Playing soccer is associated with higher BMD of the skeleton at all sites measured. Running is associated with higher BMD at directly loaded sites (the calcaneus) but not at relatively unloaded sites (the spine). Specific loading conditions, seen in ball sports or in running, play a pivotal role in skeletal adaptation. The importance of including an appropriate control group in clinical studies is underlined.

Within the limitations of our study involving the testing of 1 type of screw purchase in ovine tibiae, results demonstrate that clinical levels of lag screw tightening (86% Tmax) are past the yield point of bone. Tightening to these high torque levels can cause damage leading to compromised holding strength. Further research is still required to establish the appropriate level of torque required for achieving optimal fracture fixation and healing.

No abstract

HUTCHINSON, T. M., R. T. WItALEN, T. M. CLEEK, J. M. VO-GEL, and S. B. ARNAUD. Factors in daily physical activity related to calcaneal mineral density in men. Med. Sci. Sports Exert., Vol. 27, No. 5, pp. 745-75(i, 1995. To determine the factors in daily physical activity that influence the mineral density of the calcaneus, we recorded walking steps and the type and duration of exercise in 43 healthy 26-to 51-yr-old men. Areal (g-cm 2) calcaneal bone mineral density (CBMD) was measured by single energy x-ray densitometry (SXA, Osteon, Inc., Wahiawa, HI). Subjects walked a mean (_+SD) of 7902 ('+_2534)steps per day or approximately 3.9 (+-1.2) miles daily. Eight subjects reported no exercise activities. The remaining 35 subjects spent 143 (2-772) (median and range) min.wk _ exercising. Twenty-eight men engaged in exercise activities that generate single leg peak vertical ground reaction forces (GRF:_) of 2 or more body weights (high loaders, HL), and 15 reported exercise or daily activities that typically generate GRFL less than 1.5 body weights (low loaders, LL). CBMD was 12% higher in HI_, than LL ((I.668 + 0.074 g.cm -2 vs (I.597 +_ 0.062 g.cm -, P < 0.004). In the HL group, CBMD correlated to reported minutes of high load exercise (r = 0.41, P < 0.03). CBMD was not related to the number of daily walking steps (N = 43, r = 0.03, NS). The results of this study support the concept that the dominant factor in daily physical activity relating to bone mineral density is the participation in site specific high loading activities, i.e., for the calcaneus, high calcaneal loads.

'This is the peer reviewed version of the following article: Ryan MK, Mohtar AA, Cleek TM, Reynolds KJ. Time-elapsed screw insertion with microCT imaging. Journal of Biomechanics. pii: S0021-9290(15)00727-7.

No abstract

A smart screwdriver was developed that uses the current from the motor driving the screw to predict the current at which the screw will strip the bone threads. The device was implemented and was able to achieve motor shut-off and cease tightening at a predefined threshold, with no premature bone failures.

Changes in the material characteristics of bone marrow with aging ciiii be a significant source of error in measurements of bone density when using X-ray and LiltrasoLuid iinaging modalities. In the context of computed tomography, dual-energy computed techiiiqiies have been used to correct for changes in marrow composition. However, dual-energy quantitative computed toinogrnpliy (DE-QCT) protocols, while iiicreasing the accur~icy of the measurement. reduce the precision and increase the radiation dose to the patient in coniparison to siiigle-enei.gy quantitative computed tomography (SE-QCT) protocols. If thc attenuation properties of tlic iiiarrow [or ;I particular bone can be shown to be relatively constant with age. it sliotild be possible to use single-energy techniqties without experiencing errors caused by unknown marrow composition.Marrow was extracted by centrifiigation from 10 iiim thick frontal sections of 34 adult cadaver calcaiiei (28 males, 6 females, ages 17-65 years). The density and energy-dependent linear X-ray nttcnuation coeficieut of each inarrow sample were determincd. For p i i r p o~e~ of comparing our results, we then computed iiii elrective CT number at two G E CTli scan voltages (SO and 120 kVp) for each specirnen. The coelljcients of variation for the density, CT number at SO kVp and CT number a t 120 kVp were each less than IY,~, and the paraineters did not change siguificantly with age ( p > 0.2, 1. ' < 0.02, power > 0.8 where the minimum acceptable = 0.21 6). We could demonstrate no significant gender-associated diflercnces in these relationships. These data suggest that calcaneal bone marrow X-ray attenuation properties and marrow density are essentially constant from the third through sixth d e c d e s of life.