To further improve the surgical outcome of early femoral head necrosis, trabecular metal (tantalum) is designed to interfere with stage I or II femoral necrosis and may be used in conjunction with bone grafts. As a bone replacement material, trabecular bone metal has great advantages in terms of physical properties. It is a structural biomaterial with a porosity of 80%, which is made of tantalum metal through gasification and precipitation technology and consists of interconnected micropores. The cellular structure of trabecular bone metal is very similar to cancellous bone structure. And it is closer to bone in its physical and mechanical properties than any other prosthetic metal. This unique, highly porous, trabecular structure facilitates bone induction and enables rapid and extensive soft tissue penetration and strong attachment. Trabecular metal has a high load-bearing strength and a low elastic modulus, which allows stress shielding to be minimized under physiological load-bearing conditions. Moreover, trabecular metal is a very structured biomaterial that can be made into very complex prosthetic shapes without the need for a metal substrate.
Thousands of clinical applications have shown that trabecular bone metals can be applied to a variety of bone and soft tissues. Trabecular metal has shown physiological bone healing, and in a 24-week animal study, the bone ingrown density of the tantalum cup was very similar to that of the acetabulum surrounding the prosthesis. Moreover, in the study of the cross-cortical prosthesis, the new bone quickly crawled into the trabecular metal space. Only 8 weeks after surgery, the bone had grown in and filled most of the space, and the bone strength at the graft site was greatly improved. The pore size of the trabecular metal and the abundance of micropores support the formation of vascularization and rapid and firm insertion of soft tissue. In the dog model, soft tissue adhesion and vascularization occurred rapidly with extensive tissue ingrowth at 4 to 8 weeks postoperatie, and the soft tissue adhesion strength at 4 to 8 weeks was more than 5 times greater than the surface of sintered pearl. Trabecular metal has a high strengt-to-weight ratio, and these mechanical properties allow it to withstand physiological load. Its compressive strength is closer to bone than any other prosthesis load surface material; The high malleability of bone trabecular metal can avoid deformation and fracture under excessive load. The low hardness of the material helps the physiological load to conduct effectively, thus minimizing stress shielding; In addition, it has a high coefficient of friction with the bone, ensuring immediate stability.
Overall, the trabecular metal AVN reconstructional rod system (tantalum rod) has the potential to limit the ability of early femur head necrosis to worsen further, thus delaying or preventing total hip replacement in many patients. Its great advantages are embodied in :(1) 75%~80% high void ratio, which is good for bone induction and bone ingrowth; (2) It is similar to the honeycomb structure of cancellous bone, and its elastic modulus is the same as that of bone, which is closer to the biomechanical properties of human bone; (3) Structural support for the necrotic area of the femoral head, and enhance the revascularization of the necrotic area; (4) Limit or delay disease progression and delay the need for total hip replacement; (5) A better treatment alternative to vascular bone graft.
