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The thumb is the first of the five fingers on the hand, different from the others in terms of structure and range of movements. The thumb allows a person to make grips with the hand. The most common thumb conditions are caused by injuries. Excessive thumb strain can lead to chronic inflammation. Learn how the thumb is structured, what functions the thumb performs and how to diagnose and treat the most common diseases of the thumb.
The thumb(Latin pollex) differs in many ways from the other fingers of the hand. First of all, it is the finger opposite to the other fingers on the hand. It also performs very important functions, including hand grip. Without a thumb, the hand cannot be fully functional. However, the thumb is exposed to certain injuries, diseases, inflammatory infections and even birth defects.
Thumb - construction
Although the thumb's size is relatively small, its internal structure is quite complicated. The high precision of thumb movements is possible thanks to the cooperation of numerous muscles and nerves that control its movements.
There are differences in the structure of the thumb and other fingers. The first difference is its internal skeleton. Inside the thumb are two small bones called phalanges (the proximal and distal phalanges, respectively). All other fingers have three phalanges (proximal, middle and distal).
Compared to other fingers, the phalanges of the thumb are arranged "inversely" in terms of thickness - the phalanx closer to the thumb is thinner than the distal phalanx. The two phalanges of the thumb are connected by an interphalangeal joint, which allows you to perform hinge movements. The thumb connects to the rest of the hand via the first metacarpophalangeal joint (the entire hand has five such joints).
The joints of the thumb are surrounded by an articular capsule filled with synovial fluid. Additional strengthening is provided by collateral ligaments, ensuring adequate stability of the joints. A number of muscles are responsible for the full mobility of the thumb, enabling the performance of as many as five types of movements. These include:
- bending,
- straightening,
- adduction,
- abduction
- and opposition.
The names of the muscles in the thumb come from activities that are possible due to the action of the given muscle. The thumb therefore has two abductors, extensors and flexors (respectively -long and short) and one opponent and adductor each.
Some of the thumb muscles begin on the forearm - long muscles that run superficially. The deep muscles of the thumb start in the palm of your hand. Four of them: the short abductor, short flexor, opponent and adductor are collectively called the muscles of the withers.
The muscles of the withers form a "cushion" of muscle, easily felt at the base of the thumb. The thumb has a rich innervation, both motor and sensory. There are three large nerves involved in the control of thumb movements: the median, ulnar and radial nerves, responsible for the mobility of the entire hand.
Superficial sensation in the area of the thumb is provided by two of them: on the palmar side - the median nerve, and on the dorsal side - the radial nerve. The tissue vascularization of the thumb comes from its "own" blood vessel, which is called the main artery of the thumb.
The main artery of the thumb is a branch of the radial artery. Its presence plays an important role in medics who conduct a physical examination of the pulse. When taking a patient's pulse, never do so with your thumb (both index and middle fingers are used).
The thumb pulse test runs the risk of "feeling" the pulse coming from his own artery, not from the patient's arteries. In the anatomy of the thumb, it is also worth remembering about its outermost layer - the skin with its appendages.
Some of the thumb he alth problems are relatively often caused by broken skin or poor nail hygiene. This creates a gate of infection that can be confined to the fingertip of the thumb or spread to the rest of the finger.
Thumb - functions
The full range of thumb movements is crucial for the proper functioning of our hand. It is believed that the absence of a thumb causes a handicap of as much as 40%. Basic thumb movements include flexion, extension, abduction, adduction and opposition.
The most "unique" movement of the thumb is opposition - this skill is the only one of all fingers. Opposing is a movement that connects the fingertip of the thumb with the pads of other fingers.
Opposing allows you to precisely grasp objects (the so-called tweezers grip), which is one of the most advanced human motor activities. Developing the ability to oppose the thumb takes time - a full tweezer grip is usually seen in babies around 10 months of age.
Opposing accounts for approximately 60% of the total thumb functionality. The great dexterity of the thumb followsalso with the possibility of simultaneous movements in several planes.
Thumb - diagnostics
Diagnostics of thumb disorders begins with a simple physical examination that can provide valuable information. Especially in the case of thumb injuries, the knowledge of thumb anatomy enables an approximate prediction of the location of the damage. Knowing which thumb functions are restricted, we can make inferences about possible muscle and nerve damage.
Imaging tests are used for more advanced diagnostics of thumb diseases. The choice of test always depends on the clinical data: symptoms and history reported by the patient.
As a rule, an X-ray (X-ray) of the thumb or an ultrasound examination (USG) is performed first. Both of them are characterized by high availability and speed of execution, however their applications are different.
We take an X-ray image in case of suspicion of bone damage (most often - fractures) or their mutual displacement (joint dislocation). Ultrasound examination is more valuable in the imaging of soft tissues - muscle tendons, joint ligaments, as well as the contents of the joint capsule.
Magnetic resonance imaging is used for advanced hand and thumb imaging. This examination is performed in situations where standard imaging tests have not brought sufficient information about the causes of the ailments.
Thumb - diseases
The vast majority of thumb diseases arise as a result of injuries or overstrain. Even partial loss of thumb function causes severe impairment of entire hand function.
For this reason, in injuries and inflammation of the thumb, efforts are made to restore the thumb's full range of motion. Infections can also spread within the tissues of the thumb. In the pediatric population, there are malformations of the thumb occurring during prenatal development.
Thumb injuries
Thumb injuries may involve various anatomical structures:
- bones (fractures),
- joints (sprains),
- as well as muscle tendons,
- ligaments,
- dishes
- and nerves.
The method of treating thumb injuries depends on their extent and the degree of abnormal thumb anatomy resulting from the injury. Most thumb injuries require temporary immobilization to heal the damaged tissue.
Surgical treatment is indicated in the case of bone fragments displacement, permanent instability of joints, or disruption of the continuity of vessels and nerves.
One of the most common injuries of the thumb is the so-called skier's thumb risingusually when playing sports. The essence of this disease is damage to the ligaments in the joint connecting the thumb with the rest of the hand (metacarpophalangeal).
Most often it occurs as a result of a ski accident - during a fall, there is a sudden pressure on the thumb in the abduction position. Treatment of the skier's thumb is usually conservative (immobilization followed by rehabilitation).
If the joint fails to restore normal function, or the ligament damage is accompanied by additional trauma, surgery may be required. An extreme example of a thumb injury is the complete amputation of part or all of the thumb. Replantation (re-sewing) of an amputated thumb is a difficult procedure, the success of which depends on many factors.
One of the key steps is to secure, cool and quickly transport the amputated thumb, which increases the chance of extending the life of the tissues. Thumb replantation is an advanced operation using microsurgical techniques.
Even after successful surgery, full recovery of the thumb function is often impossible. The final effect of treatment is also influenced by long-term rehabilitation, which can improve the movement and feeling of the thumb.
Inflammation
The thumb may be damaged not only as a result of sudden injuries, but also long-term overstrain. Frequent monotonous thumb movements can cause inflammation of the tissues in the thumb. An example of such a disease is the so-called mother's thumb, technically known as de Quervain's syndrome.
Inflammation mainly affects soft tissues - in the case of the disease in question, these are the tendon sheaths of the thumb extensor muscles (working, for example, during the "OK" gesture).
De Quervain's disease typically occurs in young mothers whose hands are subjected to previously absent strain during frequent lifting of the baby. Treatment of thumb inflammation requires relief (often with the use of an orthosis) and appropriate rehabilitation.
Drug therapy is based on steroid and non-steroidal anti-inflammatory drugs.
Infections
Bacterial infections may occur in the thumb area, as in the rest of the hand. Most often they occur as a result of breaking the continuity of the skin and the penetration of bacteria into deeper tissues. The two most common types of such infections are paronychia and pegs.
Parnosis is a purulent inflammation of the tissues around the nail. A thumb brace is an infection of its inner surface, which can spread through continuity and in extreme cases also involve tendons or bones.
Infections in the area of the thumb always require antibiotic treatment. In some cases, surgery may be necessary to cleanse the site of infection and allow pus to drain out.
Birth defects
Congenital thumb defects are relatively rare conditions. They usually do not appear as isolated abnormalities - they are much more likely to accompany other, complex developmental defects.
The most common birth defects are aplasia (complete absence) or hypoplasia (partial underdevelopment) of the thumb. Since the thumb is a key element of the proper functioning of the hand, the goal is to always restore it in the case of such birth defects.
One of the methods of such treatment is policing, i.e. a procedure involving the transfer of one of the fingers (usually the index) to the place of the absent thumb.
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