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
2
Q
Sternum
A
- anterior thorax
- link between axial and appendicular skeleton
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
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
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
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
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*
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
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*
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
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
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
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
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
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
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
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
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
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*
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
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
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
Gross Movement in Shoulder Region-Muscle
- 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
Scapulohumeral Rhythm
- 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
Scapulohumeral Rhythm-Scapular Motion During Elevation
- 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
Scapulohumeral Rhythm: For Total ROM in Abduction and Flexion
- 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
Muscular Function in Shoulder Region
- 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
Scapular Elevators
- upper trap
- levator scapula
- rhomboids
31
Scapular Depressors
- lower trap
- lats
- pec minor
- subclavius
32
Scapular Protractors
-serratus anterior
33
Scapular Retractors
- middle trap
- rhomboids
- lower trap
34
GH Elevators
- deltoid
- supraspinatus
- coracobrachialis
- biceps long head
- remaining RC (indirectly via GH stabilization)
35
GH Adductors/Extensors
- lats
- sternal head of pec major
- teres major
- long head of triceps
- posterior deltoid
- infraspinatus
- teres minor
36
GH Internal Rotators
- subscapularis
- anterior deltoid
- pec major
- lats
- teres major
37
GH External Rotators
- infraspinatus
- teres minor
- posterior deltoid
- supraspinatus (in some positions)
38
Rotator Cuff Muscles
- supraspinatus
- infraspinatus
- teres minor
- subscapularis
39
Gross Shoulder Elevation
- 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
Gross Shoulder De-Elevation
- 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
Shoulder Rotation
- 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
Horizontal Abduction and Adduction in Shoulder Region
- 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
Strength in Shoulder Region
-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
Therapeutic Exercise for Shoulder Region
- 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
Select Injuries in Shoulder
- shoulder complex subject to a variety of injuries
- MOI typically traumatic event, repetitive activity, or combination
- give consideration to MOI in rehab
46
SC Joint Sprain or Dislocation
- 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
Clavicular Fracture
- frequent site of injury due to direct trauma: football, MVA, falling, etc
- most common is fracture to middle 1/3
48
AC Joint Sprain or Dislocation
- MOI commonly: blunt trauma to lateral shoulder, falling on outstretched hand
- sometimes related to overuse: swimming, throwing, overhead lifting
49
GH Joint Sprain or Dislocation
- 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
Subacromial Bursitis
- 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
RC Strain or Tear
- 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
Impingement Syndrome
- 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
Bicipital Tendonitis
- 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
