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The human wrist is a complex joint that enables a wide range of movements. The primary muscles responsible for flexing the wrist are the flexor carpi ulnaris (FCU) and the flexor carpi radialis (FCR). These muscles, along with others like the palmaris longus and flexor digitorum superficialis, work together to allow for various wrist motions, including flexion, extension, and deviation. The FCU is the most powerful wrist flexor and plays a crucial role in wrist adduction and elbow and forearm flexion. On the other hand, the FCR is important for stabilizing the scaphoid bone and assisting in the abduction of the hand and wrist.
| Characteristics | Values |
|---|---|
| Muscles that flex the wrist | Flexor Carpi Ulnaris, Flexor Carpi Radialis, Palmaris longus, Flexor Digitorum Superficialis |
| Most powerful wrist flexor | Flexor Carpi Ulnaris |
| Function of Flexor Carpi Radialis | Provides flexion of the wrist and assists in abduction of the hand and wrist |
| Flexor Carpi Ulnaris tendon | Used as a landmark for locating the ulnar nerve and artery during surgery |
| Flexor Retinaculum | Travels across the palmar side of the wrist and forms the "Carpal Tunnel" |
| Extensor Retinaculum | Anchors the extensor tendons and assists in supporting the posterior structure of the wrist |
| Wrist | A series of small joints that connect the radius and ulna (the 2 bones in the forearm) to the carpals in the hand |
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What You'll Learn
Flexor Carpi Ulnaris: the most powerful wrist flexor
The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist joint. It is the most powerful wrist flexor. The muscle is attached to the hook of the hamate bone via the pisohamate ligament and the fifth metacarpal bone through the pisometacarpal ligament. The FCU tendon is a landmark for locating the ulnar nerve and artery during surgery, as these structures lie immediately lateral to the muscle.
The FCU originates from two separate heads, the humeral head and the ulnar head, which are connected by a tendinous arch. The humeral head arises from the common flexor origin on the medial epicondyle of the humerus. The ulnar head, which is more extensive than the humeral head, originates from the olecranon and the proximal part of the posterior border of the ulna.
As the muscle fibres pass towards the wrist joint, they converge on a long tendon in the distal part of the forearm. This tendon passes into the palmar surface of the hand to insert onto the pisiform and hamate carpal bones, as well as onto the base of the fifth metacarpal bone. The FCU is the most medial among the superficial anterior forearm compartment muscles, and it is the only one completely innervated by the ulnar nerve.
The FCU plays a crucial role in wrist procedures such as wrist and hand tendon transfers and cubital tunnel release. Understanding the FCU's surgical importance is essential for healthcare professionals treating conditions affecting the forearm, wrist, and hand. The muscle can also be used as a surgical landmark for exposing the ulnar shaft in certain procedures.
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Flexor Carpi Radialis: a dynamic scaphoid stabiliser
The wrist is a series of small joints that connect the radius and ulna (the two bones in the forearm) to the carpals in the hand. One of the muscles that flex the wrist is the flexor carpi radialis (FCR). The FCR muscle has been suggested to act as a dynamic scaphoid stabilizer.
The FCR tendon uses the scaphoid tuberosity as a pulley to reach its distal insertion onto the second metacarpal. When the FCR is loaded, the scaphoid rotates into flexion and supination, while the triquetrum rotates in flexion and pronation. This motion is important for weight-bearing activities and maintaining the body in an inverted position.
The positive effects of FCR muscle re-education in dynamic scapholunate instabilities can be attributed to its ability to induce supination to the scaphoid and pronation to the triquetrum, resulting in a dorsal coaptation of the scapholunate joint and relaxation of the dorsal scapholunate ligament. This understanding of the FCR's role has implications for the treatment of scapholunate ligament injuries and dynamic scaphoid instability.
Dynamic extensor carpi radialis longus tendon transfer is a procedure that can restore the slider crank mechanism of the scaphoid after scapholunate interosseous ligament (SLIL) injury. It acts synchronously with wrist motion and may be sufficient to support normal or near-normal scapholunate and midcarpal kinematics, preventing further injury propagation in patients with partial SLIL tears and dynamic scapholunate instability.
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Radial deviation: tilting the hand and wrist toward the thumb
Radial deviation is the movement of the hand and wrist towards the thumb and radius. This involves bending the wrist laterally, causing the hand to move closer to the thumb side of the forearm while the little finger side moves away. The wrist is a series of small joints that connect the radius and ulna (the two bones in the forearm) to the carpals in the hand. The eight carpal bones can be divided into two rows of four bones. The proximal (or closer) row is composed of the scaphoid bone, the lunate bone, the triquetral bone, and the pisiform bone. The distal (or farther) row is composed of the trapezium bone, the trapezoid bone, the capitate bone, and the hamate bone.
To understand radial deviation, it is important to know the anatomy of the wrist. The wrist is a complex structure that allows for a wide range of motion. Radial deviation is one of the movements that the wrist is capable of. This movement is important for many daily activities such as writing, typing, using tools, and performing activities that require a strong grip or precise movements. It is also crucial for tasks that involve grasping, gripping, and manipulating objects. For example, when holding a cup, radial deviation allows the hand to tilt towards the thumb side, providing a more stable and secure grip.
The muscles involved in radial deviation include the Flexor Carpi Radialis and Extensor Carpi Radialis. These muscles work together to cancel flexion and extension, instead pulling the hand and wrist towards the radius. This motion is important for weight-bearing activities such as those performed on a balance beam, rings, pommels, and p-bars. It helps to maintain the body in an inverted position.
There are exercises that can help improve radial deviation. One such exercise involves resting your forearm on a table or in your lap, with your palm facing up. Then, use your other hand to gently press your hand and wrist towards your thumb, feeling the stretch on the inside of your forearm. Hold this stretch for 15 to 30 seconds, then release and repeat 2-3 times with each arm. This exercise helps to improve the range of motion in the wrist and can be beneficial for those recovering from wrist injuries.
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Ulnar deviation: tilting the hand and wrist toward the pinky
Ulnar deviation is the tilting of the hand and wrist towards the pinky finger, or the little finger side of the hand. This movement is sometimes referred to as ulnar drift and is often associated with Rheumatoid Arthritis (RA). It can also be caused by other inflammatory autoimmune diseases, such as psoriatic arthritis and lupus. Ulnar deviation can also be caused by brachial plexus palsy (BPP), a type of paralysis resulting from nerve injuries in the shoulder.
The wrist is a complex structure comprising a series of small joints that connect the radius and ulna (the two bones in the forearm) to the carpals in the hand. Ulnar deviation specifically involves the movement of the wrist bones bending towards the thumb side, while the fingers simultaneously bend towards the pinky finger. This can cause difficulty in performing everyday tasks that require dexterity, such as holding a spoon, cutting up food, or opening a jar.
The muscles involved in ulnar deviation include the Flexor Carpi Ulnaris and the Extensor Carpi Ulnaris. These muscles work together to cancel out flexion and extension, resulting in a pulling motion towards the ulna. This movement is particularly important in weight-bearing activities and maintaining the body in an inverted position, as seen in sports such as gymnastics and yoga.
Ulnar deviation can be managed through the use of splints, which help to support and correct the deviation. Both day and night splints are available, and they can be used to reduce inflammation, pain, and stiffness associated with the condition. Early diagnosis and treatment of underlying conditions, such as RA, can also help slow the progression of ulnar deviation and improve overall hand function.
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Flexor Digitorum Superficialis: assists finger flexion
The Flexor Digitorum Superficialis is a muscle in the forearm that assists in finger flexion. It is the largest muscle of the anterior compartment of the forearm and is classified as a superficial forearm flexor. The muscle is divided into two heads: a humeroulnar head and a radial head. Its large muscular belly moves towards the wrist, where it divides into four tendons and attaches to the middle phalanges of the second through fifth digits of the hand.
The main function of the Flexor Digitorum Superficialis is to flex the digits 2-5 at the proximal interphalangeal and metacarpophalangeal joints. Unlike the flexor digitorum profundus, the flexor digitorum superficialis has independent muscle slips for all four digits, allowing it to flex them individually.
The tendons of the flexor digitorum superficialis muscle are easily palpable on the distal part of the forearm. At the wrist, the tendons of the flexor digitorum superficialis and flexor digitorum profundus travel together, deep below the flexor retinaculum of the hand, passing through the common flexor sheath.
The flexor digitorum superficialis is involved in multiple actions, including gripping and flexing the wrist, and is susceptible to carpal tunnel syndrome, which can cause numbness, paresthesia, and pain in the affected fingers.
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Frequently asked questions
The Flexor Carpi Ulnaris (FCU) is the most powerful wrist flexor. It is a superficial flexor muscle of the forearm that flexes and adducts the hand.
The FCU primarily flexes the wrist and assists in wrist adduction and elbow and forearm flexion. It is the only anterior forearm compartment muscle completely innervated by the ulnar nerve.
The FCU originates from two separate heads connected by a tendinous arch. The humeral head arises from a common flexor tendon origin on the medial humeral epicondyle, while the ulnar head arises from the olecranon and proximal three-fourths of the ulna's subcutaneous margin. The FCU inserts on the fifth metacarpal, hook of the hamate, and pisiform.
Yes, the Flexor Carpi Radialis (FCR) is also involved in wrist flexion. It is a long, superficial muscle of the forearm that provides flexion of the wrist and assists in the abduction of the hand and wrist.
