VARIATION IN MEASUREMENTS OF RANGE OF MOTION - A STUDY IN REFLEX SYMPATHETIC DYSTROPHY PATIENTS

Objective: To quantify the amount of variation attributed to different sources of variation in measurement results of upper extremity range of motion, and to estimate the smallest detectable difference (SDD) be tween measurements in reflex sympathetic dystrophy (RSD) patients. Des ign: Two observers each measured in two sessions the range of motion o f several upper extremity joints of RSD patients participating in an o utcome study.Setting: Department of Rehabilitation of a university hos pital. Subjects: Twenty-nine upper extremity RSD patients. Main outcom e measures: The range of motion of forward flexion and external rotati on of the shoulder, extension, flexion and supination of the elbow, pa lmar, dorsiflexion and ulnar, radial deviation of the wrist of affecte d and nonaffected sides, using a two-armed goniometer and an inclinome ter. The measurement results were analysed using an analysis of varian ce according to the generalizability theory. Results: The results indi cate that observer and patient-observer were important sources of vari ation. The random error was the most important source of variation. Av eraged over all ranges of motion the observer contributed 3.9% to the total variation, patient-observer interactions contributed 5.2% and th e random error 20.3%. The SDD was smallest for elbow flexion, 7.1 degr ees and 9.6 degrees and was largest for external rotation of the shoul der, 24.8 degrees and 28.7 degrees. The SDD was smaller for the nonaff ected side as compared to the affected side for the majority of ranges of motion except elbow extension, wrist dorsiflexion, and radial and ulnar deviation. Conclusion: Clinically, our results indicate that ran ge-of-motion measurements in RSD patients are subject to considerable variation and indicate that results of medical examinations in order t o assess disability on the basis of range-of-motion measurements are s ubject to the same variation.