Hi there;
I posted a thread, and it is being reviewed by a moderator right now, but click my profile and look at my forum posts when you get online so you can see my thread.
I have the same problem, and I am getting the rib resection + scalenectomy in the same surgery as the tenotomy. My surgeon tells me that there is no functional loss from the tenotomy; the pec minor is something of a vestigial muscle in humans, it has not served a significant purpose in our evolutionary history for millions of years. If you look at its anatomy, you see that it serves virtually the same purpose in humans as the pec major, which also occupies nearly the same location. Removal of the pec minor should not cause any loss of strength to begin with, but if it did, I'm sure that by doing symmetrical exercise like pushups, your pec major would quickly compensate for the absence of the pec minor. Exercises that balance your muscles, even with an intact pec minor, will ensure that your right and left sides are roughly equal in strength. Let's say you did lose about, say, 20N of force on one side, from the tenotomy. When you go to do a pushup, your pec major will be doing all of the work on one side, so that side will strain harder and fatigue more easily than the other side at first. During the next couple days, the compensating pec major will be sorer than the other pec major, (which has had the help of the pec minor) particularly in the spot whose function corresponds with the natural function of the pec minor. That spot will amass more muscle, likely filling in the location in which your pec minor used to be, and should probably grow to match the other side. After a couple weeks, when you go to do your pushups, you should notice the same strain and fatigue on both sides. That is when you know that your pec major has compensated for the loss of strength caused by the tenotomy.
However, I am not sure that the pec minor provides much force to begin with. You may not notice any extra strain or fatigue at all, since the pec major is so large and dominates any exercise that might activate your pec minor. There's a chance that when you do pushups, you are not even activating your pec minor at all. It is truly an auxiliary muscle. I was worried about the same thing, but my surgeon quelled my fears about this. If it was half of my biceps, then yeah I'd be pretty worried. But people get myectomies that limit strength and functionality much more severely than this one, and eventually regain the strength and functionality they had before the surgery. If one muscle is incapacitated, and you do a workout that would normally activate that muscle, the neighboring muscles strain to compensate for the incapacitated muscle, and actually repurpose themselves from their original function, to fill the role of the incapacitated muscle. The physical appearance of this development was highly noticeable in an acquaintance of mine, who had his middle deltoid removed. The anterior and rear delts literally grew into where the middle deltoid once was, forming new nerve endings in the process. It was noticeably 'off,' and one could tell that his right shoulder looked different from his left, but he told me that within 6 months there was no functional difference. In our case, the difference of physical appearance should be minimal to nonexistent, since the pec minor is very small and is located deep underneath the pec major. And the time to recover strength/functionality should also be minimal to nonexistent, since the pec minor is hardly functional to begin with.
Keep your head up, I know this **** is stressful, but your future is looking bright. I will let you know how my own tenotomy goes. My doc assures me that the surgery will do nothing but improve my strength and functionality. With your pec minor removed, your shoulder should become much more flexible, and your pec should become much more relaxed. Contrary to logic, a tight muscle is actually a weak muscle. You want maximum range of motion when you exercise, so the ability to stretch your chest to its fullest potential eventually translates to a stronger chest. My doc tells me that, after the release of my pec minor, and the recovery, I will be able to develop much stronger pecs than I had even before my symptoms became excruciating. After the surgery, however, it is essential to maintain good posture and flexibility, lest the symptoms and disability return. My chiropractor told me that after the surgery, it might serve me well to get a light brace fitted to my body, that covers my entire torso, to keep my scapula retracted so that I don't protract the shoulders, which obviously causes chronic tightness of the pectoral muscles. Restricting the shoulder protraction with a brace also makes it very inconvenient to hunch, making you more likely to sit and stand with your back straight, and shoulders back, which drastically reduces recurrence of TOS, as well as the occurrence of a plethora of other chiropractic, orthopedic, and medical problems.