Shoulder Biomechanics

Sternoclavicular and Acromioclavicular Joints

SC Joint

Saddle-type, but functions as ball & socket

4 ligaments

Strong, but MOBILE

ROM=60° elevation and 25-30° anterior and posterior movement

AC Joint

Plane synovial articulation

4 ligaments

Axioappendicular muscles cause acromion of scapula to rotate on acromial end of clavicle, which increases scapulothoracic joint movement

Glenohumeral Joint (scapulohumeral &scapulothoracic)

Ball & socket synovial joint

WIDE ROM, mobile, UNSTABLE

Cavity only accepts 1/3 of humeral head

Held in cavity with rotator cuff muscles

3 ligaments

Most freedom in body

Lateral rotation of humerus increases abduction ROM

Elevation & Depression

Clavicular elevation /depression(SC)

Subtle anterior/posterior tipping (AC)

Subtle internal/external rotation (AC)

Upward & Downward Rotation (abd/add)

2:1 humoral:scapular

Upward/downward rotation (AC)

Clavicular elevation/depression (SC)

Subtle posterior/anterior rotation (SC)

Protraction & Retraction

Clavicular protraction/retraction (SC)

Subtle internal/external rotation (AC)

Winging

Excessive internal rotation (AC)

Scapula loss of contact with thorax, medial border prominence results

https://www.youtube.com/watch?v=rRIz6oOA0Vs

Clavicular Elevation (SC joint)

Winging Protraction (SC)Upward Rotation (AC)

Group 1 Group 2 Group 3 Group 4

Trunk to Head Trunk to scapula Trunk to Humerus Shoulder Girdle to Humerus

SCM Subclavi

us 

Trapezius

Levetor scapulae

Serratus anterior

Rhomboids major & minor

Pectoralis minor

 

Latissimus dorsi

Pectoralis major

 

Deltoideus Subscapularis

* Supraspinatus

* Infraspinatus* Teres minor* Teres major 

Tests:Hawkins-Kennedy  Test Neer Impingement Test

Scapular Movement Muscles Producing MovementElevation Trapezius (superior part)

Levator ScapulaeRhomboids

Depression Pectoralis major (inferior sternocostal head)Latissimus DorsiTrapezius (inferior part)Serratus anterior (inferior part)Pectoralis minor

Protraction Serratus anteriorPectoralis major/minor

Retraction Trapezius (middle part)RhomboidsLatissimus dorsi

Upward Rotation Serratus anterior (inferior part)Trapezius (superior part)Trapezius (inferior part)

Downward Rotation Latissimus DorsiLevator scapulaeRhomboidsPectoralis minorPectoralis major (inferior sternocostal head)

Research ArticleEvaluated the effectiveness of FES in shoulder subluxation and pain for patients who have developed hemiplegia due to stroke

Shoulder pain measured during resting, passive range of motion (PROM) and active range of motion (AROM) using visual analog scale (VAS)

50 patients with shoulder subluxation and shoulder pain randomly split into either the study group or the control group

FES applied to supraspinatus and posterior deltoid muscles

Study groupconventional rehabilitation therapy and applied FES

Control group conventional rehabilitation therapy

Results decreased subluxation levels in the study group compared to the control group

Conclusion Conventional therapy with FES is more beneficial than just conventional therapy alone when examining shoulder subluxation

Shoulder InstabilityMost common are anterioinferior capsololabral auvlsions (Degen,2013), more commonly known as Bankart Lesions

Glenoid Bone Grafting

Bristow Coracoid Transfer

Latarjet Coracoid Transfer (subscapularis)

References1) Degen, R. M., Giles, J. W., Thompson, S. R., Litchfield, R. B., & Athwal, G. S. (2013).

Biomechanics of Complex Shoulder Instability. Clinics In Sports Medicine, 32(4), 625-636. doi:10.1016/j.csm.07.002

2) Itoi E, Lee SB, Berglund LJ, et al. (2000). The Effect of a Glenoid Defect on Anteroinferior Stability of the Shoulder After Bankart Repair: a cadaveric study. J Bone Joint Surg Am,82(1), 35–46.

3) Koyuncu, E., Nakipoglu-Tuzer, G., Dogan, A., and Ozgirgin, N. (2010). The effectiveness of functional electrical stimulation for the treatment of shoulder subluxation and shoulder pain in hemiplegic patients: A randomized controlled trial. Disability and Rehabilitation, 32(7), 560-566

4) Moore, K., Agur, A., and Dalley, A. . (2015). Essential Clinical Anatomy. Lippincott Williams & Wilkins, 5, 465-69

5) Netter. F. (2014). Atlas of Human Anatomy. Saunders Elsevier, (6), 405-411, 417

6) Tortora, G., Derrickson, B. (2012) Principles of Anatomy and Physiology. Biological Science Textbook Inc, 13, 614-615.