Which finding suggests that the treatment for a child with hip dysplasia was ineffective?

The identification of the child's femoral head not returning to the hip socket is a clear indication that the treatment for hip dysplasia was ineffective. In the context of this medical condition, successful treatment typically aims to properly position the femoral head within the acetabulum (the hip socket) to ensure correct development and function. If the femoral head remains dislocated or fails to stabilize in the socket, it suggests that the treatment methods (such as bracing or surgery) were not successful in achieving the desired anatomical alignment or stability.

The other options indicate varying degrees of improvement or mild complications rather than treatment failure. A pain level of 2 suggests manageable discomfort, which might be acceptable or even expected post-treatment. A slight limp could indicate residual effects of the condition rather than outright treatment failure, as some children may exhibit mild gait issues even after treatment. Improved flexibility generally denotes positive outcomes, suggesting that the treatment might be working in maintaining or enhancing mobility. Therefore, the critical factor indicating treatment ineffectiveness is the failure of the femoral head to return to the hip socket.