Biomechanics of the forefoot
The work reported in this thesis was carried out to investigate the kinematic and dynamic behaviour of the forefoot during normal locomotion activities. An extensive literature review on the subject is presented and the need for further investigations shown. Fresh autopsy specimens were studied to determine the course taken by tendons in relation to the joints of the forefoot, and the topography of joint surfaces mapped. The overall geometries of the first and second rays have been described too. Also, an experimental investigation has shown that without muscular activity the metatarsal bones are mainly loaded in bending. Locomotion studies have shown that the average peak ground forces under the pad of the great toe, the head of the 1st metatarsal, the pad of the 2nd toe, the head of the 2nd metatarsal and the head of the 5th metatarsal measure about 30% body weight (BW), 15% BW, 6% BW, 30% BW and 15% BW, respectively. Temporal graphs of these forces show their behaviour during the gait cycle. Furthermore, the magnitudes of these forces when wearing shoes-with stiff soles, when climbing up and down stairs, as well as when walking up and down a slope of 15° are reported. Based on the external forces measured, the internal forces acting along the flexor tendons and across joint surfaces of the 1st and 2nd rays during gait are estimated. The stresses that thereby develop in the shanks of the metatarsal bones indicate that the 1st metatarsal bone is subjected mainly to compression while the 2nd metatarsal bone is exposed to a high degree of bending. The relationship between the results of this study and clinical problems is considered and especially a hypothesis has been advanced to explain how under edge-loading conditions localised necrosis of the metatarsal heads could occur, thus giving rise to Koehler-Freiberg's disease.