Optimal aspiration volume of vertebral bone marrow for use in spinal fusion.

BACKGROUND CONTEXT

Bone marrow aspirate (BMA) has shown promise as a bone graft option in spinal fusion. The vertebral body is a convenient source for marrow aspirate as it is accessed in routine course of pedicle screw instrumentation. Studies have relied on data from the iliac crest to determine optimal aspiration volume from the vertebral body.

PURPOSE

This study is designed to determine the optimal aspiration volume for BMA taken from the vertebral body.

STUDY DESIGN

Prospective clinical study.

PATIENT SAMPLE

Data are drawn from 18 pedicles and 180 aspirations. The average age of the subjects was 50.3 years, and the subject pool comprised five men and seven women.

OUTCOME MEASURES

Nucleated cell count and alkaline phosphatase staining colony forming units.

METHODS

Ten 1 mL aliquots of BMA were incrementally aspirated through a cannulated pedicle tap for each instrumented vertebral body. The numbers of nucleated cells per mL of BMA were analyzed with a hemocytometer, and the percentage of osteoprogenitor cells per mL aspirate were estimated by an alk phos production assay. The study was funded through departmental funds, and none of the authors have any conflicts of interest to report related to the study.

RESULTS

Nucleated cell count decreased with increasing aspirate number (p<.001). The average cell count for the first mL was 45.8 million cells. Cell counts did not differ by age or sex (p=.943 and p=.685, respectively). Likewise, osteoprogenitor cell percentage decreased with increasing aspirate number (p<.001).

CONCLUSIONS

The 2 mL aspirate volume has been defined as ideal for the iliac crest, but there has been no analogous assessment of the effect of aspiration volume for other sources such as the vertebral body. This information is important for the clinical implementation of vertebral body aspirations if volume, cells, and presumably performance, of this potential bone graft option are to be optimized for spine cases. Our data show a direct relationship between increasing aspiration number and decreasing osteoprogenitor cellular concentration, with a drop to 50% of the original aspirate cell count by the 4th mL aspirate. The vertebral body is a potentially exciting source of osteoprogenitor cells that can be implemented for a variety of spinal uses.