If the medullary canal is narrow, it may be necessary to enlarge the canal by reaming to allow the insertion of a larger diameter nail with sufficient strength.
Reaming also increases the length of contact between the nail and the endosteal surface of the bone at the isthmus.
Although reaming may damage the endosteal blood flow, in practice the periosteal blood supply is still sufficient for fracture healing.
The position of the reamer can be checked intermittently under X-ray control.
Reaming generates heat, particularly if the reamers are blunt, so it is important not to apply excessive force whilst reaming. (A tourniquet should not be used in tibial nailing as blood flow cools the bone during reaming.)
The initial reamers will be removing cancellous bone, so they pass relatively easily. As the diameter of reamer heads increases, they start making contact with the endosteal surface of the cortex; a change in the reaming sound can be heard (chatter) and more resistance can be felt.