Intratendinous Ganglion Cyst of the Hand: A Case Report and Review of the Literature

Intratendinous ganglion of the hand is an extremely rare benign tumor, and only few cases have been reported so far in the literature. We present a case with an intratendinous ganglion of the extensor digitorum communis that treated with en bloc resection and subsequent tendon repair. According to the review of the literature and published data, the ganglion is predominantly located at hand extensor tendons (82%), and it is more frequent among females (75%) and shows a high incidence in 5th and 6th decades of life (94.5%). Surgical excision with or without side-to-side repair and/or tendon transfer leads to excellent outcome and low potential for recurrence.


Introduction
Intratendinous ganglion of the hand is a very rare entity, and only few cases have been reported so far in the literature [1][2][3][4][5][6][7][8][9]. The pathogenesis behind the intratendinous ganglion formation is still obscure, and various theories have been suggested [3]. It is believed that ganglion cysts may arise "internally" from mucoid degeneration of the tendon ground substance, forming cavities full of viscous fluid, or "externally" as the result of tendon invasion by tenosynovitis [1,2,7,9]. Despite its benign character, the lesion can be locally aggressive and impair tendons and hand function. Symptom severity is related to the location of the ganglion, degree of tendon degeneration, and presence of associated synovitis [3,8]. Although the tumor usually affects the extensor tendons, other uncommon sites of involvement have been described [3,5,6,8]. Apart from presenting a case with intratendinous dorsal wrist ganglion with a long-term follow-up, we systematically reviewed the available literature and tried to evaluate the patients and tumor characteristics as well as the clinical outcome of surgical treatment.

Case Report
We present the case of a 47-year-old, right-hand dominant woman who was referred to our department with a 6month history of a palpable soft-tissue mass at the dorsal aspect of the left hand that caused progressive pain in finger movements. A magnetic resonance imaging scanning illustrated a well-defined hourglass-shaped ganglion cyst in direct contact to the middle finger extensor digitorum communis (EDC) tendon. Under regional anesthesia, a longitudinal dorsal hand approach was utilized, and a cyst mass of approximately 10 mm × 20 mm with jelly-like contents adhered to EDC was identified ( Figure 1, Video 1). The ganglion along with the surrounding degenerative tendon tissue was excised en bloc ( Figure 2). As approximately half of the middle finger extensor tendon retained after tumor resection, simple repair of the remaining tendon was applied using three 4-0 absorbable sutures. Histologic examination confirmed the cyst nature of the lesion. Postoperatively, the wrist was immobilized in a short-arm splint for 4 weeks with the wrist in 20 degrees of extension, the metacarpophalangeal joints in 30 to 40 degrees of flexion, and the interphalangeal joints in full extension. After that period, progressive wrist and hand mobilization were commenced. The patient returned to her regular duties as a housewife after 3 months. At the latest follow-up, 10 years postoperatively, she was symptom-free, and no evidence of tumor recurrence was apparent. No flexion deficit or extension lag of the involved middle finger was recognized, and she could perform all the activities of daily living without any restriction.

Discussion
According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a systematic search of the Medline database up to May 2020, using the keywords "intratendinous AND ganglion", was performed by two independent investigators, B.C. and D. K [10]. Clinical studies relevant to intratendinous ganglions of the hand were eligible for the review. The initial search revealed 36 records, and nine articles were included in the review ( Figure 3). One article was level IV evidence [8] and eight articles level V [1][2][3][4][5][6][7]9]. The same independent investigators extracted data from the studies for the final descriptive data synthesis.
In 8 out of the 10 presented articles, the follow-up was short (range, 2 mon to 2.5 yrs) and therefore, no definite conclusion can be drawn regarding the possibility of tumor recurrence [1-6, 8, 9]. Seidman and Margles [7] reported one recurrence at 5.5 years postoperatively (4.5%). In our case, no tumor reappearance was detected at 10 yrs postoperatively. Although it seems that complete excision of ganglion   Case Reports in Orthopedics offers potentially curative treatment, long-term follow-up is essential for evaluating the potential for recurrence. In the vast majority of presented cases, tumor removal was associated with partial or incomplete tendon tear, and subsequent repair was utilized with 4-0 or 5-0 absorbable sutures. The use of absorbable sutures was proved adequate to stabilize the repair site and facilitate early mobilization of the affected tendon as no failures were reported. However, in some circumstances, en bloc resection of the tumor may leave only a small portion of intact tendon and cause significant weakness of the tendon structure. In this scenario, primary repair is not feasible, and tendon reinforcement by the side-to-side procedure or even tendon transfer should be performed to restore hand function [6,8]. Satonaka et al. [6] transferred the extensor indicis proprius (EIP) tendon to the distal stump of EPL to restore the extension of the thumb after en bloc excision of EPL intratendinous ganglion. Nevertheless, in all published cases, neither postoperative tendon rupture nor further operations were undertaken.

Conclusion
According to the current presented case and literature review, complete intratendinous ganglion excision leads to