Over the past 50 years medullary nail techniques for fracture fixation have got universal acceptance. A longitudinally slotted tube that is inserted into a long bone under pre-stress is a conventional Kuntscher nail. The radial stress caused by the insertion of an intramedullary nail leads to friction between bone and nail that secures the relative movement the two nailed fragments. Though, since these frictional forces are limited, the application of this technique is limited just to simple midshaft diaphyseal fractures. The intramedullary rod is a commonly used device in long bone fractures, mainly in the lower limb fracture. It offers the benefit that it can be implanted through a small incision and without considerable surgical exposure. Closed interlocking nail fixation is the procedure of choice for femoral shaft fractures, especially in patients of poly-trauma. This treatment modality has been the subject of controversy since its introduction due to concerns of damage to the medullary circulation, possibilities of embolism, and complications from misapplications of the technique due to lack of understanding of the biochemical principles of medullary nail fixation.
Different types of medullary nails are centromedullary nails, condylocephalic nails, centromedullary interlocking nails, cephalomedullary nails, cephalomeduallry interlocking nails. Centromedullary nails enter the bone in line with the medullary canal. They get in contact with the bone through multiple points of longitudinal interference. They depend on stability and restoration of bony contact to avoid axial and rotational deformation of the fracture. Condylocephalic nails enter the bone in the condyles of the epiphyseal-metaphyseal area. They are often inserted in groups for added rotational stability. Cephalomedullary nails have a centromedullary portion, but also allow fixation up into the femoral head.
A perfect medullary nail has not still designed. The varying contour of bones make invention of such a nail actually impossible, but improvement in the medullary nail’s design should seriously continue. A medullary nail should have the following requirements:
1. It should be strong enough and provide sufficient stability to maintain position and alignment, including prevention of rotation; it should include interlocking transfixing screws as necessary;
2. It should be constructed so that contact-compression forces may impact the surfaces of fracture, a desirable physiologic stimulus to union; and
3. It should be placed so that it is available for easy removal; attachments are provided to facilitate removal.
An interlocking nail (IN) is basically an intramedullary pin secured in position by distal and proximal transfixing bone screws which engage the bone to the nail to provide torsional stability and axial bending. This procedure, in man, usually involves power reaming and insertion by closed technique on a distraction table under fluoroscopic control. Interlocking fixation is defined as static, dynamic, and double locked. Dynamic fixation controls rotational deformation and bending but allows nearly full axial load transfer by bone. Dynamic fixation is used in some nonunions and in axially stable fractures. Static fixation controls bending, rotation, and axial load as well as makes the orthopedic implant a more load-bearing device with the potential for a reduced fatigue life. It is especially useful in comminuted, nonisthmal fractures of the tibia and femur. The double-locked mode controls rotational forces, bending, and some axial deformation, but due to capability of axial translation of the orthopedic screw within the nail, some shortening is possible. This method of fixation is used in fracture of the humerus and occasionally in delayed unions and nonunions.
The stability of fracture fixation by nailing significantly depends on the mechanical properties of the nail, the nail’s fit in the medullary space, and the mechanical properties of the locking bolts or screws. Locking bolts or bone screws can be accessible from bone screw suppliers in India. The torsional and bending stiffness of the nailed bone mainly depends on the nail’s diameter. Nails with a larger diameter provides a significantly greater stiffness compared to that of a small diameter.