LOAD CAPACITY OF TUBULAR BONE

Publisher Summary This chapter discusses the load capacity of tubular bone. Long tubular bones act as structural machine members; as such, they carry applied loads and participate in kinematic function. The chapter presents an investigation concerned with the ability of long bones to resist these loads. In fulfilling this function, the bones must resist both static or slowly applied loads and dynamic loads. It was noted that the amount of torsional load necessary to produce a fracture of a fresh human tibia was 768 kgcm. From examination of published data and application of engineering fundamentals, it is evident that the distribution of bony tissue represents an economic compromise. This condition must exist because of to the variety of loads to which the bone is subjected. Hollow circular sections of constant dimension are best suited to carry torsional loads. Representative bones were sectioned at the point of initial failure. The contiguous surfaces were photographed. The section properties were obtained by means of graphical integration. The torsional moments of inertia and section moduli and the bending moments of inertia and section moduli were calculated. Removal of cortical bone converts a portion of the bone from the closed section to the open section state. This markedly reduces its torsional load-bearing capacity and its torsional energy absorbing capacity. While not significantly reducing the torsional stiffness of the whole bone, it does greatly reduce the maximum allowable angular deflection.