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Musculoskeletal system
Published in David A Lisle, Imaging for Students, 2012
Radiographic signs of RA (Fig. 8.57): Soft tissue swelling overlying jointsBone erosions occur in the feet and hands, best demonstrated in the metatarsal and metacarpal heads, articular surfaces of phalanges and carpal bonesReduced bone density adjacent to joints (periarticular osteoporosis)Abnormalities of joint alignment with subluxation of metacarpophalangeal joints causing ulnar deviation of fingers, and subluxation of metatarsophalangeal joints producing lateral deviation of toes.
Biomechanical modelling and simulation of foot and ankle
Published in Youlian Hong, Roger Bartlett, Routledge Handbook of Biomechanics and Human Movement Science, 2008
A 3D linearly elastic ankle-foot model, consisting of the bony, encapsulated soft tissue and major plantar ligamentous structures, was developed by Chen et al.6 using CT images to estimate the plantar foot pressure and bone stresses. The joint spaces of the metatarsophalangeal joints and ankle joint were connected with cartilaginous structures while the rest of the bony structures were merged. Frictional contact between the plantar foot and a rigid support was considered. The peak stress region was found to shift from the second metatarsal to the adjacent metatarsals from midstance to push-off. Chen et al.5 further studied the efficiency for stress and plantar pressure reduction and redistribution using flat and total-contact insoles with different material combinations. Nonlinear elasticity for the insoles and the frictional contact interaction between the foot and support were considered. The predicted peak and average normal stresses were reduced in most plantar regions except the midfoot and hallux regions with total-contact insole. The percentage of pressure reduction by total-contact insole with different combination of material varied with plantar foot regions and the difference was minimal.
The Mechanics of Gait
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
The foot muscles, tibialis posterior, and peroneals respond to a similar challenge to stabilize the midtarsal and lesser joints for full weight bearing by doubling the intensity of their activity. Stability of the metatarsophalangeal joints is provided by the compressive force of the long toe flexor muscles.
Modelling the complexity of the foot and ankle during human locomotion: the development and validation of a multi-segment foot model using biplanar videoradiography
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Jayishni N. Maharaj, Michael J. Rainbow, Andrew G. Cresswell, Sarah Kessler, Nicolai Konow, Dominic Gehring, Glen A. Lichtwark
The five joints connecting the segments were the ankle (talus–tibia), subtalar (calcaneus–talus), midtarsal (midfoot–calcaneus), tarsometatarsal (forefoot–midfoot) and the metatarsophalangeal joints (digits–forefoot). The JC model constrained motion between rigid body segments by linking them via rotational joints. This allowed segments to only rotate about the defined axis at a centre of rotation and thus with 1 DoF. The axis of each joint in the foot was orientated relative to all three cardinal planes, allowing for simultaneous 3D rotations, triplane motion. The orientation of each joint axis was defined by an inclination and deviation angle as reported by previous cadaveric studies (Hicks 1953; Nester et al. 2001; Lewis et al. 2007), although slightly modified during the iterative model building process. The inclination angle was defined as the angle between the sagittal projection of the axis and the horizontal plane and the deviation angle was along the horizontal projection, and measured with respect to the long axis of the foot (straight line between calcaneus and second metatarsal) (van den Bogert et al. 1994). The joint axis at the subtalar had a 38° inclination and −21° deviation to the midline of the body, running from posterior, inferior and lateral to anterior, superior and medial through the rear-foot (Lewis et al. 2007). The midtarsal joint axis was orientated in an upward, medial direction with 35° of inclination and −24° of deviation to the midline of the body (Nester et al. 2001). The tarsometatarsal joint axis had an inclination of 36° and deviation of −60° from the midline of the body, which runs in a medial, upward direction from the fifth to the second metatarsal (Hicks 1953). These joint axes are shown in Figure 1.