Etiology of Spontaneous Extensor Tendon Injury in Northern-China Rice Farmers.

Background: Spontaneous extensor tendon injury is caused by repeated finger flexion and wrist movement. This rare disease has a relatively high incidence in northern China, mostly among rice farmers. This study aimed to elucidate the etiology of spontaneous extensor tendon injury in rice farmers.

Methods: Morphologic changes in the extensor tendons and wrist extensor retinaculum in wrist dorsiflexion were studied via ultrasound examination of the hands of 30 healthy adult men, and 34 patients with a non-rupture extensor tendon injury and 11 patients with spontaneous ruptures of the extensor tendons were also enrolled in the study. The daily workload and potential causes of injuries were assessed.

Results: Ultrasound images of healthy male hands showed that during wrist dorsiflexion, the extensor retinaculum of the wrist forms differently shaped trochleas as the dorsiflexion angle changes. Histopathologic examination of the wrist extensor retinaculum revealed that the inner face was abraded evenly, the synovial membrane on the surface of the wrist extensor retinaculum disappeared, the internal coarse fibers were exposed and there was fibrous debris, suggesting that dry friction occurred before the rupture.

Conclusions: From clinical observation it could be concluded that the severity and progress of swelling and pain are related to the force applied during rice transplantation as abrasions were found at the front of the wrist extensor retinaculum.