The oblique impact methods of motorcycle helmet standards prescribe using an isolated headform. However, in accidents the presence of the body may influence impact responses of the head and helmet. In this study, the effects of the presence of the body, in helmet oblique impacts, are investigated. Using the Finite Element method, oblique impacts of a commercially available helmet, coupled with a model of the human body, are simulated. A comparison between full-body impacts and those performed with an isolated headform show that the presence of the body modifies the peak head rotational acceleration by up to 40%. In addition, it has a significant effect on head linear acceleration and the crushing distance of the helmet's liner. To include the effect of the body on head rotational acceleration in headform impacts, modifying inertial properties of the headform is proposed. The modified inertial properties are determined for a severe and frequent impact configuration. The results of helmet impacts obtained by using the modified headform are in very good agreement with those of full-body impacts; this verifies the accuracy of the proposed method.

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Introduction. The main purpose of this study is to develop an efficient technique for generating FE models of pelvic ring fractures that is capable of predicting possible failure regions of osteosynthesis with acceptable accuracy. Methods. Patient-specific FE models of two patients with osteoporotic pelvic fractures were generated. A validated FE model of an uninjured pelvis from our previous study was used as a master model. Then, fracture morphologies and implant positions defined by a trauma surgeon in the preoperative CT were manually introduced as 3D splines to the master model. Four loading cases were used as boundary conditions. Regions of high stresses in the models were compared with actual locations of implant breakages and loosening identified from follow-up X-rays. Results. Model predictions and the actual clinical outcomes matched well. For Patient A, zones of increased tension and maximum stress coincided well with the actual locations of implant loosening. For Patient B, the model predicted accurately the loosening of the implant in the anterior region. Conclusion. Since a significant reduction in time and labour was achieved in our mesh generation technique, it can be considered as a viable option to be implemented as a part of the clinical routine to aid presurgical planning and postsurgical management of pelvic ring fracture patients.

Fatal falls are frequent and seem to be an increasing problem in the elderly. Especially ground level falls (GLFs) and falls on or from stairs and steps (stairs falls) are worth examining for forensic classification and in order to improve the development of preventive measures. We retrospectively analyzed 261 fatal falls of elderly age 65 + years, which were autopsied at the Institute of Legal Medicine in Munich between 2008 and 2014. After careful screening, the sub-set of all 77 GLFs and 39 stairs falls were analyzed towards socio-demographic characteristics, fall circumstances, injuries, and circumstances of death. A subsequent analysis of GLF cases regarding the presence of proximal femur fractures (PFF) was performed. The injury pattern of the GLFs and the stairs falls clearly differ with a higher share of injuries to the lower extremities in the GLFs. However, the most severely injured body region was the head in both groups (62% of the stairs cases, 49% of the GLF cases). Alcohol as contributing to the fall was seen more frequently in the stairs falls. PFF were not seen in the stairs falls, but then in 18 GLF cases. Yet, for 17 among them (22% of 77), their hip fracture was the only serious injury leading to hospitalization and death. Only one GLF case was already found dead. This finding indicates a potential of avoiding up to 22% of the GLF fatalities by preventing hip fractures by optimized hip protectors or other measures, especially for the elderly aged 75 + years.