I know Hit Points and injuries are supposed to be abtract in typical D&D, but we have some wound systems floating around such as Death and Dismemberment and various critical hit charts. We also have the Regeneration spell for lost limbs from Vorpal Swords and Slicer Beetles so there’s a precedent for some specific wound types in D&D.
Rather than creating new spells for healing bones or organs, reskin the old boring Cure X Wounds spells. Here’s my conversion:
CLW = Heal Flesh
CMW = Restore Blood
CSW = Mend Bone
CCW = Heal Organ
The spell would generally cure the appropriate amount of HP according to your game system. It also has other potential effects.
1: The more interesting name makes you realize just how light or critical the wounds were. If you have to cast Mend Bone and Restore Blood on someone to patch them up they’ll appreciate the amount of injury they sustained.
2: The spells now have different uses. Need to heal a lich? Gotta be Mend Bone. Vampires can get some mileage out of Restore Blood on their victims (though it wouldn’t restore lost levels obviously).
3: It actually simplifies the spell list by eliminating the need for Regeneration (unless you really wanted a spell that gives 1 HP per turn for a little while), Cure Blindness, Cure Deafness, and adds a whole slew of functionality that you’d otherwise need Regenerate Liver etc. for.
4: Critical hit charts, special monster attacks, magic item and spell effects, and roleplaying injuries like Luke’s Hand can be handled with the existing set of spells because the spells do specific things now in addition to basic HP healing.
5: The evocative spell names give interesting reversals: Rend Flesh, Drain Blood, Shatter Bones, Rupture Organ. These can have the special effect of the related critical hit in your system (rupturing the eyes would cause blindness and pain, etc.) on a failed save instead of just ramping up the damage if you like.
This mod wouldn’t work well with systems that consider HP to be mostly luck and fatigue, since in those games the PCs won’t be having organs blown out and pelvises crushed anyway.