[Biomechanical investigations on the parry fracture of the ulna (author's transl)].

108 ulnae from the cadavers of 50 men and 6 women were fractured in four positions with a tension testing machine with electronic measurement of force. Stress-strain-diagrams were registered, and the values of breaking load, breaking energy, breaking stress and ultimate deflection were correlated to the areas of cross sections of compacta and medulla. Breaking load and breaking energy decrease distally: medium breaking load in the upper portion of the ulna about 320 kp, in the lower portion about 100 kp; breaking energy in the upper portion about 65 kpcm, in the lower about 20 kpcm. Breaking stress is greatest in the middle portion of the ulna (19 kp/mm-2 in contrast to 11-14 kp/mm-2 near the joints). With increasing age the cross sections of the medulla increase significantly, but breaking load, breaking energy, breaking stress and area of cross section of the compacta decrease significantly. Ulnae from females are less resistant than those from males. Intact periosteum rises resistance to breaking and ultimate deflection. Experimental data agree with clinical observations.