I don't remember, but only, only a fractured collarbone, which I recommend to anyone that needs to break a bone, break a collarbone.
( ( ( ( ( I ( ( do n't ) remember ) ) , ) but ) ( only ( , ( ( ( ( ( only ( a ( fractured collarbone ) ) ) , ) ( which ( I ( recommend ( to ( anyone ( that ( needs ( to ( break ( a bone ) ) ) ) ) ) ) ) ) ) ) , ) ( break ( a collarbone ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP I)) (VP (VBP do) (RB n't) (VP (VB remember)))) (, ,) (CC but) (S (ADVP (RB only)) (, ,) (NP (NP (RB only) (DT a) (JJ fractured) (NN collarbone)) (, ,) (SBAR (WHNP (WDT which)) (S (NP (PRP I)) (VP (VBP recommend) (PP (TO to) (NP (NP (NN anyone)) (SBAR (WHNP (WDT that)) (S (VP (VBZ needs) (S (VP (TO to) (VP (VB break) (NP (DT a) (NN bone))))))))))))) (, ,)) (VP (VBP break) (NP (DT a) (NN collarbone)))) (. .)))
The worst bone to break is a collarbone. 
( ( ( The ( worst bone ) ) ( to break ) ) ( ( is ( a collarbone ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJS worst) (NN bone)) (SBAR (S (VP (TO to) (VP (VB break)))))) (VP (VBZ is) (NP (DT a) (NN collarbone))) (. .)))