1 Introduction

Aneurysmal bone cysts (ABC) are benign yet locally aggressive lesions, first described by Liechtenstein.¹ ABC's typically appear in the metaphysis of long bones and posterior elements of spine.² They are often seen in the first or second decade of life, comprising about ∼ 1% of primary benign bone lesions.² Most of the studies describe a marginal higher incidence in females.³ These lesions are usually lytic, expansile, blood filled with well defined margins. The matrix is separated by fibrous septations, osteoblasts and reticulated bone.³ Clinical presentation varies widely as ABC's demonstrate wide spectrum from latent variant to an aggressive form.⁴ The usual symptoms are pain and swelling in the affected region. If the cyst progresses, it may present with an expansile, palpable mass. Occasionally, pathological fracture can be the sole complaint. The management protocol of ABC has evolved over past decades. Various modalities reported in literature are wide resection, intralesional curettage with or without adjuvants, radiotherapy, argon beam, cryotherapy and intralesional instillation of polidocanol.⁵ Wide resection and curettage are associated with the complications of bone loss and thus mandates reconstruction of skeletal defect with adjuvants.⁵ Though questionable, lesser invasive methods are considered as standard of care for the management of ABC's. Intralesional polidocanol scleroses the vascular structures and thus reduces the vascular malformation of ABC.⁶ Sclerotherapy damages the endothelium and thus initiates the coagulation cascade, eventually resulting in thrombus.⁶ Intralesional polidocanol is non-invasive, safe and effective treatment modality with minimal morbidity. We report a case of an ABC of femur shaft associated with pathological fracture managed by intramedullary nailing and sequential, percutaneous, intralesional instillations of polidocanol. As per our knowledge, ABC of femur shaft has never been reported in literature. The patient and his parents were informed that data concerning the case would be submitted for publication, and they provided consent.

2 Case report

A 20-year-old, previously healthy female with insignificant past medical or surgical history, presented to our institution with significant pain in her right thigh. The patient experienced excruciating pain while trying to get up from sitting position and eventually fell down on the floor. She was assisted by her relatives to make her sit comfortably on couch. On clinical examination, she had a closed injury over her right mid-thigh. The patient had excruciating pain and swelling over the injury, predominantly on the anterolateral aspect of mid-thigh. There was a palpable defect in the shaft femur and crepitus was present. Thigh was tender and the transmitted movements were absent. The neurological examination was unremarkable and distal pulses were present. Plain radiograph of right femur showed solitary, ill-defined, expansile lesion with thin-walled cavities on antero-posterior and lateral views (Fig. 1a, Fig. 1b). Magnetic Resonance Imaging (MRI) of the lesion showed fluid levels mixed with solid component with intermediate to high intensity signal surrounded by low signals (Fig. 1c and d). The radiological picture raised the suspicion of telangiectatic osteosarcoma as a differential diagnosis. Under aseptic conditions, a biopsy was planned with an 18-gauge needle. The patient and his parents were informed about the procedure and written consent was taken. The sample was sent for histopathological examination. Histology showed blood filled cystic spaces and multinucleate osteoclastic giant cells separated by fibroblast and reactive woven bone, thus confirming the diagnosis of ABC (Fig. 2). There was no evidence of atypical mitoses.

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Fig. 1 Fig. 1a and b illustrates radiograph of right femur shaft in anteroposterior and lateral view respectively. It shows solitary, ill-defined lesion in the mid-shaft femur with a pathological fracture. Fig. 1c and d shows magnetic resonance imaging of right femur shaft in sagittal and axial view respectively. MRI shows septations with fluid levels in intermediate to high intensity.

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Fig. 2 Histology showing proliferation of fibroblasts and giant cells in a stroma of focal osteoid. Few blood filled cystic space and hemosiderin laden macrophages were seen.

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The patient and his relatives were briefed about the available treatment options with their pros and cons. We planned to manage the case with closed reduction, internal fixation with interlock nail and sequential, percutaneous intralesional sclerotherapy. The patient was managed by closed interlock nailing and fluoroscopy assisted percutaneous intralesional sclerotherapy with 3% injection polidocanol (Fig. 3a, Fig. 3b). The polidocanol was injected through 18-gauge needle under fluoroscopy (Fig. 3c). A total of 4 ml was injected after confirming the correct position (3mg per kg body weight and each ml of polidocanol contains 30mg). We instilled a total of three doses of intralesional polidocanol at one month interval.

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Fig. 3 Fig. 3a and 3b is the post-operative radiograph showing fixation of femur shaft by interlock nail. Fig. 3c shows c-arm image of fluoroscopy guided intralesional percutaneous instillation.

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The patient was mobilized full weight bearing, from the first post-operative day. We followed the patient for clinico-radiological examination at monthly interval for the first three months, and then at six-month, one year, two year and three-year follow-up (Fig. 4). The radiograph at three months showed complete union of the fracture site. At three years follow-up, the patient is having no clinical symptoms with no radiological signs of recurrence (Fig. 5).

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Fig. 4 Sequential radiograph of the right femur shaft in anteroposterior and lateral projection; Fig. 4a-one month follow up, Fig. 4b-three months follow up, Fig. 4c-one year follow up, Fig. 4d-three years follow up showing complete union in both anteroposterior and lateral projection.

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Fig. 5 Clinical picture showing full knee range of motion.

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3 Discussion

The ABC is rare, benign bone lesion with high chances of recurrence. It demonstrates wide spectrum of clinical features, ranging from asymptomatic lesions to pathological fractures.⁷ There is a lack of global consensus among orthopaedic surgeons on the optimal management of ABC's. Multiple invasive and non-invasive treatment options lead to dilemma regarding the treatment protocol.⁸ The treatment modality is shifting from invasive methods to non-invasive ones. Few decades back, the widely accepted procedure was marginal resection followed by reconstruction with adjuvants. The concept of curettage with or without bone grafting was the procedure of choice till the recent past.² High recurrence rate was reported with curettage. Non-invasive methods like radiotherapy poses risk of secondary malignancies.³ Radiotherapy may arrest physis in young adults. Selective arterial embolization is technically demanding and thus, available at few centres.⁶

Sclerosants damages the endothelium and thus initiates the cascade of thrombi formation. Polidocanol is routinely used for oesophageal varices, varicose veins and vascular malformations. Sequential instillation of percutaneous polidocanol is a safe, non-invasive and technically less demanding procedure. Varshney et al. concluded that sequential instillation of sclerosants is equally efficient as intralesional curettage.⁹ Schulze et al. reported that percutaneous polidocanol is as efficient as marginal resection and curettage.¹⁰ Rastogi et al. showed success rate of 97% in the management of primary ABC.¹¹ Batisse et al. demonstrated complete ossification in 85% of patients after polidocanol instillations.¹² Rai et al. concluded that percutaneous sclerotherapy to be considered as the first line treatment for primary ABC.¹³ A thorough search of PubMed showed six studies on the efficacy of percutaneous polidocanol in the management of primary ABC (Table 1). ABC of the femur shaft has never been reported previously in any of the studies or reports.

We present a case of ABC of right femur shaft with pathological fracture, managed by femoral interlock nail and serial instillation of monthly polidocanol. At three months follow-up, the fracture site united and the patient was able to do activities of daily living. At three years follow-up, there are no clinico-radiological signs of recurrence. The limitation of our study is a short follow-up of three years. Though the recurrence is most commonly reported in the first two years, a longer follow up may be needed to comment on long-term outcome.

4 Conclusion

Percutaneous intralesional polidocanol is safe, minimally invasive management modality for ABC. Sequential instillation of polidocanol is simple and cosmetically more acceptable. The procedure circumvents the morbidity associated with invasive procedures. Sclerotherapy is highly recommended for inaccessible lesions and for patients who are unfit for surgery.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Informed consent

Informed verbal and written consent of the patient were taken for clinical pictures and the study.

Institutional ethics approval

Prior approval was taken by Institutional Ethics Committee and Departmental Review Board.

CRediT authorship contribution statement

Jairam Jagiasi: Writing – review & editing, Supervision, Validation. Abhishek Kumar Rai: Writing – original draft, Writing – review & editing. Sudhir Sharan: Supervision, Validation. Ajinkya Bandebuche: Investigation.