The diameter of the tibial medullary canal varies significantly. It may be 8 mm or less. Reamers can be used to enlarge the medullary canal for larger diameter nails. Such nails permit larger diameter locking screws. Both nail and screw strength and durability increase with diameter. The medullary canal should be reamed a bit larger than the intended nail diameter (usually about 1.5 mm more), to ease nail insertion. The image illustrates a non-reamed nail on the left, and a reamed nail on the right.
Stability is increased with the reamed technique, because the nail fits snugly in a longer portion of the tibial shaft.
Reaming is currently favored for most tibial nailing, but this should be done gently when the tibial diaphysis is dense, and the canal diameter is small.