[Medical Q&A] How could a steel plate that is harder than bone break?

Planner: Chinese Medical Association

Reviewer: Han Liqiang, deputy chief physician, Tianjin Third Central Hospital

Plate fixation surgery after limb fracture is currently a common treatment for fractures, but postoperative plate breakage is also a common complication of this surgery. Many people think that the plate is so hard, harder than bones, how could it break? So they suspect that it is caused by poor quality of the plate, but this is not the case.

Although it is often called a steel plate in daily life, its formal name in clinical practice is "bone plate". Its material is mainly titanium alloy, which has good compatibility with human tissue and does not affect postoperative magnetic resonance imaging. The strength of the bone plate is greater than that of human bone. Its main function is to maintain the ideal position after fracture reduction and provide strong support, which is conducive to the healing of fractures. The healing time of fractures is generally 12 weeks, which is the old saying "it takes a hundred days to heal a broken bone". The role of the bone plate is to provide support during this period to facilitate early functional exercise of the limbs and restore normal function. After the fracture heals, the force required for limb movement will be provided by the bones again, and the bone plate will no longer be stressed. However, if the fracture is delayed or non-healed, the limb movement force is provided by the bone plate for a long time, which will gradually exceed the tolerance range of its metal strength and may cause fracture. To give a simple example, a wire is difficult to break when it is subjected to tension, but it will break if it is bent back and forth many times, which is the same as the fracture of the bone plate. Therefore, the fundamental reason for the fracture of the bone plate is the delayed or non-healing of the fracture, not the quality problem of the bone plate itself.