I think (and happy to be corrected if im wrong) that there were practical issues with the mother caring for her while she was in a cast. There were steps to access the home, there were issues with being able to transport her to appointments etc. Added to which, she had to care for other children at the same time.
My daughter was in a cast for her hips for a few months as a tiny baby and it presents a lot of challenges, even in a case where you can easily lift her from place to place.
I think (again open to correction) that there may have been other queries around the child's care as well, but the practical stuff was a big part of it.