase-positive colony-forming units in the 1 mL sample to 14,100 alkaline phosphatase-positive colony-forming units in the 5 mL sample was observed. However, the number of colony-forming units per aspirate decreased to 11,880 in the 10 mL sample. Conclusions: These data demonstrate that in children aspiration up to 5 mL bone marrow from the iliac crest yields a proportional increase in osteoblastic progenitor cells per aspirate. Increasing the aspiration volume beyond 5 mL results in hemodilution, rather than further selection of osteoblastic material. Level of Evidence: Level II-development of diagnostic criteria on basis of consecutive patients.