Unusual Presentation of Extensor Tendon Rupture Caused by a Dorsal Wrist Synovial Cyst

Synovial cysts are juxta-articular-fluid–filled collections that are lined by synovial cells, distinguishing them from a very close cystic lesion, which is the ganglion cyst. They usually present with pain and unpleasant appearance; here we present a case of wrist synovial cyst that caused extensor tendon rupture. A 50-year-old woman presented to our clinic with a cystic lesion on the dorsum of her wrist, with an inability to extend her index finger. The lesion was found intraoperatively engulfing the extensors of the index and causing a rupture. The cyst was excised and the tendon was reconstructed; pathology report confirmed the lesion as synovial cyst. Synovial cysts and ganglion cysts are two different entities but they have been used interchangeably in the literature; pathology is the only way to differentiate between them because they usually present with identical scenarios. None of them were reported to cause extensor tendon rupture, as presented in our article. Synovial cysts can cause rupture to extensor tendons if they arise from the sheath, and it is better to anticipate synovial cyst and remove it surgically before causing any further damage, if the lesion appeared to rise from the tendon sheath on further imaging.