Changes of elbow kinematics and kinetics during 1 year after stroke.

A precise description of the natural history of motor recovery after stroke provides a framework for understanding the mechanisms underlying this improvement and for tracking the efficacy of rehabilitation treatments. To characterize the time course of this change in motor impairment, we examined voluntary elbow movements in hemiparetic stroke survivors over a period of 1 year after stroke. Based on the possibility that both central nervous system and muscle factors could contribute to the observed clinical state, we hypothesized that we should observe at least two major recovery patterns of motor impairment. To explore these predictions, we assessed elbow movement range, movement speed, and isometric force generation. Subjects were examined five times over the 12-month period. We used the "growth mixture" model to characterize recovery of these measures, and the Fugl-Meyer scale (FMS) of upper-extremity function at 1 month to predict the recovery. We observed two distinct recovery classes. Class 1 started with low values for the physiological measures, and these increased over time, whereas class 2 tended to start with higher values and showed widely divergent recovery patterns. Using the logistic regression model, the impact of FMS on class membership was estimated for each parameter. Based on these data, we were able to accurately predict arm impairment recovery at different time-points in the first year, information of great potential value for planning targeted therapeutic interventions.

Upper limb impairments associated with spasticity in neurological disorders.

BACKGROUND: While upper-extremity movement in individuals with neurological disorders such as stroke and spinal cord injury (SCI) has been studied for many years, the effects of spasticity on arm movement have been poorly quantified. The present study is designed to characterize the nature of impaired arm movements associated with spasticity in these two clinical populations. By comparing impaired voluntary movements between these two groups, we will gain a greater understanding of the effects of the type of spasticity on these movements and, potentially a better understanding of the underlying impairment mechanisms. METHODS: We characterized the kinematics and kinetics of rapid arm movement in SCI and neurologically intact subjects and in both the paretic and non-paretic limbs in stroke subjects. The kinematics of rapid elbow extension over the entire range of motion were quantified by measuring movement trajectory and its derivatives; i.e. movement velocity and acceleration. The kinetics were quantified by measuring maximum isometric voluntary contractions of elbow flexors and extensors. The movement smoothness was estimated using two different computational techniques. RESULTS: Most kinematic and kinetic and movement smoothness parameters changed significantly in paretic as compared to normal arms in stroke subjects (p < 0.003). Surprisingly, there were no significant differences in these parameters between SCI and stroke subjects, except for the movement smoothness (p < or = 0.02). Extension was significantly less smooth in the paretic compared to the non-paretic arm in the stroke group (p < 0.003), whereas it was within the normal range in the SCI group. There was also no significant difference in these parameters between the non-paretic arm in stroke subjects and the normal arm in healthy subjects. CONCLUSION: The findings suggest that although the cause and location of injury are different in spastic stroke and SCI subjects, the impairments in arm voluntary movement were similar in the two spastic groups. Our results also suggest that the non-paretic arm in stroke subjects was not distinguishable from the normal, and might therefore be used as an appropriate control for studying movement of the paretic arm.

Critically appraised topics.

This article describes the critically appraised topic (CAT) as a means to disseminate evidence from research literature to rehabilitation professionals. A CAT is a standardized, one-page summary of research evidence organized around a clinical question. A CAT includes a clinical bottom line that reflects synthesis of a research article and clinical application of the results. The synthesis includes a critique of the internal, external, and statistical validity of the research. The process of writing CATs has been used in the preparation of evidence-based practitioners. Commonly used websites for preparation and posting of CATs are included as well as an example of a CAT on the topic of cerebral palsy.

Abnormal intrinsic and reflex stiffness related to impaired voluntary movement.

We studied the relationship between mechanical abnormalities associated with spasticity and impairments in voluntary movements of the spastic joint in chronic, hemiparetic stroke subjects. System identification techniques were used to characterize the mechanical abnormalities of the elbow joint and to identify the contribution of intrinsic and reflex stiffness to these abnormalities. Repeated voluntary movements of the elbow from full flexion to extension at maximum speed were also conducted. These movements were quantified by measuring their kinematics parameters. The correlation coefficient was measured to determine the relationship between abnormal modulation of intrinsic and reflex stiffness as function of joint position with the kinematics parameters. We found that both intrinsic and reflex stiffness were significantly larger in stroke than control sides and were strongly position dependent, increasing with elbow extension. Abnormal modulation of intrinsic and reflex stiffness with position (slope) was correlated with an increase in duration of movement (DM), and a decrease in peak-velocity (Pv), peak-acceleration (Pa) and maximum voluntary contraction (MVC). Weakness, quantified as a decrease in MVC, was also correlated with the reduction in Pv, Pa and active range of motion (AROM). These findings demonstrate that abnormal modulation of both intrinsic and reflex stiffness with position are related to antagonist muscle weakness that may cause stroke patients to move slower and take longer to complete reaching tasks.