Cementless implant fixation--toward improved reliability.

Cementless implants offer the advantage of fixation by direct bone-to-implant osseointegration, thereby avoiding the use of a synthetic intermediary material (such as acrylic bone cement) of limited mechanical strength. Successful osseointegration, however, depends on several conditions being satisfied during the peri-implant bone healing period, including the need for limited early loading resulting in minimal relative movement at the implant-bone interface. Sintered porous- and plasma spray-coated implants represent the most common cementless orthopedic implants in current clinical use, although novel cast structures also are being investigated. All stand to benefit from surface modifications currently being explored to enhance osteoconductive or osteoinductive characteristics of the implants. The faster osseointegration that such modified surface designs potentially might offer would result in more reliable and convenient (from the patient perspective) cementless implants. Encouraging results of early animal-based studies exploring such modifications have been reported.