Zimmer® Trabecular Metal™ Primary Hip Prosthesis

Design Rationale

The Trabecular Metal Primary Hip Prosthesis combines the distinctive properties and clinically proven benefits of Trabecular Metal Technology with a bone-conserving and proximal-loading stem design.

This results in an optimal combination of initial stability, enhanced, long-term biological fixation and efficient proximal load transfer. 1, 2

Trabecular Metal

Trabecular Metal Technology

Trabecular Metal material is an evolution in technology.

It is not a porous coating, but a structural biomaterial that mimics trabecular bone’s porosity, strength and flexibility.

Clinical experience has proven its versatility in diverse biological in-growth applications—making it, “The Best Thing Next to BoneTM.” 2, 3, 6

In-growth Potential of Trabecular Metal Material 

Trabecular Metal material’s cellular structure and fully connected pores result in 80% porosity—closer to trabecular bone than other prosthesis metals such as sintered beads. 4, 5

This porosity potentially allows for more rapid and thorough biological in-growth. 1 In transcortical implant studies, new bone rapidly infiltrated the Trabecular Metal implant, filling in the majority of available pore space after only eight weeks. 1, 7

Trabecular Metal

This biological in-growth results in more rapid bone interface shear strength than sintered beads. 1, 7

Trabecular Metal

Trabecular Metal

Scratch-fit of Trabecular Metal Material

Trabecular Metal material’s bone-interfacing struts (identified by the blue areas) provide a high-friction interface. 8

This results in a substantially higher coefficient of friction (scratch-fit) than sintered beads on cancellous bone, which can increase initial implant stability. 4, 5

Trabecular Metal

14-Degree Proximal Taper

The 14-Degree Proximal Taper of the Trabecular Metal Primary Hip Prosthesis promotes greater proximal loading and more effectively distributes compressive forces in the thicker proximal region of the femur than competitive three-degree tapered stems. 2, 3

This provides a greater tactile sense of initial seating, increased resistance to subsidence and decreased femoral hoop stress, which may cause femoral fracture. 2, 3

Proximal Press-fit

The press-fit created by the rasp-to-implant relationship occurs proximally in the area of the Trabecular Metal pad. Distally, there is a line-to-line fit.

This interference fit works with the properties of the Trabecular Metal material to help improve initial and rotational stability and create a barrier to minimize the potential for osteolysis.

23.5-Degree Neck Resection Angle

The 23.5-Degree Neck Resection Angle helps retain proximal bone, increasing surface area contact between proximal bone and the stem’s Trabecular Metal material.

This increases initial fixation and rotational stability as well as the potential for long-term biological fixation. 2, 3

A/P Reliefs

The Anterior/Posterior Reliefs on the Trabecular Metal Primary Hip Prosthesis are located distally to the 14-Degree Proximal Taper.

These help to avoid impingement with the posterior cortex of the femur as the stem is inserted to further promote proximal loading and reduce potential hoop stresses, which may lead to femoral fracture.

Related Articles

Overview
Surgical Issues
Product Brochure
Surgical Technique

References

  1. Bobyn JD, Hacking SA, Chan SP, et al. Characterization of new porous tantalum biomaterial for reconstructive orthopaedics. Scientific Exhibition: 66th Annual Meeting of the American Academy of Orthopaedic Surgeons; Anaheim, CA., 1999.
  2. O’Keefe TJ, Cohen RC, Averill RA, et al. Design principles of proximal locking cementless stem. Proc Australian Orthopaedic Assoc, Brisbane, Australia, 1999.
  3. O’Keefe TJ, Lewis, RJ, Unger AS. Proxilock femoral hip stem – two- to five-year results. Poster 046, The 70th Annual Meeting of the American Academy of Orthopaedic Surgeons, New Orleans, LA, 2003.
  4. Goldberg VM, Stevenson S, Feighan J, et al. Biology of grit blasted titanium alloy implants. Clin Orthop. 1995; 319:122-129.
  5. Hacking SA, Bobyn JD, Toh K-K, et al. The osseous response to corundum blasted implant surfaces in a canine total hip arthroplasty model. Clin Orthop. 1999;364:240-253.
  6. Bobyn JD, Stackpool G, Toh K-K et al. Characteristics of bone ingrowth and interface mechanics of a new porous tantalum biomaterial. J Bone Joint Surg. 1999;81-B:907-914.
  7. Christie MJ, DeBoer DK, Schwartz HS. Total Knee Arthroplasty and limb salvage with a custom tantalum femoral component. Inter Soc of Tech in Arthroplasty, Berlin, 2000.
  8. Zhang Y, Ahn PB, Fritzpatrick DC, Heiner AD, Poggie RA, Brown TD. Interfacial frictional behavior: cancellous bone, cortical bone, and a nvel porous tantalum biomaterial. Jounral of Musculoskeletal Research. 1999; 3(4): 245-251.