What is tenosynovitis of the synovial sheaths of the flexor tendons and what are its implications?

Tenosynovitis of the synovial sheaths of the flexor tendons is the infection and inflammation of the synovial sheaths that surround the long flexor tendons in the hand. It commonly results from small penetrating wounds, such as a pin prick or thorn insertion.

When infected, the digital synovial sheath becomes distended with pus, causing the affected digit to swell and become very painful due to the stretching of the sheath. The infection can spread from the digital synovial sheaths into the palmar spaces.

Specifically, infections of the digital synovial sheaths of the little finger and thumb are particularly concerning because they can quickly extend into the ulnar and radial bursae due to their continuity. If these bursae become involved and are not treated, their proximal ends may burst, allowing pus to enter the fascial space of Parona. This space is located in the forearm, between the flexor digitorum profundus muscle anteriorly and the interosseous membrane and pronator quadratus muscle posteriorly.