The present invention relates to expandable semi-compliant devices that may be used for the treatment of diseased or injured bone tissues, and methods of using the same. The semi-compliant device of the present invention is inserted into an interior space of a cancellous bone tissue, and is filled with a suitable material to provide internal structural support to the bone. The semi-compliant device may further comprise a polymer or a polymer surface coating of a biocompatible polyphosphazene polymer such as poly[bis-(trifluoroethoxy)phosphazene] or derivatives thereof. Such semi-compliant devices or surface coatings may also act as carriers for medicinal, radiological, or thermal treatments of diseased bone.