A device for measuring soft tissue pressure: application to human intervertebral disc and bovine tendon

A needle mounted strain gauge pressure sensor has been developed that has proven to be both accurate and reliable. It is a resistive strain gauge mounted on a pressure diaphragm which is exposed to pressure through a silicone window. The transducer is used in a Wheatstone bridge configuration and incorporates a dummy resister for temperature compensation. The transducer cable also contains an excitation voltage limiting circuit for protection of the sensor. The authors used a Measurements Group model 2100 amplifier to provide an excitation voltage of 3 V DC and a gain of 300. Although the sensor´s maximum deviation from linearity is over 5%, its curve can be fitted by a quadratic to within 0.4% error. Its use for intradiscal pressure measurements appears to be very satisfactory. Measurement of tendon and ligament tensile force was also good