I'm completely new to martial arts. I would like to know if there are techniques that can be used in self-defense if you had one hand tied behind your back or in the case you lose your hand?
Absolutely. Actually, one of the schools in the Bujinkan (Gikan-ryu) was reportedly heavily influenced by the inclusion of a one-armed soke.
There is, of course, a strong natural disadvantage (all else being equal) to having only one arm available (for example, the opponent knows your high attacks will largely come from that side, you are not naturally balanced, etc.), but martial arts are about learning to compensate for your disadvantages. Most (un- or under-trained) people fight as if they have an arm, an arm, a leg, and a leg; not as if they have one body.
To give an example, I have a couple of techniques from Gikan-ryu that exemplify a one-handed approach. NB: These are from my notes, according to my understanding at the time of learning, and may not be typical of all students in the Bujinkan. These should not be attempted without proper supervision as injury will likely occur. I've used the left hand so I can copy from my notes directly for ease, but the techniques are meant for either side and do not require both hands.
Gyaku Mune Dori
Reversing Lapel Grab (Left hand only, exemplifies lock and throw.)
Straight Line (Left hand only, exemplifies lock and throw.)
Hanging Bell (Left hand only, exemplifies striking and throwing.)
Breaking it down
At a very, very basic level (and since you're new, this will be the case), you fight with your arms and your legs. You likely move deliberately, each technique performed step-by-step. This is a very low-level style of training, though.
As you improve, your body is one body. The exclusion of an arm is compensated for by the actions of the unified body.
This is all well exemplified by the story of Senju Kannon (千手観音), the 1000-Armed Boddhisatva in esoteric Buddhism (mikkyo). As Takuan Souhou wrote in The Unfettered Mind:
By this same virtue, we can see that men have the preconceived notion of not understanding the idea of having more than two arms any better than having less than two. Through training, we let go of distracting thoughts to learn to act and move naturally.
Whether a man has no arms or ten, if he trains his body to move as best and as efficiently as possible, he will always be more capable than the man distracted by his own thoughts.
There are plenty of techniques available to you if you only have one hand available, but it really depends on which martial arts you're referring to.
In our Hapkido classes, we'll randomly practice our grabs in different scenarios (eyes closed, kneeling, lying down, sitting on a chair, one hand behind our back, etc).
It teaches you to really understand the concepts behind how a specific technique works and how to adapt to whatever situation you might be put in. It also forces us to learn how our entire body is used to apply techniques and generate power. From a kneeling or seated position, you really have to adapt how your apply certain locks when you no longer have the full strength/power/mobility of your body — it forces you to rely on technique rather than brute strength.
I often practice my kicks with one or both hands behind my backs, not for any practical reason, but more so just to gain a greater understanding of how my body and balance is affected in different stances or scenarios.
In real life situations, you never know what you might injuries/limitations you might have to contend with, so practicing dealing with them in class can be very beneficial. Even if you don't put that one-handed technique into practice, it still helps you expand your understanding of how the technique works.
In one school I trained at we would change the sparring rules up to
Sure, you can can do various things one handed---blocking and punching with the other hand for instance---but it is much, much harder. Use your legs for trips or kicks. Run away if time and circumstances permit. Yell for help.
Being tied will also affect your balance, and the range of motions available to you.
I knew a guy in martial arts who lost his arm in an accident. As a result, we adapted the forms so that he could use only one arm to effect the techniques. This ended up being quite a learning experience for me. The way we did it involved a lot of sticky hands type maneuvers. I dunno if you've ever seen chi sao, push hands, or hubud-lubud, but doing a search on youtube for those terms should be quite instructive. They are sensitivity drills designed to develop reflexes and trapping skills. Push hands develops sensitivity but is less about trapping, and more about unbalancing the opponent.
As an example of how to use one hand in a sensitivity drill, imagine that your partner is throwing a jab-cross combination at you repeatedly. Ordinarily, you would block each hand with a pak sao ("slap block"). This is a "sticky" palm parry that remains connected to the opponent after contact. If you have one arm, instead of doing a pak sao with the other hand, you block the cross with a tan sao ("palm up block") from the same hand you just did a pak sao with, which also remains connected to the opponent. When the next jab comes, you pak sao again with the same hand and repeat the drill until one of you gets tired.
If you have some of your arm left, don't forget that the nub can offer you at least some protection for your ribs or head, but use footwork and positioning in combination with this minimal protection rather than relying solely on your nub.
Some martial arts, like Northern Mantis, Kempo, Kajukenbo, and Boxing, use follow-up strikes with the same hand. For example, you can throw a jab and roll back out with a back-fist. Also you can try combinations like low right hook, high right hook. The low right hook will bring his guard low on the right side so you can gain access to his temple for the high right hook.
Here's a Kempo pattern that develops "rolling" strikes:
In case it's not obvious, if you only have one hand, you can only do that side of the pattern. I present the "double fists" form of the pattern to preserve the way that it was taught to me. For those with one arm, do only the forward facing portion of the drill, and the side of the drill that is facing the arm you still have.
I got attacked with a metal bar by a tuk tuk driver trying to rob me. I blocked it with my forearm which caused an open fracture in the process (would have hit me in the head otherwise). I managed to avoid the next few rush attacks and run away which is always the best defence. I've always been a bit sceptical about weapons drills as they seem unrealistic - who carries around sticks or clubs?! I see now how useful they can be. Escrima, Aikido etc. Being in good physical shape is also a good defence. But it would be reassuring now to know and drill techniques with just one arm. I've trained in lots of martial arts over the years but now want to do even more and do single arm and even single leg techniques - I could have been hit in the leg or head which would have been worse!
Various forms of fencing and swordsmanship are good for learning how to use one hand effectively. Bruce Lee applied a lot of ideas from fencing to how he performed his lead punch.
In some styles of historical fencing, notably British sabre, it is common to put the off hand (usually the left) behind the back. This both makes it less likely to be cut and, in some styles, conceals a dagger for close range. In that context the lead hand is used exclusively for both offense and defense.
Yes there are tools to work with when you can not really use your hands. The idea of loosing your hand is a bit ... As you would go through Hades.;-)) I can see use hands free techniques in sudden attack situation where you are taken aback and there is no time to rise your hands, or in a crowd where your hands are obstructed, or when you are holding someone and you get under fire.. (Just expression of being battered) So. Use your shoulders, this is a massive bone with massive muscles, if you doge with your head and get behind works well. Shoulder shrugs to deflect, get covered or even hit. Way of practising. First partner must attack slowly and be realistic you can not block Mae geri chudan with it;-) You keep your hands in your pockets and have fun. Practise in diferent distances but preferably close combat as common sense you would see attack comming from the long distance and there would be plenty time to use hands. Have fun