We report the effects of early and late ultrasound treatment protocols on healing of surgically lacerated zone 2 flexor tendons in a chicken model. Ultrasound was administered directly using a coupling gel. Treatment was shown to increase range of movement, to advance scar maturation and to decrease the amount of inflammatory infiltrate around the repair site. No adverse effects on tensile strength were noted in either group. Early (starting 7 days post-operatively) administration was more effective than late (starting 42 days post-operatively) administration in achieving these effects. These results suggest that ultrasound therapy may be of benefit in the early healing process of flexor tendon lacerations.

A photoelectric plethysmograph is described that performs a frequency analysis of the peripheral volume pulse wave using a portable computer. It was used to determine how the pulse shape varied with age using 54 subjects in three age groups, 10-29, 30-59, and 60-89 years. The youngest group had a larger power in the second harmonic, (normalized to the fundamental), with p less than 0.05 than the older two groups. The decrease of power in the harmonics of the peripheral pulse wave with age may be a useful noninvasive measure of aging and vascular disease.

Strips of human thoracic aortic wall taken at autopsy from 23 individuals aged 15-81 years have been tested in two ways: in uniaxial loading and by digestion in 0.1 M NaOH at 75 degrees C under a load of 50 g. The circumferentially oriented strips were more extensible in loading and took a longer time to fail while being digested under load than the longitudinal strips from the same location. The stress versus strain curve was fitted to an exponential equation of the form, stress = A[exp(B strain)]. For circumferentially oriented strips from 19 subjects, parameter A was independent of age. Parameter B increased by a factor of 2.75 from 19 to 81 years. For longitudinally oriented strips for 14 subjects, A was also independent of age and B increased by 2.4 times from 25 to 81. With digestion under load for 11 matched pairs of strips aged from 32 to 75 the circumferential strips failed in 117 +/- 23 min (standard error), while the longitudinal ones failed in 20.3 +/- 3.2 min (standard error) (p less than 0.003). The results have important implications for vessel attachments to the aorta in heart transplantation and in vascular surgery.

Mechanical anisotropy was found in elastin from the wall of the thoracic aorta by testing digested vessels from seven mature dogs and five pregnant ewes. The elastin was purified by removing the muscle and collagen with 0.1 N NaOH at 75 degrees C for 5 h. Strips oriented circumferentially and longitudinally with respect to the vessel axis were cycled at increasing loads until failure. Combining the results for four dogs and three sheep the ultimate tensile strength was 405 X 10(3) +/- 155 X 10(3) SD N/m2 circumferentially and 189 X 10(3) +/- 85 X 10(3) SD N/m2 longitudinally. The difference is significant at p less than 0.01. The ultimate strain was not significantly different, 1.19 +/- 0.29 SD circumferentially and 1.01 +/- 0.26 SD longitudinally. At 0.4 strain, the Young's modulus for four samples from four dogs was 404 X 10(3) +/- 64 X 10(3) SD N/m2 circumferentially; the modulus for five samples from five dogs was 245 X 10(3) +/- 60 X 10(3) SD N/m2 longitudinally. The difference is significant at p less than 0.05. At 0.7 strain, the Young's modulus for four dogs was 486 X 10(3) +/- 82 X 10(3) SD N/m2 circumferentially and 343 X 10(3) +/- 62 X 10(3) SD N/m2 longitudinally. The difference is significant at p less than 0.05. The reasons for the anisotropy in terms of the structure are not obvious from preliminary studies using the scanning electron microscope with stretched samples.