Sorry to hear about the damage. How much was your bag and how old is it?

The figures quoted in the Conventions are limits to total liability, it is still reasonable to expect any carrier or insurer to depreciate the value of the item(s) being claimed for. I doubt any airline is going to give you a like for like new for old value. Which leaves you with any travel insurance to claim the difference (if they offer a lower or zero rate of depreciation) and/or possibly a manufacturer warranty depending on which brand it is and what's wrong with it.