Synonyms for Broken-backed (same or very similar meaning)
WordNet sense 1 (not in good physical or mental condition; out of condition):
unfitWordNet sense 2 (harmed or injured or spoiled):
damagedWordNet sense 3 ((of a ship) so weakened as to sag at each end):
hoggedWordNet sense 4 (curving or bulging outward):
convex, bulgingFrom the ODE community, based on WordNetadd/edit