Current strategies for the treatment of solitary and aneurysmal bone cysts: A review of the literature

Abstract

This review of the literature aims to compare the etiology, the pathogenesis, the clinical diagnostics and the relevant treatment options of two different types of cystic bone lesions: the solitary bone cyst (SBC) and the aneurysmal bone cyst (ABC). Whereas the clinical symptoms and the radiographic appearance can be similar, the diagnostic pathway and the treatment options are clearly different. The solitary bone cyst (SBC) represents a tumor-like bone lesion, occurring most frequently in the humerus and femur in children and adolescents. Pain caused by intercurrent pathological fractures is often the first symptom, and up to 87% of the cysts are associated with pathological fractures. In the majority of cases SBCs can be treated conservatively, especially in the upper extremity. However, if a fracture is completely dislocated, joint affecting, unstable or open, surgical treatment is necessary. Pain under weight bearing or regaining the ability to mobilize after fracture timely can necessitate surgical treatment in SBCs affecting the lower extremity. Spontaneous resolution can be seen in rare cases. The aneurysmal bone cyst (ABC) is a benign, locally aggressive tumor that occurs in childhood and early adulthood. It usually affects the metaphysis of long bones but can also occur in the spine or the pelvis. ABC can be primary but also secondary to other bone pathologies. The diagnosis has to be confirmed by biopsy and histopathological examinations. With cytogenetic studies and the detection of specific translocations of the ubiquitin-specific protease (USP) 6 gene primary ABCs can be differentiated from secondary ABCs and other bone lesions. Among various modalities of treatment i.e. en bloc resection, intralesional curettage with adjuvants, embolization or the systemic application of denosumab, intralesional sclerotherapy using polidocanol is an effective and minimally invasive treatment of primary ABCs.

Keywords: ABC, aneurysmal bone cyst; Aneurysmal bone cyst; Juvenile bone cyst; SBC, solitary bone cyst; Simple bone cyst; Solitary bone cyst.

Fig. 1

Imaging of a 6-year-old male patient with SBC and pathological fracture of the proximal humerus. Anteroposterior and lateral radiographs showing the fracture with 10° axis deviation in the lateral plane (a). Anteroposterior and lateral radiographs four weeks after conservative treatment showing progressive consolidation of the fracture (b). Anteroposterior and lateral radiographs (c) and MRI scans (d) twelve months after fracture showing partial sclerosis of the SBC and complete consolidation of the fracture.

Fig. 2

Solid parts of an ABC showing scattered mononuclear lesional cells intermingled with multinuclear giant cells and well discernible osteoid formation.

Fig. 3

ABC of the proximal tibia of a 12 years old boy – preoperative MRI scans with typical fluid-fluid levels (a + b), intraoperative fluoroscopy after curettage and defect reconstruction with bone substitute (c) and progressive osseous integration of the bone substitute (d + e; arrow).

Fig. 4

ABC of the proximal fibula of an 18 years old patient – preoperative radiographs (a + b) and after curettage and reconstruction with PMMA (c + d).

Fig. 5

ABC of the proximal ulna of a 3 years old girl – initial MRI scan (a); fluoroscopy of instillation of polidocanol (b); progressive resolution of the cyst (after 3 instillations) with residual cystic elements and scattered fluid–fluid levels (c); healing grade I according to Rastogi et al. with complete resolution of fluid–fluid levels (d + e; arrow).