My dream is that Samuel can stand for transfers and maybe even learn to walk. You are wise to be concerned about Samuel's hips. Hip dislocations and bone deformities can be the result of lying or sitting in one position for extended periods of time. It is not surprising, then, that hip displacements often begin early in the life of a child with severe disabilities. Bones grow and are formed based on the way muscles pull on them, so low or high muscle tone has an impact on bones.
Hips are particularly vulnerable to deformity.
In many joints, the structure of the joint itself is what keeps the bones aligned. In the hip, muscles must align the bones. With normal muscle activity and weight bearing, the pull from the muscles actually shapes the angle and orientation of these two bones. Without this pull or weight bearing, the joint can fail to form properly. There are two separate issues to consider.