Biomedical subjects

Jacqueline J Wertsch

Publications and source records attributed to Jacqueline J Wertsch.

4 recordsLinked to original sources

PubMed2003

Quantitative electromyography.

Quantitative EMG is an MUAP analysis technique providing objective information on the NEE. The concept and techniques are not new; however, with the advancement of computer technology, quantitative EMG is now more easily performed. The study requires solid knowledge of basic neurophysiology and access to the appropriate instrument to provide smooth technique and accurate interpretation. Despite recent technical advances, the original MUAP parameters defined by Buchthal are still widely used today as reference values. It is increasingly recognized that many factors can influence the obtained parameters. The ability to measure something does not mean that it is fully understood. The future of quantitative EMG will depend on increased understanding of the physiologic and pathophysiologic significance of the detailed numeric parameters that are generated.

Action Potentials↗

PubMed2002

Effect of reference electrode position on the compound muscle action potential (CMAP) onset latency.

Compound muscle action potential (CMAP) onset latency is interpreted to reflect the arrival time at the muscle of impulses in the fastest-conducting motor nerve fiber. However, we have observed that the position of the reference or indifferent electrode (E2) affects CMAP onset latency. Motor nerve conduction studies (NCS) of the median, ulnar, and deep ulnar motor (DUM) nerves on 20 normal hands were performed using both traditional bipolar and experimental monopolar (referenced to the contralateral hand) montages. As the position of E2 was altered, the CMAP onset latency varied 0.1-0.5 ms for the median NCS, 0.1-0.3 ms for the ulnar NCS, and 0.1-1.5 ms for the DUM NCS. This study demonstrates that E2 recorded potentials are significant and vary with positioning, affecting motor onset latency. This has implications both for reference values and the physiologic interpretation of the CMAP waveform.

Action Potentials↗

PubMed2002

Analysis of postural control synergies during quiet standing in healthy children and children with cerebral palsy.

OBJECTIVE: To estimate the contribution of body transverse rotation using weighted differential center of pressure signals during quiet standing in healthy children and in children with cerebral palsy. DESIGN: Body sway was indirectly measured through center of pressure data, which was calculated using dual force platforms. BACKGROUND: Assessment of postural control synergies using center of pressure data provides a unique method for center of mass data analysis in characterizing complex balance sway. METHODS: Using dual force platforms, linear expressions for the coordinates of right and left center of pressure signals were developed to identify and characterize balance control synergies during quiet standing. Subjects were also tested during eyes open and eyes closed trials to determine the significance of visual input on these control synergies. RESULTS: The limb protraction/retraction control was found to be dominant during medial-lateral sway, whereas the estimated body transverse rotation contribution was found to be more significant than the previously reported measures of anterior-posterior balance. These findings were consistent in healthy children and in children with cerebral palsy during both eyes open and eyes closed trials. CONCLUSION: The weighted differential center of pressure signals show that the estimated body transverse rotation contribution is significant in healthy children and critical for postural stability in children with cerebral palsy. RELEVANCE: This study identifies the significance of body transverse rotation control contribution in upright posture. Children with cerebral palsy with relatively poor ankle control demonstrate the importance of body transverse rotation for postural stability.

Ankle Joint↗

PubMed2002

Development of a quantitative reflex hammer for measurement of tendon stretch reflex.

Quantification of tendon stretch reflex requires precise measurement of the tapping force of a reflex hammer. A quantitative reflex (QR) hammer consisting of two cut rubber pieces from a generic rubber reflex hammer and a uniaxial force transducer was constructed. Finite element stress analyses were conducted to estimate the natural frequency characteristics of the hammer and to find the stress distributions during the impact. Pendulum impact testing was conducted at four different heights to assess the calibration linearity and repeatability of the measurement. The QR hammer had a fundamental natural frequency of 515 Hz and showed minimal displacement and stress at the tip from the finite element simulation of the impact. The QR hammer also provided reliable and repeatable measurements as demonstrated with high coefficients of determination, exceeding 0.994 and small coefficients of variations, less than 4%. The calibration linearity was 0.64% compared with the reference force platform measurement. The QR hammer demonstrated sufficient accuracy and reliability for precise clinical assessment of tendon stretch reflexes.

Calibration↗