I agree with Alan but it would also be possible to say "who needed to be treated..." if you meant to refer to the patients rather than their wounds, It is of course possible to "treat" both the patient or their wound. I would also use "injuries" instead of "wounds' unless you really wanted to specify that that their injuries were "wounds" - that is a cut or incision to the skin, otherwise "injuries" can be used.

Not by itself, but as part of a larger sentence it would. For example: "THEY WERE patients with wounds which needed to be treated regularly due to the risk of infection." or "I have seen patients with wounds which needed to be treated regularly due to the risk of infection." or "The hospital had many patients with wounds which needed to be treated regularly due to the risk of infection."

Patients with wounds WHICH xx needed to be treated regularly due to the risk of infection. xx > Patients with wounds have to be treated regularly over a period of time to prevent the risk of infection. Patients with wounds WHO do not want to be infected have to have get their wounds treated as soon as possible. "WHICH" >use this only for animal or thing.

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