Cross-sectional area measurements for tendon specimens: a comparison of several methods.

Several methods for measuring cross-sectional areas of cat extensor digitorum communis tendons. were evaluated in terms of repeatability. Estimates of correction factors to be used in relating measurements by different methods were also obtained. The measurements examined included: (1) moist specimen weight per unit length, (2) moist specimen displacement volume per unit length, (3) dry specimen weight per unit length, (4) dry specimen displacement volume per unit length, (5) area measured with an area micrometer similar in principle to the instrument described by Walker et al. (1964), (6) area by shadow amplitude contour reconstruction, and (7) planimeter measurements on photomicrographs of histological sections. The results obtained suggested that dry specimen weight per unit length could be expected to yield the most repeatable single measurements for cross-sectional areas of tendon specimens. For measurements of fresh, moist specimens, gravimetric methods and measurements with the area micrometer were found roughly comparable in repeatability and better than shadow amplitude contour reconstruction. The area micrometer measurements seemed less sensitive to slight drying of the specimen, but were considerably influenced by the pressure applied to the specimen during measurement. Comparisons of the values for cross-sectional area obtained by the various methods showed significant systematic differences, with several pairs of methods giving measurements which differed by factors of 2 or more. Measurements by methods which were more or less local in nature demonstrated sizable regional variations in cross-sectional areas of the specimens even though they had a relatively uniform appearance.