Functional Anatomy: Exam 2 - Chapter 6 Elbow and Forearm

Musculocutaneous Nerve what vertebral level? what muscles does it innervate? sensory innervation?

- C5-C7 - Anterior compartment of the arm: biceps brachii, brachialis, coracobrachialis (shldr add/IR) - lateral forearm

Radial Nerve what vertebral level? what muscles does it innervate? sensory innervation?

- C5-T1 (direct continuation of the posterior cord of brachial plexus) - triceps, anconeus, brachioradialis (and lateral brachialis), supinator, wrist extensors, finger/thumb extensors, abductor pollicis longus - posterior arm, posterior lateral forearm, aspects of posterior/lateral hand

Distal Radioulnar Joint: ROM loose-packed position: closed-packed position: normal ROM: expected end-feel:

- loose-packed position: 10 supiantion - closed-packed position: 5 supination - normal ROM: trasnverse plane 80-0-80; frontal variable valgus 10-20 - expected end-feel: pronation and supination - soft tissue; capsular

Humero-ulanr Joint: ROM loose-packed position: closed-packed position: normal ROM: expected end-feel:

- loose-packed position: 70 flexion and 10 supination - closed-packed position: extension - normal ROM: sagittal plane 0-150; frontal variable valgus 10-20 - expected end-feel: extension-bony and flexion-soft tissue approximation

Proximal Radioulnar Joint: ROM loose-packed position: closed-packed position: normal ROM: expected end-feel:

- loose-packed position: 70 flexion and 35 supination - closed-packed position: 5 supination - normal ROM: trasnverse plane- 80-0-80 and frontal variable valgus 10-20 - expected end-feel: pronation and supination - soft tissue; capsular

Humeroradial Joint: ROM loose-packed position: closed-packed position: normal ROM: expected end-feel:

- loose-packed position: full extension and supination - closed-packed position: 90 flexion and 5 supination - normal ROM: sagittal place 0-150; frontal variable valgus 10-20 - expected end-feel: pronation and supination-soft tissue; capsular

what are the nerves that provide motor and sensory innervation to the muscles, ligaments, joint capsule, and skin of the elbow, forearm, wrist, an hand:

- musculocutaneous - radial - median - ulnar

what are the two primary elbow extensors? both muscles inert where?

1. Triceps brachii 2. Anconeus (more type 1 fibers, elbow stabilizer) - olecranon process

if a muscle functions as a pronator or supinator it must do what two things?

1. attach on boths ides of the axis of rotation (origin will either be on humerus or ulna and insert on radius) 2. muscle must produce internal moment arm about the axis of rotation for pronation and supination

what are the three primary elbow flexors

1. biceps brachii 2. brachialis 3. brachioradialis - pronator teres is weak elbow flexor - muscles that act on the wrist cross the elbow, thus they may either weakly flex/extend the elbow

what three things make up the interosseous membrane?

1. central band - most fibers - 2x as thick as other regions - tensile strength of the patella tendon 2. Oblique Cord - may help limit distal migration of the radius on the ulna (helps not move the radius downward) 3. Distal oblique fibers - present in only 40% of IM - runs distal-laterally from the distal ulna to the distal radio-ulnar joint - located deep to the pronator quadratus - stabilize the distal radio-ulnar joint

the central band of the interosseous membrane does what three functions?

1. firmly binds the radius to the ulna 2. serves as an attachment site for extrinsic hand muscles 3. transmits force proximally through the upper limb - about 80% of the compression force that crosses the wrist is directed to the radiocarpal joint (lunate/scaphoid) - only 20% of the force crosses the medial side of the wrist - so forces are more equally shared at the elbow

what are the two primary supiantor muscles?

1. supinator - active first in supination (Biceps recruited in more powerful supination activities) 2. biceps brachii - has 3x CSA compared to supinator - when pronated, biceps has increased leverage to "unwrap" the radius back to supination - greatest ability to supinate when elbow is at 90 degrees

PROM of the elbow? what is the ROM of the elbow needed for normal function?

- 5 degrees beyond neutral (0 degrees) extension through 140-150 degrees - 30-130 degrees (100 degree functional arc)

what is the normal range of pronation and supination? what is the normal functional range?

- 80 degrees to 80 degrees - 50 to 50 (100 degree functional arc) usually have more supination that pronation

what is the angle of normal cubitus valgus? cubitus valgus? cubitus varus?

- 13-15 degrees - >20-25 degrees - about -5 degrees (gunstock deformity)

Median Nerve what vertebral level? what muscles does it innervate? sensory innervation?

- C6-T1 - Anterior Forearm: pronator teres, pronator quadratus, all wrist flexors except for flexor carpi ulnaris, lateral half of flexor digitorium profundus, lateral two lumbricals, flexor pollicis longus, thenar muscles (innervates most muscles attaching to medial epi) - lateral 2/3 palm, palmar surface of the thumb, 1st two fingers, and lateral half of ring finger

Ulnar Nerve what vertebral level? what muscles does it innervate? sensory innervation?

- C8-T1 (direct continuation of the medial cord of brachial plexus, transverse posterior to medial epi, crosses the wrist external to the carpal tunnel) - flexor carpi ulnaris, medial half of FDP, adductor pollicis, hypothenar muscles, all interossei (palmar and dosal), and medial 2 lumbircals - mid 1/3 of medial hand and little finger and medial half of ring finger

elbow flexion: largest moment arm = ______ elbow extension (triceps): largest moment arm= ____

- about 100 degrees - close to full extension (longer moment arm because olecranon process is involved) (thus, muscle length and subsequent force is probably more important than moment arm in determing peak elbow extension torque

Arthokinematics of the Humeroradial Joint: what does it articulate between? what does it provide?

- between the fovea of the radial head and capitulum - about 50% of the resistance against a valgus stress (not much sagittal plane stability)

Arthrokinematics of the Humero-Ulnar Joint: what does it articulate with? to achieve full elbow extension, the following must allow it to happen: what can prolonged immobilization lead to? to achieve full elbow flexion, the following must allow it to happen:

- between trochlea and trochlear notch - anterior dermis, forearm flexor muscles, anterior capsule, anterior MCL, olecranon process fitting into the olecranon fossa - flexion contractures - forearm extensor muscles, posterior capsule, ulnar nerve, and certain portions of the collateral ligaments (esp. posterior fibers of the MCL)

during what activities, is supination needed? is pronation needed?

- bringing the hand toward the face (feeding, shaving) - placing an object down or hand on object (computer mouse, pushing up from chair)

Arthrokinematics of Pronation: (same basic principles as supination) what do the dorsal capsular ligaments help increase? slackens the palmar capsular ligaments by about ____% in full pronation

- compression forces which help stabilize the distal radioulnar joint during pronation - 70%

Joint Structure and Periarticular Cartilage of the Distal Radioulnar Joint: what makes up the "triangular fibrocartilage"? what does the triangular fibrocartilage attach to?

- convex head of the ulna, the concavity of the ulnar notch of the radius, and the proximal surface of an articular disc - attaches to the ulnar notch of the radius and fans out medially int a triangular shape and attaches to the ulnar styloid process

what are the common injuries that can occur to the LCL conplex? what is the position of comfort? (where they hold when injured)

- dislocation of the radial head (posterior/lateral): can cause posterior-lateral rotary instability - 70-80 degree flexion (contracture, muscle shortening)

what are common injuries that can damage the MCL

- falling on outstretched extended arm (supinated), with forced valgus - may be associated with a radius fracture or a compression fracture within the humeroradial joint - may also damage ulnar nerve or proximal attachment of the wrist flexor/pronator muscles - may also damage the anterior capsule with hyperextension - overhead throwing (pitching) - pain with late cocking and acceleration (when valgus torque is greatest) - Tommy John Surgery

contraction of the triceps prevents the bicep from?

- flexing the elbow and shoulder during every supiantion effort

Triangular Fibrocartilage Complex: TFCC makes up most of the "ulnocarpal space" between what two things? TFCC is made up of what three things what is the primary function of the TFCC

- head of the ulna and the ulna side of the wrist - 1. disc 2. dorsal and palmer capsular ligament 3. ulnar collateral ligament - primary stabilizer of the distal radioulnar joint (other stabilizers include: pronator quadratus, tendon of the ECU, distal oblique fibers of the IM)

what does the articular capsule of the elbow enclose? it is relatively thin anteriorly and reinforced by what? what does the MCL consists of?

- humero-ulnar and humeroradial joints and the proximal radio-ulnar joint - olblique and vertical bands of the fibrous tissue MCL and LCL - provide triplanar stability motion - MCL consists of anterior (strongest, thick), posterior (thin, fan-like), and transverse parts (help prevent valgus)

Joint Structure and Periarticular Cartilage of the Proximal Radioulnar Joint: which joints all share one capsule? what does the annular ligament do? what does the quadrate ligament do?

- humeroradial, humero-ulnar, and proximal radioulnar - holds the head of the radius against the radial notch - attaches distally from below the radial notch of the ulna to the medial surface of the neck of the radius (stabilizes the proximal radioulnar joint)

when is interosseous membrane less taught (less laxativity)? when is it most taught?

- least: full pronation (as radius moves proximally there's no pull through ulna) - most: full supination

LCL Complex where does it originate? what are the ligaments that make up the LCL complex? what is the purpose of the LCL complex?

- on the lateral epicondyle and splits into two primary bundles - (1) Radial collateral ligament: fans out to primarily merge with the annular ligament (& ECRB and supinator) (2) Lateral ulnar collateral ligament: thicker and attaches to the supinator crest - provides resistance against a varus stretch LUCL: prevents excessive supination

elbow extension is often combined functionally with what other movement? what does the anterior deltoid do during this?

- shoulder flexion (while flexing shoulder and extending elbow, it reduces the rate and amoutn of shortening of the triceps brachii) - produces shoulder flexion torque that counteracts the shoulder extension torque of the anterior delt

biceps brachii max EMG activity involves what two actions of the elbow? low EMG activity?

- simultaneous elbow flex and supination - simultaneous elbow flex and pronation (elbow flex torques supiantion are about 20-25% stronger than when fully pronated)

what causes the ulna to deviate laterally relative to the humerus? what is this called? what is the average carrying angle in adults

- the axis of rotation from medial to lateral goes slightly superior through the convex trachlea, capitulum, and lateral epicondyle - normal cubitus valgus or carrying angle - about 13 degrees with a SD of 6 (women >men by about 2 degrees, greater on dominant arm, and increases with age)

Arthrokinematics of Supination: what prohibits the standard roll-and-slide arthokinematics at the proximal radioulnar joint? what happens at the distal radioulnar joint? during extreme supination/pronation, how much of the ulnar head is in contact with the ulnar notch? mid-position? what do the palmar capsular ligaments help increase?

- tight constraint of the fibro-osseus ring - concave ulnar notch rolls and slides in the same direction on the convex head of the ulna - about 10%, 60% - compression forces which help stabilize the joint during supination

Supinator muscles produce about ___% greater isometric torque compared to the pronators

25% - have 2x the CSA compared to pronators

elbow flexor torques are about ___% greater than extensor torques (opposite in the knee)

70%

elbow flexor torques are about ___% greater than extensor torques (opposite in the knee)

70% greatest elbow flexion torque is produced at about 85-90 degrees of elbow flexion

greatest elbow flexor torque is produced at about ___-___ degrees of elbow flex

85-95 degrees

maximal elbow extension torque is produced at about __-__ degrees elbow flexio

85-95 degrees

what are the 3 bones and 4 joints that make up the elbow and forearm complex

Bones: humerus, radius, ulna Joints: humero-ulnar and humeroradial, proximal radioulnar and distal radioulnar

Arthrokinematics of Supination: what prohibits the standard roll-and-slide arthokinematics at the proximal radioulnar joint

the tight constraint of the fibro-osseous ring

how does the elbow provide stability

through the tight fit between the trachlea and trachlear notch

spinal cord injuries above ____ nerve root cause inability to flex the elbow and this severe functional limitation

C5

Biceps Brachii Muscle Origin: Insertion: Action:

Origin - long head: supraglenoid tubercle - short head: coracoid process Insertion - radial tuberosity (and deep fascia of the through fibrous lacterus) Action - elbow flex - forearm supination (most powerful supinator) - shoulder flexion

Brachialis Muscle Origin: Insertion: Action:

Origin - proximal humerus Insertion - coronoid process of ulna - ulnar tuberosity Action - elbow flex (has the largest CSA of any muscle crossing the elbow - expected to generate most force)

the central band of the interosseous membrane is not designed to resist what type of force

distally applied (distraction) forces on the radius -holding weight in hand causes a distracting force almost entirely through the radius (puts demand on the oblique cord and annular ligament) - strenous pull on the hand (typically pronated) can cause a slip of the radial head through the annular ligament - injury called "pulled-elbow syndrome", "Nurse's maid elbow", and "babysitter's elbow"

why is the fiber orientation of the interosseous membrane important

Dictates line of pull - radius moves proximally into capitulum - IM pulls ulna to distribute the force

Elbow Extension Analysis (EMG) during submaximal efforts of elbow extension, different parts of muscles are recruited only at certain levels of effort: what order are they recuited?

First: typically anconeus, to initiate and maintain low levels of elbow extension force - as effort increases, the medial head of triceps becomes engaged to assist anconeus ("workhouse of extensors" because it stays active for most elbow extension movements) - effort increase to mod-high levels, lateral head and then finally long head is recruited by nervous system anconeus -> medial -> lateral -> long (recruitment process)

Supinator Muscle Origin: Insertion: Action:

Origin - lateral epi of humerus - radial collateral ligament and annular ligaments - proximal ulna near the superior crest Insertion - prximal 1/3 of the radius Action - supinate forearm

Anconeus Muscle Origin: Insertion: Action:

Origin - lateral epicondyle of humerus Insertion - posterior aspect of the proximal ulna extending distally from the olecranon process Action - weakly extend elbow - produces 15% of total elbow extension torque due to its small moment arm and small CSA

Brachioradialis Muscle (longest of all elbow flexors) Origin: Insertion: Action:

Origin - lateral supracondylar ridge of humerus Insertion - styloid process of radius Action - elbow flex - rotation of forearm to neutral (has moment arm greater than the other elbow flexors -- causes bowstring effect during max-effort isometric action)

Triceps Brachii Muscle Origin: Insertion: Action:

Origin - long head: infraglenoid tubercle of scapula - lateral head: lateral and posterior surface of humerus - medial head: posterior humerus Insertion - olecranon process - part of medial head attaches to the posterior capsule of the elbow Action - long head: extends and adducts the should and extends the elbow - lateral and medial: extends the forearm at the elbow - medial head: helps draw the capsule taut during extension

what are the two primary pronator muscles? what are the secondary pronator muscles?

Primary: 1. Pronator teres - two heads: humeral and ulnar (site for possible nerve compression) 2. produces most pronation force during hihg-power pronation activities - also weak elbow flexor Secondary: - flexor carpi radialis - palmaris longus - extensor indices - brachioradialis (from a supinated position)

what is the most active and consistently used pronator?

Pronator Quadratus

annular ligament is lined with what type of cartilage

articular

contraction of the pronator teres causes what two things to happen?

compression force and proximal migration of the radius esp. when the elbow is near full extension - compressive force and migration: pronation>supination (due to less taught IM in pronation) - "screw home" mechanism - pronate ane contract also have proximal migration

do muscles that cross the elbow and attach to the ulna have the ability to pronate and supinate? flex and extend elbow?

no, have to attach to radius yes

what is the axis of rotation of the forearm

obliquely from radial head through the ulnar head (intersects and connects both radioulnar joints)

what is the most active and consistently used pronator?

pronator quadratus (longer moment arm,mosre torque with same force)

most elbow flexors and all primary supinator/pronator muscles have their distal attachment on the ____

radius

with the hand and radius held fixed to the ground, pronation occurs when?

when the ulna and the humerus externally rotate around the radius - force-couple between the infraspinatus and pronator quadratus externally rotate shoulder - pronate internally rotate shoudler - supinate Close chain hand: move ulna around fixed radius