Unlike in a healthy shoulder, where the humerus ends in a ball shape and fits into the shoulder blade to form a shoulder, in reverse shoulder replacement surgery the anatomy is reversed.

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He still occasionally blacksmiths in a little tin shed on the Patagonia campus, and he showed me his latest project, a metal mussel knife that he's been beating into perfect shape sharp at the blade to pry open the shells, blunt at the handle to knock away the barnacles.

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