If you study orthopaedics, you’ll know for sure that the femur is the longest, heaviest and strongest bone in the human body. One day, by chance, it happens that you see a bar like the one in the picture on the right. Well, maybe you’ll also notice two things: it is as long as your femur bone and it has more or less the same curvature. With a bit of fantasy and science fiction mood, you could even get to figure out a strange surgery where such long bars are plugged into the bones of some patients in order to strengthen their skeleton and create an army of solid soldiers.
There’s no need to invent anything like that, since we are talking about a surgery that already exists (but not for military purposes). Intramedullary nailing consists in forcing a metal nail (or rod) into the medullary cavity of a bone. Normally, IntraMedullary (IM) nails are employed to treat fractures of long bones of the body. Nowadays, this surgery is regarded as the standard of treatment for both femoral and tibial shaft fractures.
Let’s focus on an IM femoral nail. What about its surgery?
First, the surgeon makes use of a Reamer. Wikipedia defines it as a “metalworking tool used to create an accurate sized hole“. The medical version of this device is actually employed to hollow out the center of the medullary canal of the femur, by accessing it from the top (next to the pelvis bone). This doesn’t affect too much the bone solidity and is necessary when the medullary cavity is not continuous (for example, in the case of broken leg injuries).
Once the femur has been properly drilled, an intramedullary nail is tapped into place. This means that a hammer is used to push the rod down into the hollow medullary cavity. In a sense, this action recreates a well-defined medullary cavity in the case of displaced or unstable fractures. Moreover, it obviously provides stabilization for the healing bone (that starts growing again in a proper “shape”).
Finally, screws are usually placed in the head of the femur to secure the nail and prevent its collapse or rotation. During the progressive return to activity, the leg of the patient will take benefit from the fact that the loads will be shared by both the healing bone and its solid metal core. This leads also to a faster rehabilitation period (which requires a first non-weight bearing stage followed by specific exercise programmes).
After the implantation, the intramedullary nail is usually left inside the bone forever. In some cases, the patient may develop some long-term complications that cause pain and general ache at the insertion site. In such cases, a second surgery might be necessary to remove the IM nail from the recovered bone. Wikipedia gives us some interesting data about long-term complications of IM nailing for the femur, that “may include persistent or permanent knee pain (present in 73.2% of patients), atrophy of the calf muscle (27.3%), atrophy of the quadriceps (27.3%), and arthritis (35.4%)“.
The following image shows the femoral fracture (A) and the IM nail inserted all along the bone (B), the relatively small scar on the patient’s leg (C) and the recovered bone (D, E).