Should the instructions issued to the subject in traditional static posturography be standardised?

The postural ability of a subject is usually evaluated through the observation of the centre of pressure parameters obtained through posturography. These parameters are known to be sensitive to various factors and standards have consequently been proposed for data acquisition and analysis. A factor usually not taken into due consideration but likely to influence the postural exam is the kind of standing posture (e.g. natural or immobile) a subject is instructed to maintain. This study aimed at investigating whether instructions issued in a traditional static posturographic test influence its outcome and hence should be considered in the standardisation of the posturography protocols. Two groups of young healthy subjects were each issued one of two common instructions, "stand quietly" or "stand as still as possible", by means of projected instructions. Differences between the two groups were investigated for commonly calculated centre of pressure parameters. All these parameters, but the mean frequency, were significantly different, with variations in the range between 8% (mean velocity) and 71% (confidence circle area). These results suggest that instructions given to the subjects strongly influence the outcome of posturography and should, hence, be standardised.

Mobility assessment of patients with facioscapulohumeral dystrophy.

BACKGROUND: Facioscapulohumeral muscular dystrophy is the third most common form of inherited myopathies with a prevalence of 1:20,000. Since both muscle involvement and disease progression are heterogeneous and unpredictable, quantitative assessment tools are needed to evaluate the effects of pharmacological and physical training treatments. METHODS: The instrumented movement analysis of 12 patients with facioscapulohumeral dystrophy and 12 control subjects was conducted using a 9-camera stereophotogrammetric system and 2 force platforms. Subjects performed four tasks of different difficulties: arm movement, level walking, step ascending, and squatting. Manual muscle test, clinical severity scale and magnetic resonance imaging were used to clinically assess the patients. FINDINGS: Walking speed and centre of mass vertical displacement during squatting were reduced in patients and can be used to assess their motor capacity. Features common in the patient sample were: the reduction of shoulder range of motion, the excessive ankle plantar-flexion during walking and step ascending, and the reduction of knee flexion-extension moment during squatting. These parameters were correlated with magnetic resonance imaging results at relevant structure level and can be used to assess the corresponding body functioning. Furthermore, instrumented movement analysis was able to distinguish from normal controls also a group of patients in which clinical assessments did not show any obvious abnormalities and had been evaluated as normal. INTERPRETATION: The quantitative assessment tool devised in this study provides suitable information in terms of both motor capacity and impairment severity of patients with facioscapulohumeral dystrophy, and, thus, encouraging its use for the evaluation of therapeutic trial outcomes for this disease.