Joint contact

Reference [20] notes that any such system should be easy to learn and use, accurate, easy to update, flexible, well based and linked to existing design methods and tools. It should recognise innovation, include diverse environments and be acceptable to all partners in the construction process. The authors point out that the clear statement of assumptions enables them to limit the number of factors. Apart from the environment and the material, joints, contact with other materials and local movement all provide sites for degradation. Protective layers help provided that they remain intact, but degradation proceeds rapidly once they are penetrated. 

Parker, D.T., Parker, A.C. and Ramachandran, C.K. (1996) Ricin. Joint CB Technical Data Source Book Toxin Agents. U.S. Army Dugway Proving Ground, Utah, Joint Contact Point Directorate. 

In this chapter, various aspects of joint-articulating motion are covered. Topics include the anatomical characteristics, joint contact, and axes of rotation. Joints of both the upper and lower extremity are discussed. 

The talocrural joint contact area varies with flexion of the ankle (Table 49.1). During plantarflexion, such as would occur during the early stance phase of gait, the contact area is limited and the joint is incongruous. 

TABLE 49.1 Talocalcaneal (Ankle) Joint Contact Area... 

Kimizuka M., Kurosawa H., and Fukubayashi T. 1980. Load-bearing pattern of the ankle joint. Contact area and pressure distribution. Arch. Orthop. Trauma Surg. 96 45-49. 

Rosenbaum D., Eils E., and Hillmann A. 2003. Changes in talocrural joint contact stress characteristics after simulated rotationplasty. /. Biomech. 36 81-86. 

Stormont T.J., An K.A., Morrey B.E et al. 1985. Elbow joint contact study comparison of techniques. 

Hg = gasket load, operating, lb Hp = total joint-contact surface compression load, lb... 

Aj, = actual joint-contact area of gasket, in. b = effective gasket seating width, in. d = root diameter of threads, in. d,n = pitch diameter of threads, in. 

Because muscle, ligament, and joint-contact forces cannot be measured noninvasively in vivo, estimates of these quantities have been obtained by combining mathematical models with either the inverse-dynamics or the forward-dynamics approach (Sec. 6.6). Below we review the levels of musculoskeletal loading incurred in the lower-limb during rehabilitation exercises, such as isokinetic knee extension, as well as during daily activity such as gait. 

The forces exerted between the femur and patella and between femur and tibia depend mainly on the geometry of the muscles that cross the loiee. For maximum isometric extension peak forces transmitted to the patellofemoral and tibiofemoral joints are around 11,000 N and 6500 N, respectively (i.e., 15.7 and 9.3 times body weight, respectively) (Fig. 6.27). As the knee moves faster during isokinetic extension exercise, joint-contact forces decrease in dire proportion to the drop in quadriceps force (T. Yanagawa and M. G. Pandy, unpublished results). 

FIGURE <>.29 Joint contact forces acting at the hip, knee, and ankle during gait. The results were obtained by solving a dynamic optimization problem for normal walking (see Fig. 6.28 for details). [Modifiedfrom Anderson and Pandy (2001a).]... 

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