Intradiscal pressure measurements above an instrumented fusion. A cadaveric study.

Study Design: An in vitro study to determine the intradiscal pressure changes during flexion in levels above a simulated fusion was performed.

Objectives: To determine if intradiscal pressure increases more during flexion in discs above an instrumented spinal segment compared to an uninstrumented segment.

Summary Of Background Data: The progressive degeneration of intervertebral discs adjacent to a fused or fixed segment is a phenomenon that is noted but poorly understood.

Measurement of angular displacements using Hall effect transducers.

Hall effect transducers were studied as an alternative to limited-wear precision potentiometers and optical encoders in measuring angular displacements. Various design parameters are identified, and the optimum Hall effect transducer configuration is presented. Using this configuration, it was possible to measure an angular rotation of 140 degrees with a standard deviation of 0.