Running with a fractured fibula

Although the Olympics are over, there is still time to examine some of the things that occurred over the past two and a half weeks.  One of the most impressive was US sprinter Manteo Mitchell finishing has leg of the men's 4 x 400 meter relay despite the fact that he was running on a fractured fibula.  How was he able to do this?  There are many factors that come into play, including his psychological condition and motivation, pain tolerance, and the fact that he is a world class elite athlete.  The only factors that I am able to analyze are the anatomical and biomechanical factors.

The fibula is the smaller, thinner bone located on the lateral (outer) side of your lower leg.  At the proximal (top) end, it articulates with the tibia (knee), and at the distal (bottom) end, it articulates with the tibia and helps form the ankle.  The "bump" on the lateral side of your ankle is the lateral malleolus, which is part of the fibula.  Due to the placement and size of the fibula, it does not play as large of a role in force absorption and weight bearing as the larger tibia does.  In fact, about 10-15 % of the force from the ground during walking and running is absorbed by the fibula, and the other 85-90% is absorbed by the tibia.  Even though it does not absorb as much force as the tibia, it is still a critical bone to transfer force from the foot and ankle up to the knee, and without a fibula, it would be nearly impossible to walk or run.  If Mitchell had fractured his tibia, he likely would not have been able to finish the race.  Since he fractured his fibula, he was able to finish, which was a very impressive accomplishment, not only because of the intense pain he was in, but also because the fractured fibula disrupted the normal transfer of force between the ground, and his foot, and ankle, and lower leg.  This is just speculation, but there is probably not a high percentage of people that would be able to continue running with a fractured fibula.