IF fixed the embalmed leg in 10% formalin, will it be useful for preservation

10% formaline solution (or 4% formaldehyde solution) should be sufficient, but I would not count on fixation by immersion, all the more so because amputated limbs may be contaminated. So, you should consider perfusion fixation (arterial embalming). During the procedure, you should find the main arteries to perform injection of the fixative into the vascular network (volume of the injected fixative depends on the weight of the specimen). To avoid leakage of the fixative you should ligate or clamp the other blood vessels. After the injection arteries used during procedure should also be ligated and the specimen should be placed in preservative liquid for about 3 months. In some cases I used also dr Salafia's embalming technique. And remember - formaldehyde is toxic! You should wear appropriate protective equipment during the embalming procedure.

In my opinion, the anatomy may be altered by the disease process, so you should describe the source of the research material (including reasons of amputations) in the "material and methods" section. 

Thanks!