CONCLUSIONS: We have previously shown DEL1 KO mice heal fractures with less bone. We describe here a mechanism for this phenotype based upon the role of Del1 in preventing chondrocyte apoptosis. This suggests modulating apoptosis might be a therapeutic tool in aiding fracture healing. Current clinical protocols for cervical spine clearance in level I trauma centers in the United States Alexander Antonios Theologis, MD, Robert Dionisio, BA, Geoffrey Manley, MD, PhD, Robert Mackersie, MD, Trigg McClellan, MD, Murat Pekmezci, MD University of California, San Francisco, San Francisco, CA INTRODUCTION: Cervical (C) spine clearance protocols have been developed to prevent neurological deficits secondary to missed un- stable spine injuries. With new imaging techniques available, C-spine clearance guidelines have evolved. The purpose of this study is to evaluate the C-spine clearance practices in Level I trauma centers in the United States (US). METHODS: The trauma managers in all Level I Trauma centers in the US were contacted via e-mail/phone calls. An institution’s official C-spine clearance protocols were analyzed, if applicable. RESULTS: The response rate was 83%. 66% of participants had an official C-spine clearance protocol. American College of Surgeons’ accredited centers had a higher rate of protocols (75%) when com- pared non-accredited centers (54%). The majority of the centers had 24-hour access to CT (93%) and MRI (87.5%). The majority of the centers (89%) use NEXUS (National Emergency X-Radiography Utilization Study) criteria with/without painless range of motion to clear asymptomatic patients. A CT scan was the most commonly (52%) utilized first line of imaging. In symptomatic patients with a negative CT scan flexion-extension plain radiographs (51%) and MRI (13%) were the most common next steps of imaging. In ob- tunded patients, CT scans followed by MRI was the most common method (34%) to clear C-spine, but 6% of the centers were still using dynamic flexion-extension views that are now contraindicated. CONCLUSIONS: 66% of participating Level I trauma centers in the US have an official C-spine clearance protocol. The protocols were highly variable and standardized protocols are encouraged in all trauma centers in order to prevent neurological sequelae. Is odontoid lateral mass interspace (OLMI) asymmetry a normal anatomical variant in patients after trauma? Franck Georges Billmann, MD, PhD, FACS, Therezia Bokor-Billmann, MD, FACS, Marcus Leicht, MD, Erhard Kiffner, MD St. Vincentius Kliniken, Karlsruhe, Germany INTRODUCTION: Considering the great number of cervical spine traumatisms, the knowledge of the CT scan anatomy of the occip- itoatlantoaxial complex is essential. The odontoid lateral mass inter- space (OLMI) corresponds to the space between dens axis and the medial circumference of massa lateralis atlantis. Being of particular clinical interest, the position of OLMI asymmetry as normal variant or pathological finding is still subject of debate. METHODS: 358 adulte patients, admitted for cervical spine trauma, underwent CT imaging. We investigated: (1) the presence of an OLMI asymmetry, as well as its measurment; (2) the presence of a bone/ligamentous lesion of the occipitoatlantoaxial complex. A par- allel study, based on cadaveric transversal sections, investigated OLMI asymmetry. A review of the literature was performed. RESULTS: 86 patients out of 301 (28.6%) were found to have an OLMI asymmetry; 15 patients out of the 86 patients with OLMI asymmetry (17.4%) were diagnosed to have a bony/ligamentous le- sion of the occipitoatlantaxial complex. 19 patients out of the 215 patients without OLMI asymmetry (8.8%) were diagnosed to have a bony or ligamentous lesion of the occipitoatlantaxial complex. Table. Incidence of CT/MRI confirmed pathological lesion (instability, subluxation, fracture) in relation to the OLMI asymmetry metric value among the 301 patients included in the present study OLMI asymmetry and metric value (mm) No. of cases Incidence of CT/MRI confirmed C1 or C2 lesion n (%) p Value With asymmetry 86 15 (17.4) 0.03† 0-1 34 6 (17.6) NS* 1-2 44 8 (18.2) NS* 2-3 5 0 (0.0) NS*  3 3 1 (33.3) NS* Without asymmetry 215 19 (8.8) 0.03† Total 301 34 (11.3) — p Value calculated using Chi-squared (†) or Fisher’s exact test (*); significant when p  0.05; NS: non significant. CONCLUSIONS: OLMI asymmetry is overestimated in the litera- ture, probably due to technically inadequate studies. Considering our results, one could propose the following advice: to rule out a lesion, an MRI examination should be performed: (1) if OLMI asymmetry is demonstrated in a CT scan in neutral position, (2) if clinical symptoms persist after a CT scan showing an OLMI asym- metry, (3) if OLMI asymmetry is diagnosed associated to a high degree of clinical suspicion. Influence of metal ions on human lymphocytes and the generation of titanium-specific T-lymphocytes Dieter Cadosch, MD, PhD, Erwin Chan, PhD, P Oliver Gautschi, MD, Luis Filgueira, MD, Hans-Peter Simmen, MD University Hospital of Zurich, Zurich, Switzerland INTRODUCTION: There is mounting evidence to suggest the in- volvement of the immune system by means of activation by metal ions released via biocorrosion, in the pathophysiologic mechanisms of aseptic loosening of orthopedic implants. However, the detailed mechanisms of how metal ions become antigenic and are presented S63 Vol. 215, No. 3S, September 2012 Abstracts