Depends how much muscle is there. I assume that you do have mucle there otherwise you couldn't use your arm properly.
If that is the case, it can help.
If you have no muscle there, then obviously it cannot.
The reason why I recomend to most not to use Syntherol in the horseshoe is because most don't lack it, and putting Syntherol there will make it out of proportion. But if you are lacking in that muscle area, then of course it's useful at making everything in proportion.