After the accident, the surgery became his only hope for recovery.

his 是代词 he 的所有格形式，表示"他的"。 only 是形容词，意思是"唯一的、仅有的"。 hope 是名词，意思是"希望、期望"。 his only hope 表示"他唯一的希望"，强调没有其他选择或可能性。