Advertisement
Journal of Shoulder and Elbow Surgery

Increased horizontal shoulder abduction is associated with an increase in shoulder joint load in baseball pitching

      Background

      Soft tissues of the shoulder undergoes substantial stresses due to humeral head movement, and this may contribute to throwing shoulder injuries in baseball pitchers. Prevention and management of throwing shoulder injuries critically rely on reduction of shear force at the shoulder joint. However, the amount and direction of the force applied to the shoulder during the throwing motion have not been clarified. The purpose of this study was to analyze forces applied to the shoulder during a baseball pitch.

      Methods

      We performed biomechanical analysis of 213 baseball pitchers of various ages and skill levels. Throwing motion was analyzed with a 3-dimensional motion capture system. The Euler angle sequence was adopted to describe angular values of the upper arm relative to the trunk for shoulder rotation, and inverse dynamics was used to estimate the resultant joint forces at the shoulder.

      Results

      There was a significant relation between horizontal abduction/adduction angle and resultant anterior/posterior force at the point of maximum external rotation (MER) (r = −0.63, P < .01), whereby increased horizontal abduction was associated with increased resultant anterior force. There was a significant but weak correlation between abduction/adduction angle and superior/inferior force at MER (r = 0.24, P < .01). Comparison among the groups with variable ages and skill levels showed larger horizontal abduction and smaller external rotation angles at MER in the adult amateur player group, whereas normalized compression force and internal rotation torque values at MER were smaller in the junior high school– and elementary school–aged groups.

      Discussion

      These results suggest that excessive horizontal abduction at MER increases anterior shear force in the shoulder and may lead to shoulder injuries. Focusing on reducing horizontal abduction at MER in the throwing motion may be key to preventing and managing shoulder injuries in baseball pitchers.

      Level of evidence

      Keywords

      To read this article in full you will need to make a payment

      References

        • Ae M.
        • Tang H.
        • Yokoi T.
        Estimation of inertial properties on the body segments in Japanese athletes.
        in: Society of Biomechanisms Biomechanisms 11: form, motion, and function in humans. University of Tokyo Press, Tokyo1992: 23-33
        • Andrews J.R.
        • Kupferman S.P.
        • Dillman C.J.
        Labral tears in throwing and racquet sports.
        Clin Sports Med. 1991; 10: 910-911
        • Burkhart S.S.
        • Morgan C.D.
        • Kibler B.
        Current concepts. The disabled throwing shoulder: spectrum of pathology. Part I: pathoanatomy and biomechanics.
        Arthroscopy. 2003; 19: 404-420https://doi.org/10.1053/jars.2003.50128
        • Fleisig G.S.
        • Andrews J.R.
        • Dillman C.J.
        • Escamilla R.F.
        Kinetics of baseball pitching with implications about injury mechanisms.
        Am J Sports Med. 1995; 23: 233-239
        • Heyworth B.E.
        • Williams III, R.J.
        Internal impingement of the shoulder.
        Am J Sports Med. 2009; 37: 1024-1037https://doi.org/10.1177/0363546508324966
        • Jobe F.W.
        • Giangarra C.E.
        • Kvitne R.S.
        • Glousman R.E.
        Anterior capsulolabral reconstruction of the shoulder in athletes in overhand sports.
        Am J Sports Med. 1991; 19: 428-434
        • Laudner K.G.
        • Moline M.T.
        • Meister K.
        The relationship between forward scapular posture and posterior shoulder tightness among baseball players.
        Am J Sports Med. 2010; 38: 2106-2112https://doi.org/10.1177/0363546510370291
        • Mihata T.
        • Lee Y.
        • McGarry M.H.
        • Abe M.
        • Lee T.Q.
        Excessive humeral external rotation results in increased shoulder laxity.
        Am J Sports Med. 2004; 32: 1278-1285https://doi.org/10.1177/0363546503262188
        • Mihata T.
        • McGarry M.H.
        • Kinoshita M.
        • Lee T.Q.
        Excessive glenohumeral horizontal abduction as occurs during the late cocking phase of the throwing motion can be critical for internal impingement.
        Am J Sports Med. 2010; 38: 369-374https://doi.org/10.1177/0363546509346408
        • Miyashita K.
        • Kobayashi H.
        • Koshida S.
        • Urabe Y.
        Glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation in throwing.
        Am J Sports Med. 2010; 38: 363-368https://doi.org/10.1177/0363546509347542
        • Myers J.B.
        • Oyama S.
        • Hibberd E.E.
        Scapular dysfunction in high school baseball players sustaining throwing-related upper extremity injury: a prospective study.
        J Shoulder Elbow Surg. 2013; 22: 1154-1159https://doi.org/10.1016/j.jse.2012.12.029
        • Nakamizo H.
        • Nakamura Y.
        • Nobuhara K.
        • Yamamoto T.
        Loss of glenohumeral internal rotation in little league pitchers: a biomechanical study.
        J Shoulder Elbow Surg. 2008; 17: 795-801https://doi.org/10.1016/j.jse.2008.02.013
        • Nobuhara K.
        The shoulder: its function and clinical aspects.
        in: Nobuhara K. The shoulder in sports. World Scientific, Singapore2003: 401-460
        • Nobuhara K.
        • Ikeda H.
        Rotator interval lesion.
        Clin Orthop Relat Res. 1987; 223: 44-50
        • Sabick M.B.
        Humeral torque in professional baseball pitchers.
        Am J Sports Med. 2004; 32: 892-898https://doi.org/10.1177/0363546503259354
        • Sabick M.B.
        • Kim Y.K.
        • Torry M.R.
        • Keirns M.A.
        • Hawkins R.J.
        Biomechanics of the shoulder in youth baseball pitchers: implications for the development of proximal humeral epiphysiolysis and humeral retrotorsion.
        Am J Sports Med. 2005; 33: 1716-1722https://doi.org/10.1177/0363546505275347
        • Stodden D.F.
        • Fleisig G.S.
        • McLean S.P.
        • Andrews J.R.
        Relationship of biomechanical factors to baseball pitching velocity: within pitcher variation.
        J Appl Biomech. 2005; 21: 44-56
        • Walch G.
        • Boileau P.
        • Noel E.
        • Donell S.
        Impingement of the deep surface of the supraspinatus tendon on the posterosuperior glenoid rim: an arthroscopic study.
        J Shoulder Elbow Surg. 1992; 1: 238-245
        • Whiteley R.
        Baseball throwing mechanics as they relate to pathology and performance—a review.
        J Sports Science Med. 2007; 6: 1-20

      Linked Article