U2™ Matrix Porous Stem

U2™ Matrix Porous Stem

Overview

The U2™ Matrix porous stem is designed to enhance stability through the tri-wedge geometry and proximal porous coating while reducing stress shielding via the polished teardrop distal end. By applying the matrix concept of size distribution, proximal stem sizes have multiple corresponding distal stems to obtain the ideal geometric fit in both metaphyseal and diaphyseal areas.

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The U2™ Matrix Porous Stem is a fit and fill primary hip prosthesis with porous coating circumferentially and a matrix design that promotes initial stability and fixation of the implant. Key design features include:


  • 1 12/14 Morse taper — compatible with CoCrMo metal head and BIOLOX®delta ceramic head.

  • 2 Tri-wedge design — the U2 hip stem has tri-wedge geometry design in proximal side which can make
    the proximal stress transmit more easier to the medial-proximal side of the femur to prevent the stress
    shielding effect1. Furthermore, the tri-wedge design provides rotational stability and
    limits stem subsidence2-4.

  • 3 Proximal porous coating — circumferential coating of sintered Ti beads and optimally sized
    pores provide better proximal fixation and uniform bony ingrowth5

  • 4 Polished fluted distal — reduces stem stiffness and prevents proximal stress shielding

  • 5 Teardrop tip — allows easy insertion and minimizes cortical impingement

  • 6 Matrix design — addresses both proximal and distal canal fit and fill in order to facilitate
    load transfer and achieve excellent initial stability6

References

1 Leali A, Fetto J, Insler H, Elfenbein D. The effect of a lateral flare feature on implant stability. Int Orthop;26(3):166-9. Epub 2002.
2 Dorr LD., and Wan Zhinian, 'Comparative Results of a Distal Modular Sleeve, Circumferential Coating, and Stiffness Relief Using the Anatomic Porous Replacement II', J. Arthroplasty, 1996
3 Barton LL, Friedman AD, Locke CJ. Stress in pediatric faculty. Results of a national survey. Arch Pediatr Adolesc Med. Jul;149(7):751-7,1995
4 Puskas D. A., Davey J. R., 'Noncemented fixation in total hip arthroplasty: basic science and clincal results', Current Opinion in Orthopedics, 8; l:22-2, 1997
5 Bobyn, JD., Pillar, RM., Cameron, HU., Weatherly, GC: The optimum pore size for the fixation of porous-surfaced metal implants by the ingrowth of bone. Clin Orthop Relat Res. 1980,150, 263270
6 Mai KT et al. Cementless femoral fixation in total hip arthroplasty.Am J Orthop.2010 Mar; 39(3):125-30