Trabecular TitaniumTM is a three dimensional, multiplanar, regular, hexagonal cell structure characterised by a high open porosity that imitates the morphology of the trabecular bone 1 (Figure 1).
This innovative material is made from Titanium, one of the metals mostly used in orthopedics thanks to a unique combination of attributes, as light weight, high biocompatibility and excellent mechanical properties, especially in terms of resistance to fracture and fatigue2.
The interconnected geometric structure is created with Electron Beam Melting technology in a single manufacturing phase. EBM allows the production of titanium (or titanium alloy) using an extremely high power electron beam that selectively melt the powders and precisely creates any three-dimensional design involving either dense or porous parts. TT is not a coating: the absence of an interface between the trabecular structure and the bulk guarantees structural solidity, high resistance and prevents the risk of detachment and galvanic effects1.
The geometric repetition of the base cell produces a uniform and highly porous external surface that is responsible for a very high friction coefficient. This is fundamental to maximise primary stability, both in cortical and cancellous bone, because a tight initial press-fit between implant and bone provides the optimal conditions for secondary fixation by bone in-growth.
Several factors have been identified as being crucial for the optimisation of bone remodeling: intrinsic factors like bone stock quality and extrinsic factors like implant design and materials properties. Three-dimensional architecture and surface texture of prosthetic elements play a main integral role in biological performance. Indeed, osteogenesis is reported to be strongly affected by pore size, geometry and porosity. Higher porosity and an adequate pore size are expected to enhance cell migration and vascularisation, facilitating the transport of oxygen, nutrients, ions and bone inducing factors, favoring new bone formation3,4. All these features (biocompatibility, optimal pore size, high porosity, elastic module) are joined together to create the Trabecular TitaniumTM structure.
In vitro analys is of genetic expression on human osteoblast-like cells has demonstrated that Trabecular TitaniumTM is able to stimulate osteoblasts prolife
ration and differentiation and to limit osteoclastogenesis. Furthermore, it has been proven that it induces a down-regulation of several genes involved in the inflammatory process and modulates genes related to immune system5.
Trabecular TitaniumTM demonstrates to have an osteoinductive behavior. Human adipose stem cells (hASCs) grown on TT have been able to adhere, proliferate and differentiate into osteoblast-like phenotype thus producing a mineralized extracellular bone matrix6 (Figure 2). The quality and quantity of the extracellular matrix is important to determine the effective osseointegration of a material therefore the resistance and the survivorship of an implant. If compared to other biocompatible scaffolds of different materials and structure, the amount of proteins of the extracellular bone matrix produced by hASCs differentiated in osteoblast phenotype on TT was significantly higher (Figure 3). These results have led to the conclusion that not only the material but the structure significantly affects cell proliferation7.
The effective osteointegrative potential of TT has been analysed in comparison to traditional porous Titanium coatings in a bilateral implantation sheep model. Histomorphometric results demonstrated that TT is able to ensure significantly high bone in-growth percentages, both in cancellous and cortical bone8 (Figure 4).
Preliminary results from a multicentre prospective densitometric study on 89 patients (91 hips), that underwent primary THA with a DELTA-TT cup, reported a postoperative recovery of bone mineral density in DeLee and Charnley zones 12 and 24 months from surgery.
Radiographic assessment confirmed the optimal osseointegration therefore the stability of the acetabular cups9 (Figure 5). Already at 12 months, x-rays showed all the most sensitive signs that are reported to be indicative of bone in-growth10: the absence of radiolucent lines, the presence of a supero-lateral dense bone buttress at the bone-cup interface, the presence of medial stress-shielding in DeLee and Charnley zone II, the presence of radial trabeculae oriented in a direction perpendicular to the cup surface in DeLee and Charnley Zone I or Zone II and the presence of an infero-medial bone buttress.
Relevant clinical outcomes have been reported: the average Harris Hip Score and range of motion significantly improved from preoperative evaluation to 24 months after surgery, with a constant progression in the intermediate follow-ups. A subjective evaluation of the general health status by SF-36 revealed a significant improvement in patients’ quality of life with values higher than normalised ones for all scales already at 12 months9. The early improvement in clinical and functional recovery after THA with DELTA-TT cup has been also confirmed by a clinical study performed on 150 patients with an average follow-up of 12 months11.
Silvia Burelli, MSc
Clinical Research Manager
1. Marin E, Fusi S, Pressacco M, Paussa L, Fedrizzi L. Characterization of cellular solids in Ti6Al4V for orthopaedic implant applications: Trabecular TitaniumTM. J Mech Behav Biomed Mater 2010 Jul; 3 (5):373-81.
2. Buddy D Ratner. A Perspective on Titanium Biocompatibility. In: Brunette DM, Tengvall P, Textor M, Thomsen P, editors. Titanium in Medicine: Material Science, Surface Science, Engineering, Biological Responses and Medical Applications. New York: Springer Verlag; 2001. pp 1-12.
3. Frosch KH, Barvencik F, Viereck V, Lohmann CH, Dresing K, Breme J, Brunner E, Stürmer KM. Growth behavior, matrix production, and gene expression of human osteoblasts in defined cylindrical titanium channels. J Biomed Mater Res A. 2004 Feb 1; 68(2):325-34.
4. Karageorgiou V, Kaplan D. Porosity of 3D biomaterial scaffolds and osteogenesis. Biomaterials. 2005 Sep;26(27):5474-91.
5.Sollazzo V, Massari L, Pezzetti F, Palmieri A, Girardi A, Farinella F, Lorusso Vincenzo, Burelli S, Bloch HR, Carinci F. Genetic effects of Trabecular Titanium™ on human osteoblast-like cells (MG-63): an in vitro study. ISRN Materials Science. In press 2011.
6. Gastaldi G, Asti A, Scaffino MF, Visai L, Saino E, Cometa AM, Benazzo F. Human adipose-derived stem cells (hASCs) proliferate and differentiate in osteoblast-like cells on trabecular titanium scaffolds. J Biomed Mater Res A. 2010 Sep 1;94(3):790-9.
7. Asti A, Gastaldi G, Dorati R, Saino E, Conti B, Visai L, Benazzo F. Stem cells grown in osteogenic medium on PLGA, PLGA/HA, and Titanium scaffolds for surgical applications. Bioinorg Chem Appl. 2010:831031.
8. Arens D, Devine DM, Burelli S, Bouré L. In vivo evaluation of the osteointegration of new porous Trabecular Titanium™. Final report. AO Foundation, Davos (Switzerland); 2011 Mar. Report No.IMAOV0108-FTD-m , pp. 95.
9. Massari L, Bistolfi A, Grillo PP, Causero A, Burelli S, Gigliofiorito G, Menosso P, Carli G, Bloch HR. Multicenter Longitudinal Densitometric Clinical Study on Periprosthetic Osteointegration and Bone Remodeling of Trabecular TitaniumTM. Proceedings of the 23rd Annual Congress of the International Society for Technology in Arthroplasty (ISTA); 2010 Oct 6-9; Dubai, United Arab Emirates.
10. Moore MS, McAuley JP, Young AM, Engh CA Sr. Radiographic signs of osseointegration in porous-coated acetabular components. Clin Orthop Relat Res. 2006 Mar; 444: 176-83.
11. Benazzo F, Rossi SMP, Piovani L, Perticarini L, Ghiara M. Our experience with the use of TT (Trabecular TitaniumTM) in hip arthroplasty surgery. J Orthopaed Traumatol. 2010; 11 Suppl 1: S53–S62.