What does 'delayed union' refer to in bone healing?

Delayed union refers to a situation in bone healing where the process of healing takes longer than expected. Ideally, a fractured bone should begin to show signs of healing within a specific time frame, typically several weeks. However, in cases of delayed union, the fractured bone ends may experience a setback in healing due to various factors.

The correct answer addresses that the fractured bone ends become resistant to healing, indicating that the physiological processes involved, such as the formation of callus and subsequent remodeling, are not progressing sufficiently. This resistance can result from several underlying conditions such as poor blood supply, inadequate stabilization, or systemic health issues that impede healing.

Understanding delayed union is important, as it highlights the necessity for timely interventions, which may include surgical evaluation, bone grafting, or other treatments to facilitate proper healing and restore functionality.