MECHANICAL-PROPERTIES OF WRIST EXTENSOR TENDONS ARE ALTERED BY THE PRESENCE OF RHEUMATOID-ARTHRITIS

The in vitro mechanical properties of 14 wrist extensor tendons salvag ed at surgery from patients with inflammatory (rheumatoid) arthritis a nd noninflammatory arthrosis were measured in uniaxial tension and com pared. The rheumatoid tendons had higher extensibility at low stresses , lower stiffness in the linear portion of the stress-strain curve, gr eater rates of stress relaxation, and lower ultimate strengths than di d the nonrheumatoid tendons. Differences in tangent modulus, stress re maining at 100 seconds, and ultimate tensile strength were significant at the 95% confidence level. In vivo, mechanically impaired tendons m ay play an important role in destabilization of the wrist in patients with rheumatoid arthritis.