In vivo assessment of scapulohumeral rhythm during unconstrained overhead reaching in asymptomatic subjects

Jonathan P. Braman, Sean C. Engel, Robert F. LaPrade, Paula M. Ludewig

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Background: The contribution of scapulothoracic and glenohumeral motion to overall shoulder motion remains difficult to determine. We sought to determine the exact ratio between these two motion components in order to better understand overall shoulder kinematics in asymptomatic individuals in unconstrained reaching. Materials and methods: This study assessed shoulder motion using bone-fixed sensors to quantify scapulohumeral motion during unconstrained raising and lowering of the arm. Electromagnetic tracking devices rigidly fixed to bone pins recorded active scapular and humeral motion. Results: We found a significant difference in the ratio of glenohumeral elevation to scapular upward rotation during arm raising (2.3) and lowering (2.7). Each degree of glenohumeral elevation yielded scapular upward rotation of 0.43° (raising) compared with downward rotation of 0.37° (lowering), across the motion arc. Until 125° of glenohumeral elevation, the scapula internally rotated and then externally rotated with further elevation. Scapular upward rotation and posterior tilting progressively increased until maximal elevation. Scapulohumeral rhythm was greatest in the first increment of raising the arm and higher overall when lowering the arm. Discussion: Understanding these data allows improved evaluation of potential motion abnormalities in patients with shoulder pathology and may improve treatment for restoration of normal shoulder motion.

Original languageEnglish (US)
Pages (from-to)960-967
Number of pages8
JournalJournal of Shoulder and Elbow Surgery
Volume18
Issue number6
DOIs
StatePublished - Nov 1 2009

Keywords

  • Scapulohumeral rhythm
  • glenohumeral
  • scapular motion
  • shoulder biomechanics

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