Pressure dependence of "the area micrometer" method in evaluation of cruciate ligament cross-section

The intricate geometry of the cruciate ligament and the lack of adequate description of the methods used to obtain its cross-sectional area have complicated the normalization of the load-elongation data in terms of stress and strain respectively. An experimental study was undertaken to quantify the dependence on the applied pressure of cross-sectional area in canine ligaments. Twenty-two canine preparations were compressed with a non-rotating spindle blade micrometer (Mitutoyo, 122), whose thimble breakaway tongue develops a constant force of 1.96 N. By the use of matching pairs of plexiglass blocks of various widths, the applied pressure on the ligament could be varied between 0.041 and 0.355 MPa. Data from all the ligaments were reduced to a single curve which illustrates a decrease in the normalized cross-sectional area by 25% for pressures ranging from 0.04 to 0.36 MPa. For all pressures between 0.20 and 0.35 MPa the normalized cross-sectional area remained constant.