by Bryn Rowe DPM PGY21*, Jeffrey Christensen DPM FACFAS2, Daniel Lowinger DPM FACFAS3
The Foot and Ankle Online Journal 13 (3): 5
Intraosseous ganglia are benign, non-neoplastic lesions of bones that are histologically similar to their soft tissue equivalents. They most often occur in the femoral head, proximal tibia, and carpal bones. A 70-year-old female presented with a complaint of pain to the right dorsal forefoot. The patient was diagnosed with a third metatarsal intraosseous ganglion based on multiple imaging modalities and confirmed by histopathology. A case report and review of the literature is presented.
Keywords: bone cyst, ganglion, subchondral cyst, geode
ISSN 1941-6806
doi: 10.3827/faoj.2020.1303.0005
1 – Swedish Medical Center Resident – Swedish Medical Center, Seattle, WA, PGY-2
2 – Attending Physician – Swedish Medical Center, Seattle, WA
3 – Attending Physician – Swedish Medical Center, Seattle, WA
* – Corresponding author- Bryn.Rowe@swedish.org
Intraosseous ganglia are benign cystic lesions that typically occur in long bones. These lesions should be an included differential for any cystic osteolytic lesion seen in the foot or ankle. Intraosseous ganglia can be painful and have the potential to cause pathologic fractures. The standard treatment includes curettage with bone grafting, with or without internal fixation.
The etiology of intraosseous ganglion is unknown and multiple theories exist. They are most widely accepted to be primary lesions and may arise de novo with no imaging or pathological evidence of degenerative process in neighboring joints [1]. Differential diagnoses for intraosseous ganglia include any well circumscribed cystic lesion with marginal sclerosis located in the subchondral bone adjacent to a joint, such as a subchondral bone cyst, giant cell tumor, enchondroma, chondrosarcoma/blastoma, Brodie’s abscess, and fibrous dysplasia among others [3]. Intraosseous ganglia can be differentiated from other potential diagnoses based on the age of the patient as well as characteristics seen on radiographs and other imaging modalities. Diagnosis, however, can only be confirmed by histopathological analysis.
Intraosseous ganglia appear as well-defined lytic lesions with marginal sclerosis on radiographs. They can regularly be distinguished as they often do not often exhibit calcifications, cortical expansion, or cortical destruction. They can be unilocular or multilocular. Magnetic resonance imaging (MRI) of these lesions shows low intensity signal in T1 and high intensity signal in T2. Computed Tomography (CT) imaging is useful to determine intra articular involvement or pathologic fracture not easily identified on radiographs [7].
Conservative treatment includes non-operative observation and symptom relief. Sclerosing injections have been performed however their effectiveness have not been reported in literature. The gold standard treatment is surgical curettage of the cyst and surrounding zone of sclerosis with or without bone grafting. The deficit is often packed with bone cement, autograft, or allograft either with or without internal fixation [5]. Pathologic fracture is a reported complication caused by these lesions. Arthroscopy has also been performed but is more commonly done in the wrist. There are no current studies comparing the outcomes between arthroscopy versus open curettage. Recurrence rate for intraosseous ganglion after surgical curettage is around 6.1%, however there is a variable overall reported recurrence rates ranging from 7-43% in the literature [8]. The recurrence is thought to not necessarily be from inadequate excision but rather from connective tissue metaplasia after surgery [1].
Grossly, intact cysts are round or oval in shape and appear opalescent and blue-grey in color. The walls of the cyst do not contain any epithelial or synovial lining but are rich in collagenous fibers. The unroofed cyst is made up of a largely fibrous membrane containing mucinous material. Acid mucopolysaccharide storage within the cyst leads to the myxoid degeneration seen within the ganglion wall [2]. Intraosseous and extraosseous ganglion are indistinguishable histologically. The diagnosis is confirmed by histopathological analysis.
Intraosseous ganglia are benign, non-neoplastic lesions of bones that are histologically similar to their soft tissue equivalents. They most often occur in the femoral head, proximal tibia, and carpal bones. A 70-year-old female presented with a complaint of pain to the right dorsal forefoot. The patient was diagnosed with a third metatarsal intraosseous ganglion based on multiple imaging modalities and confirmed by histopathology. A review of the literature found only one reported case of an intraosseous ganglion in the third metatarsal and two other reports occurring in the first metatarsal [2, 6]. She was treated operatively by curettage with bone allograft with no recurrence at one year follow-up. Of note, the patient’s postoperative course was complicated by delayed consolidation of the bone allograft with subsequent malunion of the third metatarsal base with dorsal angulation.
Figure 1-3 AP, MO, and lateral radiographs of the right foot with subtle marginal sclerosis noted to the base of the third metatarsal.
Case Report
The patient is a 70-year-old female who presented with chief complaint of pain with activity on the central and dorsal aspect of her right foot. The pain had been present for two years with gradual onset. There was no history of trauma. Of note, the patient also complained of first metatarsal phalangeal joint pain with a progressively worsening bunion deformity causing shoe irritation. On physical exam there was a moderate hallux valgus deformity and mild tenderness to palpation of the dorsal aspect of the 3rd metatarsal base. Radiographs of the right foot demonstrated a long 1st metatarsal, mild narrowing of the 1st metatarsophalangeal joint, and slight increase of the 1st and 2nd intermetatarsal angle.
Figure 4 Sagittal T2-weighted MR imaging with high signal intensity in the base of the third metatarsal extending distally within the metatarsal shaft.
There was a subtle discrete radiolucent area in the base of 3rd metatarsal accompanied by marginal sclerosis laterally and proximally, most pronounced on the medial oblique view (Figures 1-3).
An MRI was ordered to further assess the irregular sclerotic area as well as to rule out potential stress fracture or arthropathy. T2-weighted MR images demonstrated high intraosseous signal intensity in the proximal third metatarsal base extending to the articular surface of the third tarsometatarsal joint as well as marrow edema extending distally in the metatarsal shaft (Figure 4). The area measured 1.8 x 1.1 cm. There was no cortical irregularity, calcification, or periosteal reaction. A CT scan demonstrated a unilocular mixed lytic and lucent intramedullary lesion at the proximal aspect of the third metatarsal with no visualized tarsometatarsal joint involvement (Figs. 5-6).
Operative Technique
The patient was placed under general anesthesia in a supine position. A linear incision was made over the third tarsometatarsal joint after the position of the bone lesion was triangulated with fluoroscopy. Sharp dissection was carried down to the extensor tendons which were retracted. The periosteum over the base of the third metatarsal was incised longitudinally and reflected medially and laterally. A dorsal rectangular shaped window was created in the cortex of the base of the third metatarsal (Figure 7).
Figures 5-6 Sagittal and coronal CT imaging demonstrating the third metatarsal lesion with intact cortex present at the 3rd metatarsal-cuneiform joint with no apparent intraarticular extension.
Figure 7 Intraoperative image of the third metatarsal base after the dorsal cortical window was removed, revealing a soft gray mass and cystic cavity.
A well-encapsulated gelatinous gray tissue mass was visualized in the marrow cavity and excised completely with a curette. There was no apparent intra-articular involvement or extension in the tarsometatarsal joint noted. The cortical wall was curetted and bone allograft was packed into the deficit. The cortical window was press fit into the graft and positioned in its original position. The graft was not fixated as it was stable after positioning. The gross pathology report described the mass as a 1.6 x 0.8 x 0.7 cm disrupted pale, tan-red cyst, containing mucoid material. The final diagnosis was benign intraosseous ganglion.
Discussion
Intraosseous ganglions are benign non-neoplastic bone lesions that are histologically similar to their soft tissue homologues. They are most commonly found in the epiphyseal-metaphyseal area of long bones with higher occurrences in the medial malleolus, femoral head, and carpal bones. There are few case reports in literature describing intraosseous ganglia of metatarsals, with only one case being reported in the third metatarsal and two additional cases reported in the first metatarsal [1,6]. This may be due to underreporting and confusing nomenclature leading to this lesion being named under a different pathologic entity. Peak incidence for both males and females in the fourth or fifth decade. They infrequently occur in skeletally immature individuals or the elderly, although cases have been reported in the literature [5]. Communication with surrounding joints and extension into the soft tissues are frequently reported, however, there are variable occurrence rates in literature due to differences in which imaging modality was used. In a study of patients with confirmed intraosseous ganglia, there was soft tissue extension present in 38% and intra-articular involvement present in 17% of the 29 patients who underwent MRI [7]. These lesions were evaluated using T1-weighted, T2-weighted, and short tau inversion recovery (STIR) sequences. In a similar study of 17 patients, there was 24% soft tissue extensions present. The authors also noted that among their patients, 12% had associated osteoarthritis and 18% had pathological fracture [4]. Preventing potential pathologic fracture in patients with intraosseous ganglion is an important rationale for surgical treatment
Although benign and uncommon, intraosseous ganglia should be considered in the potential diagnosis of any bony subchondral cystic lesion in the foot or ankle. Without proper clinical observation and potential treatment, intraosseous ganglia have the potential to cause significant pain, cause pathologic fracture, and exhibit secondary pathological effects by displacing surrounding soft tissues. Ideally curettage with grafting would be performed for both treatment and diagnostic purposes.
References
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