The LATERAL FLARE hip stem features a unique new design for femoral components. The addition of a lateral expansion to the proximal body of the stem allows for a more physiologic distribution of the body weight over the entire proximal femur.
This new design was based on an updated hip biomechanical model which includes the muscles and ligaments in a dynamic, more physiologic situation. By including these soft tissue factors, particularly the Iliotibial band (ITB) as a tension band lateral to the femur and the vastus lateralis muscle, a more accurate picture on how the loads are transmitted through the hip joint was recreated. Contrary to what it was traditionally held, the lateral cortex of the femur bears compression loads. Consequently it can be used to provide additional base of support for a femoral component.
The Lateral Flare hip design for femoral components has been reported in international studies to more effectively distribute weight to the proximal femur than do conventional hip devices. As a consequence and unlike conventional cemented and non-cemented total hip replacement (THR) devices which can lose 20% to 40% of proximal femoral bone mass within the first 24 months following surgery; the Lateral Flare components have shown in bone densitometry studies to preserve 95+% of original bone in primary THR surgeries and regeneration of bone in revision THR surgeries where prior bone loss has occurred. It has also proved to be an inherently stable stem: due to the addition of a lateral flare feature to a conventional stem, the prosthesis rests on top of both medial and lateral femoral cortices. The axial migration values of the stem are consistently below 1mm, even after nine years of follow-up. As a result, the need for a second surgery due to aseptic loosening of the device after a primary Lateral Flare implantation has been reduced to practically zero.
Joseph F. Fetto, MD | New York University Langone Medical Center | Department of Orthopaedic Surgery
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