Hand Kinetics Pt. 1 PDF

Hand kinetics pt.1 Dr.Om r Ahmed H ss n Te ching ssist nt Biomech nics unit-MUST a a a a a a a ...

Hand kinetics pt.1 Dr.Om r Ahmed H ss n Te ching ssist nt Biomech nics unit-MUST a a a a a a a  Topic Mapping -Muscles that control the digits (Classi ication-Flexors- Extensors) -Flexor pulleys (Anatomy - Function ) -Extensor digitorum as a proximal stabilizer during active inger lexion -Tenodesis action -Wrist extensors role in inger lexion f f f f f Digits musculature  Classi ication of the muscles which control digits -Extrinsic muscles : have their proximal attachments in the forearm or humerus epicondyles and their distal attachments in the hand -Intrinsic muscles : have their proximal and distal attachments within the hand f Extrinsic exors of the digits fl  What are they ? What are the extrinsic lexors of the digits ? -Flexor digitorum super icialis (FDS) -Flexor digitorum profundus (FDP) -Flexor pollicis longus (FPL) These muscles have extensive proximal attachments from the medial epicondyle of the humerus and forearm. f f  A closer look into : FDS Flexor digitorum super ici lis Its four tendons cross the wrist and enter the palmar aspect of the hand and split to attach to PIP joints -Its primary action is to lex PIP joints. However, It lexes all the joints it crosses (including the wrist). -Each tendon can be controlled independently of the other except for small ingers — It is evident at the index inger f f a f f f  Flexor digitorum super ici lis (FDS) f a  A closer look into : FDP Flexor digitorum profundus -Its 4 tendons runs along with the FDS tendons but the FDP is the only one to reach the DIP so it is considered the sole lexor of the DIP -Its tendon to the index inger can also be controlled independently -The remaining 3 tendons are interconnected through muscular fasiculi which inhibits the islolated DIP lexion of a single inger f f f f  A closer look into : FPL Flexor pollicis longus -Attach to the base of distal phalanx of the thumb -So it is the sole lexor of IP joint of the thumb f Extrinsic ngers extensors fi  Who are they ? -Extensor digitorum -Extensor incidis -Extensor digiti minimi  A return to the map The extensor digitorum is the predominant inger extensor according to its cross-sectional area -It is also has an excellent moment arm as a wrist extensor f  Action of the extrinsic inger extensors Especi lly the extensor digitorum Isolated contraction of the extensor digitorum produces hyper- extension of the MCP joints. -When intrinsic inger muscles are active, the extensor digitorum can fully extend the PIP and DIP joints. a f f  Topic Mapping -Muscles that control the digits (Classi ication-Flexors- Extensors) -Flexor pulleys (Anatomy - Function ) -Extensor digitorum as a proximal stabilizer during active inger lexion -Tenodesis action -Wrist extensors role in inger lexion f f f f f Flexor pulleys  Once upon a time … There was a sheath ! Fibrous digit l she th.. Wh t is it ? The extrinsic lexor tendons of the digits travel to their distal attachment in protective ibro-osseous tunnels known as ibrous digital sheaths -These sheaths starts proximally as a continuation of the thick aponeurosis just under the skin of the palm (Palmar aponeurosis pulley). a a f a f f  Palmar plate : Ligamentous-like structure consist of dense, thick ibrocartilage located palmar to each joint within the inger f f  And then there was Flexor Pulley ! Throughout the length of each digit, the digital sheaths are anchored to the phalanges and the palmar plates -And there is a thickened areas in the ibrous digital sheath or bands of tissue are called FLEXOR PULLEYS f  Flexor pulleys : General classi ication 1-Palmar aponeurosis pulley 2-Annular pulleys (Major and Minor) A1 to A5 3-Cruciate pulleys. C1 to C3 f  Flexor pulleys : 1-Annular pulleys M jor pulleys Major Pulleys : - A2 and A4 -Attach to the shafts of the proximal and middle phalanges. a  Flexor pulleys : 1-Annular pulleys Minor pulleys Minor Pulleys : - A1, A3 and A5 -Attach directly to the palmar plate at each of the three joints within a inger f  Flexor pulleys : 2-Cruciate pulleys Cruciate Pulleys : - C1 : Between A2 and A3 - C2 : Between A3 and A4 -C3 : Between A4 and A5  Flexor pulleys : 2-Cruciate pulleys Description and function : -Crisscross (Crossing ibers )between the components of annular pulleys at regions where the digital sheaths bend during lexion -Attach directly to the palmar plate at each of the three joints within a inger (Like the minor pulleys) -They provide the necessary lexibility for the approximate annular pulley at lexion and also maintaining integrity of the lexor sheaths. f f f f f f  Flexor pulleys : Function The main function is holding the underlying tendons at a relatively close distance to the joints. This prevents the force of a strong contraction of the extrinsic inger lexors to cause the tendon to pull away from the joint’s axis of rotation — Bowstringing f f  Topic Mapping -Muscles that control the digits (Classi ication-Flexors- Extensors) -Flexor pulleys (Anatomy - Function ) -Extensor digitorum as a proximal stabilizer during active inger lexion -Tenodesis action -Wrist extensors role in inger lexion f f f f f  Extensor digitorum as a proximal stabilizers during active nger exion fi fl  A return to FDS The essenti l presence of proxim l st bilizer Consider the lexor digitorum super icialis performing isolated PIP joint lexion.The extensor digitorum must act as a proximal stabilizer to prevent the lexor digitorum super icialis from lexing the MCP joint and the wrist. f a f f a a a f f f  A return to FDS Why do we need this proxim l st bility so b dly ?? Because the lexor moment arm length of the lexor digitorum super icialis progressively increases at the more proximal joints, a relatively small force applied to a distal joint is ampli ied to a greater torque at the more proximal joints. The greater the force produced by the lexor digitorum super icialis, the greater the force demands placed on the proximal stabilizers f f f f a a a f f  Topic Mapping -Muscles that control the digits (Classi ication-Flexors- Extensors) -Flexor pulleys (Anatomy - Function ) -Extensor digitorum as a proximal stabilizer during active inger lexion -Tenodesis action -Wrist extensors role in inger lexion f f f f f Tenodesis Action  Secondary muscles perk As you previously know, The extrinsic lexors of the digits are secondary set which also attaches to the wrist. So,The position of the wrist alters the length and accordingly the passive tension in these muscles. That can appreciated in the passive lexion of the ingers and thumb during active wrist extension f f f  Digits joins the party in lexion The digits automatically lex with wrist extension because of the increased passive tension in the stretched digital lexor muscles.(Which are also wrist lexors) This is the tenodesis action Because when a polyarticular muscle stretches across one joint it creates passive movements (tension) across the other joints. f f f f  Tenodesis, How much ? The amount of passive lexion of the ingers caused by the tenodesis action is surprisingly LARGE, Full active wrist extension produces : - DIP lexion 20 deg -PIP lexion 50 deg -MCP lexion 35 deg f f f f f  A Reverse Tenodesis ? In the position of full wrist lexion, the ingers, most notably the index, passively extend because of a similar tenodesis action of the stretched extrinsic digital extensor muscles. (Which are also wrist extensors) f f  Topic Mapping -Muscles that control the digits (Classi ication-Flexors- Extensors) -Flexor pulleys (Anatomy - Function ) -Extensor digitorum as a proximal stabilizer during active inger lexion -Tenodesis action -Wrist extensors role in inger lexion f f f f f Function of Wrist Extensors during Finger Flexion  Return to the wrist kinetics -Making a strong ist requires strong synergistic activation from the wrist extensor muscles (ECRB) -Wrist extensor activity can be veri ied by palpating the dorsum of the forearm while a ist is made -the primary function of the wrist extensors, including the extensor digitorum, is to neutralize the strong wrist lexion tendency of the activated extrinsic inger lexor muscles. f f f f f f  Return to the wrist kinetics -While the ingers are actively lexing, wrist extension also helps maintain more optimal length of the extrinsic inger lexors. -If the wrist extensors are paralyzed, attempts at making a ist result in a posture of wrist lexion and inger lexion f f f f f f f f  Topic Mapping -Muscles that control the digits (Classi ication-Flexors- Extensors) -Flexor pulleys (Anatomy - Function ) -Extensor digitorum as a proximal stabilizer during active inger lexion -Tenodesis action -Wrist extensors role in inger lexion f f f f f  Thank you See you in part 2