The tweezer grip is established by the thumb saddle joint. Babies can only grasp simply at the beginning of life, but the tweezer grip establishes itself by the sixth to ninth month of life. The thumb saddle joint establishes the connection between the thumb and the metacarpal bone, and the large polygonal bone becomes involved. This allows the thumb and the other fingers to face each other and work together to provide very fine grasping.
What is the tweezer grip?
Tweezer grip takes the place of the grasp reflex, babies can then grasp smaller objects. Illustration shows tweezer grip in an occupational therapy session. Tweezer grip disengages the grasping reflex, baby can now grasp smaller objects. He no longer grasps with the entire palm of his hand, but is able to exert the tweezer grip. Now no speck of dust goes unnoticed and perhaps the toddler can already hold the baby spoon. The child will quickly perfect the tweezer grip and reach for anything nearby. It will even drop certain objects extra to pick them up again. But this is normal, it helps develop the grasping motor skills. The grasping reflex should be completely gone by the ninth month of life. With the tweezer grip, the baby becomes more dexterous, it won’t be long at all before he can eat on his own. The tweezer grip is important for a child’s development, because it allows him to move and use his hand properly.
Function and task
The thumb joint is held in place by several ligaments, and two muscles are available for each rotational movement. The muscles of the hand are supplied by the ulnar and median nerves. The thumb saddle joint is responsible for all grasping actions, and it is also heavily used in the tweezer grip. Especially women after menopause have to expect changes at this joint, it is mostly arthrosis, which is called rhizarthrosis in this area. The thumb saddle joint is not a ball and socket joint, but a typical saddle joint. This is what makes bending and stretching the hand possible in the first place, optimizes spreading and bending, and ultimately makes all gripping movements possible in the first place. Compared to the finger joints, the thumb saddle joint is quite elastic, but it is held in place by ligaments and is very stable. Thus, safe movement in all directions is possible. The thumb can therefore perform fine motor movements, which includes the tweezer grip, but it can also grip firmly. The thumb saddle joint is responsible for many movements, it can perform fine motor movements but can develop a lot of strength for grasping movements. As a result, the opposition of the thumb has a special load. The thumb has two planes of rotation, it is thus able to perform the tweezer grip. By the way, each of the remaining four fingers can make a “tweezer”. The tip of the thumb is placed on the end of any finger. The fingers of the same hand are squeezed together to a greater or lesser extent. Thus, the tweezer grip can be exercised very sensitively and carefully, but it can also grip forcefully.
Diseases and ailments
Almost all movements place a lot of stress on the thumb saddle joint. Especially in the tweezer grip with the ring finger and the little finger. Here, the joint surfaces are displaced against each other and much smaller surfaces are exposed to the stresses. In this way, the [[articular cartilage]] can be prematurely worn away, which in turn leads to arthrosis. This manifests itself in pain on movement, which can later also be experienced at rest. Often projections of the bones form, which can already be palpated from the outside and are easily recognized as deformities. There is a special X-ray procedure that makes the bony changes visible. Anyone who works extremely hard on a smartphone with their thumb is particularly at risk. Writing a lot of text messages or playing a lot of games can cause pain in the thumb. The phenomenon already occurs frequently in adolescents, as the load on the thumb is very high and it is subjected to unusually high stress. The thumb is then also referred to as SMS thumb and the overuse manifests itself in tendonitis or through bursitis. In the so-called Finkelstein test, it is even possible to feel the tendon, which then makes a crunching sound. Here, the thumb is closed in the fist and jerkily bent in the direction of the little finger.The discomfort is very painful and if the thumb is not treated, this disease can become chronic very quickly. Treatment may well take a month or more. In very bad cases, minor surgery may also be necessary, which is performed on an outpatient basis. A small incision into the connective tissue or bursa can provide relief. After surgery, the thumb can be moved again immediately.
