Head injury potential and the effectiveness of headgear in women's lacrosse.

Over the past 10 years, lacrosse has grown increasingly popular, making it one of the fastest growing team sports in the country. Similar to other sporting activities, head injuries in lacrosse can and do occur, and the number of lacrosse-related head injuries has increased in recent years. In women's lacrosse, protective headgear is not required, but U.S. Lacrosse and the American Society for Testing and Materials are currently working to develop a headgear standard for the women's game. In the interim, some female lacrosse programs and individual players are wearing soft headgear during play. The effectiveness of this headgear is unknown. Testing was conducted to better understand the material properties of various types of headgear that may be used in lacrosse and the effect of this headgear on head impact response and head injury potential. For the evaluation of head impact response, an instrumented Hybrid III anthropomorphic test device (ATD) was impacted on the side of the head with lacrosse balls and the front and side of the head with a lacrosse stick. The linear and rotational impact response of the head and corresponding acceleration-based injury metrics are reported. Testing was then repeated with the ATD wearing different types of headgear. Tested headgear included a men's lacrosse helmet and two brands of commercially-available soft headgear. For the higher velocity ball impacts, there was no statistically-significant difference in the measured linear and rotational response of the head for the no headgear and soft headgear test conditions. For the lower velocity ball impacts, there was a small, yet statistically-significant, reduction in head linear acceleration for one of the soft headgears tested in comparison to the no headgear test condition, but there was not a statistically-significant difference in the rotational impact response with this headgear. These results indicate that the soft headgear would not be effective in reducing head injury potential during higher velocity ball impacts, such as ball speeds associated with shooting in women's lacrosse. The men's lacrosse helmet reduced both the linear and rotational response of the head for the higher and lower velocity ball impacts. Material testing showed that the padding in the hard helmet exhibited larger strain energy than the padding within the soft headgears when tested in compression. These results correlate with the larger reductions in head accelerations during ball impacts by the hard helmet. For the stick impacts, there were no statistically-significant differences in the lateral impact response of the head for the helmeted and soft headgear test conditions in comparison to the no headgear test condition, but there were statistically-significant, albeit small, differences in the frontal impact response of the head. The similar impact responses of the head during the stick impacts with and without headgear can be attributed to the relatively low severity of these impacts and the characteristics of the impactor.

Determination of the mechanical properties of DOPC:DOPS liposomes using an image procession algorithm and micropipette-aspiration techniques.

Quantification of the mechanical properties of liposomes is critical in helping to predict their behavior during various applications such as targeted drug delivery, response to mechanical characterization or their interactions with isolated cytoskeletal elements. A numerical implementation of the Evans aspiration technique, and an image processing algorithm for measuring deformation of spherical DOPC:DOPS liposomes is presented. Liposomes were aspirated to pressures of -10mmHg (∼-1300Pa). The area expansion and Young's moduli of the liposomes were found to be 0.067Nm⁻¹ (67±4dyn/cm) and 15±1 MPa.

Diaphragm muscle shortening modulates kinematics of lower rib cage in dogs.

We tested the hypothesis that diaphragm muscle shortening modulates volume displacement and kinematics of the lower rib cage in dogs and that posture and mode of ventilation affect such modulation. Radiopaque markers were surgically attached to the lower three ribs of the rib cage and to the midcostal region of the diaphragm in six dogs of ∼8 kg body masses, and the locations of these markers were determined by a biplane fluoroscopy system. Three-dimensional software modeling techniques were used to compute volume displacement and surface area of the midcostal diaphragm and the lower three ribs during quiet spontaneous breathing, mechanical ventilation, and bilateral phrenic nerve stimulation at different lung volumes spanning the vital capacity. Volume displaced by the diaphragm relative to that displaced by the lower ribs is disproportionately greater under mechanical ventilation than during spontaneous breathing in the supine position (P < 0.05). At maximal stimulation, diaphragm volume displacement grows disproportionately larger than rib volume displacement as lung volume increases (P < 0.05). Surface area of both the diaphragm and the lower ribs during maximal stimulation of the diaphragm is reduced compared with that at spontaneous breathing (P < 0.05). In the prone posture, mechanical ventilation results in a smaller change in diaphragm surface area than spontaneous breathing (P < 0.05). Our data demonstrate that during inspiration the lower rib cage moves not only through the pump- and bucket-handle motion, but also rotates around the spine. Taken together, these data support the observation that the kinematics of the lower rib cage and its mechanical interaction with the diaphragm are more complex than previously known.