There are some great responses here from the 'not-herbalists' - the wonderful kitchen-witches I so appreciate. I'd consider myself somewhere in the 'journeyman' stage of herbalist at this point, with some serious study and a few months of clinical practice under my belt. What follows is off-the-cuff, and if you were my patient I'd want to ask questions like: What medicines will the surgeon be prescribing for pain/inflammation post-op? What's his history with this injury? How tolerant is he of nasty-tasting things? Can he have alcohol tinctures? Without any of those answers, here's my tuppence:
Comfrey: As someone said, root externally, leaves internally. I'd add: only Symphytum officinale; other species have different, less well-studied allantoin and pyrrolizidine alkaloids contents. Traditionally the leaves are only eaten in the spring, so I'd recommend limiting length of consumption time, maybe 6 six weeks.
Pre-op: Everything for building the body up: Bone broth, nettles, oatstraw, alfalfa, clover, chickweed. Eleuthero (Siberian ginseng, which is non-stimulating), licorice root, astragalus; reishi mushroom and other medicinal mushrooms such as turkeytail and shiitake. Possibly ashwagandha.
Avoid St. John's Wort internally. Notify anaesthetist of anything you're using beforehand, and be prepared to stop a week beforehand.
Great article here: the http://www.sfherbalist.com/docs/KSigler_TransSURGERY.pdf
(it's for trans* folks having surgery, but it covers all the same bases)
After surgery: echinacea (internal and external, promotes wound-healing as well as preventing infection), turmeric with ~5% black pepper, can be mixed in honey and taken straight or in hot water, milk, etc (tasty!)
Topically: Add yarrow and if you can get it goldenseal powder (or barberry or oregon grape - Mahonia spp.) to the comfrey to prevent infection. Arnica is a great anti-inflammatory that doesn't slow wound-healing. Calendula helps heal tissue and prevent scarring.
Let me know if you have any more questions!