Biomechanical Conditions of Triceps Functioning in Calcaneal Fracture
Mathematical model was created to investigate the biomechanical conditions of musculus triceps surae functioning in calcaneal fractures with displacement of peripheral fragment. There occurs the shortening of musculus triceps surae and its dysfunction, associated with simultaneous shortening of its length and moment arm. Less triceps dysfunctions are observed with decreased moment arm and constant length of the muscle, or shortening of the muscle length, but preserved moment arm. Lengthening, as well as shortening, of triceps due to calcaneal fracture with displacement of peripheral fragment causes a decrease in muscle excursion and strength, as well as increase in energy expenditure during its operation. Even small displacements of peripheral fragment forward and upward lead to a rapid stress increase in the Achilles tendon. With significant displacements of fragment, the stress in the Achilles tendon may exceed the limit of its strength. There is a need for mandatory restoration of anatomic integrity and spatial geometry of the calcaneus due to its fracture with displacement of fragments.