Reciprocal inhibition post-stroke is related to reflex excitability and movement ability.

OBJECTIVE: Decreased reciprocal inhibition (RI) of motor neurons may contribute to spasticity after stroke. However, decreased RI is not a uniform observation among stroke survivors, suggesting that this spinal circuit may be influenced by other stroke-related characteristics. The purpose of this study was to measure RI post-stroke and to examine the relationship between RI and other features of stroke. METHODS: RI was examined in 15 stroke survivors (PAR) and 10 control subjects by quantifying the effect of peroneal nerve stimulation on soleus H-reflex amplitude. The relationship between RI and age, time post-stroke, lesion side, walking velocity, Fugl-Meyer, Ashworth, and Achilles reflex scores was examined. RESULTS: RI was absent and replaced by reciprocal facilitation in 10 of 15 PAR individuals. Reciprocal facilitation was associated with low Fugl-Meyer scores and slow walking velocities but not with hyperactive Achilles tendon reflexes. There was no relationship between RI or reciprocal facilitation and time post-stroke, lesion side, or Ashworth score. CONCLUSIONS: Decreased RI is not a uniform finding post-stroke and is more closely related to walking ability and movement impairment than to spasticity. SIGNIFICANCE: Phenomena other than decreased RI may contribute to post-stroke spasticity.

An upper extremity inverse dynamics model for pediatric Lofstrand crutch-assisted gait.

The objective of this study was to develop an instrumented Lofstrand crutch system, which quantifies three-dimensional (3-D) upper extremity (UE) kinematics and kinetics using an inverse dynamics model. The model describes the dynamics of the shoulders, elbows, wrists, and crutches and is compliant with the International Society of Biomechanics (ISB) recommended standards. A custom designed Lofstrand crutch system with four, six-degree-of-freedom force transducers was implemented with the inverse dynamics model to obtain triaxial UE joint reaction forces and moments. The crutch system was validated statically and dynamically for accuracy of computing joint reaction forces and moments during gait. The root mean square (RMS) error of the system ranged from 0.84 to 5.20%. The system was demonstrated in children with diplegic cerebral palsy (CP), incomplete spinal cord injury (SCI), and type I osteogenesis imperfecta (OI). The greatest joint reaction forces were observed in the posterior direction of the wrist, while shoulder flexion moments were the greatest joint reaction moments. The subject with CP showed the highest forces and the subject with SCI demonstrated the highest moments. Dynamic quantification may help to elucidate UE joint demands in regard to pain and pathology in long-term assistive device users.

Upper extremity biomechanical model of crutch-assisted gait in children.

A 3D biomechanical model with a novel instrumented Lofstrand crutch system is presented. The novel Lofstrand crutch system consists of two six-axis load cells incorporated in the crutch to study the reaction forces occurring at the crutch handle and the cuff. The goal of this study is to quantify the effect of the cuff forces with the help of this improved crutch system. The kinematic model developed is verified based on previous studies. The kinetic model, consisting of the forces, is derived using the kinematic data, anthropometric data and the reaction forces generated from the load cells. The kinetic data is also in accordance with previous studies. Thus, the novel crutch system has been verified for evaluating the force loading on shoulder, elbow and wrist. This model would be further implemented on children suffering from Osteogenesis Imperfecta (OI), which would help in evaluating injury prevention criteria for long-term crutch users.