Why does the INTERTAN nail have a trapezoidal shape?
The smaller cross-section of the INTERTAN nail has the advantage of preserving the Gluteus Medius Tendon while at the same time not compromising the overall strength of the implant. The trapezoidal shape of the nail places more material at the lateral side of the implant where tensile forces are typically the strongest. In addition, the nail's trapezoidal profile also provides enhanced anatomical fit and added rotational stability in the proximal femoral metaphysis similar to that offered by conventional hip stems.
What is an Integrated Interlocking Screw configuration and how will it help my patients?
The integrated interlocking screws of the INTERTAN system increase stability and resistance to both intra and post-operative fracture rotation about the implant by providing two points of fixation within the femoral neck and head. This directly reduces rotational instability and eliminates the possibility of implant failure due to Z-Effect.6 The integrated screw configuration is a fourth generation intramedullary nail concept combining the enhanced rotational stability of the TRIGEN Reconstruction Nail with the superior controlled sliding and compression of the IMHS™ implant. The INTERTAN system incorporates aspects of both devices by providing both single and dual integrated lag screws for the treatment of most major fracture patterns.
What is Z-Effect and how does INTERTAN solve it?
Z-Effect6 is an unfortunate by-product of most intramedullary nails that utilize two screws placed up into the femoral neck and head. Typically, the superior screw is of smaller diameter than the inferior and bears a disproportionate amount of load during weight bearing. Excessive varus forces placed on the smaller screw at the lateral cortex cause it to toggle and either back out or migrate through the femoral head into the acetabulum. The larger inferior screw is neither keyed in rotation nor locked in place, and it too will either back out or migrate medially. The resultant Z-Effect where the two screws move in opposite directions is one mode of failure for the conventional two screw reconstruction device. The INTERTAN nail turns that construct upside down and integrates the two screws so that they act as one device to bear all load, enact all compression and prevent excessive medial or lateral migration thus negating the Z-Effect.
Why does the short nail have a clothespin distal tip?
The clothespin distal tip of the INTERTAN short nail reduces the overall cross-sectional stiffness of the implant to minimize the risk of iatrogenic fracture during insertion, to ease the actual process of nail insertion and to offer enhanced rotational stability within the proximal femoral canal. As the distal tip of the INTERTAN nail encounters the AP bow of the proximal femur, it closes slightly changing the implant's straight profile to bent. This has the advantage of lessening point stresses about the distal tip of the nail and reducing the possibility of fracture due to a stress riser at that location.
I have been using a single screw IM device for the last 20 years and have yet to have one cut out. Do I have to use the integrated screws?
Absolutely not. One of the advantages of the INTERTAN system is that it provides you with options to treat a wide variety of fracture patterns. However, you are probably well aware that approximately 25% of all hip fractures are unstable and one in five (20%) will actually fail due to implant cut out.
Our designing surgeons feel that rotational instability is a major contributing factor to that failure rate and propose the INTERTAN nail as the solution to this dilemma. The problem lies in the fact that even implants that are keyed to prevent rotation can still experience rotation of the fragments about the axis of the lag screw. Placement of a secondary point of fixation into the femoral neck and head reduces the chances of rotation but adds the secondary concern of Z-Effect.
Watch video of head rotations with a conventional single lag screw device
The INTERTAN nail solves that problem by integrating two screws so that they function as one unit to prevent rotation and excessive screw migration. Mechanical testing of the two screw construct was stopped at 100,000 cycles with no evidence of implant cut out, further reinforcing the INTERTAN nail philosophy.
For additional questions, please contact your local sales representative.
3. Koval KJ; Zuckerman JD. Functional recovery after fracture of the hip. J Bone Joint Surg (A). 1994: 76-1, 751-758.
4. AAOS Position Statement 1144. Hip fracture in seniors: A call for health system reform.
5. Rueger Johannes; Moore Chris. Shortening of the Femoral Neck Following Peritrochanteric Fracture. Bone & Joint Science. Vol. 2, No. 5, May 2011
6. Rueger J, Moore C. Shortening of the Femoral Neck Following Peritrochanteric Fracture. Bone&Joint Science ( www.KLEOS.md) 2011; 2(5)