( ( necrosis ( of ( surrounding ( bone tissue ) ) ) ) . )
(ROOT (NP (NP (NNS necrosis)) (PP (IN of) (NP (VBG surrounding) (NN bone) (NN tissue))) (. .)))
necrosis of surrounding bone tissue.
(ROOT (S (NP (NNS Bones)) (VP (VBP are) (VP (VBN made) (PRT (RP up)) (PP (IN of) (NP (NNS tissues))))) (. .)))