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DPT 726: Orthopaedic Foundations > Functional Anatomy and Biomechanics of the Shoulder Complex > Flashcards

Functional Anatomy and Biomechanics of the Shoulder Complex Flashcards

1
Q

Introduction

A
  • shoulder girdle or complex has many articulations
  • some isolated motion is possible at each joint
  • motion usually occurs simultaneously
  • allows for great mobility, increases function of UE
  • keys to understanding UE motion
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2
Q

Sternum

A
  • anterior thorax

- link between axial and appendicular skeleton

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3
Q

Clavicle

A
  • anterior surface is convex medially and concave laterally
  • medial end articulates with sternum
  • lateral with acromion process of scapula
  • long axis oriented ~20* posterior to frontal plane oriented slightly above horizontal plane
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4
Q

Scapula

A
  • site of attachment for multiple mm and ligaments
  • located on posterior thorax
  • triangular shape
  • 3 angles-superior, inferior, lateral
  • 3 borders: superior, medial, lateral
  • 2 surfaces: anterior, posterior
  • its spine separates posterior surface into superior and inferior fossa then flattens laterally and becomes acromion
  • glenoid fossa extends laterally and anteriorly
  • coracoid process over glenoid fossa
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5
Q

Humerus

A
  • long bone of arm
  • head, neck, shaft at superior end
  • head is 1/2 full sphere
  • crests project from greater and lesser tubercle and bicipital groove lies between these tubercles
  • spiral groove runs at angle on posterior surface
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6
Q

SC Joint

A
  • only direct contact of UE to axial skeleton
  • jt btwn clavicle and manubrium of sternum
  • synovial joint with fibrocartilage disc
  • reinforced by 3 ligaments…
  • interclavicular, costoclavicular (main support for jt), sternoclavicular (posterior and anterior)
  • strong jt capsule resists dislocation
  • also supported by muscles in area particularly subclavius
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7
Q

Osteokinematics at SC Joint

A
  • 3* freedom
  • clavicle can move upward-downward (elevation, depression), motion occurs between clavicle and meniscus of SC joint, ROM 30-40*
  • can move anterior-posterior (protraction and retraction) motion occurs between sternum and meniscus ROM 30*
  • clavicle can rotate along its long axis, rotation occurs about medial-lateral axis ROM 40-50*
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8
Q

Arthrokinematics at SC Joint

A
  • manubrium: lateral, superior
  • clavicle: medial, inferior
  • concave jt surface: manubrium lateral superior and clavicle medial inferior
  • loose pack position not cited
  • close pack position when arm fully elevated
  • elevation: upward roll, downward glide
  • depression: downward roll, upward glide
  • clavicular rotation: spin
  • protraction/retraction: roll and glide in same direction
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9
Q

AC Joint

A
  • between clavicle and acromion
  • plane synovial jt often possessing fibrocartilage disc
  • positioned over humeral head and can cause bony restriction to elevation of UE
  • reinforced by dense capsule and AC ligaments above and below joint
  • nearby coracoclavicular ligament: assists scapular motion by serving an axis of rotation
  • plane joint
  • 3 degrees of freedom
  • scapula can rotate anterior-posterior about a vertical axis: aka protraction and retraction, motion occurs process and meniscus-rotates about an axis of coracoclavicular ligament
  • ROM for protraction and retraction 30-50*
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10
Q

Osteokinematics at AC Joint

A
  • scapula can rotate lateral-medial in frontal plane: upward and downward rotation
  • clavicle moves on meniscus
  • scapula rotates on trapezoid portion of lateral coracoclavicular ligament
  • ROM 60*
  • scapula can elevate and depress: occurring at AC joint, ROM 30*
  • scapular motions influenced by AC joint mobility
  • movements opposite for SC and AC joints for elevation, depression, protraction, and retraction
  • elevation at AC joint –> depression at SC joint, vice versa
  • protraction at SC joint –> retraction at AC joint, vice versa
  • yet rotation of clavicle occurs in same direction for AC and SC joints: accommodates scapular movements, rotates anteriorly with elevation and protraction, rotates posteriorly with depression and retraction
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11
Q

Arthrokinematics at AC Joint

A
  • joint orientation: acromion-superior, medial, anterior; clavicle-inferior, lateral, posterior
  • concave joint surface: acromion
  • loose pack position: not cited
  • close pack: 90* of abduction
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12
Q

Scapulothoracic Joint

A
  • a physiologic or functional joint rather than bone to bone
  • scapula rests on subscapularis and serratus anterior: both mm move across each other as scapula moves, thorax lies beneath these two muscles
  • scapula moves across thorax with help from motion at SC and AC joints: total ROM 60-180, 65 occurs at SC joint, 35* at AC
  • elevation, depression, protraction, retraction, upward rotation, downward rotation
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13
Q

Osteokinematics at ST Joint

A
  • elevation ROM 60*
  • scapular plane oriented at 35* anterior to frontal plane
  • motion in this plane is called scaption
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14
Q

Arthrokinematics at ST Joint

A
  • joint orientation: thorax-posterior, lateral, superior; scapula-anterior, medial, inferior
  • concave joint surface: scapula
  • loose pack position: not cited
  • close-pack position: none not a synovial joint
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15
Q

Glenohumeral Joint

A
  • synovial
  • movements represented in arm
  • greatest ROM in body
  • large motion related to shallow ball and socket joint, lax joint capsule, limited ligamentous support
  • glenoid fossa is small, shallow socket on scapula
  • glenoid labrum deepens socket: increased contact area to 75%, fibrocartilage rim anchored to rim of fossa, secondary support comes from surrounding ligaments and tendons, varies from individual to individual
  • joint capsule possesses two times the volume of humeral head-accommodates great ROM
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16
Q

Ligaments in GH Joint

A
  • primary source of GH joint stability
  • anatomical support on anterior portion of joint: joint capsule, GH ligaments: superior, middle, inferior; coracohumeral ligaments
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17
Q

Additional Stability of GH Joint

A
  • anatomical support provided by: glenoid labrum, long head of biceps brachii, rotator curr
  • static stability comes from gravity and capsular ligaments; these create static force directed at 90* to fossa
  • supraspinatus and p. deltoid provide additional static support
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18
Q

Coracoacromial Arch

A
  • formed by coracoacromial ligaments and acromion process
  • functions as superior, bony limit to GH motion
  • contains bursa: helps to reduce friction in the area, subacromial bursa often irritated in impingement syndromes
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19
Q

Osteokinematics at GH Joint

A
  • flexion ROM 120*
  • extension ROM 45-55*
  • abduction ROM 120*
  • adduction ROM 120*
  • IR ROM 75-85*
  • ER ROM 60-70*
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20
Q

Arthrokinematics at GH Joint

A
  • joint orientation: glenoid-lateral, anterior, inferior; humerus-medial, posterior, superior
  • concave joint surface: glenoid
  • loose-pack position: 55* of ABD and 30* of horizontal ADD (55* of scaption), slight ER; 30-40* of ABD, no FLEX
  • close-pack position: full elevation
  • flexion/extension: spinning, little or no roll or glide occurs
  • abduction: upward roll, upward glide
  • adduction: downward roll, upward glide
  • IR: humeral head rolls anteriorly, humeral head glides posteriorly
  • ER: rolls posteriorly, glides anteriorly
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21
Q

Gross Movement in Shoulder Region-Approximate ROM in Sagittal Plane

A
  • considerable ROM possible secondary to aforementioned motion in SC, AC, ST, and GH joints
  • about 180* flexion-less if humerus is ER, about 30* flexion with max ER
  • about 60* hyperextension
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22
Q

Gross Movement in Shoulder Region-Approximate ROM in Frontal Plane

A
  • about 180* of abduction-less if humerus IR
  • about 60* with max IR
  • 75%* hyperadduction (arm adducted past anatomical position)
23
Q

Gross Movement in Shoulder Region-Approximate ROM in Horizontal Plane

A
  • 180* of total rotation possible
  • 90* internal and 90* external
  • rotation limited by abduction of arm: ~180* of total rotation in anatomical position; 90* available at 90* abduction
  • 135* of horizontal flexion or adduction
  • 45* horizontal extension
24
Q

Gross Movement in Shoulder Region-Ligaments

A
  • ligaments with arm in anatomical position
  • ligaments and many supporting mm are loose
  • if arm is ER capsule tightens
  • IR does not tighten capsule when shoulder in anatomical position
  • inferior GH joint capsule: loose, allowing for full abd and Er
25
Q

Gross Movement in Shoulder Region-Muscle

A
  • in abd thru 45* joint becomes more stable: secondary tension from subscapularis and lower glenohumeral ligament; even greater stability with addition of more ER
  • other mm contribute to stability thru 90: in particular supraspinatus, infraspinatus, and teres minor; compress humeral head into glenoid fossa; their contribution decreases after 90
26
Q

Scapulohumeral Rhythm

A
  • describes scapular and clavicular motions which accompany any normal elevation of arm-such as in flexion and abduction
  • clavicular motion during elevation: rotates posteriorly, elevates, and protracts with flexion or abduction
27
Q

Scapulohumeral Rhythm-Scapular Motion During Elevation

A
  • small movement of scapula with initiation of elevation: either toward or away from spinal column; serves to help stabilize scapula on thorax; most evident in 1st 30* of abduction and 1st 45-60* of flexion
  • after stabilization scapula moves laterally, anteriorly, and superiorly
  • these movements are described as upward rotation, protraction, and elevation
28
Q

Scapulohumeral Rhythm: For Total ROM in Abduction and Flexion

A
  • 2:1 ratio of GH to ST motion
  • 120 from GH
  • 60 from ST
  • contributing joint actions to total UE elevation: 20* produced at AC, 40* produced at SC, 40* produced thru posterior rotation of clavicle
  • some extension of spine is evident in pts with full elevation of UE
29
Q

Muscular Function in Shoulder Region

A
  • proximal stabilizers: originate in spine, ribs, cranium; attach at scapula, trapezius, serratus anterior, etc
  • distal mobilizers: originate on scapula, attach at humerus; deltoid, supraspinatus, etc
30
Q

Scapular Elevators

A
  • upper trap
  • levator scapula
  • rhomboids
31
Q

Scapular Depressors

A
  • lower trap
  • lats
  • pec minor
  • subclavius
32
Q

Scapular Protractors

A

-serratus anterior

33
Q

Scapular Retractors

A
  • middle trap
  • rhomboids
  • lower trap
34
Q

GH Elevators

A
  • deltoid
  • supraspinatus
  • coracobrachialis
  • biceps long head
  • remaining RC (indirectly via GH stabilization)
35
Q

GH Adductors/Extensors

A
  • lats
  • sternal head of pec major
  • teres major
  • long head of triceps
  • posterior deltoid
  • infraspinatus
  • teres minor
36
Q

GH Internal Rotators

A
  • subscapularis
  • anterior deltoid
  • pec major
  • lats
  • teres major
37
Q

GH External Rotators

A
  • infraspinatus
  • teres minor
  • posterior deltoid
  • supraspinatus (in some positions)
38
Q

Rotator Cuff Muscles

A
  • supraspinatus
  • infraspinatus
  • teres minor
  • subscapularis
39
Q

Gross Shoulder Elevation

A
  • mm action similar for flexion and abduction
  • deltoid produces ~50% force for moth motions
  • its contribution increases as elevation increases
  • most active between 90-180*
  • most fatigue resistant between 45-90*: related to functional activities; this range most popular for arm raising exercises
  • during elevation scapula must abduct, elevate, upwardly rotate: clavicle also rotates posteriorly; maintains fossa in optimal position thru full ROM
  • serratus anterior and trapezius work as functional force couple: creating lateral, superior, and rotational motions of scapula; starts after deltoid and teres minor have initiated elevation and continues to 180; greatest activity of these mm occur between 90-180
  • serratus also holds scapula to thorax and prevents winging of medial border
40
Q

Gross Shoulder De-Elevation

A
  • opposite motions of flexion and abduction (extension and adduction)
  • seen when arm is forcefully lowered, lowered against resistance or with hyperextension/hyperadduction: involves concentric muscular action; seen in swimming, weight training, etc
  • primary movers in concentric adduction or extension against ER
  • lats active with or without resistance
  • teres major active only against resistance
  • sternal portion of pec major
  • as arm extends or adducts the scapula retracts, depresses and downwardly rotates: rhomboid works in force couple with teres major and lat dorsi to control this motion; pec minor also depresses and downwardly rotates; mid and lower traps help rhomboid to retract scapula
41
Q

Shoulder Rotation

A
  • needed for efficient motion above 90* (combing hair, changing bulb, raising arm)
  • IR force capacity much greater than ER yet most UE activities seldom require such force
42
Q

Horizontal Abduction and Adduction in Shoulder Region

A
  • combinations of elevated arm positions
  • as elevation is a component same mm described before also contribute
  • in h. adduction increased activity of pec major and anterior deltoid: brings arm across body; important in UE power movements
  • in h. abduction increased activity of infraspinatus, teres minor, and posterior deltoid: arm is brought back in elevated position, also important in UE functional activities
43
Q

Strength in Shoulder Region

A

-here is hierarchy of force production in shoulder region
-ADD > EXT > FLEX > ABD > IR > ER
-greatest force possible during shoulder adduction: secondary to contributions of lats and teres major and pec major; two times the strength of abduction yet abd used much more frequently
-extension also relies heavily upon lats, teres major, and pec major: slightly stronger than its opposite motion-flexion
-weakest motions are rotational IR > ER; arm position affects strength output
=IR strength greatest at neutral position
-ER strength greatest at 90* shoulder flexion
-imbalance between ER and IR above 90* may contribute to instability, impingement, etc

44
Q

Therapeutic Exercise for Shoulder Region

A
  • complete isolation of specific muscle very difficult
  • because shoulder mm work in combination functionally
  • stretching exercise, manual resistance, isotonic resistance commonly used in rehab
  • look at pictures in notes p 20
  • some resistance exercises may irritate the shoulder joint: avoid and/or modify for those with injury in area
  • E: resisted abduction may cause subacromial impingement: magnified if humerus internally rotated; modify motion via ER, etc, such modifications slightly modify mm recruitment and internal forces
  • anterior and/or posterior instability presents challenges with resistance exercise: bench press, push ups, behind neck pull-downs, horizontal adduction/adduction, end-range rowing; can place increased strain on capsule
  • may need to avoid or modify exercise (i.e. perform with less IR, ER, or decrease ROM)
  • irritation in rotator presents special issues: avoid or minimize heave abduction movements; avoid heavy overhead lifting
45
Q

Select Injuries in Shoulder

A
  • shoulder complex subject to a variety of injuries
  • MOI typically traumatic event, repetitive activity, or combination
  • give consideration to MOI in rehab
46
Q

SC Joint Sprain or Dislocation

A
  • MOI commonly blunt trauma to area of middle deltoid: landing from fall, MVA, etc
  • typically presents with pain upon horizontal abduction: golf swing, backstroke, etc
  • posterior dislocations can be serious: typically results from anterior blow, threat to trachea, esophagus, veins, and arteries in area, symptoms may include coughing, SOB, difficulty swallowing
47
Q

Clavicular Fracture

A
  • frequent site of injury due to direct trauma: football, MVA, falling, etc
  • most common is fracture to middle 1/3
48
Q

AC Joint Sprain or Dislocation

A
  • MOI commonly: blunt trauma to lateral shoulder, falling on outstretched hand
  • sometimes related to overuse: swimming, throwing, overhead lifting
49
Q

GH Joint Sprain or Dislocation

A
  • commonly injured via trauma or repeated overuse: lack of bony restraint places high demand on ligaments/capsule
  • anterior and inferior dislocations account for 95% of dislocations: usual cause is force applied to arm when it’s abducted and ER overhead
  • posterior dislocations are rare (~2%): caused by force to arm when adducted and IR below shoulder level
  • recurrent dislocations depend on extent of damage, addition of labral tear
50
Q

Subacromial Bursitis

A
  • irritation of bursa above supraspinatus muscle and beneath acromion
  • often brought on by repetitive activity above shoulder height
  • may develop in WC propulsion: abnormal distribution of stress in area
51
Q

RC Strain or Tear

A
  • RC mm very susceptible to injury: associated with repetitive or overhead activities
  • for example in throwing subscap at risk for injury during prep phase, infraspinatus and teres minor undergo great stress during many phases (late cocking, early acceleration, and follow through)
  • supraspinatus under stress for many work-related activities
52
Q

Impingement Syndrome

A
  • MOI usually stress to tissues between humeral head and acromion: supraspinatus, supraspinatus tendon, bursa
  • typically accelerated with prolonged or repetitive internal rotation: factor work, follow through in throwing, etc.
  • typically marked by a painful arc thru ~60-120*
53
Q

Bicipital Tendonitis

A
  • typically irritated in area of bicipital groove
  • ex: high stress during throwing, biceps decelerates elbow extension last 30* during follow through, highest tensile load during this deceleration, may also tear anterosuperior portion of labrum
  • often present with painful arc similar to RC injury

DPT 726: Orthopaedic Foundations (14 decks)

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