If you have owned or cared for horses for any length of time, I'm sure you're aware that they're prone to wounds or trauma. I think this tendency for horses to suffer wounds is the result of the horse's nature, both psychological and physical. The horse evolved by developing reflexes of fight or flight that relied on speed and strength. These survival techniques tend to also be responsible for horses hitting fences, etc…and, considering the horse's mass and strength, significant skin trauma is often the result.
Wounds in horses are separated into different types, depending on where on the body they occur and what type of trauma causes them. Wounds on the head are often slice or clean-cut type wounds. This factor seems to me to be the result of skin directly over bone structure or where an inquisitive horse puts his head, and sometimes what is the first part of an escaping horse's body that contacts a fence or other stationary structure.
Wounds on the head, in my experience, respond to treatment by suturing (stitching up) better than wounds on other parts of the body. I believe this healing success is due to good blood supply and no stress on the skin from the motion as you have with wounds on the lower limbs.
Wounds on the horse's upper body over large muscle masses also heal very well, but differently than head wounds. These wounds are often the result of blunt trauma, so you not only have skin damage, but also damage to the underlying muscle or fascia. The underlying damaged tissue leaks serum or tissue fluid for quite a while, days to weeks depending on the wounds. If you suture these wounds closed, oftentimes the swelling that takes place will bust open the suture line.
These wounds do quite well without attempting to suture them. I have had to do a lot of convincing of anxious owners over the years that their horse will be just fine without stitches. Good blood supply and no great stress of motion are responsible for successful healing of these open wounds, in my opinion.
Wounds on the legs of horses below the knee or hock are the most problematic to deal with. Poor blood supply of the distal limbs and stress of motion over and around joints seem to be factors that delay the healing process. These wounds have to be treated differently, usually with the aid of proper bandaging, and certain types of topical medication your veterinarian may prescribe.