Ganglion cysts are common, benign, soft-tissue tumors found in the hand and wrist. These are synovial cysts containing gelatinous mucin. Ganglion cysts originating from the dorsal wrist joint are usually found on the dorsal side, and those originating from the volar wrist joint are usually found on the volar side. Herein, a rare case is presented of a large dorsal ganglion cyst originating from the volar scaphotrapeziotrapezoidal (STT) joint that pierced the first dorsal interosseous muscle, bulging dorsally.

This study was approved by the Institutional Review Board of the Korea National Institute for Bioethics Policy (No. P01-202408-01-039). Written informed consent was obtained from the patient for the publication of this report including all clinical images.

A 40-year-old woman presented with a progressively growing mass over the dorsal radial aspect of her left wrist and mild pain with wrist flexion/extension. The patient had no underlying disease or traumatic injury. The mass had been evident for 6 months and was palpable on the radial side of the dorsal wrist, with no tenderness. On ultrasound, a well-defined hypoechoic lesion was revealed. Magnetic resonance imaging (MRI) indicated a multilocular cystic mass, measuring 28 × 12 mm, which appeared as a ganglion cyst. The cyst extended to the volar STT joint, lying much deeper than the flexor pollicis longus and flexor carpi radialis (FCR) of the volar wrist. The cyst was attached to the radial artery at the position where the deep palmar arch is formed from the terminal part of the radial artery (Fig. 1). The ganglion cyst was identified as originating from the volar side of the STT joint, where it bulged dorsally, passing through the position between the superficial head and deep head of the first dorsal interosseous muscle with radial artery. It was decided to surgically remove the cyst. Two incisions were made at the first dorsal web space and volar side of the STT joint. Since the cyst was adherent to the radial artery, it was meticulously dissected so as not to damage the radial artery. After it had been checked, the stalk arising from the STT joint was removed (Fig. 2). Pathological examination confirmed the diagnosis of a ganglion cyst. The patient had no loss of function in the hand, and no symptoms of recurrence were observed one year after surgery.

Dorsal wrist ganglion cysts that originate from the scapholunate ligament or scapholunate joint are the most common ganglion cysts (70%). Volar wrist ganglia (20%) occur in the radiocarpal or STT joint. When the ganglion originates from the volar joint surface of the STT joint, it is most likely to be seen as a volar side lump. In previous case reports, most ganglion cysts originating from wrist joint volar surfaces were viewed as lumps on the volar side (volar wrist, thenar area, and palm) [1-4]. A case report exists of a patient with a dorsal wrist ganglion originating from the scapholunate ligament and appearing at a volar location [5]. However, no cases of volar wrist ganglia appearing on the dorsal wrist have been reported. Hence, a rare case in which a ganglion cyst originated from the volar STT joint to appear on the dorsal wrist is presented here.

There are two theories explaining the development of rare ganglion cysts. First, ganglion cysts originating from the STT do not directly pierce the volar side, owing to the FCR sheath. So, in most cases, they grow proximal or distal to the FCR sheath [6]. Second, the radial artery that runs to the deep palmar arch lies between the deep head and superficial head of the first dorsal interosseous muscle, and this part is much looser relative to the surrounding tissue. Consequently, ganglion cysts originating from the STT joint bulge distally due to the FCR sheath and grow dorsally via a loose space where the radial artery progresses to the deep palmar arch.

Several studies have suggested that finding the exact origin of a ganglion cyst for removal reduces recurrence [1-4]. A mass in the distal radial dorsal wrist area can be thought to be a ganglion cyst originating from the dorsal carpometacarpal (CMC) joint, or a protrusion resulting from an extended ganglion cyst originating from the dorsal scapholunate ligament. However, since this mass may originate from the volar STT joint or volar CMC joint, as was the case with the patient presented in this report, especially if deviated to the radial side, preoperative MRI may accurately reveal its origin, thereby facilitating surgery to reduce recurrence.

Similarly, also to the patient under discussion, in many cases, ganglion cysts originating from the volar STT joint are close to the radial artery. Preoperative MRI may be helpful in determining a locational relationship between the radial artery and ganglion cyst, thereby assisting the surgeon in avoiding damaging the radial artery. Moreover, if the radial artery is attached to the ganglion cyst, as in this case, there is a high likelihood that the radial artery may be damaged. Therefore, Allen’s test must be conducted before surgery to confirm whether ulnar artery blood flow is adequate.

If possible, an asymptomatic wrist ganglion should be managed with conservative treatment, to see if it disappears spontaneously. However, when it is accompanied by movement pain, more aggressive treatment is necessary. There is still controversy regarding the preferability of open surgery or arthroscopy. Previous studies have reported that arthroscopy used to treat both dorsal wrist and volar wrist ganglia has been associated with favorable outcomes [2,3]. A recent report has suggested that ganglions from the STT joint can be removed by using arthroscopy [7]. However, arthroscopic volar wrist ganglion excision is reportedly more effective for the radiocarpal joint compared to open surgery; meanwhile, arthroscopic excision has not been reported to be useful for surgery of the midcarpal joint, including the STT joint, owing to the narrow space and poor outcomes [2,3]. In the case presented here, arthroscopy could not be conducted because the dorsal portion of the ganglion was located on the STT port and the radial artery and ganglion were merged, making arthroscopic surgery harder to perform. Open surgery was, accordingly, conducted as it was determined to be most beneficial for the patient, and it was completed with minimal damage to the radial artery.

In conclusion, since ganglion cysts occurring in the dorsal wrist, especially if deviated to the radial side, may originate from the volar midcarpal joint, a preoperative MRI must be conducted to decrease the recurrence and to perform surgery with minimal complications. If a preoperative MRI reveals a ganglion cyst originating from the volar midcarpal area and close to the radial artery, an effort should be made to remove the cyst within the area of origin while minimizing injury to the radial artery.