However, overall results of implants are reported and some differences can be seen. These may or may not be based on the material make-up of the implant. Time and further study will tell.

For now, we know that results have improved for all implants from the very first one used. Advances have been made in the materials and in the design. At first there were problems with fractures of the implants. Sometimes they would sink down into the bone too far. Infection and loosening of the implant were also early problems.

Complications of this type occur much less often now. Movement of the prosthesis (implant) called migration is rare. Dislocation of the implant, more common in the early days, is also rare.

The metal-on-metal implants may reduce wear and creep that occur with the polyethylene (plastic) implants. Creep refers to the tendency of the implant to slowly move or deform to relieve stress or load.

But metal implants are more likely to cause tiny particles of metal debris to flake off. The debris can gather in crevices of the implant and cause problems with motion. Or these flecks may cause injury to the soft tissues in the area. Release of the metal debris is small but can still cause inflammation and toxicity.

The choice of implant used may be dependent on the surgeon's experience with the procedure. There are pros and cons with each one. Ask your surgeon to review these with you and guide you in your decision-making process.