Orthopaedic Titanium Rod Types

Orthopaedic titanium rods are lighter, more flexible and more compatible in the body than other orthopaedic rods. Titanium rods may be pure titanium or alloys containing aluminum or vanadium. The ends of titanium rods may be hooked or threaded but their major classification is either expanding or non-expanding. The surfaces of titanium rods may be coated or treated to encourage their incorporation into the bone or improve their strength.

Pure Titanium Rods versus Titanium Alloys

• Orthopaedic implants increase stability and promote healing.

  Pure titanium is extremely flexible but isn't as strong as titanium alloys, according to the orthopaedic products company Zimmer Inc. Titanium alloys make the strongest of orthopaedic rods. Titanium alloys do have a high friction component, reports researchers from the University of Puerto Rico, Mayaguez (UPRM), and components of titanium implants should not rub against one another. Pure or concentrated titanium rods are used when the orthopaedic implant needs to be bent, formed and shaped. Titanium alloys are used when strength is the most important consideration. Titanium rods are often named after their inventors or manufacturers as in Bailey-Dubow or Zimmer rods.

Expanding versus Non-Expanding Titanium Rods

• Expanding rods can grow along with children.

  Expanding orthopaedic rods lengthen as bone grows. This can be useful for bone implants in children as the need for replacement surgery is lessened. Expanding rods are thick and require anchoring at the joints so they are only appropriate for large bone implants, according to the Osteogenesis Imperfecta Foundation (OIF). Non-expanding rods are more versatile and come in a variety of sizes but may require replacement as bone grows.

Coated and Treated Titanium Rods

• The mirror surface of titanium must be coated and treated.

  Orthopaedic implants are often coated or treated to improve their resistance to wear or increase bone growth. Authors of the 2008 "Interface" article explain that titanium rods may be coated with bioactive ceramic or chemically modified to improve the adhesion of bone cells on the orthopaedic implants. Titanium rods may be coated through radio waves or ionic rays, lasers, hot pressure or plasma-spraying. Acid-etching with sodium hydroxide or hydrogen peroxide are examples of chemical treatments that help make titanium rod surfaces bioactive. Acid etching works better at bonding bone to orthopaedic implants than ceramic coating, a 2000 study published in the "Journal of Biomedical Materials Research" found. The addition of the bone mineral hydroxyapatite to either coated orthopaedic implants or chemically-treated implants improves bone adhesion, a "Journal of Orthopaedic Surgery and Research" 2010 study found.

  Roughened and textured surfaces help bone cells and tissue to adhere to titanium rods. Sometimes, bone implants are coated with bone cement when they are manufactured. Porous coatings of metal beads or fibers can help a bone implant to stay in place; according to Zimmer, Inc. Orthopaedic implants may also be infused with gaseous nitrogen or bombarded with nitrogen ions to increase their hardness and wear-resistance.

Titanium Nanotubes and Stem Cells

• Stem cells can be extracted from the patient's own marrow.

  Michigan Technological Institute's PhD candidate Tolou Shokufar developed an economic way to etch nanotubes into titanium rods. These nanotubes provide a better surface for bone cells to adhere to the bone implants. Instead of using expensive platinum, Shokufar had developed a method that involves ammonium fluoride, titanium alloy, copper and the use of an electrical current to "grow" ideal nanotubes.

  University of California at San Diego (UCSD) researchers are taking the use of nanotubes and titanium rods a step further. They placed stem cells along nanotubes and found that by manipulating the diameter of the tubules, they could affect the differentiation of bone cells. Larger diameter nanotubes cause cells to elongate much more, increasing the speed and strength of bone growth.