Can Tendon Sheath Cysts Occur on the Dorsal Extensor Tendon of a Digit?
Yes, tendon sheath cysts (ganglion cysts) can occur on the dorsal extensor tendons of digits, though they are less common than dorsal wrist ganglia. 1
Location and Occurrence
Ganglion cysts are detectable on dorsal aspects of the hand and fingers using ultrasound, as documented in standard musculoskeletal imaging protocols that specifically include dorsal longitudinal and transverse scans to evaluate extensor tendons and associated pathology 1
These cysts can occur in multiple anatomic relationships to extensor tendons: adjacent to the tendon, within the tendon sheath, or rarely within the tendon substance itself (intratendinous) 2, 3
Clinical Significance and Diagnostic Considerations
Ultrasound is the preferred initial imaging modality to confirm the fluid-filled nature of ganglion cysts and assess their relationship to extensor tendons 4, 5
A critical pitfall is failing to recognize intratendinous ganglion cysts, which may not be diagnosed until surgical exploration and carry increased risk of spontaneous tendon rupture 2
When imaging shows a ganglion in close contact with tendons, maintain a high index of suspicion for tendon involvement, as this changes surgical planning to potentially include tendon repair, transfer, or tenodesis 2
Differential Diagnosis
The extensor digitorum brevis manus (EDBM) muscle is a supernumerary muscle present in approximately 1.6% of upper limbs that is frequently misdiagnosed as a dorsal wrist ganglion or tendon sheath cyst 6
Synovial cysts arising from tendon sheaths can also occur on dorsal extensor tendons and have been reported to cause extensor tendon rupture, though they are pathologically distinct from ganglion cysts 7
Management Implications
Surgical excision should have a lower threshold when ganglion cysts involve extensor tendons to prevent progression and potential tendon rupture 2
Surgeons must be prepared to modify procedures intraoperatively if tendon involvement is discovered, including performing primary tendon repair in addition to cyst excision 2, 3
MRI is reserved for cases where ultrasound is inconclusive or when there is concern about solid tumors rather than simple ganglion cysts 4, 5