Original Article
Copyright ©2012 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Orthop. Jun 18, 2012; 3(6): 87-94
Published online Jun 18, 2012. doi: 10.5312/wjo.v3.i6.87
Assessment of scapulohumeral rhythm for scapular plane shoulder elevation using a modified digital inclinometer
Jason S Scibek, Christopher R Carcia
Jason S Scibek, Department of Athletic Training, School of Health Sciences, Duquesne University, John G Rangos, Sr., Pittsburgh, PA 15282, United States
Christopher R Carcia, Department of Physical Therapy, School of Health Sciences, Duquesne University, John G Rangos, Sr., Pittsburgh, PA 15282, United States
Author contributions: Scibek JS and Carcia CR were responsible for conceptualizing the study, developing and designing the methodology, collecting and analyzing the data, and contributing to the development, writing and editing of the manuscript.
Supported by Pennsylvania Athletic Trainers’ Society Research Grant, No. G0900028
Correspondence to: Jason S Scibek, PhD, ATC, Associate Professor, Duquesne University, 600 Forbes Avenue, 118 HLSB, Pittsburgh, PA 15282, United States. scibekj@duq.edu
Telephone: +1-412-3965960 Fax: +1-412-3964160
Received: January 10, 2012
Revised: May 11, 2012
Accepted: June 5, 2012
Published online: June 18, 2012

AIM: To develop a better understanding of scapulohumeral rhythm during scapular plane shoulder elevation.

METHODS: Thirteen healthy, college-aged subjects participated in this study. Subjects were free from any upper extremity, neck or back pathology. A modified digital inclinometer was utilized to measure scapular upward rotation of the subject’s dominant shoulder. Upward rotation was measured statically as subjects performed clinically relevant amounts of shoulder elevation in the scapular plane. Testing order was randomized by arm position. Scapular upward rotation was assessed over the entire arc of motion and over a series of increments. The percent contributions to shoulder elevation for the scapula and glenohumeral joint were calculated. Scapulohumeral rhythm was assessed and represented the ratio of glenohumeral motion to scapulothoracic motion (glenohumeral elevation: scapular upward rotation). A one-way ANOVA was used to compare scapular upward rotation between elevation increments.

RESULTS: Scapulohumeral rhythm for the entire arc of shoulder elevation was equal to a ratio of 2.34 :1 and ranged from 40.01:1 to 0.90:1 when assessed across the different increments of humeral elevation. Total scapular motion increased over the arc of shoulder elevation. The scapula contributed 2.53% of total motion for the first 30 degrees of shoulder elevation, between 20.87% and 37.53% for 30o-90o of shoulder elevation, and 52.73% for 90o-120o of shoulder elevation. Statistically significant differences in scapular upward rotation were identified across the shoulder elevation increments [F(3,48) = 12.63, P = 0.0001].

CONCLUSION: Clinically, we must recognize the usefulness of the inclinometer in documenting the variable nature of scapulohumeral rhythm in healthy and injured shoulders.

Keywords: Biomechanics, Kinematics, Scapula, Shoulder