Microsensor for Intramuscular Pressure

Principal Investigator: Kenton R. Kaufman, Ph.D., PE
Project Coordinator: Duane Morrow — morrow.duane@mayo.edu
Funding Source: NIH HD31476

Figure 1. Magnified image that shows a human hair compared to the sized of the pressure sensor mounted at the end of an optical fiber and a sensor with an attached protective sheath.

Currently, no practical method exists for direct measurement of force production from individual muscles. Manual muscle tests do not give an accurate estimate of muscle strength. Measurements of joint torque are inadequate because several muscles often contribute to torque development. Implantation of a buckle transducer on a tendon is highly invasive and impractical for regular use. The integrated electromyogram is customarily used to provide quantification of muscle contraction. However, the problem remains that the electromyographic activity cannot provide a quantitative measure of muscle tension under dynamic conditions. An alternative, measurable parameter related to muscle force is intramuscular pressure. Commercially available intramuscular pressure transducers are too large for optimum comfort. Microsensor technology is now available to construct transducers that are approximately the same size as the fine wires used for electromyographic analysis.

The overall objective of this project is to develop and test a fiber optic microsensor (see Figure 1) that can be used for routine, clinical measurement of muscle function. The specific aims of this study are:

1. to continue development of a fiber optic microsensor to measure intramuscular pressure,
2. to determine the relationships between intramuscular pressure and muscle tension under dynamic conditions for normal muscle in an animal model,
3. to develop a finite element model of intramuscular pressure in order to establish a theoretical basis for understanding the experimental measurements, and
4. to perform in-vivo human experiments to evaluate the ability of intramuscular pressure to reflect the recruitment of motor units, number of active motor units, and the size of the compound muscle action potential.

Publications

• Jenkyn T, Koopman HFJM, Huijing PA, Lieber RL, Kaufman KR: "Finite Element Model of Intramuscular Pressure During Isometric Contraction of muscle" Physics in Medicine and Biology 47:4043-4061, 2002.
• Kaufman KR, Wavering T, Morrow D, Davis J, Lieber RL: "Performance Characteristics of a Pressure Microsensor" Journal of Biomechanics 36:283-287, 2002.
• Davis J, Kaufman KR, Lieber RL: "Correlation Between Active and Passive Isometric Stress and Intramuscular Pressure in the Isolated Rabbit Tibialis Anterior Muscle" Journal of Biomechanics 36:505-512, 2002.
• Yang C, Zhao CF, Kaufman KR: "Biocompatibility of a Physiological Pressure Sensor" Biosensors and Bioelectronics 19(1):51-58, 2003.
• Chen S, Pislaru C, Kinnick RR, Morrow DA, Kaufman KR, Greenleaf JF: "Evaluating the Dynamic performance of a fiber optic pressure microsensor." Physiologic Measurement 26(4):N13-N19, August 2005.
• Ward SR, Davis J, Kaufman KR, Lieber RL: "Relationship Between Muscle Stress and Intramuscular Pressure During Dynamic Muscle Contractions" Muscle Nerve 36(3):313-319, 2007.
• Odegard G, Haut Donahue T, Morrow D, Kaufman KR: "Constitutive Modeling of Skeletal Muscle Tissue with an Explicit Strain-Energy Function" J Biomechanical Engineering 130:061017-1 – 061017-9, December 2008.
• Morrow, DA, Haut Donahue TL, Odegard GM, Kaufman KR: "Transversely Isotropic Tensile Material Properties of Skeletal Muscle Tissue" Journal of the Mechanical Behavior of Biomedical Materials Accepted for Publication.