Reliability of Elbow Trajectory Tracking in Chronic Post-stroke Hemiparesis

Carolynn Patten, PhD PT; Jennifer A. Whitney, MPT; Dhara Kothari, PT MS; Peter S. Lum, PhD

Objectives: The current investigation was conducted in an effort to determine test-retest reliability of elbow flexion/extension trajectory tracking in hemiparetic persons. Reliable data for determining clinically important changes in motor function are limited in the hemiparetic population, thus our aim is to establish a basis for estimating minimal clinically important differences (MCID) in upper extremity motor control resulting from therapeutic intervention.

Methods: Ten adults (mn age=59 yrs.) with post-stroke hemiparesis of greater than six months duration (mn=47.9 mos) participated in two test sessions separated by one week. Both the non-paretic (NP) and paretic (P) arms were tested within each session. The task involved tracking a ‘W’ presented on a video monitor by performing transverse plane elbow flexion and extension at three target periods (Slow: 25o/s, Medium: 45o/s, and Fast: 65o/s). Subjects were provided ongoing visual feedback of the kinematic signal and instructed to match the criterion trajectory as accurately as possible. Following ten practice and familiarization trials at each target period, data were obtained from five trials at each of the three target periods. Root-mean-square (RMS) differences between the criterion and performed trajectories were calculated and analyzed using intraclass correlation (ICC) to determine the stability of test-retest measurements.

Results: As expected, RMS was significantly greater in the P versus the NP arm at all target periods (p < .001). In both arms, RMS was least at the medium trajectory speed (NP arm - Slow: 7.10o .45, Med: 5.68o .45, Fast: 7.46o .45) (P arm - Slow: 10.45o .50, Med: 7.63o .38, Fast: 9.85o .56). ICCs for all target periods and both sides exceeded the acceptable threshold of .750 for reliability.

Conclusions: Results of the ICC analysis indicate reliable tracking can be observed in both NP and P arms of hemiparetic persons. Differences in the ICC magnitude and allocation of the variance between target periods suggest that performing the task at the medium and slow velocities involves considerable inter-trial variation in motor control strategy which may result from ongoing incorporation of feedback. These data suggest an MCID of 12% will allow for demonstration of treatment effects at all velocities in both NP and P arms.

Funding Acknowledgment: Funded by the VA Rehabilitation Research & Development Service, Project #B2405R