since the bones are composed of proteins and minerals, these are the most essential nutrients needed to heal a broken bone. Silica, calcium and magnesium are the most vital minerals, silica is available at most health food stores, vitamins C and D promote the absorption of calcium
It would also be a good idea to take zinc to promote the repair of the tissue surrounding the broken bone. Kelp happens to be very rich in calcium and other minerals (I think you can take anywhere from 1,000 to 1,500 mg daily-ish). Also, if you want a more natural way of getting silica you can take an herb called horsetail. Oh yeah...no caffeine...or at least less caffeine.
you would need to be very careful when taking so much kelp since it is high in iodine.......iodine can disrupt the thyroid gland giving you a whole new set of problems....and thyroid dysfunction is not an easy fix