[Ultrastructure of the long flexor and extensor tendons of the hand in rheumatic tenosynovitis].

Tendon ruptures are a frequent problem in patients affected by rheumatoid arthritis. The aim of the present study was to further characterize the known macroscopic changes of tendon tissue by micromorphological methods. Flexor and extensor tendon samples (n = 28) in rheumatoid arthritis were investigated by light- and transmission electron microscopy. In all cases, marked alterations in fibril architecture and structure were found. The fibril diameter showed a higher variability (range = 20-490 nm, x = 98.9 nm, s = 49.1 nm) in comparison with the control group of normal tendons (range = 20-290 nm, x = 119.0 nm, s = 34.9 nm). The average distance between the major bands in rheumatoid arthritis was reduced (from 57.3 nm down to 54.8 nm). Rare minor bands were detected. Oxytalan and mature elastic fibres were destroyed. These findings suggest that a causal correlation exists between altered matrix substructure and insufficient function of the tendon tissue in rheumatoid arthritis.