Is it permissible to use an ointment made from pig bone marrow to treat foot fissures?

It is impermissible to benefit from a pig because it is impure and forbidden. However, if there is a necessity for treatment and no permissible alternative is available, then its use is allowed to the extent required by that necessity, as Allah the Almighty says: "But whoever is forced [by necessity], neither desiring [it] nor transgressing [its limit], there is no sin upon him. Indeed, Allah is Forgiving and Merciful." Furthermore, porcine materials may transform into other substances, thereby acquiring a new ruling.