An interlocking nail is a Steinmann nail with holes, through which screws can be inserted and fixed to bone cortex. In so speaking it is an intramedullary plate. The interlocking nail nullifies all the forces acting over the fracture line, and thanks to screw fixation, it prevents implant migration that--in accordance with our opinion--is a frequent complication associated with intramedullary nails. They can be used in all types of diaphyseal fractures in the humerus, femur and tibia.
Primarily, interlocking nails are metallic implants used for the repair of traumatic long bone fractures. They consist of a large diameter rod, inserted into a bone medullary cavity and secured to it with locking bolts going from one cortex to another and capturing the nail inside the medullary cavity.
In unique locking technology, the I-Loc can be used in a variety of fracture configurations including metaphyseal and periarticular fractures. The implant is designed to prevent post-operative instability through an innovative mechanical interlock between the nail and the bolts, which allows for immediate weight bearing activity.
Interlocking nails may also be used to stabilize corrective osteotomy such as those performed in cases of medial patellar luxation secondary to severe femoral varus deformity.
Indications of Interlocking Nail
- Closed fractures of the shaft, which are not very close to the joints (for the femur, its ideal when the fracture is between the lesser trochanter and condyles)
- Pathological fractures
- Non-Unions and pseudoarthrosis
- Malunions and deformities
- Open fractures up to Gustillo III A
Surgical Overview of Interlocking Nail
The first surgical step is the insertion of the nail into the medullar cavity. The nail insertion must be normograde to enable proper placement of the aiming guide or jig used for bolt insertion. The medullary cavity is prepared to accommodate the adequate nail (diameter and length) using a series of dedicated awls. The fracture is reduced and the preparation is carried into the distal fragment prior to inserting the final implant. The nail is introduced using a handle secured to an extension affixed temporarily to the nail. The handle is ergonomic to allow easy insertion and also serves as a base for the aiming jig used to accurately guide the drilling of the holes for the locking bolts.
Once the bolt holes have been drilled, the bolts are secured to the interlocking nail thanks to the threaded Morse taper locking system. Since they do not require contouring and since implant insertion and fixation can be performed through remote incisions, interlocking nails are ideal for minimally invasive application. Using an interlocking nail following the principals of minimally invasive osteosynthesis is called MINO (as opposed to MIPO when using a bone plate) and is considered the standard of care in people.