Biocompatibility and Safety
Titanium produces no toxic or allergenic corrosion products in the body, and the surrounding tissue accepts it without a significant foreign-body reaction. This biocompatibility is the fundamental reason titanium dominates implant surgery.
Implant grades are produced with extra-low interstitial content to guarantee purity and consistent mechanical properties, and every batch is tested for chemistry and mechanical performance before release.
Osseointegration with Living Bone
Titanium surfaces bond directly with living bone in a process called osseointegration, where bone cells grow into the surface texture and lock the implant mechanically. This direct bond distributes load and prevents the fibrous encapsulation seen with other metals.
Surface treatments such as grit blasting, acid etching and porous coating enlarge the surface area and accelerate osseointegration, which improves the long-term stability of joint replacements and dental implants.
Mechanical Compatibility with Bone
The elastic modulus of titanium alloys is about 110 GPa, roughly half that of stainless steel and cobalt-chromium alloys. A closer modulus match reduces stress shielding, where the stiff implant carries load that should pass through the bone, causing bone loss around the implant.
Lower modulus, combined with high fatigue strength, allows implants to survive decades of cyclic loading while preserving the surrounding bone.
Corrosion Resistance in the Body
The body is an aggressive chloride environment, and implants must survive it for decades without corroding. The protective titanium dioxide film makes titanium effectively immune to pitting and crevice corrosion in body fluids.
Because no metal ions are released, there is no local tissue staining and no accumulation of metal in the organs, which is an important safety advantage over other implant alloys.
Implant Grades and Applications
Commercially pure titanium Grades 1 to 4 per ASTM F67 is used for dental implants and porous coatings, while Ti-6Al-4V ELI per ASTM F136 and Ti-6Al-4V per ASTM F1472 are used for load-bearing hip and knee components, bone plates and screws.
Titanium implants cover the full range of orthopedics, including hip stems, acetabular cups, knee prostheses, spinal fixation systems, fracture plates, intramedullary nails and suture anchors.
Frequently Asked Questions
Q: Why is titanium used for orthopedic implants?
A: Titanium is biocompatible, bonds with bone, resists corrosion and has a modulus closer to bone than other implant metals.
Q: What is osseointegration?
A: Osseointegration is the direct structural and functional bond between living bone and the titanium implant surface.
Q: Which titanium grade is used for implants?
A: Commercially pure grades per ASTM F67 serve dental and porous applications, and Ti-6Al-4V ELI per ASTM F136 serves load-bearing implants.
Q: Does titanium cause stress shielding?
A: Less than stiffer metals, because the titanium modulus of about 110 GPa is closer to bone, reducing bone loss around the implant.
Q: Is titanium corrosion resistant in the body?
A: Yes, the protective oxide film makes titanium practically immune to corrosion in body fluids.
