IOGs of the carpal bones are common but rarely cause persistent pain and wrist stiffness. Different from degenerative cysts, most IOGs have a direct or indirect connection with the extraosseous ganglion cysts with the same origin (intrinsic or extrinsic ligaments). Nazerani et al. reported an anatomically gross soft tissue ganglion communicating with the lunate IOG through a defect on the posterior side of the lunate. Ashwood et al. noted that 7 out of their 8 patients had an extraosseous extension of the IOGs, but strategies performed to manage this extension were not mentioned in their study. The pathogenesis of these cysts remains unclear. There are some theories about the origins of these cysts including the following: traumatic mucoid degeneration of connective tissue, metaplasia of mesenchymal precursor cells, synovial herniation, and neoplasia.[7, 16] We believe that these lesions, both the intraosseous and extraosseous ganglion cysts, are observed as a result of the mucoid degeneration of the adjacent ligaments according to the histopathologic findings, including a thin wall with fibrous collagen and myxoid degeneration containing a clear viscous fluid that has high hyaluronic acid concentration.[4, 17] Histologically, Schrank et al. conducted a cadaveric study and furtherly proved that the IOGs were associated with the insertion of the degenerated ligaments, which were the extrinsic ligaments in 37.5% of their patients, and the intra-articular ligaments (scapholunate and lunotriquetral ligaments) in 52% of their patients. We found that the laxity of the ligaments was observed more frequently among these patients, relatively contributing to the partial symptoms.
Surgical intervention for IOGs will be introduced after a failure of conservative treatment, including either open exposure or minimally invasive method. Traditional open curettage with bone grafting has provided some successful experiences and lessons as well. Tham and Ireland treated 9 patients with 1 poor and 2 fair results due to pain at the scapholunate region, where the lesions originated from, with the possible occurrence of scapholunate instability. Waizenegger reported incomplete pain relief and work decrement for 6 patients, but reasons behind this finding were not explained in the study. With the development of the wrist arthroscopic technology, a minimally invasive procedure has been widely used in the field of wrist surgery. This minimally invasive approach irritates significantly less soft tissue; thus, the capsules and ligaments remain intact, reducing the risk of arthrofibrosis and damage to the vascular system of the carpal bones that might possibly lead to open exposure.[7, 15, 19] Using an arthroscope, a complete and clear view of the joint could be achieved, subsequently treating the intra-articular lesions. Furthermore, concomitant morbidities such as extraosseous cysts and intercarpal joint instability can also be treated arthroscopically with a better esthetic result. Arthroscopic treatment for IOGs through small incisions has been used for approximately a decade since Ashwood first described its use. They treated 8 patients with IOGs of the lunate, and the results were significant; pain scores, grip strength, ROM, and function scores of all patients improved. However, scapholunate or lunotriquetral joint stability was not assessed in their study, or the patients included in their study had isolated wrist IOGs without intercarpal instability.
Patients with wrist IOGs who were treated had frequently experienced intercarpal instability ranging from grade Ⅰ to Ⅱ according to Geissler’s classification. Among the 45 patients in the study of Edwards et al., every patient with a wrist ganglion cyst had scapholunate joint laxity, with the highest grade of IV observed in 1 patient. Evaluating the arthroscopic treatment for patients who have IOGs combined with intercarpal joint instability is required. Previous studies had confirmed the effectiveness of radiofrequency shrinkage in modifying joint stability as a result of the thermally induced contraction of the capsules and ligaments.[9–11,20−21] Arthroscopic procedure of thermal shrinkage using a bipolar radiofrequency probe was performed in our series to prevent further joint instability development, which is considered a potential source of wrist pain. Follow-up studies confirmed better results compared to several previous studies. Our study also suggested that the occult soft tissue ganglion cyst could coexist with carpal IOGs, considering that they had similar histopathologic features. However, the association between these two is still unclear. Therefore, surgeons should pay careful attention when dealing with patients with carpal IOGs and should determine whether wrist pain is associated with the carpal IOGs so that necessary treatment can be properly performed. On the contrary, the soft tissue ganglion cysts are frequently associated with the intercarpal ligaments, which is considered one of the reasons of wrist instability.
The present study has some limitations. First, this retrospective follow-up case study has no control group. Second, the sample size of the case group was relatively small; hence, a large-scale controlled study should be performed in the near future. Regarding the surgical technique, the learning curve for arthroscopic operation is long. Senior surgeons with sufficient knowledge on the wrist’s anatomy are more likely to avoid cartilaginous and soft tissue complications. To minimize the complications of donor sites for bone grafting after the curettage of the IOGs, calcium phosphate bone cement injection is considered an alternative option.