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 Table of Contents  
EDITORIAL
Year : 2013  |  Volume : 48  |  Issue : 4  |  Page : 327-329

The myths of trabecular metal: 'the next best thing to bone'


Department of Orthopaedics & Traumatology, Faculty of Medicine, University of Alexandria, Egypt

Date of Submission01-Dec-2013
Date of Acceptance05-Dec-2013
Date of Web Publication11-Apr-2014

Correspondence Address:
Yousry Eid
Department of Orthopaedics & Traumatology, Faculty of Medicine, University of Alexandria
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-1148.130387

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How to cite this article:
Eid Y. The myths of trabecular metal: 'the next best thing to bone'. Egypt Orthop J 2013;48:327-9

How to cite this URL:
Eid Y. The myths of trabecular metal: 'the next best thing to bone'. Egypt Orthop J [serial online] 2013 [cited 2017 Dec 11];48:327-9. Available from: http://www.eoj.eg.net/text.asp?2013/48/4/327/130387

Orthopedic-related disease is one of the leading clinical burdens worldwide. It represents one of the top three core service areas in many hospitals in the USA. With the increasing longevity in most of the countries, a good percentage of the population is over the age of 65 years. Most of the patients suffer from either primary or secondary arthritis, and joint replacement surgery has emerged as the treatment of choice. In fact, the demand for total joint replacement (TJR) is substantial and growing rapidly. This is measured by the number of total hip replacements and total knee replacements performed every year.

Further, there is an increasing rate of joint replacements among the younger and more active population. This incidence is expected to grow because of the expanded range of indications for TJR.

As expected, with the increasing number of primary TJRs the rate of revisions also increased. The most common causes of revision are infection and aseptic loosening. Generally, revisions are characterized by longer operating times, lengthy hospital stay, and increased requirements for bone grafts, especially in total hip replacement.

Implants manufactured using conventional orthopedic implant materials, including titanium and cobalt-chromium alloys, often use cement to achieve fixation and stability. The relatively high stiffness of some solid metal implants may cause low load transfer to the host bone, leading to the potential for stress shielding and bone resorption over time.

In contrast, some other implants have porous bone interface surfaces designed to allow for biological fixation through bone ingrowth into the implant. However, this does not address the need for the host bone to be physiologically loaded. In addition, some bone defects would need massive bone grafts that would not be available in many instances.

Trabecular metal material is a unique, highly porous biomaterial that is designed with structural and functional properties similar to those of trabecular metal. It is made of elemental tantalum, which has been used to make implantable materials for over 50 years. It is known as a material with a porous structure. In addition, it is biologically inert, ductile, corrosion resistant, and has high fatigue strength [1],[2] .


  What is trabecular metal technology? Top


Trabecular metal is a three-dimensional material and not an implant surface or coating. Its structure is similar to that of cancellous bone [3],[4],[5] [Figure 1].
Figure 1: (a, b): Trabecular Metal Material's structure is similar to cancellous bone.

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Tantalum

Tantalum is element number 73 in the periodic table. It is a highly biocompatible and corrosion-resistant metal [6],[7],[8] . It has been used in various implantable devices, including dental implants, for decades [9],[10] .

Although the high biocompatibility and passive characteristics of tantalum have been documented long ago, its cost and methods of production have limited its use until recently [11] .


  How is trabecular metal material made? Top


The trabecular metal material preparation process demands strict specifications for pore size, shape, and interconnectivity to ensure that a cancellous bone-like structure is obtained. Through a thermal deposition process, elemental tantalum is deposited onto a substrate, creating a nanotextured surface topography to build trabecular metal material, one atom at a time. This process utilizes the physical and biological properties of tantalum to create a unique material that has a structure similar to that of cancellous bone. Now it is used to produce many implants that have proven to be of great help in difficult primary and revision TJR, as well as in spinal surgery [3],[4],[5] [Figure 3].
Figure 2: (a-e): Numerous Zimmer Implants contain Trabecular Metal Material.

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Figure 3: Ductility without mechanical failure.

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Material properties

Trabecular metal material has a low modulus of elasticity (2.5-3.9 GPa), which is closer in value to that of cancellous bone, compared with titanium (106-115 GPa) [3],[4],[5] . In compression testing, trabecular metal material exhibits high ductility without mechanical failure [3],[4],[5] [Figure 5]. Because of its high coefficient, trabecular metal material has been shown to contribute to the primary stability of the implant, on the basis of in-vitro insertion torque testing [12],[13] [Figure 6].
Figure 4: Trabecular metal material forms a frictional interface with bone.

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Figure 5: Three-dimensional uniformity with up to 80% porosity.

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Figure 6: Nano-textured surface topography of Trabecular Metal struts.

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A glimpse into the trabecular metal material reveals its uniform three-dimensional cellular architecture with up to 80% porosity [14] [Figure 7]. This would allow for profuse vascular invasion and bone ingrowth. Further, the entire surface area of the trabecular metal material exhibits a nanotextured topography [15] .
Figure 7: Ingrowth of bone into the trabecular Metal.

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Osseoincorporation

Conventional textured or coated implant surfaces achieve bone-to-implant contact, or ongrowth. However, trabecular metal material's consistent, open and interconnected network of pores is designed for both ongrowth and ingrowth, or for osseoincorporation. Bone has the potential to grow onto the nanosurface of the trabecular metal material, into its interconnected pores, and around its struts. Evidence of ingrowth by maturing bone has been documented as early as 2 weeks after implantation. The cancellous-like structure, interconnected porosity, and bone ingrowth potential are a unique combination of attributes that contribute to the osseoconductive properties of trabecular metal technology [16],[17] .

The promising clinical value of trabecular metal

The quality-of-life considerations leading to joint arthroplasty are substantial when compromised functional status impairs a patient's ability to perform routine activities of daily living.

Patients with TJR complications have reduced quality of life and functioning as compared with patients without complications. Patient function after revision TJR is lower than that after primary TJR, indicating a potential unmet need for more successful revision surgical techniques and implants.

Porous technology has several clinical advantages. The mechanical properties of tantalum metal material are similar to those of bone, with less stress shielding. It is also highly porous, which permits more conducive bone ingrowth. Finally, its high strength/rigidity ratio allows its usage as a stand-alone load-bearing structure [Figure 2], [Figure 4].


  Acknowledgements Top


 
  References Top

1.Macheras GA, Papagelopoulos PJ, Kateros K, Kostakos AT, Baltas D, Karachalios TS. Radiological evaluation of the metal-bone interface of a porous tantalum monoblock acetabular component. J Bone Joint Surg Br 2006; 88-B:304-309.  Back to cited text no. 1
    
2.Nasser S, Poggie RA. Revision and salvage patellar arthroplasty using a porous tantalum implant. J Arthroplasty 2004; 19:562-572.  Back to cited text no. 2
    
3.Unger AS, Lewis RJ, Gruen T. Evaluation of a porous tantalum uncemented acetabular cup in revision total hip arthroplasty. Clinical and radiological results of 60 hips. J Arthroplasty 2005; 20:1002-1009.  Back to cited text no. 3
    
4.Cohen R. A porous tantalum trabecular metal: basic science. Am J Orthop 2002; 31:216-217.  Back to cited text no. 4
[PUBMED]    
5.Bobyn JD. UHMWPE: the good, bad, & ugly. Fixation and bearing surfaces for the next millennium. Orthop 1999; 22:810-812.  Back to cited text no. 5
    
6.Black J. Biological performance of tantalum. Clin Mater 1994; 16:167-173.  Back to cited text no. 6
[PUBMED]    
7.Matsuno H, Yokoyama A, Watari F, Uo M, Kawasaki T. Biocompatibility and osteogenesis of refractory metal implants, titanium, hafnium, niobium, tantalum, and rhenium. Biomaterials 2001; 22:1253-1262.  Back to cited text no. 7
    
8.Welldon KJ, Atkins GJ, Howie DW, Findlay DM. Primary human osteoblasts grow into porous tantalum and maintain an osteoblastic phenotype. J Biomed Mater Res A 2008; 84:691-701.  Back to cited text no. 8
    
9.Pudenz RH. The use of tantalum clips for hemostasis in neurosurgery. Surgery 1942; 12:791-792.  Back to cited text no. 9
    
10.Linkow LI, Rinaldi AW. Evolution of the Vent-Plant osseointegrated compatible implant system. Int J Oral Maxillofac Implants 1988; 3:109-122.  Back to cited text no. 10
[PUBMED]    
11.Zimmer internal Trabecular Metal component sales data from January 2002 through July 2010.  Back to cited text no. 11
    
12.Shirazi-Adl A, Dammak M, Paiement G. Experimental determination of friction characteristics at the trabecular bone/porous-coated metal interface in cementless implants. J Biomed Mater Res 1993; 27:167-175.  Back to cited text no. 12
    
13.Zhang Y, et al. Interfacial frictional behavior: cancellous bone, cortical bone, and a novel porous tantalum biomaterial. J Musculoskel Res 1999; 3:245-251.  Back to cited text no. 13
    
14.Bobyn JD, Stackpool GJ, Hacking SA, Tanzer M, Krygier JJ. Characteristics of bone ingrowth and interface mechanics of a new porous tantalum biomaterial. J Bone Joint Surg Br 1999; 81-B:907-914.  Back to cited text no. 14
    
15.Tsao AK, Roberson JR, Christie MJ, Dore DD, Heck DA, Robertson DD, Poggie RA. Biomechanical and clinical evaluations of a porous tantalum implant for the treatment of early-stage osteonecrosis. J Bone Joint Surg Am 2005; 87-A:22-27.  Back to cited text no. 15
    
16.Bobyn JD, Toh KK, Hacking A, Tanzer M, Krygier JJ. Tissue response to porous tantalum acetabular cups. J Arthroplasty 1999; 14:347-354.  Back to cited text no. 16
    
17.Bobyn JD, Poggie RA, Krygier JJ, Lewallen DF, Hanssen AD, Lewis RJ, et al. Clinical validation of a structural porous tantalum biomaterial for adult reconstruction. J Bone Joint Surg Am 2004; 86-A:123-129.  Back to cited text no. 17
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]



 

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