Reliability of a New Instrument to Measure Scapular Position

Abstract

The purpose of this study was to develop an objective method to measure scapular position as it relates to the frontal, sagittal and transverse reference planes of the human body. Contemporary shoulder rehabilitation programs place great emphasis on the role of the scapula in the treatment of shoulder pathology. While clinicians employ many treatment techniques aimed at improving scapular function, a literature review reveals that clinicians lack objective measurement techniques to measure scapular position. A Scapular Measurement Instrument (SMI) was used to objectify scapular position. Eleven subjects, who reported no current history of shoulder pain or pathology, were included in the study. Testers obtained measurements of scapulae position with respect to the frontal, sagittal, and transverse planes of the body. Inferior angle scapular measurements (IAM) and spine of the scapula measurements (SM) were taken. Two test positions were used. Position 1 was termed the “rest position” and involved subjects sitting with their arms resting at their side; position 2 involved subjects placing their arms in a “reach position” touching their opposite shoulder blade. Statistical analysis was carried out in an attempt to estimate reliability. Intratester and intertester correlation coefficients (ICC), and Standard Error of Measurement (SEM) values were calculated for all measurements. In an attempt to validate the frontal and sagittal plane referenced measurements, subjects' scapulae positions were quantified via radiographic (x-ray) analysis. Pearson Moment Correlation Coefficients were used to assess the measurement relationships between x-ray and (SMI) obtained values. Intratester ICC values for the rest condition ranged from .68 to .88 (IAM) and .68 to 86 (SM). Intratester ICC values for the reach condition ranged from .51 to .91 (IAM) and .60 to .95 (SM). Intertester ICC values for the rest condition ranged from .68 to .80 (IAM) and .80 to .95 (SM), and intertester ICC for the reach condition ranged from .48 to .66 (IAM) and .30 to .86 (SM). These values indicate better reliability for the rest condition. Intratester reliability values were generally greater than intertester values. SEM was 1 cm or less for all measurements. In regard to the validation of testers' measurements via x-ray, Pearson Moment Correlation Coefficients revealed a general trend of greater validity for rest versus reach conditions. Rest-condition correlation data ranged from .87 to .96, while reach-condition correlation data ranged from .23 to .93. The large range in correlation data was believed to be representative of random error of measurement. The authors feel that this technique is a viable option for objective measurement of at-rest scapular position. Further research is suggested, including refinement of the SMI and investigation into alternative radiographic and measurement procedures.