The hand is made up of the thumb and finger metacarpals and phalanges. The phalanges make up the digits. The metacarpals and digits are identified numerically, laterally to medially, one through five.
METACARPALS
- Each of the five metacarpals has a base that articulates proximally with one or more carpal bones and with its adjacent metacarpals
- The shaft of metacarpal is slightly curved with a palmar concavity, and a head that articulates with the base of a proximal phalanx.
- The head of each metacarpal bone is a biconvex articular surface that becomes part of the metacarpophalangeal (MCP) joint
PHALANGES
- The base of each proximal phalanges is biconcave and has a smaller articular surface than the metacarpal head.
- The distal phalangeal heads are bicondylar with an intercondylar depression.
- The middle phalanges and the base of the distal phalanges have articulating surfaces similar to the proximal phalanges.
JOINTS OF HAND
The hand is comprised of five digits with four fingers and one thumb, the digits include
- Carpometacarpal
- Metacarpophalangeal
- Interphalangeal
CARPOMETACARPAL JOINT
The carpometacarpal joint is the joint of the thumb and intermetacarpals
ARTICULATION: it is formed by
- The articulation between the trapezium and the first metacarpal.
- The trapezoid articulates with the second metacarpal
- The capitate with the third metacarpal
- The hamate with the fourth and fifth metacarpals
LIGAMENTS; All carpometacarpal joints are surrounded by joint capsules, which are reinforced by the dorsal, volar, and interosseous CM ligaments.
TYPE; it is a saddle joint
PLANE; Non axial plane
MOTION;
- 2nd 3rd cmc joint is minimal
- 4th cmc joint has 10◦ - 15◦
- 5th cmc joint has 25◦ – 30
TYPE OF MOTION;
The motion of the thumb includes ;
- Abduction and Adduction in a plane at a right angle to the palm
- Flexion and Extension in a plane parallel to the palm
- Opposition, a rotation of the first metacarpal on the trapezium to place the pad of the thumb opposite the pads of the fingers. Is a combination of flexion and abduction, with “built-in” accessory motion of rotation.
- Reposition is the reverse of opposition, return to anatomical position. It is because of this accessory rotation that the CMC joint is usually considered a “modified” biaxial joint.
METACARPOPHALENGEAL JOINT
The metacarpophalangeal (MCP) joints of the fingers, it forms the knuckles of the hand.
ARTICULATION; The rounded distal heads of the metacarpals articulate with the concave proximal ends of the phalanges.
LIGAMENTS; Each joint is enclosed in a capsule that is reinforced by strong collateral ligaments. A dorsal ligament also merges with the MP joint of the thumb.
ROM -MECHANISM, three-quarters of the circumference of the metacarpal heads are covered with articular cartilage, which extends onto the volar surface. The articular surfaces of the base of the phalanges are extended by fibrocartilaginous volar plates. As the joint flexes, the volar plate slides proximally under the metacarpal with a folding of its membranous part. This mechanism provides a large range of motion for a small articulating phalangeal surface.
TYPE OF JOINT; Biaxial condyloid type with two degrees of freedom.
CLOSE-PACK POSITION; The MP joints in the fingers and thumb are full flexion and opposition
TYPE OF MOTION; The motions allowed at these joints are flexion, extension, and hyperextension, plus abduction and adduction.
Abduction occurs when the second, fourth, and fifth fingers move away from the middle (third) finger and also when the middle finger moves in either direction.
Adduction is the return from abduction and occurs with the second, fourth, and fifth fingers. There is no adduction of the middle finger, only abduction occurring in either direction.
INTERPHALENGEAL JOINT
Each of the digits 2 through 5 has two interphalangeal (IP) joints
- The proximal interphalangeal (PIP) joint is between proximal and middle phalanges
(19° to 70° of flexion)
- The distal interphalangeal (DIP) joint is between middle and distal phalange
(12° to 31° of flexion)
The thumb has only two phalanges and, therefore, only one IP joint.
TYPE OF JOINT; uniaxial hinge joints with one degree of freedom
LIGAMENTS; An articular capsule joined by volar and collateral ligaments surrounds each IP joint.
CLOSE-PACK POSITION; joints are most stable in the close-packed position of full extension.
TYPE OF MOTION. Allow only flexion and extension.
MUSCLES OF HAND
The muscles of the hand are divided into two basic groups,
EXTRINSIC MUSCLES,
Proximal attachments in the forearm or humerus and distal attachments in the hand.
FUNCTION; The main function of the extrinsic muscles is to provide strength and gross motor control in hand function.
Muscles in this group includes Dorsal muscles and Ventral muscles
DORSAL MUSCLES
- EXTENSOR DIGITORUM
- EXTENSOR INDICIS
- EXTENSOR DIGITI MINIMI
- EXTENSOR POLLICIS LONGUS
- EXTENSOR POLLICIS BREVIS
- ABDUCTOR POLLICIS LONGUS
VENTRAL MUSCLES
- FLEXOR DIGITORUM SUPERFICIALIS
- FLEXOR DIGITORUM PROFUNDUS
- FLEXOR POLLICIS LONGUS
EXTENSOR DIGITORUM
Itis a superficial muscle on the posterior forearm and hand.
ORIGIN Lateral epicondyle of the humerus
INSERTION Base of distal phalanx of the second through fifth fingers
ACTION The extensor digitorum is the only muscle that extends all four fingers and Extends all three joints of the fingers (MCP, PIP, and DIP)
NERVE SUPPLY Radial nerve (C6, C7, C8)
APPLICATION The extensor digitorum, also known as the extensor digitorum communis, is the only muscle involved in extension of all four fingers. This muscle divides into four tendons on the dorsum of the wrist to insert on each of the fingers. It also assists with wrist extension movements.
STRENGHTENING It may be developed by applying manual resistance to the dorsal aspect of the flexed fingers and then extending the fingers fully. When performed with the wrist in flexion, this exercise increases the workload on the extensor digitorum.
FLEXIBILITY to stretch the extensor digitorum, the fingers must be maximally flexed at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints while the wrist is fully flexed.
EXTENSOR INDICIS
ORIGIN proximal attachment on the posterior surface of the Distal ulna
INSERTION Base of distal phalanx of the second finger
ACTION Extends all three joints of the second finger (MCP, PIP, and DIP)
NERVE SUPPLY Radial nerve (C6, C7, C8)
APPLICATION The extensor indicis muscle is the pointing muscle. That is, it is responsible for extending the index finger, particularly when the other fingers are flexed. It also provides weak assistance to wrist extension
STRENGHTENING Developed through exercises similar to those described for the extensor digitorum.
FLEXIBILITY The extensor indicis is stretched by passively taking the index finger into maximal flexion at its metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints while fully flexing the wrist.
Extensor Digiti Minimi Muscle
It is a long, narrow muscle (Fig. 13-21) that is deep to the extensor digitorum and extensor carpi ulnaris muscles near its proximal attachment. It becomes superficial before crossing the wrist
ORIGIN Lateral epicondyle of humerus
INSERTION Base of distal phalanx of fifth finger
ACTION Extends all three joints of fifth finger (MCP, PIP, and DIP)
NERVE SUPPLY Radial nerve (C6, C7, C8)
APPLICATION The primary function of the extensor digiti minimi muscle is to assist the extensor digitorum in extending the little finger
STRENGHTENING It is strengthened with the same exercises described for the extensor digitorum
FLEXIBILITY The extensor digiti minimi is stretched by passively taking the little finger into maximal flexion at its metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints while fully flexing the wrist and elbow.
Extensor Pollicis Longus Muscle
ORIGIN Middle posterior ulna and interosseous membrane
INSERTION Base of distal phalanx of thumb
ACTION Extends all three joints of the thumb (CMC, MCP, and IP)
NERVESUPPLY Radial nerve (C6, C7, C8)
APPLICATION The primary function of the extensor pollicis longus muscle is extension of the thumb, although it does provide weak assistance in wrist extension.
STRENGHTENING It may be strengthened by extending the flexed thumb against manual resistance. It is stretched by passively taking the entire thumb into maximal flexion at its carpometacarpal, metacarpophalangeal, and interphalangeal joints while fully flexing the wrist with the forearm in pronation
FLEXIBILITY The tendons of the extensor pollicis longus and extensor pollicis brevis, along with the tendon of the abductor pollicis longus, form the “anatomical snuffbox,” the small depression that develops between these two tendons when they contract. Due to its posterolateral relationship to the wrist it also assists in wrist abduction.
Extensor Pollicis Brevis Muscle
It is located deep on the posterior forearm and spans the wrist just medial to the abductor pollicis longus muscle.
ORIGIN Posterior distal radius
INSERTION Base of the proximal phalanx of thumb
ACTION Extends CMC and MCP joints of thumb
NERVESUPPLY Radial nerve (C6, C7)
APPLICATION The extensor pollicis brevis assists the extensor pollicis longus in extending the thumb. Because of its dorsal relationship to the wrist, it, too, provides weak assistance in wrist extension.
STRENGHTENING It may be strengthened through the same exercises described for the extensor pollicis longus muscle
FLEXIBILITY It is stretched by passively taking the first carpometacarpal joint and the metacarpophalangeal joint of the thumb into maximal flexion while fully flexing and adducting the wrist. Due to its lateral orientation at the wrist it assists in wrist abduction.
Abductor Pollicis Longus Muscle
It is located deep on the posterior forearm (Fig. 13-15). It attaches to the radius just distal to the supinator, the interosseous membrane, and the middle portion of the ulna. It becomes superficial just proximal to crossing the wrist and attaches to the base of the first metacarpal on the radial side
Origin Posterior radius, interosseous membrane, middle ulna
Insertion Base of the first metacarpal
Action Abducts thumb (CMC)
Nerve supply Radial nerve (C6, C7)
APPLICATION The primary function of the abductor pollicis longus muscle is abduction of the thumb
STRENGHTENING It may be developed by abducting the thumb from the adducted position against a manually applied resistance
FLEXIBILITY Stretching of the abductor pollicis longus is accomplished by fully flexing and adducting the entire thumb across the palm with the wrist fully adducted and in slight flexion.
VENTRAL MUSCLES
Flexor Digitorum Superficialis Muscle
It lies deep to the wrist flexors and palmaris longus muscle and divides into four tendons and crosses the wrist
ORIGIN Common flexor tendon on the medial epicondyle, coronoid process, and radius
INSERTION Sides of the middle phalanx of the four fingers
ACTION Flexes the MCP and PIP joints of the fingers
NERVESUPPLY Median nerve (C7, C8, T1)
APPLICATION The flexor digitorum superficialis muscle, also known as the flexor digitorum sublimis, divides into four tendons on the palmar aspect of the wrist and hand to insert on each of the four fingers.
STRENGHTENING Squeezing a sponge rubber ball in the palm of the hand, along with other gripping and squeezing activities, can be used to develop these muscles.
FLEXIBILITY The flexor digitorum superficialis is stretched by passively extending the elbow, wrist, metacarpophalangeal, and proximal interphalangeal joints while maintaining the forearm in full supination
Flexor Digitorum Profundus Muscle
It lies deep to the flexor digitorum superficialis muscle; these two muscles traverse the forearm and hand together
ORIGIN Upper three-fourths of the ulna
INSERTION Distal phalanx of the four fingers
ACTION Flexes all three joints of the fingers (MCP, PIP, and DIP)
NERVE SUPPLY Median and ulnar nerves (C8, T1)
APPLICATION The flexor digitorum profundus muscle assist in wrist flexion
STRENGHTENING The flexor digitorum profundus is used in any type of gripping, squeezing, or handclenching activity, such as gripping a racket or climbing a rope. It is the only muscle that flexes the finger DIP joints and disruption of the tendon at or near its insertion is known as a jersey or sweater finger and should be addressed surgically within approximately one week
FLEXIBILITY The flexor digitorum profundus is stretched similarly to the flexor digitorum superficialis, except that the distal interphalangeal joints must be passively extended in addition to the wrist, metacarpophalangeal, and proximal interphalangeal joints while maintaining the forearm in full supination.
Flexor Pollicis Longus Muscle
ORIGIN Radius, anterior surface
INSERTION Distal phalanx of thumb
ACTION Flexes all three joints of the thumb (CMC, MCP, IP)
NERVE SUPPLY Median nerve (C8, T1)
APPLICATION The primary function of the flexor pollicis longus muscle is flexion of the thumb
STRENGHTENING It is vital in gripping and grasping activities of the hand, it provides some assistance in wrist flexion. It may be strengthened by pressing a sponge rubber ball into the hand with the thumb and by many other gripping or squeezing activities.
FLEXIBILITY The flexor pollicis longus is stretched by passively extending the entire thumb while simultaneously maintaining maximal wrist extension
INTRINSIC MUSCLES
The intrinsic muscles are responsible for the hand’s fine motor movements. have their proximal attachment at, or distal to, the carpal bones.
FUNCTION;
They have a function on the thumb or fingers. These muscles are responsible for the hand’s fine motor control and precision movement.
The intrinsic muscles can be further divided into the thenar, hypothenar, and deep palm muscles.
Thenar
The thenar muscles are those that function to move the thumb. They form the thenar eminence, or ball of the thumb.
The thenar muscles include;
- OPPONENS POLLICIS
- ABDUCTOR POLLICIS BREVIS
- ADDUCTOR POLLICIS
- FLEXOR POLLICIS BREVIS
Hypothenar
The hypothenar muscles, forming the hypothenar eminence, act primarily on the little finger.
The hypothenar muscles include;
- OPPONENS DIGITI MINIMI
- ABDUCTOR DIGITI MINIMI
- FLEXOR DIGITI MINIMI BREVIS
Deep palmer muscles
The deep palm muscles are located deep in the palm of the hand between the thenar and hypothenar muscles. They perform some of the more intricate motions that usually involve multiple muscles
The deep palmer muscles include;
- FOUR LUMBRICALS
- THREE PALMAR INTEROSSEI
- FOUR DORSAL INTEROSSEI
Flexor Pollicis Brevis Muscle
ORIGIN Trapezium and flexor retinaculum
INSERTION Proximal phalanx of the thumb
ACTION Flexes the CMC and MCP joints of thumb
NERVE SUPPLY Median nerve (C6, C7)
Abductor Pollicis Brevis Muscle
ORIGIN Scaphoid, trapezium, and flexor retinaculum
INSERTION Proximal phalanx of the thumb
ACTION Abducts the thumb (CMC joint)
NERVE SUPPLY Median nerve (C6, C7)
Opponens Pollicis Muscle
ORIGIN Trapezium and flexor retinaculum
INSERTION First metacarpal
ACTION Opposes the thumb (CMC joint)
NERVE SUPPLY Median nerve (C6, C7)
Adductor Pollicis Muscle
ORIGIN Capitate, base of the second metacarpal, palmar surface of the third metacarpal
INSERTION Base of proximal phalanx of thumb
ACTION Adducts thumb (CMC joint)
NERVE SUPPLY Ulnar nerve (C8, T1)
Palmar Interossei Muscles
ORIGIN 1st, 2nd, 4th, and 5th metacarpals
INSERTION Base of respective proximal phalanx
ACTION Adduct fingers at MCP joint
NERVE SUPPLY Ulnar nerve (C8, T1)
Dorsal Interossei
There are four dorsal interossei muscles.
ORIGIN Adjacent metacarpals
INSERTION Base of proximal phalanx
ACTION Abduct fingers at MCP joint
NERVE SUPPLY Ulnar nerve (C8, T1)
Lumbrical Muscles
These are four, have no bony attachment. They are located quite deep and attach only to tendons.
ORIGIN Tendon of the flexor digitorum profundus muscle
INSERTION Tendon of the extensor digitorum muscle
ACTION Flex the MCP joint while extending the PIP and DIP joints
NERVE SUPPLY First and second lumbricales: medial nerve Third and fourth lumbricales: ulnar nerve (C6, C7, C8)
MOTION Proximally, they attach to the tendon of the flexor digitorum profundus muscle, spanning the MCP joint anteriorly. This allows them to flex the MCP joint.
They then pass posteriorly at the proximal phalange to attach to the tendinous expansion of the extensor digitorum muscle. This allows them to extend the PIP and DIP joint.
Therefore, their action is to flex the MCP joint and extend the PIP and DIP joints of the second through fifth fingers. This combined motion is referred to as the “tabletop position’’.
Flexor Digiti Minimi Muscle
ORIGIN Hamate and flexor retinaculum
INSERTION Base of proximal phalanx of the fifth finger
ACTION Flexes CMC and MCP joints of the fifth finger
NERVE SUPPLY Ulnar nerve (C8, T1)
Abductor Digiti Minimi Muscle
ORIGIN Pisiform and tendon of flexor carpi ulnaris
INSERTION Proximal phalanx of fifth finger
ACTION Abducts the MCP joint of the fifth finger
NERVE SUPPLY Ulnar nerve (C8, T1)
Opponens Digiti Minimi Muscle
ORIGIN Hamate and flexor retinaculum
INSERTION Fifth metacarpal
ACTION Opposes the fifth finger (CMC joint)
NERVE SUPPLY Ulnar nerve (C8, T1)
THUMB MUSCLES
EXRINSIC MUSCLES OF THUMB
- FLEXOR POLLICIS LONGUS
- EXTENSOR POLLIICS
- EXTENSOR POLLICIS LONGUS BREVIS
- ABDUCTOR POLLICIS LONGUS
INTRINSIC MUSCLES OF THUMB
- ADDUCTOR POLLICIS
- FLEXOR POLLICIS BREVIS
- ABDUCTOR POLLICIS BREVIS
- OPPONENS POLICIS
REFERENCES
- Brunnstrom's clinical kinesiology
- Clinical kinesiology and Anatomy (Lynn S. Lippert)
- Manual of Structural Kinesiology (R.T.Floyd)
- Basic biomechanics (Susan J. Hall)
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