Question

Which of the following may cause failure of bone implants?

• A. Stress shielding – reduction of bone density due to removal of a typical stress from bone by an implant
• B. Aseptic loosening – loss of bond between bone and implant in the absence of an infection
• C. Fretting fatigue – progressive deterioration of material by small scale rubbing
• D. Osseointegration – formation of a direct interface between an implant and a bone, without intervening soft tissues

Hint:

Implant failure can occur due to stress shielding, aseptic loosening, and fretting fatigue. Osseointegration is essential for the success of bone implants.

Answer 1

The Correct Option is A, B, C

1. Stress shielding: - Stress shielding occurs when the implant takes on most of the mechanical load, thus reducing the stress placed on the surrounding bone. Over time, this leads to bone resorption and decreased bone density, which weakens the surrounding bone. This phenomenon can result in implant failure. Thus, (A) is correct.
2. Aseptic loosening: - Aseptic loosening refers to the gradual loss of bonding between the bone and implant in the absence of infection. This is a common cause of failure in implants, particularly those in the hip and knee. The loss of bond between the bone and implant leads to instability and eventual failure. Thus, (B) is correct.
3. Fretting fatigue: - Fretting fatigue is a mechanical wear process caused by the rubbing of materials, leading to small scale progressive deterioration. This is common in joints where there is repeated motion, and it can cause the implant material to degrade over time. Thus, (C) is correct.
4. Osseointegration: - Osseointegration is a process where the implant forms a direct bond with the bone without any intervening soft tissue, which is actually a desirable phenomenon, as it improves the implant's stability and longevity. Therefore, (D) does not cause implant failure.
Thus, the correct answers are (A), (B), and (C).