Lines of action and stabilizing potential of the shoulder musculature

The objective of the present study was to measure the lines of action of 18 major muscles and muscle sub‐regions crossing the glenohumeral joint of the human shoulder, and to compute the potential contribution of these muscles to joint shear and compression during scapular‐plane abduction and sagittal‐plane flexion. The stabilizing potential of a muscle was found by assessing its contribution to superior/inferior and anterior/posterior joint shear in the scapular and transverse planes, respectively. A muscle with stabilizing potential was oriented to apply more compression than shear at the glenohumeral joint, whereas a muscle with destabilizing potential was oriented to apply more shear. Significant differences in lines of action and stabilizing capacities were measured across sub‐regions of the deltoid and rotator cuff in both planes of elevation (P < 0.05), and substantial differences were observed in the pectoralis major and latissimus dorsi. The results showed that, during abduction and flexion, the rotator cuff muscle sub‐regions were more favourably aligned to stabilize the glenohumeral joint in the transverse plane than in the scapular plane and that, overall, the anterior supraspinatus was most favourably oriented to apply glenohumeral joint compression. The superior pectoralis major and inferior latissimus dorsi were the chief potential scapular‐plane destabilizers, demonstrating the most significant capacity to impart superior and inferior shear to the glenohumeral joint, respectively. The middle and anterior deltoid were also significant potential contributors to superior shear, opposing the combined destabilizing inferior shear potential of the latissimus dorsi and inferior subscapularis. As potential stabilizers, the posterior deltoid and subscapularis had posteriorly‐directed muscle lines of action, whereas the teres minor and infraspinatus had anteriorly‐directed lines of action. Knowledge of the lines of action and stabilizing potential of individual sub‐regions of the shoulder musculature may assist clinicians in identifying muscle‐related joint instabilities, assist surgeons in planning tendon reconstructive surgery, aid in the development of rehabilitation procedures designed to improve joint stability, and facilitate development and validation of biomechanical computer models of the shoulder complex.

[1]  H. Devries.  MUSCLES ALIVE-THEIR FUNCTIONS REVEALED BY ELECTROMYOGRAPHY , 1976 .

[2]  K. An,et al.  Effects of the Glenoid Labrum and Glenohumeral Abduction on Stability of the Shoulder Joint Through Concavity-Compression: An in Vitro Study , 2001, The Journal of bone and joint surgery. American volume.

[3]  J. Saunders,et al.  Observations of the Function of the Shoulder Joint , 1996, Clinical orthopaedics and related research.

[4]  D Karlsson,et al.  Towards a model for force predictions in the human shoulder. , 1992, Journal of biomechanics.

[5]  V C Mow,et al.  Glenohumeral Stability: Biomechanical Properties of Passive and Active Stabilizers , 1996, Clinical orthopaedics and related research.

[6]  N. Poppen,et al.  Forces at the glenohumeral joint in abduction. , 1978, Clinical orthopaedics and related research.

[7]  A. Cappozzo,et al.  Human movement analysis using stereophotogrammetry. Part 2: instrumental errors. , 2004, Gait & posture.

[8]  V. Spitzer,et al.  The visible human male: a technical report. , 1996, Journal of the American Medical Informatics Association : JAMIA.

[9]  N. Sharkey,et al.  The entire rotator cuff contributes to elevation of the arm , 1994, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[10]  K. An,et al.  Dynamic Stabilizing Function of the Deltoid Muscle in Shoulders with Anterior Instability , 2003, The American journal of sports medicine.

[11]  J. Insall,et al.  Chondromalacia Patellae. A prospective study. , 1976, The Journal of bone and joint surgery. American volume.

[12]  M. Pandy,et al.  The Obstacle-Set Method for Representing Muscle Paths in Musculoskeletal Models , 2000, Computer methods in biomechanics and biomedical engineering.

[13]  S M Howell,et al.  Normal and abnormal mechanics of the glenohumeral joint in the horizontal plane. , 1988, The Journal of bone and joint surgery. American volume.

[14]  M Vitti,et al.  Simultaneous EMG of latissimus dorsi and sternocostal portion of pectoralis major muscles during butterfly natatory stroke. , 1984, Electromyography and clinical neurophysiology.

[15]  Marcus G Pandy,et al.  Contributions of the individual muscles of the shoulder to glenohumeral joint stability during abduction. , 2008, Journal of biomechanical engineering.

[16]  G. Johnson,et al.  Modelling the muscles of the scapula morphometric and coordinate data and functional implications. , 1996, Journal of biomechanics.

[17]  Brian A. Garner,et al.  Estimation of Musculotendon Properties in the Human Upper Limb , 2003, Annals of Biomedical Engineering.

[18]  Kai-Nan An,et al.  Dynamic Glenohumeral Stability Provided by Three Heads of the Deltoid Muscle , 2002, Clinical orthopaedics and related research.

[19]  G Németh,et al.  Muscle activity and coordination in the normal shoulder. An electromyographic study. , 1990, Clinical orthopaedics and related research.

[20]  Patrick J McMahon,et al.  Stability and instability of the glenohumeral joint: the role of shoulder muscles. , 2005, Journal of shoulder and elbow surgery.

[21]  M G Pandy,et al.  Musculoskeletal Model of the Upper Limb Based on the Visible Human Male Dataset , 2001, Computer methods in biomechanics and biomedical engineering.

[22]  N. O’Connell,et al.  An investigation into EMG activity in the upper and lower portions of the subscapularis muscle during normal shoulder motion. , 2006, Physiotherapy research international : the journal for researchers and clinicians in physical therapy.

[23]  E. Crelin.  Atlas of Human Anatomy , 1965, The Yale Journal of Biology and Medicine.

[24]  Marcus G Pandy,et al.  Moment arms of the muscles crossing the anatomical shoulder , 2008, Journal of anatomy.

[25]  G R Johnson,et al.  Application of spherical and cylindrical wrapping algorithms in a musculoskeletal model of the upper limb. , 2001, Journal of biomechanics.

[26]  P. Herberts,et al.  Intramuscular pressure and electromyography in four shoulder muscles , 1991, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[27]  N. Poppen,et al.  Normal and abnormal motion of the shoulder. , 1976, The Journal of bone and joint surgery. American volume.

[28]  B F Morrey,et al.  Dynamic inferior stabilizers of the shoulder joint. , 2001, Clinical biomechanics.

[29]  E. Kaplan.  Muscles Alive. Their Functions Revealed by Electromyography. J. V. Basmajian. Baltimore, The Williams and Wilkins Co., 1962. $8.50 , 1962 .

[30]  P. McMahon,et al.  A novel cadaveric model for anterior-inferior shoulder dislocation using forcible apprehension positioning. , 2003, Journal of rehabilitation research and development.

[31]  F. Netter.  Atlas of Human Anatomy , 1967 .

[32]  B F Morrey,et al.  Dynamic Glenohumeral Stability Provided by the Rotator Cuff Muscles in the Mid-Range and End-Range of Motion: A Study in Cadavera* , 2000, The Journal of bone and joint surgery. American volume.

[33]  M. Pandy,et al.  Moment arm of the patellar tendon in the human knee. , 2004, Journal of biomechanics.

[34]  Patrick J McMahon,et al.  Thoracohumeral muscle activity alters glenohumeral joint biomechanics during active abduction , 2006, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[35]  T. Santner,et al.  Changes in the moment arms of the rotator cuff and deltoid muscles with abduction and rotation. , 1994, The Journal of bone and joint surgery. American volume.

[36]  D. Weiner,et al.  Superior migration of the humeral head. A radiological aid in the diagnosis of tears of the rotator cuff. , 1970, The Journal of bone and joint surgery. British volume.

[37]  G Sjøgaard,et al.  A model predicting individual shoulder muscle forces based on relationship between electromyographic and 3D external forces in static position. , 1998, Journal of biomechanics.

[38]  Poppen Nk,et al.  Forces at the glenohumeral joint in abduction. , 1978 .

[39]  J A Ringelberg,et al.  EMG and force production of some human shoulder muscles during isometric abduction. , 1985, Journal of biomechanics.

[40]  A. Cappozzo,et al.  Human movement analysis using stereophotogrammetry. Part 1: theoretical background. , 2005, Gait & posture.

[41]  A. Farron,et al.  Effect of supraspinatus deficiency on humerus translation and glenohumeral contact force during abduction. , 2007, Clinical biomechanics.

[42]  P. Herberts,et al.  Electromyographic analysis of shoulder muscle load , 1984, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.