The most important mechanical characteristics of a nailing system are related to its stiffness (rigidity) and strength. This study evaluates the properties of three commercially available interlocking intramedullary nail systems using standardized test methods. An understanding of the mechanical properties along with the clinical data will assist the surgeon in choosing the optimum implant. Testing indicates that the bending strength and stiffness of the Grosse & Kempf, the AO/ASIF Universal, and the Russell-Taylor interlocking intramedullary nail designs are comparable. It is therefore not surprising that all of these nail systems have excellent clinical results. However, the nonslotted design is approximately 30 times more resistant to torsional loading than either the partially slotted design of the Grosse & Kempf nail or the fully slotted design of the AO/ASIF nail. The clinical relevance of the torsional values may not be known until a long-term comparison of the complication rates for these different systems is available. Analysis of screw design reveals a tradeoff in bending strength when compared to amount of bone purchase. The bending strength of fully threaded screws (allowing bicortical fixation) is less than that of partially threaded screws (allowing only unicortical fixation), which shows that for the implants tested, increased bone purchase requires a compromise in strength for similar sized screws.
"An interlocking nail is an intramedullary steel rod with transverse openings at both ends. Locking screws are inserted into the openings; they are anchored in the cis-and trans-cortex to block the nail relative to the main bone fragments (Georgiadis et al., 1990; Russel et al., 1991; Brumback, 1996; Dueland et al., 1996; Moses et al., 2002; Moores, 2008; Lu et al., 2009). In most nails, one end features a trocar point or a blunt end, and the other end has a threaded center. "
[Show abstract][Hide abstract] ABSTRACT: Interlocking nails (ILN) are effective tools for the fixation of long bone fractures, including humeral, femoral and tibial fractures. An interlocking nails are a steel rods which are placed in medullary canal of fractured bone. They have transverse openings which are use to put inside a transcortical screws. Those screws block the nail relative to the main bone fragments. Interlocking nails counteract all forces at the fractured site, thus they are an alternative to bone plates. Simultaneously, the intramedullary nail is placed in a natural position relative to the bone's biomechanical axis and neutralizing bending forces across bone fragments. Unlike bone plates that are eccentrically positioned, the nail has an intramedullary position which makes it much more resistant to compressive, torsional and bending force. This technique requires a relatively low surgical approach to compare with plate osteosynthesis. Most importantly, interlocking nails support biological osteosynthesis and fracture management with minimal surgical intervention. The first application in veterinary medicine of the interlocking nail was at the late 1980s. Since this moment, the technique still evolves providing the next generations of interlocking nails. At these days we have several generations of it. This paper discusses the use of interlocking nails in fracture stabilization in veterinary practice and overviews the development of nail implants and their applications. The advantages of the analyzed technique and the associated complications are discussed. (C) 2011 PVJ. All rights reserved
[Show abstract][Hide abstract] ABSTRACT: The nail-osteosynthesis is an established concept for shaft-fractures of long bones. The compression-nail ICN enables a favourable primary-stability and also a former full weight-bearing over a pre-compression of the nail-bone-system. The indications of the compression-nail include beside more diaphyseal cross fractures and short oblique fractures non-unions and correction-osteotomies. Newer modular nail-types like the tandem compression nail (TCN) can improve the biomechanical prerequisites of the compression nail principle. Our investigations were done with a simple biomechanical model of single leg stance. We used composite femur for our biomechanical testings. All femurs were coated with a photo elastic coating, under polarized light the superficial strain distribution could be seen in an overall view. The resuts showed in comparison between the two type of nails that the TCN has lower loads under the proximal screws due to load sharing; the compression forces at the osteotomy site showed similar forces. To achieve a stable bone-implant system in compression nailing a mean of 2/3 of the diameter of bone is needed at least.
[Show abstract][Hide abstract] ABSTRACT: Fracture management is becoming less conservative, and more frequently surgical intervention is the treatment of choice. Intramedullary mailing is a modern surgical method of internal fracture used in long bones such as the femur, tibia and humerus. The nails' function is to stabilize the fracture fragments, allowing load transfer across the fracture site while maintaining anatomic alignment of the bone. There are a large number of different intramedullary nails available commercially but no universal guideline stating the conditions at which each nail will perform at its optimum. Numerous animal, biomechanical and clinical studies have documented the performance of the nails. Biomechanical studies have shown that in torsion, slotted nails have a considerably lower rigidity than non-slotted nails but that in bending, the slot makes little difference to the nails' behaviour and so the two nail types have similar stiffnesses. Studies also recommend that in unstable fractures an interlocked intramedullary nail is essential if limb shortening or malunion is to be avoided. It is the aim of this review to outline the work that has been published to date on the biomechanical testing of intramedullary nails and to highlight areas that require further investigation.
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