Unicameral bone cyst of the lunate in an adult: case report
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We report a case of a symptomatic unicameral (simple) bone cyst of the lunate in a 42-year- old woman. The lesion was treated with curettage and cancellous autogenous iliac bone grafting. At five years of follow-up the wrist was pain free, there were no limitations of motion, and the radiographs showed complete obliteration of the cavity. To the best of our knowledge, no other unicameral bone cyst of the lunate has been reported in an adult. Cysts with significant cavities at the carpal bones in an adult should be approached cautiously, as they may require early curettage and bone grafting for healing, before collapse and degenerative changes occur.
KeywordsFibrous Dysplasia Bone Cyst Giant Cell Tumor Osteoid Osteoma Demineralized Bone Matrix
Unicameral bone cysts (UBCs), also known as simple bone cysts are benign, fluid-filled lesions involving the metaphysis of long bones [1, 2, 3]. On radiography they demonstrate a centrally located lytic lesion with well-defined margins . The cyst wall is lined with a fibrous membrane which contains serous yellow fluid . 80% of UBCs occur in the proximal humerus and proximal femur [1, 3]. Most UBCs occur in childhood where one third of the cases will resolve spontaneously by skeletal maturity [1, 2, 3]. Occurrence of a single symptomatic radiolucent lesion in the lunate is rare [4, 5]. A differential diagnosis of a painful radiolucent lesion in the lunate would include intraosseous ganglion, Kienböck's disease, osteoid osteoma, giant cell tumor, aneurysmal bone cyst and enchondroma [4, 5, 6, 7, 8, 9]. The incidence of UBCs involving the wrist bones and lunate has not been clearly defined in the literature .
Most diagnosed UBCs occur in childhood [1, 2, 3]. UBC etiology is unknown [1, 3]. They account for 3% of all bone tumors, and usually involve the metaphysis of long bones, and have a predilection for the proximal humerus and proximal femur [2, 3]. A debate exists whether treatment is necessary (because of spontaneous resolution) and what treatment is most appropriate . Patients with UBCs usually present with a pathological fracture or a complaint of mild pain in the affected region [2, 3]. The main indication for surgery is to prevent or treat pathological fracture . Benign bone lesions are often treated with intralesional curettage, and autogenously bone grafts or various substitutes have been used to fill the defect . Curettage alone is often the standard treatment for benign bone tumors giving the similar recurrence and fracture rates . Described treatment options for a UBC include simple observation, curettage and grafting (autogenous or allogenous), steroids, demineralized bone matrix, and bone marrow injection [1, 3]. The incidence of UBCs involving the wrist bones and lunate has not been clearly defined in the literature. The differential diagnosis of a radiolucent lesion of the lunate most commonly includes an intraosseous ganglion cyst or osteoid osteoma . Kienböck's disease, osteoid osteoma, giant cell tumor, enchondroma, aneurismal bone cyst (ABC), nonossifying fibroma and fibrous dysplasia are less likely possibilities [4, 5, 6, 7, 8, 9]. There are no established guidelines for when and how to treat UBCs. Injections of steroids, demineralized bone matrix, and bone marrow aspirate have been reported as methods of treatment with various success rates [1, 3]. Standard surgical treatment consists of curettage and cancellous bone grafting . The main indication for surgical intervention is to prevent or treat a pathological fracture [1, 3].
In our case herein, indications for surgery were clinical history of pain and radiographic findings of a cystic formation in the lunate.
UBCs of carpal bone in adulthood had been reported before . This was a case report of bilateral unicameral bone cysts located in the hamate bones of a 22-year-old man . Our patient was unique in that she had a UBC in her lunate bone. To the best of our knowledge, no other unicameral bone cyst of lunate has been reported in the literature. The etiology of this symptomatic lesion remains unknown. Cysts with such large cavities at the carpal bones in an adult should be approached cautiously. They may require early curettage and bone grafting for healing. Early treatment has its' definitive benefits as it prevents collapse and degenerative changes as in our case .
Conflict of interest statement
Authors certifies that they have no commercial associations (e.g., consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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