Sentence:  Everywhere else his ideas lay or hung in visible form : his models , drawings , ten foot canvases in monochromes from his painting days , and underfoot a windfall of <WSD>broken-backed</WSD> books that looked as though their insides had been ransacked by a maniac . 
Meaning of the word marked with <WSD> tags:  (of a horse) having bones of the back united by a bony growth