I’m not a doctor and do not pretend to know a great deal about medical matters. However, there are things I’ve learned over time that could be useful for you to know.
Too often, we see injuries that simply aren’t believable, because the reader doubts such a thing is possible.
For instance, if I want an attacker to stab someone in the head with a pocketknife, writing that it pierced the skull, entered the brain and caused instant death is very unlikely. That’s why we do research. What’s inside our faces? A skull. A bony skull. A sturdy bony skull. Damage is possible, but it is designed to protect the brain, so it is pretty durable. Is it possible to stab through it? Maybe. In your research you may find that such a thing has happened once or twice, though there may be extenuating circumstances that made it possible. But in general, it probably doesn’t happen a lot.
So, if it isn’t at all possible, don’t write it. No one will believe you. If it is possible, though not probable, write it, but address the issue of unusual circumstances making it possible. Say that it’s rare, and mention how the knifer either got very lucky in their attack, or was so skilled that they knew how to circumvent the difficulties. Give your reader a reason to believe anything that isn’t common.
We often see depicted in movies/stories someone being stabbed or their throat slit or such, and then they silently die instantly. Only trouble is, that isn’t at all likely. Most people will cry out when stabbed or even attacked, so you need to silence or muffle any outcry. Most of the time the person isn’t dying from the injury so much as bleeding to death and that doesn’t happen instantaneously. Knowing human physiology increases the likelihood that your attacker stabs them in an extremely vulnerable spot, to improve the possibility of killing their victim. I ran into this when I had someone kill a person who was holding a hostage. I had to find a way of quickly killing the person without the hostage being injured in the process. And in researching the issue, it wasn’t simple to come up with a believable solution.
We see this often, also, when someone breaks a leg and then is running marathons a week later. Bones don’t knit that fast. Know how long it takes to recover from an injury – that is how long your ‘victim’ is going to be hampered. And that means complete recovery. If you don’t use an arm or leg for 6 weeks while a bone mends, the muscles are going to be weakened by lack of use and need to regain their former ability. Keep that in mind.
Maybe not all of your readers will know when you fudge something. Maybe if the story is really good they won’t bother to question whether or not it could happen. But maybe they will. If you have a sound basis for an injury/illness, you don’t have to go into all the details of it, just what is important to the story. But having the details in the back of your mind can add to the telling of it, or guide you where to make advisory comments, such as, “Don’t see that often. Once in a blue moon. The killer was either very good or very lucky to accomplish it.”
I spent hours researching the attack I mentioned earlier, but it amounted to only a couple of seconds/minutes “on screen” and I didn’t go into it in great detail. I, in essence, had 50 pages of research for 3 sentences. But having the details in my mind made it possible to write those 3 sentences more believably than before I did the research.
Keep your credibility – stay believable.