Abstracts / Injury Extra 41 (2010) 131–166 155 fixing such condylar fractures is frequently akin to joining eggshells. However, our previous work has also shown that the clamping forces (in the case of the T2SCN), and the stiffness of the cancel- lous bone and cortical shell contribute to the different mechanisms of load transfer that can occur in these devices. This paper shows some recent work that examines variations in cortical shell thickness, cancellous bone modulus, and the com- pression force from condylar bolts. A significantly reduced cortical thickness is used while a range of cancellous bone moduli rep- resenting good quality bone and weak osteoporotic bone are examined. The model examines both strength and stiffness. In general the pre-compression from the condylar bolts (T2SCN) produces localised compressive stress in the region adjacent to the end washer, but can provide a stiffer construct for subsequent load- ing. However, this outcome is also dependent on the quality of the cancellous bone adjacent to the nail. With low modulus cancel- lous bone cortical engagement may restrict the friction developed between bone and nail. Under torsion, the nail constructs are always more effective than side plate constructs, and generally the locked nail provides good load-carrying capacity against torsion loads. Keywords: Finite element modelling; Fracture fixation; Distal femur. doi:10.1016/j.injury.2010.07.467 1A.56 A novel form of electrical stimulation increases osteoblast activ- ity: potential implications for enhanced fracture healing M. Griffin (BSc) * , A. Sebastian (PhD), A. Bayat (MD, PhD) Plastic and Reconstructive Surgery Research (PRSR), Manchester Inter- disciplinary Biocentre (MIB), University of Manchester, 131 Princess Street Manchester, M1 7DN, England, UK E-mail address: michelle.griffin@postgrad.manchester.ac.uk (M. Griffin). Delayed facture repair and bony non-unions pose a clinical chal- lenge. Understandably, novel methods to enhance bone healing have been studied by researchers worldwide. Electrical stimula- tion (ES) has shown to be effective in enhancing bone healing, however the best wave form and mechanism by which it stimu- lates osteoblasts remains unknown. Interestingly, it is considered that osteoblast activity depends on specific waveforms applied. Therefore, the aim of this study was to evaluate whether partic- ular waveforms have a differential effect on osteoblast activity. An osteoblast cell line was electrically stimulated with either capac- itive coupling (CC) or a novel degenerate wave (DW) using a unique in vitro ES system. Following application of both waveforms, the extent of cytotoxicity, proliferation, differentiation and min- eralisation of the osteoblasts were assessed using various assays. Differentiation and mineralization were further analysed using quantitative real-time PCR (qRT PCR) and immunocytochemistry (ICC). DW stimulation significantly enhanced the differentiation of the osteoblasts compared to CC stimulation, with increased protein and gene expression of alkaline phosphatase and type 1 collagen at 28 h (p < 0.01). DW significantly enhanced the mineralization of the osteoblasts compared to CC with greater Alizarin Red S stain- ing and gene expression of osteocalcin, osteonectin, osteopontin and bone sialoprotein at 28 h (p < 0.05). Moreover, immunocyto- chemical assays showed higher osteocalcin expression after DW stimulation compared to CC at 28 h. In conclusion, we have shown that ES waveforms enhanced osteoblast activity to different extent but importantly demonstrate for the first time that DW stimu- lation has a greater effect on differentiation and mineralisation of osteoblasts than CC stimulation. DW stimulation has potential to provide a secure, controlled and effective application for bone healing. These findings have significant implications in the clinical management of fracture repair and bone non-unions. doi:10.1016/j.injury.2010.07.468 1A.57 Can DCP and LCP plates generate more compression? F. Yaish * , M. Sukeik, A. Nanu, A. Cross Sunderland Royal Hospital, UK Aims: This is a biomechanical study aiming to assess the advan- tage in using more than one eccentric screw in DCP and LCP fixation, the appropriate order of their insertion, the advantage in using dif- ferent drill guides in DCP fixation, and compare the compression generated by the DCP and LCP. Methods: A customized load cell placed in a transverse osteotomy performed on synthetic generic bone models was used to measure compression. The staring pressure across the osteotomy site was standardized to allow comparison. 4.5 mm narrow DCP and LCP plates were used for fixation. The compression screws were inserted in two sequences: all on the compression side, or alternat- ing between the initial compression and neutral sides. Loading and universal drill guides were compared in DCP fixation. Results: A second compression screw increases compression significantly in both sequences (p = 0.002). In the DCP, a third compression screw improved compression only when placed in alternating sequence (p = 0.002). Fourth compression screw resulted in no significant compression (p = 0.23) and loss of reduc- tion. The universal guide generated higher compression than the loading guide (p = 0.002). There was no significant difference in the compression gener- ated by the first or second eccentric screws in DCP and LCP plate fixation (p = 0.28, 0.25). Conclusion: Fracture compression can be improved by using extra eccentric screws in LCP and DCP, and the universal drill guide in DCP fixation. Although the compression hole in the LCP is shorter, it generates compression comparable to the DCP. doi:10.1016/j.injury.2010.07.469 1A.58 Extraction of high numbers of mesenchymal stem cells (MSCs) from intramedullary cavities of long bones George Cox (BMBS) a,* , Peter V. Giannoudis (MD) a , Sally Boxall (PhD) b , Conor Buckley (PhD) c , Elena Jones (PhD) b , Dennis McG- onagle (PhD) b a Academic Department of Trauma & Orthopaedics, School of Medicine, University of Leeds, United Kingdom b Academic Unit of the Musculoskeletal Diseases, Leeds NIHR Biomed- ical Research Unit, United Kingdom c Trinity College, Dublin, Ireland Introduction: Iliac crest bone marrow aspirate (ICBMA) is fre- quently cited as the ‘gold-standard’ source of MSCs. It was the first location MSCs were identified and its ease of access/handling have encouraged its use as the standard. Previous studies have suggested that MSCs are resident in the intramedullary (IM) cavities of long- bones. However, a comparative assessment in terms of number, phenotype and differentiation capacity with matched ICBMA has not yet been performed. View publication stats View publication stats