Functional Anatomy and Biomechanics of the Shoulder Complex Flashcards Preview

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

Flashcards in Functional Anatomy and Biomechanics of the Shoulder Complex Deck (53)
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-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



-anterior thorax
-link between axial and appendicular skeleton



-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



-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



-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


SC Joint

-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


Osteokinematics at SC Joint

-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*


Arthrokinematics at SC Joint

-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


AC Joint

-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*


Osteokinematics at AC Joint

-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


Arthrokinematics at AC Joint

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


Scapulothoracic Joint

-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


Osteokinematics at ST Joint

-elevation ROM 60*
-scapular plane oriented at 35* anterior to frontal plane
-motion in this plane is called scaption


Arthrokinematics at ST Joint

-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


Glenohumeral Joint

-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


Ligaments in GH Joint

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


Additional Stability of GH Joint

-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


Coracoacromial Arch

-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


Osteokinematics at GH Joint

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


Arthrokinematics at GH Joint

-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


Gross Movement in Shoulder Region-Approximate ROM in Sagittal Plane

-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


Gross Movement in Shoulder Region-Approximate ROM in Frontal Plane

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


Gross Movement in Shoulder Region-Approximate ROM in Horizontal Plane

-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


Gross Movement in Shoulder Region-Ligaments

-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


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*


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


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


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


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


Scapular Elevators

-upper trap
-levator scapula