  Strokes are a leading cause of disability, with many experiencing difficulty
in recovering arm movement, particularly hand function and grasping ability.
There is currently no objective measure of movement quality, and without it,
rehabilitative interventions remain at best estimations of the underlying
neural structures response to produce movement. In this paper, we utilize a
novel modification to Procrustean distance to quantify curve dissimilarity and
propose the Reach Severity and Dissimilarity Index (RSDI) as an objective
measure of motor deficits. All experiments took place at the Medstar National
Rehabilitation Hospital; persons with stroke were recruited from the hospital
patient population. Using Fugl-Meyer (FM) scores and reach capacities, stroke
survivors were placed in mild or severe impairment groups. Individuals
completed sets of reach-to-target tasks to extrapolate kinematic metrics
describing motor performance. The Procrustes method of statistical shape
analysis was modified to identify reaching sub-movements that were congruous to
able-bodied sub-movements. Movement initiation proceeds comparably to the
reference curve in two- and three-dimensional representations of mild
impairment movement. There were significant effects of the location of
congruent segments between subject and reference curves, mean velocities, peak
roll angle, and target error. These metrics were used to calculate a
preliminary RSDI score with severity and dissimilarity sub-scores, and subjects
were reclassified in terms of rehabilitation goals as Speed Emphasis, Strength
Emphasis, and Combined Emphasis. The Modified Procrustes method shows promise
in identifying disruptions in movement and monitoring recovery without adding
to patient burden. The proposed RSDI score, while limited in scope, can be
adapted and expanded to other functional movements and used as an objective
clinical tool.
