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Interlocking Nails combines the advantages of closed medullary nailing with added fixation of inserted transfixion screws, introduced through predrilled holes at proximal or distal end of nail or both. When both the proximal and distal end of nail are locked, it is termed, “static” and when only proximal or distal end of nail is locked, it is termed, “dynamic”. The static fixation may be converted to dynamic during later stages of healing. Interlocking nails provide a stable nail-bone construct during the healing process.
The advantages of interlocking Nails are that they can be used for fractures which are unsuitable for standard medullary fixation, those with severe comminution, bone loss and those beyond the isthmic zone if transfixing interlocking screws are used. Whittle and co-workers have reported the development and use of closed section interlocking intramedullary nails designed with smaller diameters and modified section modules to allow insertion with non reamed techniques in open fractures with low infection rates.
Interlocking Nails system requires sophisticated equipment for insertion and extraction of nails. Certain systems require a separate inventory of nails for right and left sides. Image intensifier is necessary. Procedure is difficult and the learning curve is long. Interlocking pins/bolts at times break/bend and wings may get stuck inside medullary cavity leading to difficulty in extraction of nails. There may be fatigue failure of nails.
Interlocking Nails are the preferred mode of treatment for fractures of long bones viz. femur, tibia and humerus. Presently, more than 95 per cent of femoral fractures and unstable tibial fractures can be treated with interlocking nails.
Interlocking Nail is a nail placed within the medullary cavity of a long bone secured in position by proximal and distal transfixing screws to provide axial, bending and torsional stability. They are best suited for diaphyseal fractures and particularly useful in cases with extensive comminution. They permit early return to limb function with the added advantage of minimal soft tissue morbidity. Common places for application are the femur, humerus, and tibia. Due to the curvature of the canine femur, shorter nails than would ideally be used are often required. In some cases, the femur is repaired in a slightly straighter alignment than it was prior to fracture. This is referred to as overreducing a fracture.
Interlocking Nails widens the range of indications for medullary osteosynthesis of femoral and tibial shaft fractures. Stability is achieved by transverse threaded bolts in prefabricated holes in the nail, which anchor the implant directly to cortical bone, thereby controlling length, alignment, and rotation of the limb. Two hundred eighty-three femoral and 401 tibial fractures were treated with an Interlocking Nail and followed for an average of 20 months. Overall, 97% of the femurs and 94.3% of the tibias were judged to have an excellent or good result, based on both clinical and radiographic parameters. Delayed union or nonunion requiring bone grafts occurred in 2% of the femurs and 0.7% of the tibias following Interlocking Nailing. Deep infection developed in 2.4% of the femurs and 2.2% of the tibias. All of these patients eventually healed their fractures without evidence of chronic osteomyelitis. The main advantage of Interlocking Nails are that surgery can be performed using closed nailing techniques, allowing early protected weight-bearing and joint motion. The rates of nonunion and infection are very low, and there is little risk of refracture after implant removal.
Interlocking Nails come in different lengths, thicknesses, and vary in their number of screw holes. There are many instruments used in Interlocking Nails systems, some of them are given below.
Cannulated Guide Rod with Ram
T Handle with Jacob Chuck
Distal Aiming Device
T Handle for Flexible Shaft
Flexible Reaming Shaft
Shaft for Reamers
Nail Holding Bolt