Kinesiology- The Hand (C8) Pt-2

So to summarize the layers from superficial to deep:

#1. Fibrous digital sheaths #2. flexor pulleys are embedded in #1 #3. digital synovial sheaths are deep to #1&2

Embedded within each fibrous digital sheath are discrete bands of tissue called? -what is their function?

'flexor pulleys' -function: hold tendons close to joints to prevent bowing that would occur during a strong contraction force of the extrinsic finger flexors. (note: the flexor retinaculum also does this)

Know the anatomy of the ED tendon. -central band -lateral band -what are their functions?

-A slip from the ED attaches to the dorsal base of the proximal phalanx. -The remaining tendon flattens into a CENTRAL BAND. Runs distally along the shaft of the proximal phalanx and attaches to the base of the middle phalanx. -Before crossing the PIP jt., the central band splits into 2 LATERAL BANDS. -Lateral bands fuse together into a single TERMINAL TENDON

OTHER MUSCLES: Interossei (4 palmar, 4 dorsal)

-ADDuction/ABduction of MCP -Flexion at MCPs, torque provided is greater than lumbricles -Extension at IPs -MCP stability (dynamic collaterals) and control axial MCP rotations.

CARPAL TUNNEL SYNDROME: (p265) -All ___ extrinsic flexor tendons of the digits and the ________ nerve pass through the carpal tunnel. -These tendons are surrounded by __________ sheaths designed to reduce friction. -what can irritate the tendons? -swelling of the membranes can compress the __________ nerve. -what can occur as a result?

-All 9 extrinsic flexor tendons of the digits and the MEDIAN nerve pass through the carpal tunnel -These tendons are surrounded by SYNOVIAL sheaths. -hand activities that require prolonged , repetitive, or extreme wrist positions. -swelling of the membranes can compress the MEDIAN nerve. -pain and paresthesia in the sensory distribution of the median nerve. muscular weakness & atrophy

OPENING THE HAND: FINGER EXTENSION EARLY PHASE: -What is the main mm. that extends the MCP jts? -What two muscles counter the MCP jt extension torque from the ED mm.? -Wrist ______ counter?

-ED extends MCP jt mainly -LUMBRICLES AND INTERROSSUI counter MCP extension torque of the ED -Wrist FLEXORS counter wrist extension torque of the ED.

OTHER MUSCLES: Lumbricles (4)

-Flexion at MCPs - "wormlike" structures -Extention of IPs -Sensory feedback (high in # of mm. spindle fibers) -Help to coordinate interactions b/w extrinsic and intrinsic finger mms.

in the FDP muscle fingers 3-5 are interconnected through various muscular fasciculi, which prohibit which type of motion? -What happens when you grasp finger 3 and maximally extend all of its jts, while trying to flex the DIPs of fingers 4 & 5?

-The interconnection of the FDP muscles attachments at fingers 3-5 prohibit isolated DIP joint flexion of a single one of these fingers. (note that the index finger can be controlled relatively indep. over the other profundus tendons) -If you max. extend Finger 3 and try to flex 4 & 5 DIPs you realize you can't, b/s the excessive elongation (stretch) of the FDP mm. belly (from the 3rd finger), (this is me thinking...). thereby making the flexors of the other IP joints passively insufficient? -Overall, you are taking out one of the 3 mms. that are interconnected, which does not go over well. This position can be used to MMT to inhibit the FDP action, thereby allowing the FDS to be the more dominant flexor of the PIP jt.

Tenodesis grip

-To open hand: gravity induced wrist flexion causes ED, EPL passive tension to extend digits. -To close hand: Active wrist extension slackens ED and stretched paralyzed FDS,FDP,FP

ULNAR NERVE INJURY: -complete paralysis of the thenar muscles possible, causing limited __________. -flattened eminence from the _________ of muscles. -Anesthesia to entire ____ digit, further impedes functional loss.

-complete paralysis of the thenar muscles possible, causing limited OPPOSITION. -flattened eminence from the ATROPHY of muscles. -Anesthesia to entire 5TH digit, further impedes functional loss.

Extrinsic Extensors of the Thumb: ABductor Pollicis Longus -extends ______ jt. -ABducts _______ jt. -_________ deviates wrist.

-extends CMC jt. -ABducts CMC jt. -RADIALLY deviates wrist.

Intrinsic Thenar Muscles: -main function = -only muscles that can position thumb in ____________. -each is innervated by the __________ nerve.

-main function = position thumb for opposition & grasp. -only muscles that can position thumb in OPPOSITION. -each is innervated by the MEDIAN nerve.

-Where do the fibrous digital sheaths start from? -where do they continue to/attach to?

-sheaths start proximally as a continuation of the thick apopneurosis just under the skin of the palm. -Throughout the length of each digit, the sheaths are anchored to the phalanges and the palmer plates

EXTRINSIC EXTENSORS: Extensor digitorum -unable to independantly extend _____ jts. -Hyperextends _____ jts. -Extends _________. -Active during?

-unable to independently extend IP jts. -Hyper-extends MCP jts. -Extends WRIST. -Active during - hand closing

Extrinsic Extensors of the Thumb: Extensor Pollicis Longus -what parts of the thumb does it extend? - ADDucts _______ Joint. -assist with all _____________ actions -___________ deviates wrist.

-what parts of the thumb does it extend? IP, MCP, and CMC (everything) - ADDucts CMC Joint. -assist with all REPOSITION actions -RADIALLY deviates wrist.

CLOSING HAND EARLY PHASE: -FDS & FDP flexion of IPs -Interosseous flexes MCP as needed -Wrist extensors counter wrist flexion torque -ED counters MCP flexion torque od FDS & FDP so the force they generate can be focused on preventing active insufficiency

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HAND CLOSING LATE PHASE -same mm. activity that occurs in early phase. -Lumbricles show little EMG activity during both phases they can provide passive MCP flexion torque by having the FDP actively pull on lumbricles proximal attachment extensor hood migrates distally, stretching the distal attachments of lumbricles.

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OPENING THE HAND: FINGER EXTENSION LATE PHASE: -Same mm. activity as MIDDLE PHASE with addition of: Wrist flexors- flex wrist slightly provideing max tension for ED -ORL- stretches during IP extension, providing additional passive extension torque to DIP. -Lumbricles also decrease FDP passive tension (main inhibitor to opening hand) by reverse action of lumbricles helping to slacken tendon of FDP

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OPENING THE HAND: FINGER EXTENSION MIDDLE PHASE: -ED extends the DIP & PIP jts. -Lumbricles and interrosei countinue to counter MCP extension torque od ED. Also, EXTEND PIP and DIP via attachment to dorsal hood of extensor. -Wrist Flexors continue to counter-extension torque at wrist caused by ED.

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Remember that the extrinsic flexors often contract in unison, especially when a firm grip of the entire hand is required.

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What intrinsic muscles make up the HYPOTHENAR EMINENCE?

1. ABductor digiti minimi 2. Flexor digiti minimi 3. Opponens digiti minimi 4. Palmaris brevis

What intrinsic muscles make up the THENAR EMINENCE?

1. ABductor pollicis BREVIS 2. Flexor pollicis BREVIS 3. Opponens pollicis

The extensor mechanism serves as a primary distal attachment for which 3 primary extensor muscles?

1. Ext. DIGITORUM 2. Ext. INDICIS 3. EXT. DIGITI MINIMI (and most intrinsic mms. acting on the fingers

what 3 actions occur with reposition of the thumb?

1. Extension 2. ADDuction 3. Lateral rotation

What are the 3 extrinsic muscles of the forearm that extend the fingers?

1. Extensor digitorum 2. Extensor indicis 3. Extensor digiti minimi

What are the 3 extrinsic muscles of the forearm that extend the thumb?

1. Extensor pollicis LONGUS 2. Extensor pollicis BREVIS 3. ABductor pollis LONGUS

What are the 3 extrinsic muscles of the forrearm that flex the digits of the hand?

1. Flexor digitorum superficialis 2. Flexor digitorum profundus 3. Flexor pollicis longus

Here are the other 3 intrinsic muscles or muscle groups:

1.Abductor pollicis (2 heads) 2. Lumbricles (4) 3. Interossei (4 palmar & 4 dorsal)

Explain what can happen when a flexor pulley become lacerated.

A lacerated or incised pulley significantly alters the hand bio-mechanics.

OTHER MUSCLES: ADDUctor Pollicis - oblique & transverse head. -greatest combination of flexion/adduction torque at _____ jt. -Functional activites such as pinching an object b.w thumb and index finger.

ADDUctor Pollicis (two heads) -greatest combination of flexion/adduction torque at CMC jt. -Functional activites such as pinching an object b.w thumb and index finger.

Which band(s) is the backbone of the extensor mechanism?

Central band=backbone

Deep to the flexor pulleys is a _________ synovial sheath.

Deep to the flexor pulleys is a DIGITAL synovial sheath.

With normal hand closing, why is ED activated?

ED counteracts MCP & wrist flexion torque of the FDP & FDS so the digital flexors can focus on IP flexion. If ED was NOT activated it would cause active insufficiency w/ MCP and wrist flexion.

Extrinsic Extensors of the Thumb: Extensor Pollicis Brevis -Extends _______ and ______ jt.

Extends MCP and CMC jts.

The extrinsic flexor tendons travel to their distal attachment in protective fibro-osseous tunnels known as?

Fibrous digital sheaths

Extrinsic flexors or the digits are activated together for what type of motion?

Gripping

In carpal tunnel syndrome, what thenar motions are disabled?

One will have a flattened thenar and thumb opposition will be disabled. (sensory loss to the tips of the lateral digits)

Extrinsic flexors or the digits flex the digits and assist in: a) oppopsition b) reposition

Opposition

What is the difference between paresthesia and numbness?

Paresthesia = tingling Numbness = loss of sensation *going from numb to tingling is good! :)

The extensor tendons eventually become integrated into a fibrous expansion of connective tissues, located along the length of the dorsum of each finger. The complex set of tissues is called?

The Extensor Mechanism.

I don't think this is in the notes, but I think it helps one understand the syngistic relationships of the hand. (p266 Role of Proximal Stabilizer Muscles During Active Finger Flexion)

The extrinsic digital flexors (i.e. FDS, FDP..) are capable of flexing any jt. they cross. -In order for these muscles to isolate their flexion at a single joint, other muscles must contract synergistically with the "oppsosite" motion. -example: In order for the FDS to perform isolated PIP jt. flexion the ED must act as a proximal stabilizer to prevent the FDS from flexing at the MCP jts. & wirst (which they are mechanically suited for) -going deeper... WHY? b/c the moment arm of the FDS increases at the proximal joints, a relatively small force is applied to a distal jt. is amplified to a greater torque at the more proximal joints. THE GREATER THE FORCE PRODUCED BY THE FDS, THE GREATER THE FORCE DEMANDS PLACED ON THE PROXIMAL STABILIZERS (ED). -ultimately the ED counteracts the force of the MCP jts and wirst to allow for isolated PIP flexion from the FDS :).

What tendon does the radical synovial sheath surround?

The radial synovial sheath surrounds the FPL tendon all the way to its distal attachment (palmar view)

Are ED and FDS/FDP anagonists?

They are potential antagonist. (Because they are paired on opposite side of the jt.)

What are synovial sheath in the hand surrounds the FDS and FDP tendons?

Ulnar synovial sheath (see blue in pic; palmar view)

ULNAR NERVE PARALYSIS

causes asynchronous finger closure (radially versus distally) -"Injury to the ulnar nerve can cause paralysis of most of the intrinsic mms. that act on fingers. As a result, grasp is noticeably altered, especially in the sequencing of flexion across the joints. Normally, at least in the radial 3 fingers, the PIP and DIP jts. flex 1st, followed closely in time by the MCP jts. With parlayed intrinsic mms. the initiation of flexion at the MCP jts. appears slightly delayed. The resulting asynchronous flexion may interfere w/ the quality of grasp. " (p280)

The usefulness of the tenodesis action action in some persons with quadraplegia: A person w/ C6 quad who has near or complete paralysis of the digital FLEXORS and EXTENSORS, but well innervated wrist extensors can use the tenodesis action to grip objects (i.e. a cup) -step 1: allow gravity to flex the wrist. this will stretch the partially paralyzed extensors of the fingers and thumb taut. step 2: active contraction of the wrist extensor muscle slackens the extensor digitorum, but more important stretches the paralyzed finger and thumb flexor muscles. -the stretch in these flexor muscles creates enough passive tension to effectively flex the digits and grasp the cup. -the amt. of passive tension of the digital flexors is controlled indirectly by the degree of active wrist extension

https://www.youtube.com/watch?v=j0RBU_phUKw

Tenodesis grip

in a healthy person, as the wrist extends, the thumb and fingers automatically flex because the stretch placed on the extrinsic digital flexors. The flexion occurs PASSIVELY, without effort from the subject. Extrinsic digital flexors = FDP, FDS, FPL

EXTRINSIC FLEXOR: Flexor digitorum superficialis: primary action? assist in? active during?

primary action = flexes PIP jts assist in - flexing the wrist & MCP jts active during: -moderate to high powered grip -raises ulnar border of hand for cupping actions

EXTRINSIC FLEXOR: Flexor digitorum profundus primary action? assist in? active during?

primary action = sole flexor of DIP (only flexor that crosses DIP) assist in - flexing w/ everything it crosses (PIP,MCP, Wrist, some action @ elbow) active during: -light to high-powered grip -raises ulnar border of hand for cupping actions

EXTRINSIC FLEXOR: Flexor pollicis longus primary action? assist in? if unopposed flexes __________.

primary action = sole flexor of thumb IP jts. assist in - substantial flexion torque at thumb CMC, MCP jts. if unopposed flexes WRIST