VOL. 95-B, No. 9, SEPTEMBER 2013 1269  TRAUMA: RESEARCH The viability of cells obtained using the Reamer–Irrigator–Aspirator system and in bone graft from the iliac crest H. S. Uppal, B. E. Peterson, M. L. Misfeldt, G. J. Della Rocca, D. A. Volgas, Y. M. Murtha, J. P. Stannard, T. J. Choma B. D. Crist From University of Missouri, Columbia, Missouri, United States  H. S. Uppal, MD, MS, Assistant Professor, Orthopaedic Surgery Medical College of Wisconsin, Department of Orthopaedic Surgery, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.  B. E. Peterson, MD, Orthopaedic Surgery Resident  G. J. Della Rocca, MD, PhD, Associate Professor of Orthopaedic Trauma Surgery  D. A. Volgas, MD, Associate Professor of Orthopaedic Trauma Surgery  Y. M. Murtha, MD, Assistant Clinical Professor of Orthopaedic Trauma Surgery  J. P. Stannard, MD, Professor of Orthopaedic Trauma and Sports Medicine, Chairman and Medical Director  T. J. Choma, MD, Professor, Chief of Spine Division, Co-Chair  B. D. Crist, MD, Associate Professor of Orthopaedic Trauma Surgery University of Missouri, Department of Orthopaedic Surgery, One Hospital Drive, N119 Columbia, Missouri 65212, USA.  M. L. Misfeldt, PhD, Professor of Molecular Microbiology and Immunology University of Missouri, Department of Molecular Microbiology & Immunology, Ma 204c Medical Sciences Building, Columbia, Missouri 65212, USA. Correspondence should be sent to Dr B. D. Crist; e-mail: cristb@health.missouri.edu ©2013 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.95B9. 31756 $2.00 Bone Joint J 2013;95:1269–74. Received 11 February 2013; Accepted after revision 8 May 2013 We hypothesised that cells obtained via a Reamer–Irrigator–Aspirator (RIA) system retain substantial osteogenic potential and are at least equivalent to graft harvested from the iliac crest. Graft was harvested using the RIA in 25 patients (mean age 37.6 years (18 to 68)) and from the iliac crest in 21 patients (mean age 44.6 years (24 to 78)), after which ≥ 1 g of bony particulate graft material was processed from each. Initial cell viability was assessed using Trypan blue exclusion, and initial fluorescence-activated cell sorting (FACS) analysis for cell lineage was performed. After culturing the cells, repeat FACS analysis for cell lineage was performed and enzyme-linked immunosorbent assay (ELISA) for osteocalcin, and Alizarin red staining to determine osteogenic potential. Cells obtained via RIA or from the iliac crest were viable and matured into mesenchymal stem cells, as shown by staining for the specific mesenchymal antigens CD90 and CD105. For samples from both RIA and the iliac crest there was a statistically significant increase in bone production (both p < 0.001), as demonstrated by osteocalcin production after induction. Medullary autograft cells harvested using RIA are viable and osteogenic. Cell viability and osteogenic potential were similar between bone grafts obtained from both the RIA system and the iliac crest. Cite this article: Bone Joint J 2013;95-B:1269–74. Intramedullary nailing is the standard treat- ment for diaphyseal long bone fractures of the lower limb. Some authors have suggested that the deposition of autogenous bone graft at the fracture site during reaming increases the rate of union. 1-4 However, whether cells from the reamings remain viable is controversial, as high temperatures 5 and pressures and mechan- ical damage from reaming may affect the endosteal cells. 6 The Reamer–Irrigator–Aspirator (RIA; Syn- thes, Paoli, Pennsylvania) system was initially developed to reduce pulmonary complications associated with reamed femoral intramedullary nailing. The RIA device irrigates the reamer head in order to keep the intramedullary contents cool during vacuum evacuation of the reamed con- tents. 7 Husebye et al 8 demonstrated lower pres- sures within the medullary canal when using RIA compared with standard reamers. Since this device can capture reamings with the addition of a filter, it has been used for harvesting intra- medullary autogenous bone graft. 2,9-11 Using a filter system, RIA provides a method of harvesting bone graft that is distinct from iliac crest graft. The disadvantages of iliac crest graft include a limited quantity of graft and donor site morbidity. 12,13 The intramedullary canal of long bones is known to contain many pluripotent cell types, 14 and the osteogenic via- bility of these cells collected from standard reamers is known. 1,2 However, RIA also adds potential mechanical damage to these cells dur- ing irrigation and aspiration. The effluent col- lected using RIA also contains many osteogenic growth factors, 4,15,16 and the filter system can provide large volumes of bone graft. 17 Although RIA has been used clinically, 18 there is no evidence to suggest that these cells remain viable. Therefore the questions raised are, is the apparent clinical success related to the growth factors or due to the osteogenic cells?; and how do the cells from the RIA compare with autograft harvested from the iliac crest? The purpose of this study was to quantify the viability of cells in autograft obtained via RIA and the iliac crest and compare their osteogenic potential. We hypothesised that cells obtained via RIA retain substantial osteogenic potential and are equivalent to cells harvested from the iliac crest. Patients and Methods The study received institutional review board approval. Patients were included if they were aged > 18 years and were undergoing a bone