VARIABLES AFFECTING THE MEASUREMENT OF STRENGTH COMPONENT IN CONSTANT- MURLEY SHOULDER SCORING SYSTEM.

Abstract

The Constant-Murley score has gained wide acceptance for evaluation of shoulder function. The strength component of the Constant score accounts for 25 out of 100 points. It has been criticized for lack of consistency in defined measurement method.

The aim of this study was to evaluate the effect of various variables on the strength component measurement of the Constant score.

Material & Methods We conducted a series of experiments using a digital force gauge (EZ force). We evaluated the effect of strength measurements with 1) patient in sitting & standing positions 2) strength gauge fixed to an immobile platform or hanging free fixed to the floor by the examiners foot 3) patient’s arm in 45 degrees and 90 degrees of abduction 4) plane of elevation in frontal or scapular plane and 5) patient making a fist or keeping the palm open during the test. These experiments were done in groups of 20 patients. We have compared as well this device and the Isobex Myometer.

Results No statistical differences were found between individual measurements with regard to patient’s position (standing-sitting), device setting (Fixed –Hanging), position of the arm in varying degrees of abduction or the plane of elevation. Strength assessment obtained when patient made a fist compared to open palm was found to be higher (p=0.006). The measurements showed good intra-observer reliability.

The readings of the EZ force and the Isobex myometer were comparable.

Conclusions It seems that the shoulder strength measurements as part of the Constant functional score may be performed with the patient sitting or standing, with the arm at varying degrees of abduction and in different planes of elevation without causing any significant deviation in the measurement.

No influence was found as well to the device being either fixed to an immobile platform or fixed to the floor by the examiner’s foot. These make these measurements easy to perform and reproducible using the newly designed digital force gauge (EZ force).