Why is a Robert-Jones bandage contraindicated for a broken femur?

A Robert-Jones bandage is designed to provide immobilization and support, primarily for soft tissue injuries. However, when dealing with a broken femur, the structure of this bandage can lead to significant issues.

The correct reason is that the bandage can act as a fulcrum and displace fragments of the broken femur. When the bandage is applied, the rigid nature of the dressing and the pressure exerted can create pivot points around which the bone fragments can rotate. This movement can exacerbate the fracture, leading to misalignment or worsening of the injury.

In cases of femur fractures, maintaining proper alignment is critical for optimal healing, and any device that could shift the position of the bone fragments is undesirable. Thus, using a Robert-Jones bandage in this scenario could compromise the integrity of the fracture site.

The other options suggest potential issues with the Robert-Jones bandage but do not encompass the primary concern regarding the displacement of femur fragments. While it's true that pressure can be damaging, especially if applied unevenly, the specific mechanics of how the bandage can disrupt fracture alignment is the primary reason for its contraindication in this situation.