The Hand - Upper Extremities PDF

Upper Extremities Functional B Lecturer: Beáta Seregély assistant lecturer; [email protected] Semmelweis University Faculty of Health Sciences Department of Physiotherapy The hand Theory Lecturer: Beáta Seregély assistant lecturer [email protected] Semmelweis University...

Upper Extremities Functional B Lecturer: Beáta Seregély assistant lecturer; [email protected] Semmelweis University Faculty of Health Sciences Department of Physiotherapy The hand Theory Lecturer: Beáta Seregély assistant lecturer [email protected] Semmelweis University Faculty of Health Sciences Department of Physiotherapy The function and the structure The hand serves as a very important sensory organ for the perception and is also a primary effector organ for our most complex motor behaviors, and helps to express emotions through gesture, touch, music, and art. The human hand owes its ability to its architecture, which allows it to close down on itself either when the fist is clenched or when the hand is wrapped around an object. A normal healthy hand has a harmonious architecture with well- delined structural elements, shown here as spirals linking the homologous joints and converging to a focal point (star). On a flat surface, e.g. a glass, the hand spreads out and becomes flattened as it makes contact at the thenar eminence (1), the hypothenar eminence (2), the metacarpal heads (3) and the palmar surface of the phalanges (4) we find a specific imprint that is unique to the human hand. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The architecture of the hand When ones grip a large object, the hand becomes hollow, with the formation of 3 arches running in 3 different directions: Transversely, the carpal arch corresponds to the concavity of the wrist and is continuous distally with the metacarpal arch formed by the metacarpal heads. The long axis of the carpal gutter crosses the lunate, the capitate and the third metacarpal, which is the deepest part. Longitudinally, the carpo-rnetacarpophalangeal arches fan out from the wrist and are formed for each finger by the corresponding metacarpal bone and phalanges. These arches are concave on the palmar surface and the keystone of each arch lies at the level of the metacarpophalangeal joint. The two most important longitudinal arches are these: the arch of the middle finger, which is collinear with the axis of the carpal gutter, SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The architecture of the hand the arch of the index finger, which most often interacts with that of the thumb. Obliquely, the opposition or diagonal arches consist of the thumb and other fingers one by one: The most important is the one linking the thumb and the index finger. The most extreme is that linking the thumb to the little finger. As a whole, when the hand becomes hollow, it forms an anteriorly concave gutter. It stretches from the base of the hypothenar eminence - where the pisiform bone can be palpated - to the second metacarpal head and corresponds to the palmar crease known as the 'life line'. This is also the direction taken by a cylindrical object, e.g. the handle of a tool, when gripped by the hand. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The architecture of the hand When the fingers are voluntarily spread out, the axes of the five fingers converge towards the base of the thenar eminence overlying the easily palpated tubercle of the scaphoid. In the hand the movements of the fingers in the coronal plane, adduction and abduction, are referred to the long axis of the hand. During these movements the middle finger is almost stationary but it is possible to abduct and adduct this finger voluntarily with respect to the axis of the body, the abduction is called radial and the adduction is ulnar deviation. When the fingers are voluntarily brought together, their axes are not parallel but converge towards a point lying far distal to the hand. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The architecture of the hand When the fingers are allowed to assume a natural position, a position from which they can be both approximated and separated, they lie a short distance away from one another but their axes do not meet at one point. In the example given, the last three fingers are parallel and the first three fingers diverge from one another, while the middle finger represents the axis of the hand and also the 'zone of transition'. When the fist is clenched while the DIP joints are still extended, the axes of the two distal phalanges of the four fingers and the axis of the thumb converge at a point corresponding to the 'radial pulse'. Note that in this situation the axis of the index is parallel to the long axis of the hand, while the axes of the other lingers become progressively more oblique the farther they are from the index. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Arches of the Hand Simplifying the domed structure of the hand, the palmar concavity is supported by three integrated arch systems: 2 transverse and 1 longitudinal. The proximal transverse arch is formed by the static, rigid distal row of carpal bones, forms the carpal tunnel. Like most arches in buildings and bridges, the arches of the hand are supported by a central keystone structure. The capitate is the keystone of the proximal transverse arch. The distal transverse arch of the hand passes through the MCP joints. The sides of the distal arch are mobile. It occurs as the peripheral MCPs (1st, 4th, and 5th) “fold” around the more stable central (2nd and 3rd) MCPs. The keystone of the distal transverse arch are the central metacarpals. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Arches of the Hand The longitudinal arch of the hand follows the shape of the 2nd and 3rd rays. The proximal end of this arch is firmly linked to the carpus by the CMC joints. These relatively rigid articulations provide an important element of longitudinal stability to the hand. The distal end of the arch (the fingers) is very mobile. The keystone of the longitudinal arch consists of the 2nd and 3rd MCP joints; note that these joints serve as keystones to both the longitudinal and the distal transverse arches. All 3 arches of the hand are mechanically interlinked. Both transverse arches are joined together by a “rigid tie-beam” provided by the 2nd and 3rd metacarpals. In the healthy hand, this mechanical linkage reinforces the entire arch system. In the hand with joint disease, however, a structural failure at any arch may weaken another. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The structure At the wrist we discussed the carpus and the carpal bones. The hand has 5 metacarpals, referred to collectively as the “metacarpus.” Each of the 5 digits contains a set of phalanges. A ray describes one metacarpal bone and its associated phalanges. The articulations between the proximal end of the metacarpals and the distal row of carpal bones form the carpometacarpal (CMC) joints. The articulations between the metacarpals and the proximal phalanges form the metacarpophalangeal (MCP) joints. Each finger (II.-V.) has two interphalangeal (IP) joints: a proximal (PIP) and a distal (DIP) joint. The thumb has only 2 phalanges and 1 interphalangeal (IP) joint. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The dorsal surface of the hand Muscles that originate: Dorsal interossei (I-IV) Muscles that insert: Extrinsic: ECRL, ECRB, ECU Extensor pollicis brevis Extensor pollicis longus Extensor digitorum Extensor indicis Extensor digiti minimi Intrinsic: Adductor pollicis Dorsal interossei (I-IV) SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The palmar surface of the hand Muscles that originate (intrinsic): Thenar: Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Adductor pollicis with 2 head Mesothenar Palmar interossei (I-IV) Hypothenar Abductor digiti minimi Flexor digiti minimi Opponens digiti minimi SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The palmar surface of the hand Muscles that insert: Extrinsic: FCR, FCU Flexor digitorum superficialis Flexor digitorum profundus Abductor pollicis longus Flexor pollicis longus Flexor digiti minimi Intrinsic: Palmar/volar interossei Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Abductor digiti minimi Opponens digiti minimi SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The movements of the hand The movements start from the anatomic position, with the elbow extended, forearm fully supinated, and wrist in a neutral position. Movement is described in the cardinal planes of the body: Flexion/extension occur in the sagittal plane, and abduction/adduction occur in the frontal plane, where the middle finger is the reference digit (A-D). Because the entire thumb is naturally rotated almost 90° in relation to the fingers, the terminology describe the thumb movement is different. Flexion is the movement of the palmar surface of the thumb in the frontal plane across the palm. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The movements of the hand Extension returns the thumb back toward its anatomic position and laterally away from anatomic position. Abduction is the forward movement of the thumb away from the palm in a near sagittal plane. Adduction returns the thumb to the plane of the hand. Opposition is the movement of the thumb across the palm, making direct contact with the tip of any of the fingers. Reposition is a movement from full opposition back to the anatomic position. This terminology serves as the basis for the naming of the muscles that act on the thumb (e.g., opponens pollicis, extensor pollicis longus) SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The Carpometacarpal Joints II-V Relative mobility at the CMC joints. The 2nd and 3rd metacarpals are rigidly joined to the distal carpus, forming a stable, fixed central pillar throughout the hand. In contrast, the more peripheral CMC joints form mobile radial and ulnar borders, which are capable of “folding” around the hand’s central pillar. The function of the CMC joints allows the concavity of the palm to fit around many objects. This feature is one of the most impressive functions of the human hand. The 2 ulnar CMC joints contribute a subtle but very important element of mobility to the hand. This mobility—often referred to as a “cupping” motion— occurs primarily by flexion and “internal” rotation of the ulnar metacarpals toward the middle digit. The range of flexion and extension of the fifth CMC joint increases, when the closely positioned fourth CMC joint is free to move. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The Carpometacarpal Joints II-V There is a strong kinematic linkage between the fourth and fifth CMC joints due in part to well-developed intermetacarpal ligaments. The greater relative mobility allowed at the ulnar CMC joints is apparent by the movement of the fourth and fifth metacarpal heads while clenching a fist. The increased mobility of the fourth and fifth CMC joints improves the effectiveness of grasp, as well as enhances the functional interaction with the opposable thumb. The 5th CMC joint between the hamate and a 5th metacarpal is somewhat a saddle shape joint with 2 DoF, including flexion/extension, some abduction/adduction, and a limited amount of opposition. The motion of the 4th and 5th metacarpals facilitates the ability of the ring and little fingers to oppose the thumb. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Metacarpophalangeal Joints II-V The metacarpophalangeal (MCP) joints of the fingers are relatively large, ovoid articulations formed between the convex heads of the metacarpals and the shallow concave proximal surfaces of the proximal phalanges. The MP joint is surrounded by a capsule that is lax in extension. The incongruent articular surfaces and the capsular laxity in extension allows some passive axial rotation of the proximal phalanx. 2 collateral ligaments and the volarly located deep transverse metacarpal ligament enhance joint stability. Flexion stretches and increases the passive tension in the dorsal capsule and the slightly dorsali originate collateral ligaments. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Metacarpophalangeal Joints II-V This incongruent joint also have an accessory joint structure, the volar plate (2) to enhance the congruency in extention as adds to the amount of surface in contact with the large metacarpal head, and the stability by limiting hyperextension and, therefore, providing indirect support to the longitudinal arch. The volar plate is composed of fibrocartilage and is firmly attached to the base of the proximal phalanx distally but not to the metacarpal proximally. The flexible attachment of the plate to the phalanx permits the plate to glide proximally down the volar surface of the metacarpal head in flexion without restricting motion, while also preventing pinching of the long flexor tendons in the MP joint. The fibrocartilage plate has ability to resist both tensile stresses in restricting MP hyperextension and compressive forces needed to protect the volar articular surface of the metacarpal head from objects held in the palm. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. MCP Joints II-V, osteokinematics neutral (0°) position The MP joint is condyloid, with 2 axis and 2 DoF: Flexion/extension incease gradually, the 2nd (index) flexes to about 90°, and the 5th to about 110 to 115°. The MCP joints active extension varies with the subject and can reach 20-40°. Passively can be extend beyond the neutral (0°) position for a considerable range of 30-45°, but it can reach up to 90° in subjects with hyperlaxity of the ligaments. Abduction/adduction at the MCP joints occur to about 20° on both sides of the midline reference formed by the third metacarpal. The axis of rotation for each movement passes through the head of the metacarpal. By a combination of various degrees of abduction, adduction, extension and flexion, the index finger can perform limited circurnduction. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. MCP Joints II-V, arthrokinematics Arthrokinematics at the MCP joint are based on the biconcave articular surface of the phalanx moving against the biconvex metacarpal head. Therefore the direction of the arthrokinemetic, which is gilde dominantly with a slight roll and the direction of osteokinematic movement are same. Flexion stretches and increases the passive tension in the dorsal capsule and the collateral ligaments, this increased passive tension helps guide the joint’s natural arthrokinematics and maintain firm contact between the articular surfaces. The increased natural joint stability of the flexed MCP joints helps activated muscles stabilize these joints during grasp. The extension are similar to the flexion but the roll and slide occur in a dorsal direction. By 0° of extension, the collateral ligaments slackened, this accounts for the increased passive mobility (“joint play”) while the palmar plate unfolded to support the head of the metacarpal. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. MCP Joints II-V, arthrokinematics “Joint play” is an accessory motion. This movement of one articular surface on another is not under voluntary control and must be tested by the application of an external force. Motion in joint play is usually nonaxial. During abduction of the index MCP joint, for instance, the proximal phalanx rolls and slides in a radial direction. The extent of active abduction and adduction at the MCP joints is significantly less when the motions are performed in full flexion compared with full extension, because of the collateral ligaments are taut and the stored passive increases the compression force between the joint surfaces, thereby reducing available motion. But there is joint play SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Interphalangeal Joints II-V (PIP, DIP) Each of the PIP and DIP joints of the fingers is composed of the head of a phalanx and the base of the phalanx distal to it. Each IP joint is a hinge joint with one degree of freedom (flexion/extension), a joint capsule, a volar plate, and two collateral ligaments. The base of each middle and distal phalanx has two shallow concave facets with a central ridge. The distal phalanxes sit on the pulley-shaped head of the phalanxes proximal to it. Each IP joint is surrounded by a relatively loose capsule that is reinforced collateral ligaments, which significantly limits abduction and adduction motion. The palmar plate limits hyperextension of the IP joint and it serves as the attachment for the base of the fibrous digital sheath—the houses the tendons of the extrinsic finger flexor muscles throughout the digits, and extend the surface, so improve the congruency and stability. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. IP Joints II-V (PIP, DIP), osteokinematics The index is flexed in a strictly sagittal plane (P) passing near the base of the thenar eminence. The axes of the fingers during flexion all converge at a point corresponding to the distal margin of the 'radial pulse'. The axes of flexion of the MP and IP joints are not unchanging. They are perpendicular to the joint in fuIl extension and become progressively more oblique during flexion. This change is due to the asymmetry of the articular surfaces of the MP and the IP joints and also because the collateral ligaments are stretched differentially. The greater available range ulnarly also produces a grip that is tighter, or has greater closure, on the ulnar side of the hand. The PIP joints flex ~100-120°(PRoM 135°). The DIP joints allow less flexion, ~80-90°. Extension is occurring from flexion back to the neutral (0°). SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. IP Joints II-V (PIP, DIP), arthrokinematics Similarities in joint structure cause similar arthrokinematics at the PIP and DIP joints. During active flexion at the PIP joint, for instance, the concave base of the middle phalanx rolls and slides in a palmar direction by the pull of the extrinsic finger flexors. During flexion, the passive tension created in the dorsal capsule helps guide and stabilize the roll-and-slide arthrokinematics. PIP is stabile in both full extension and flexion, only in semiflexed position allows some joint play. DIP can be passively hyperextended 30° beyond the neutral position. And there is also some passive ab- and adduction. The closepacked position of the PIP and DIP joints is considered to be full extension, most likely because of the stretch placed on the palmar plates. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Muscular Function of the Hand Muscles that control the digits are classified as either extrinsic or intrinsic to the hand. Extrinsic muscles have their proximal attachments in the forearm or, in some cases, as far proximal as the epicondyles of the humerus. Intrinsic muscles, in contrast, have both their proximal and their distal attachments within the hand. Most active movements of the hand, such as opening and closing the fingers, require precise cooperation between the extrinsic and the intrinsic muscles of the hand and the muscles of the wrist. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Flexion of the fingers II-V - FDS The extrinsic flexor muscles of the digits are the flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP). The FDS is proximally located in the anterior forearm, just deep to the three wrist flexors and the pronator teres muscle. Its 4 tendons cross the wrist and enter the palmar aspect of the hand. At the level of the proximal phalanx, each tendon splits to allow passage of the tendon of the FDP. The two split parts of each tendon partially reunite, cross the PIP joint, and attach on the sides of the palmar aspect of the middle phalanx. The primary action of the FDS is to flex the PIP joints. This muscle, however, flexes all the joints (Radiocarpal, MCP, PIP) it crosses. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Flexion of the fingers II-V - FDS It is a weak flexor of the MCP joint only when the PIP joint is fully flexed. Its efficiency on PIP is maximal when the MCP joint is kept extended by contraction of the extensor digitorum (synergistic action). The FDS help to stabilize the MCP in neutral position in a synergistic action with EDC. During active finger flexion (as in grasp activities), the counterbalancing wrist extensor force is usually supplied by an active wrist extensor such as the ECRB muscle or, in some instances, the EDC muscle. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Flexion of the fingers II-V - FDP The muscle belly of the FDP is located in the deepest muscular plane of the forearm, deep to the FDS. Once in the digit, each tendon passes through the split tendon of the FDS. Each FDP tendon then attach distally to the palmar side of the base of the distal phalanx. The FDP is the sole flexor of the DIP joint, but this flexion is soon followed by flexion of PIP because there is no extensor to oppose this action. So to measure the strength of the FDP, the 2nd phalanx (P2) must be kept extended manually. When P1 and P2 are flexed to 90° the FDP is unable to flex P3 because it has become too slack for any useful contraction (insufficient). It works best when P, is kept extended by contraction of the extensor digitorum (antagonistic-synergistic action). It can assist flexing every joint it crosses (Radiocarpal, MCP, PIP, DIP). The radial extensors and the ED are stabilizing synergist of the flexors! SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Flexion of the fingers II-V – the pulleys The extrinsic flexor tendons of the digits travel to their distal attachment in protective fibro-osseous tunnels (digital sheaths). Within each digital sheath are bands of tissue called flexor pulleys. 5 annular pulleys exist for each finger, A1 to A5. The major pulleys (A2 and A4) attach to the shafts of the proximal and middle phalanges. The minor pulleys (A1, A3, and A5) attach directly to the palmar plate at each of the 3 joints within a finger. 3 less distinct cruciate pulleys (C1 to C3) exist. Flexor pulleys, palmar aponeurosis, and skin all share a similar function of holding the underlying tendons at a close distance to the joints. Without them the force of a strong contraction of the extrinsic finger flexors causes the tendon to pull away from the joint’s axis of rotation. So they have an important role in preventing bowstringing of the tendons. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Extension the of fingers II-V The extensor digitorum is the predominant finger extensor, originate from a common tendon off the lateral epicondyle of the humerus and the terminal tendon to insert into the base of the distal phalanx. In adition it has an excellent moment arm as a wrist extensor. The EDC is essentially an extensor of the MCP joint. It is a powerful extensor and active in all positions of the wrist, but its action is facilitated by flexion at the wrist. It extends P1 via the extensor expansion (1),which arises from the deep surface of the tendon, crosses the MCP joint and inserts at the base of P1. Its action on P2 via its median band (2) and on P3 via its two lateral bands (3) depends on the degree of tension in the tendon, so on the position of the wrist and on the degree of flexion at the MP joint: This action is appreciable only when the wrist is flexed (A). SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Extension the of fingers II-V It is partial and weak when the wrist is straight (B). It is nil when the wrist is extended (C). In effect the action of the EDC on P2 and P3 depends on the degree of tension in the digital flexors: If the flexors are taut because the wrist or the MP joint is extended, the EDC cannot by itself extend the two distal phalanges. If the flexors are relaxed by flexion of the wrist or of the MP joint, the EDC can easily extend the last two phalanges. The tendons of the extensor indicis and of the extensor digiti minimi behave in the same way as the EDC with which they blend. They allow the index and little fingers to be extended singly. There is an accessory movements produced by the EDC (A) abducts while the EI (B) adducts, but only when the interossei are inactivated by flexion of P2 and P3 and extension of P1. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Extensor Mechanism of the Fingers The attachment of the central and lateral bands into the phalanges allows the extensor digitorum to transfer extensor force distally throughout the entire finger. The most prominent feature of the proximal end of the extensor mechanism is the dorsal hood, assists the EDC muscle in extending the MCP joint. As a general rule, the intrinsic muscles of the hand (the lumbricals and interossei) attach into the extensor mechanism via the oblique fibers and the transverse fibers of the dorsal hood. Isolated contraction of the EDC produces hyperextension of the MCP joints. Only in the presence of activated intrinsic muscles of the fingers can the EDC fully extend the PIP and DIP joints. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Mesothenar - Interosseus Muscles The interosseus muscles are named according to their general location between the metacarpal bones. In general, the interossei act at the MCP joints to spread the digits apart (abduction) or bring them together (adduction). The 4 palmar interossei of the hand are single-headed muscles that occupy the palmar region of the interosseous spaces. The 3 PI to the fingers have their proximal attachments on the palmar surfaces and sides of the 2nd, 4rth, and 5th metacarpals. The muscles’ distal attachments include the oblique fibers of the dorsal hood, and the sides of the bases of the proximal phalanges. They adduct the 2nd, 4th, and 5th MCP joints toward the midline of the hand. The PI muscle to the thumb is likely a small part of the oblique head of the AddP or FPB, it is inconclusive. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Mesothenar - Interosseus Muscles The 4 dorsal interossei fill the dorsal sides of the interosseous spaces. They have a bipennate shape. The general rule is that the DI have distal attachments to the oblique fibers of the dorsal extensor hood, as well as to the sides of the bases of the proximal phalanges. Some distal attachments may blend with the palmar plate. With the index finger well stabilized, the first dorsal interosseus can assist the adductor pollicis in adducting the thumb at the CMC joint As a set, the dorsal interossei abduct the MCP joints of the index, middle, and ring fingers away from an the middle digit. Abduction of the fifth MCP joint is performed by the abductor digiti minimi of the hypothenar group. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Mesothenar - Interosseus Muscles In addition to abducting and adducting the fingers - the interossei acting in pairs -, and AbdDM provide an important source of dynamic stability to the MCP joints, and this interosseus musculature also controls the extent of axial rotation permitted at the MCP joints. The interossei, via their attachments into the extensor mechanism, pass dorsal to the IP joints of the fingers, therefore, contraction of the interossei flexes the MCP joints and extends the IP joints, but their actions depend on the degree of flexion of the MCP joint and the state of contraction of EDC: With the MCP extended by EDC, the extensor hood (a) is pulled over the MP joint. The lateral bands can be stretched (b) and extend P2 and P3. With the MCP joint flexed by EDC relaxation (a) and contraction of the lumbrical, the extensor hood slides over the dorsum of P1 (b), and the IO and the lumbrical acting on the extensor expansion strongly flex the MCP joint (primary flexor). SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Mesothenar - Interosseus Muscles There is a synergistic balance between the extensor actions of EDC and IO on P2 and P3: With the MCP joint flexed at 90° EDC is fully active on P2 ancl P3, as are the lumbricals, which retighten the lateral bands while lO are inactive. With the MCP joint in the intermediate position, ED and IO are synergistic. With the MCP joint extended EDC has no effect on P2 and P3, whereas IO are maximally active as they retighten the lateral bands. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Mesothenar - Lumbricals Muscles The lumbricals are 4 slender muscles that have a movable origin off the tendons of the flexor digitorum profundus. From their tendinous proximal attachments, the lumbricals course palmar to the deep transverse metacarpal ligament and then radial to the MCP joints. Distally, a typical lumbrical attaches to the oblique fibers of the dorsal hood. The function of the lumbricals is that their contraction produces flexion at the MCP joints and extension at the PIP and DIP joints. The lumbrical are very rich source of muscle spindles—sensory organs that monitor changes in the length of the muscle. This suggests a role in providing proprioceptive sensory feedback during complex movements. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Mesothenar - Lumbricals Muscles By also attaching to the tendons of the flexor digitorum profundus, the lumbricals are in position to help coordinate the interactions between the intrinsic and extrinsic muscles. They flex MCP and extend PIP and DIP but, unlike IO, they act whatever the degree of flexion at the MCP joint. They are thus extremely valuable for finger movements. They owe their efficiency to two anatomical factors: Lying more anteriorly than IO and palmar to the transverse metacarpal ligament, they form a 35° angle of traction with P1, so they flex the MP joint even when it is hyperextended. They are thus the flexor starters of P1, since the IO only act secondarily on the dorsal expansion. They are inserted into the lateral bands distal to the extensor hood, which does not bind down their tendons; hence their ability to retighten the extensors of P2 and P3, regardless of the degree of flexion of the MCP joint. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Function The everyday rnovements of the fingers: During writing: When the pencil is moved forwards, the interosseus flexes MCP and extends P2 and P3. When the pencil is brought back, EDC extends MCP and FDS flexes P2. When the hand assumes the shape of a hook FDS and FDP both contract and the interossei relax. This movement is essential for rock climbers as they clutch at the vertical face of a rock. During tapping movements of the fingers EDC extends MCP, while FDS and FDP flex P2 and P3. This is the initial position of the pianist's fingers. The finger strikes the key as the interossei and lumbricals contract and flex the MCP joint, while EDC relaxes. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The Hypothenar The muscles of the hypothenar eminence are the flexor digiti minimi, abductor digiti minimi, opponens digiti minimi, and palmaris brevis. Function of these muscles is to raise and “cup” the ulnar border of the hand. This action deepens the distal transverse arch, and enhances digital contact with held objects. The ODM opposes, the 5th metacarpal toward the middle digit. PB tightens the palmar aponeurosis while contracting, deepening the concavity of the palm, helps to position and stabilize the palm during a spherical power grip. The AbdDM has extensive proximal attachments from the pisohamate ligament, pisiform bone, and flexor carpi ulnaris tendon. During resisted or rapid abduction of the small finger, the FCU contracts to stabilize the pisiform, this can deviate ulnarly the wrist, whichis opposed by the AbPL. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. Actions of muscles that cross the joints of the small finger SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The thumb – I. Carpometacarpal Joint The CMC joint of the thumb is between the trapezium and the base of 1st metacarpal. This unique saddle shape joint with 2 DoF flexion/extension and abduction/adduction, allows the thumb to fully oppose, thereby easily contacting the palmar tips of the other digits, which greatly enhances the dexterity of human prehension. The thumb is able to encircle objects held within the palm. The joint also permits some axial rotation (~17°), which occurs concurrently with the other motions, because the joint has a spherical portion located near the radial tubercle of the trapezium. The net effect at this joint is a circumduction motion termed opposition. The saddle-shaped portion of the trapezium is concave in the sagittal plane (abd/add) and convex in the frontal plane (flex/ext).The spherical portion is convex in all directions. The base of the 1st metacarpal has a reciprocal shape to that of the trapezium. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The thumb – I. CMC Joint The capsule of the CMC joint is relatively lax but is reinforced by radial, ulnar, volar, and dorsal ligaments. There is an intermetacarpal ligament that helps preventing extremes of radial and dorsal displacement of the base of the 1st metacarpal joint. The dorsoradial and anterior oblique ligaments are reported to be key stabilizers of the CMC joint. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The thumb – I. CMC Joint arthrokinematics Unusually the Abduction and adduction occur generally in the sagittal plane, and flexion and extension occur generally in the frontal plane. Maximum abduction positions the thumb metacarpal about 45° (40-50°) anterior to the plane of the palm, In the position of adduction of the CMC joint, the thumb lies within the plane of the hand. During abduction, the convex articular surface of the metacarpal rolls in a palmar direction and slides dorsally on the concave surface of the trapezium. Full abduction at the CMC joint elongates the adductor pollicis muscle and most ligaments at the CMC joint. The arthrokinematics of adduction occur in the reverse order from those described for abduction. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The thumb – I. CMC Joint arthrokinematics In the anatomic position, the CMC joint can be extended an additional 10-15°. From full extension the thumb metacarpal flexes across the palm about 45-50°. During flexion, the concave surface of the metacarpal rolls and slides in an ulnar (medial) direction, and there is a slight medial rotation of the metacarpal. Full flexion elongates tissues such as the radial collateral ligament. During extension of the CMC joint, the concave metacarpal rolls and slides in a lateral (radial) direction on the trapezium and there is a slight lateral rotation. Full extension stretches ligaments situated on the ulnar side of the joint, such as the anterior oblique ligament. These rotations are not considered a third degree of freedom because it cannot be executed independently of the other motions. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The thumb – I. CMC Joint opposition The full arc of opposition divided into two phases. In phase 1 the thumb metacarpal abducts. In phase 2 the abducted metacarpal flexes and medially rotates across the palm toward the small finger. It stretches the posterior oblique ligament, and in addition to activation of muscles such as the OP, guides much of the kinematics of the flexion–medial rotation phase. The last few degrees continue to stretch capsular ligaments, and the radial collateral ligament. Forces from both activated muscle and stretched ligaments are promoting maximal congruity and stability of the CMC joint in full opposition, which is considered the close-packed position. Reposition of the CMC joint returns the metacarpal from full opposition back to the anatomic position. This motion involves arthrokinematics of both adduction and extension–lateral rotation of the thumb metacarpal. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 27. The thumb – I. MCP Joint This joint consists of the articulation between the convex head of the 1st metacarpal and the concave proximal surface of the proximal phalanx of the thumb. The basic structure and arthrokinematics of the I. MCP joint are sesamoid similar to those of the fingers. bone But differences exist in osteokinematics. Active and passive motions at the I. MCP joint are significantly less than those at the MCP joints of the fingers. For all practical purposes, the I. MCP joint allows only 1 DoF: flexion and extension within the frontal plane. From full extension, the proximal phalanx of the thumb can actively flex about 60° across the palm toward the middle digit, while passive flexion can attain 80°. Revers motion back to neutral is the extension. No active, and little passive hyperextension is possible normally. The metacarpal head moves palmar direction against the proximal phalanx. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The thumb – I. MCP Joint Active abduction and adduction of the I. MCP joint are very limited and therefore are considered accessory motions. Collateral ligaments and the bony configuration, and the muscles (AbPL, AbPB, FPB) are responsible for restricting these motions and provide longitudinal stability the entire ray of the thumb. The I. MP joint is reinforced extracapsularly on its volar surface by palmar plate and 2 sesamoid bones. These are maintained in position by fibers from the collateral ligaments and by an intersesamoid ligament. There is also some accessory rotation. Accessory motions can only be initiated in an extended or semi- reflected position. Full flexion is the close packed joint position. Accessory motions play an important role in certain grip actions. In a closed kinematic chain, the accessory motions of the CMC and MCP joints are combined. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The thumb – I. IP Joint The interphalangeal (IP) joint of the thumb is a hinge joint articulation between the head of the proximal phalanx and the base of the distal phalanx. The structure and function are similar to those of the IP joints of the fingers. Motion is limited primarily to 1 DoF. The active flexion about 70°-80°, but passively can be 90°. The joint can be actively extend 5-10° and passively beyond neutral to about 20° (30°). This motion is often employed to apply a force between the pad of the thumb and an object, such as pushing a thumbtack into a board. There is also some accessory medial rotation. This component to the overall movement of the opposition of the thumb. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28.  Lateral view (right) Thumb musculature They fall into 2 groups: the extrinsic or long muscles: The AbPL (1), inserted into the A-L aspect of the base of the 1st metacarpal (M1). The EPB (2) running parallel to the previous muscle and inserted into the base of proximal phalangs (P1). The EPL (3), inserted into the dorsal aspect of the base of the distal phalangs (P2). Their 3 tendons, on the dorsal and lateral aspects of the thumb, bound a triangular space with its apex located distally (anatomical snuffbox). Functionally, each of these 3 muscles acts on a particular segment of the thumb and all 3 are extensors, whereas the FPL (4) is a palmar muscle. It traverses the carpal tunnel, runs between the 2 heads of the FPB and between the 2 sesamoid bones and inserted into the palmar aspect of the base of P2. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29.  Anterior view (right) Thumb musculature and the 2 groups of intrinsic muscles : The lateral group consists of 3 muscles in the thenar eminence, supplied by the median nerve, from deep to superficial: The FPB (5), arises by 2 heads, 1 from the carpal tunnel and the other from the flexor retinaculum and the tubercle of TZ. Its single tendon is inserted into the outer sesamoid bone and the lateral tubercle of the base of P1. The OP (6), arising from the flexor retinaculum runs to the anterior aspect of M1. The AbPB (7) arises from the flexor retinaculum and the crest of the scaphoid. It is inserted into the lateral tubercle of the base of P1, but join the dorsal hood of the thumb along with the 1st anterior interosseus (9). The FPB and the AbPB are called the lateral sesamoid muscles. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28.  Anterior view (right) Thumb Musculature The medial group consists of 2 muscles supplied by the ulnar nerve at the 1st osseus place and inserted into the medial side of the MCP joint: the 1st palmar interosseus (9) inserted by tendon into the medial tubercle of the base of P1 and into the dorsal hood. the AddP(8) with its 2 (transverse and oblique) heads converging by a common tendon upon its insertion into the medial sesamoid bone and the medial aspect of P1. For reasons of symmetry these two muscles are called the medial sesamoid muscles and are synergists- antagonists of the lateral sesamoid muscles. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – AbPL (1) The AbPL moves CMC (M1) laterally and anteriorly. Therefore it produces both slight abduction and strong extension (primary) of M1, especially when the wrist is slightly flexed. When the wrist is not stabilized by the radial extensors, especially the ECRB, the AbPL also flexes the wrist; When the M1 stabilized in adduction it has weak radial deviating effect. Formes a force couple with the lateral group of intrinsic muscles and plays a very important role in opposition. (1st stage of the opposition – extension of M1) SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – EPB (2) It has 2 actions: It extends P1 over M1 (MCP joint) - primary function. It moves M1 and the thumb directly laterally, extension-adduction at the CMC (TM) joint. For pure extension to occur, the wrist joint must be stabilized by the synergistic contraction of the FCU and ECU; otherwise the EPB also produces radial deviation at the wrist. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – EPL (3) It has 3 actions: It extends P2 over P1 (IP joint) – primary function. It extends P1 over M1 (MCP joint). It moves M1 medially - 'closes' the 1st interosseous space (flexion) and posteriorly - adduction of M1 because it is bent at the Lister's tubercle. It helps to flatten the palm, so EPL is an antagonist of the muscles of opposition. The EPL forms a functional set of antagonistic- synergistic muscles with the lateral thenar group. If the thenar muscles are paralyzed the thumb is irresistibly moved medially and posteriorly. EPL can extend the wrist, unless cancelled by the action of the FCR. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – FPL (4) The FPL flexes P2 over P1 (IP joint) – primary function. For flexion of P2 to occur alone, the EPB must contract and prevent flexion of P1 (synergistic action). Secondarily it flexes P1 over M1 (MCP joint). It has indispensable role in terminal prehension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – FPB (5) The FPB takes part in the overall movements produced by the lateral group of thenar muscles. When it is made to contract on its own, it is primarily brings the pulp of the thumb into opposition with the last 2 digits. It has a similar action to that of the opponens. It also flexes P1 on M1 (MCP) with the help of the AbPB (synergists), another medial sesamoid muscle, and of the 1st palmar interosseus. It produces a marked degree of medial rotation. It has an effect of flexion and abduction on the CMC joint. The combined action of the lateral thenar muscles produces opposition of the thumb with the help of the AbPL. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – OP (6) The OP has 3 actions, both primary: Abduction of M1 with respect to the carpus (CMC), especially in the long path of opposition. Flexion, bringing M1 and M2 closer together during maximal movements of opposition. Axial rotation in medial direction. These 3 simultaneous movements are essential for opposition. The opponens therefore is active in every type of grip involving the thumb. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – AbPB (7) The AbPB pulls farthest apart M1 and M2 at the end of opposition: It moves M1 (CMC) anteriorly (abduction) and medially (flexion) during the opposition. It produces flexion of P1 on M1 (MCP) - primarily. It causes medial rotation of P1. Finally, it extends P2 on P1 (IP) via an expansion, which joins the EPL. When it contracts on its own, it brings the pulp of the thumb into contact with the index and the middle finger. It is thus an essential muscle for opposition. As shown previously, it forms with the AbPL a force couple essential for opposition. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – AdP (8) The Adp moves CMC. The direction of the movement depends on the starting-point of M1 It is effective adductor or flexor if M1 starts from a position of full abduction or full extension (1, 4), but it can be an abductor or an extensor as well. It is active during full palmar, pulp-to-pulp, and especially during pulp-to-side prehension. On P1 (MCP) it has a slight flexion and lateral rotation (curved white arrow) action. On P2 (IP) it acts as an extensor insofar as its insertion blends with that of the first interosseus. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb muscules one by one – I. PIO The first palmar interosseus has very similar actions then AdP: adduction, i.e. M1 (CMC) is drawn towards the axis of the hand. flexion of P1 (MCP) via the dorsal extensor expansion. extension of P2 (IP) via the lateral extensor expansion. The global contraction of the medial thenar muscles brings the pulp of the thumb into contact with the radial aspect of P1 of the index. These muscles, supplied by the ulnar nerve, are essential for holding an object firmly between the thumb and the index finger. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Thumb - opposition It is a comlex motion. For opposition to start, M1 must be raised directly above the plane of the palm. During this motion the plane of the nail is turned at an angle of 90- 120°. This action is produced by the functional couple of AbPL and the thenar muscles in the following 2 stages: In the 1st stage the AdPL abducts and extends M1 (CMC) anteriorly and laterally. In the 2nd stage, from that position the lateral group of muscles, i.e. FPB , AbPB and OP, tilt M1 flexion and slight adduction while rotating it slightly on its long axis. These stages in a reality occur simultaneously and the final position of M1 is the resultant of the simultaneous forces exerted by these two sets of muscles. The musculus adductor pollicis acts at the end of the range of motion when the thumb is brought close to the IV, V finger. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Actions of Muscles That Cross the Joints of the Thumb SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29.  The modes of prehension SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The prehension Prehension describes the ability of the fingers and thumb to grasp or to seize, often for holding, securing, and picking up objects. It classified based on the need for force: power (high force with less regard to the exactness of the task, the fingers are flexed, the thumb used for stabilization ) or precision (high level of exactness with low force, the fingers and the thumb hold the object, the palm is not involved). Both can be differentiated on the basis of the dynamic and static. Power grip is the result of a sequence of (1) opening the hand, (2) positioning the fingers, (3) bringing the fingers to the object, and (4) maintaining a static phase that actually the grip and the object can be moved through the space. The precision handling shares the first 3 steps of the sequence but does not contain a static phase at all. The fingers and thumb grasp the object for the purpose of manipulating with it. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. The power grip The fingers clamp on and hold an object into the palm, the assume a position of sustained flexion that varies in degree with the size, shape, and weight of the object. The palm is likely to contour to the object as the palmar arches form around it. The thumb may serve as an additional surface to the finger- palm vise by adducting against the object. 4 type of power grip are: cylindrical grip, spherical grip, Hook grip, and lateral prehension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 28. Cylindrical Grip Cylindrical grip almost exclusively involves use of the flexors. The function in the fingers is performed largely by the FDP muscle, especially in the dynamic closing action of the fingers. In the static phase, the FDS muscle assists when the intensity of the grip requires greater force. The interossei muscles are considered to be functioning primarily as MCP joint flexors and abductors/adductors. They ulnarly deviate the MCP joint (adduction for the index and abduction for the middle, ring, and little fingers) to direct the distal phalanges of the fingers toward the thumb, for the position that optimizes the force of the long finger flexors and achieve a better alignment of the object in the hand. This combination of MCP joint flexion and ulnar deviation also tends to produce ulnar subluxation forces at the MCP joint. This forces are counteracted by the radial collateral ligaments, by the annular pulleys that anchor the flexor long tendons in place, and by the sagittal bands that connect the volar structures to the extensor mechanism. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Cylindrical Grip Active or passive tension in the EDC muscle can further stabilize the restraining mechanisms, as well as increase joint compression and enhance overall joint stability during power grip. Thumb position is depends on the size and the shape of the object. The thumb usually comes around the object, then flexes and adducts to close the vise, for this the FPL and thenar muscles are all active. The activity of the thenar muscles vary with the width of the web space, with the CMC rotation required, and with increased pressure or resistance. In general, during power grip the activity in the AdP muscle greater, than in precision handling. The EPL muscle may active as an MP joint stabilizer or as an adductor. Muscles of the hypothenar usually are active. The ADM functions as a proximal IO muscle to flex and abduct (ulnarly deviate) the 5th MP joint. The ODM and the FDM muscles are active in direct proportion to the amount of abduction and rotation of the 1st metacarpal. In fact, increased activity of the OP muscle automatically results in increased activity of the ODM and FDM muscles. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Cylindrical Grip Cylindrical grip is typically performed with the wrist in neutral flexion/extension and slight ulnar deviation (finger flexors force optimal). The heavier an object is, the more likely it is that the wrist will ulnarly deviate. In addition, a strong contraction of the FCU muscle at the wrist will increase tension on the transvers carpal ligament (TCL). This provides a more stable base for the active hypothenar muscles that originate from that ligament. The ring and little fingers can generate only 70% of the flexor force of the index and middle fingers. They seem to serve as weaker but more mobile assists to the more stable and stronger index and middle fingers. They adjust more to the shape of the object. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Spherical Grip Spherical grip is similar in most respects to cylindrical grip. The extrinsic finger and thumb flexors and the thenar muscles follow similar patterns of activity. The main distinction is the greater spread of the fingers to encompass the object. This evokes more interosseous activity than in other forms of power grip. The MCP joints do not deviate in the same ulnar direction, but tend to abduct. The phalanges are not parallel to each other, as they are in cylindrical grip. The MCP joint abductors must be joined by the adductors to stabilize the joints that are in the loose-packed position of semiflexion. Although flexor activity predominates in the digits, the extensors do have a role. The extensors not only provide a balancing force for the flexors but also are essential for smooth and controlled opening of the hand and release of the object. Opening the hand during object approach and object release is primarily an extensor function, calling in the lumbrical, EDC, and thumb extrinsic muscles. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Hook Grip Hook grip is actually a specialized form of power grip, because it is a function primarily of the fingers. It may include the palm but never includes the thumb. It can be sustained for prolonged periods of time, as anyone who has carried a briefcase or hung onto a commuter strap on a bus can attest. The major muscular activity is provided by the FDP and FDS muscles. The load sustained depends on the position of the load in relation to the phalanges. If the load is carried more distally so that DIP flexion is mandatory, the FDP muscle must participate. If the load is carried more in the middle of the fingers, the FDS muscle may be sufficient. In hook grip, the thumb is held in moderate to full extension by thumb extrinsic muscles. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Lateral Prehension Lateral prehension is a rather unique form of grasp. Contact occurs between two adjacent fingers. The MCP and IP joints are usually maintained in extension as the contiguous MCP joints simultaneously abduct and adduct. This is the only form of prehension in which the extensor musculature predominate in the maintenance of the posture; the EDC and the lumbrical muscles are active to extend the MCP and IP joints, and MCP joint abduction and adduction are performed by the interossei muscles. It is included of power grip because lateral grip involves the static holding of an object that is then moved by the more proximal joints of the upper extremity. Although not a “powerful” grip, neither is it used to manipulate objects in the hand. It is generally typified by the holding of a cigarette. Thumb amputees can develop this grip to an astonishing degree. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Precision Handling The positions and muscular requirements of precision handling are somewhat more variable than those of power grip, require much finer motor control, and are more dependent on intact sensation. The thumb serves as one “jaw” of what has been termed a “two-jaw chuck”; the thumb is generally abducted and rotated from the palm. The 2nd and opposing “jaw” is formed by the distal tip, the pad, or the side of a finger. When 2 fingers oppose the thumb, it is called a three-jaw chuck. The 3 varieties of precision handling are: pad-to-pad prehension, tip-to-tip prehension, and pad-to-side prehension. Each tends to be a dynamic function with little static holding. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Pad-to-Pad Prehension Pad-to-pad prehension involves opposition of the pulp, of the thumb to the pulp, of the finger. The pad of the distal phalanxes has the greatest concentration of tactile corpuscles found in the body. Of all forms of precision handling, 80% are considered to fall into that category. The finger used in two- jaw chuck is usually the index; in three-jaw chuck, the middle finger is added. The MCP and PIP joints of the fingers are partially flexed, the DIP may be fully extended or in slight flexion. When the DIP is extended, the FDS muscle perform the function alone. Extension of the DIP is caused passively by flexion of the middle phalanx (FDS) against the thumb in a closed kinematic chain. When partial DIP flexion is required the FDP muscle must be active. Interosseous activity is present both to supplement MCP joint flexor force and to provide the MCP joint abduction or adduction required in manipulation. In dynamic manipulation, the VI and DI muscles work reciprocally, rather than in the synergistic co-contraction observed during power grip. In a static but firm pad-to-pad pinch, the interossei muscles may again co-contract. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Pad-to-Pad Prehension The thumb is held in CMC flexion, abduction, and rotation (opposition). The first MCP and IP joints may be partially flexed or fully extended. The thenar muscle control is provided by the OP, FPB, and APB muscles, each of which is innervated by the median nerve. The AdP activity (ulnar nerve) increases with increased pressure of pinch. Flexion of the distal phalanx, when required, is provided by the FDP muscle for the finger and by the FPL muscle for the thumb. As is found in power grip, the extensor musculature is used for opening the hand to grasp, for release, and for stabilization when necessary. In the thumb, the EPL muscle may be used to maintain the IP joint in extension when contact is light and on the proximal pad. Synergistic wrist activity must also occur to balance the forces created by the FDS and FDP muscles. The wrist is more typically held in neutral radial/ulnar deviation and slight extension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Tip-to-Tip Prehension The muscular activity in tip-to-tip prehension is nearly identical to that of pad- to-pad prehension, but there are some key differences. The IP joints of the finger and thumb must have the range and available muscle force to create nearly full joint flexion. The MCP joint of the opposing finger must also be ulnarly deviated (adducted - with fingertip pointed radially) to present the tip of the finger to the thumb. In the remaining fingers (III-V), MCP abduction produces ulnar deviation. If the flexion range for the distal phalanx in either the opposing finger or the thumb is not available, or if the active force for IP flexion and MCP joint ulnar deviation cannot be provided, tip-to-tip prehension cannot be performed effectively. As the most precise form of grasp, it is also the most easily disturbed. It has the same muscular requirements as pad-to-pad prehension in both fingers and thumb. In addition, activity of the FDP, FPL, and interossei muscles is a necessity here, whereas they are not in pad-to-pad prehension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Pad-to-Side Prehension This is the least precise of the forms of precision handling. It differs from the other forms of precision handling only in that the thumb is more adducted and less rotated. The activity level of the FPB muscle increases and that of the OP muscle decreases, in comparison with tip-to-tip prehension. Activity of the AdP muscle also increases over that in either tip-to-tip or pad-to- pad prehension. Slight flexion of the distal phalanx (IP joint) of the thumb is required. The least precise of the forms of precision handling, because when the hand muscles are paralyzed as they would be in a person with a spinal cord injury above the C7 level, active wrist extensors (assuming they are present) can create pad-to-side prehension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Pad-to-Side Prehension and tenodesis action Wrist extension provided by at least one of the intact and active ECU, ECRL, and ECRB muscles create the force needed to flex the MCP and IP joints of the fingers and thumb by generating passive tension in the extrinsic finger flexor tendons as the tendons are stretched. The grip may be released by relaxing the wrist extensor muscles and allowing gravity to flex the wrist. As the wrist flexes, the tendons of the FDS and FDP muscles become slack, and the tendons of the EDC (with EIP and EDM) and EPL become stretched. The passive tension in the long finger extensors in a dropped wrist is partially extending both MCP and IP joints. The phenomenon of using active wrist extension to close the fingers and passive wrist flexion to open the fingers is known as tenodesis. This can also achieve a cylindrical grip. The flexors must be loose enough to permit the partially flexed fingers to surround the object in wrist flexion (passive insufficiency) while still being tight enough to hold the object when the wrist is extended, in a person without any active control of finger or thumb. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Opening the hand: finger extension Opening the hand is often performed in preparation for grasp. The primary extensors of the fingers are the EDC and the intrinsic muscles (L and IO). The EDC exerting a force on the extensor mechanism, pulling the MCP joint toward extension. The intrinsic muscles direct effect is provided by the proximal pull on the extensor mechanism; the indirect effect is provided by the production of a flexion torque at the MCP joint prevents the EDC from hyperextending the MCP joint. Only with the MCP joint blocked from being hyperextended can the EDC effectively tense the extensor mechanism to completely extend the IP joints. Activation of the wrist flexors accompanies active (rapid) finger extension. The wrist flexors offset the large extension potential of the EDC at the wrist. Slight flexion helps maintain optimal length of the EDC during active finger extension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Closing the hand: finger flexion The muscles used to close the hand depend in part on the specific joints that need to be flexed and on the force requirements of the action. Flexing the fingers against resistance or at relatively high speed requires activation of the FDP, FDS, and, to a lesser extent, the IO muscles. The lumbricals passively assist with the action. During active flexion, the lumbricals are stretched in a proximal direction because of the contracting FDP and at the same time are stretched in a distal direction owing to the distal migration of the extensor mechanism. This stretch generates a passive flexion torque across the MCP joint. Normally, the PIP and DIP joints flex first, followed closely in time by the MCP joints. Paralysis of the intrinsic muscles alters the chronologic sequence and flexion at the MCP joints is significantly delayed. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29. Closing the hand: finger flexion Making a strong fist requires strong synergistic activation from the wrist extensor muscles. The primary function of the wrist extensors, including the EDC, is to neutralize the strong wrist flexion tendency of the activated extrinsic finger flexors. The wrist extension also helps maintain more optimal length of the extrinsic finger flexors. If the wrist extensors are paralyzed, attempts at making a fist result a wrist and finger flexion. When combined with the increased passive tension in the overstretched extensor digitorum, the overshortened, activated finger flexors are incapable of producing an effective grip. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 09. 29.