Aneurysmal bone cyst of the clavicle in a 9 years old patient:
A case report and review of the literature

K. BABLIAKIS[1], D. KOSTOPOULOS[1], I.P PSICHARIS[1], I. TRIANTAFILLOPOULOS[1],
P. KYRIAZOPOULOS[2], A. KANELLOPOULOS[2], S. ELIOPOULOS[2]
11st Orthopaedic Department, University Of Athens
[2]Pediatric Orthopaedic Department, KAT HOSPITAL

ABSTRACT
We present a 9 years old patient who was diagnosed having an aneurysmal bone cyst of the acromial third of his right clavicle. He was treated surgically with curettage and autologous iliac crest bone grafting. He went on to healing at the latest follow up, 48 weeks post operatively. This represents a rare condition for this age group which is challenging to diagnose and treat.
Key words: Aneurysmal Bone Cyst, Clavicle, Curretage.

INTRODUCTION
Aneurysmal bone cyst is a rare non-neoplastic expansible osteolytic bone lesion of unknown etiology. It represents 6% of all bone tumors and affects 0.14 patients per 100000 individuals every year[5]. Approximately 3% occur in the clavicle[9]. Treatment remains empirical because the etiology and pathogenesis of this lesion remain unclear[3]. The treatment options include surgery, sclerotherapy, vascular occlusion or combinations of these methods[4]. Recurrence is higher in patients younger than 15 years old[8].

1A
1B
1C
Figure 1.A. Bulging of skin secondary to underlying lesion.
B. Anteroposterior plain radiograph of the right shoulder at the time of initial diagnosis.
It is shown the aneurysmal expansion of the acromial third of clavicle.
C. Close up view.

CASE REPORT
A nine years old boy presented to the Orthopaedic Clinic of our hospital, complaining of right shoulder pain. He reported an injury to the pertinent shoulder, fifteen days previously, playing sports. The exact mechanism was described as a direct injury. This injury was interpreted as a trivial one by the patient and his family who did not seek medical advice at that point. His past medical history was unremarkable.
On presentation he reported a painful right shoulder on any attempt for movement. He denied any symptoms to this region prior to his recent injury. He is an otherwise healthy appearing active young lad. His clinical examination was remarkable for a 1.5 x 2.5 cm size mass that was prominent at the acromial end of his right clavicle (figure 1A). The mass was bony hard and tender on palpation. The overlying skin could be moved freely. It had also normal appearance and temperature.
The initial radiograph revealed a cystic expansible lesion of the acromial third of the right clavicle with significant thinning of the cortex. There was also an area of a possible pathologic fracture. (Figure 1B,C) Based on that appearance the working differential diagnosis at that point included simple bone cyst, aneurysmal bone cyst, eosinophilic granuloma and enchordoma.
A collar and cuff was prescribed as well as analgesics for pain relief. A basic hematological work up that included complete blood count with differential, ESR, C-reactive protein, alkaline phosphatase was within normal limits. The lesion was then studied further with Technetium 99 whole body bone scan (figure 2), CT scan and MRI (figure 3). The findings were all consistent with aneurysmal bone cyst.
Treating options for this lesion that were considered at that point included resection of the lesion and curettage with autologous iliac crest bone grafting. The latter was preferred based on the fact that a strong strip of cortical bone was preserved at the bottom part of the lesion while the true acromial end (lateral to the coracoid process) was free of disease. It was also felt that resection could result in weakening of the shoulder. The patient and his family agreed to this treating option.
Intraoperatively, the lesion was approached after incising the periosteum longitudinally. The cyst was entered and found containing streaks of thrombi. The inner wall was curetted and electrocautery was utilized to seal the bleeding walls of the cavity which was then irrigated with an iodine containing alcoholic solution. The void was then filled with cortico-cancellous strips of autologous iliac crest bone graft. The periosteal tube was then repaired. His postoperative period was uneventful. A collar and cuff was used as the only mean of immobilization. We did not used any form of internal fixation. The preoperative diagnosis was confirmed with the histopathology of the curetted specimen. The patient was then seen at 4,12, 24 and 48 weeks post operatively. The latest follow up visit was at 24 months post operatively. The cyst was clinically and radiographically completely healed (figure 4A,B). The patient resumed full and pain free use of the right upper extremity.

Figure 2. Anterior view of Tc99m bone scan at the time of initial diagnosis.
Increased uptake of radiofarmaceutical by the lesion.

Figure 3. MRI of the right shoulder preoperatively. Coronal T2 weighted
show fluid- fluid levels, a specific sign of aneurysmal bone cyst.

DISCUSSION
The methods of treating aneurysmal bone cysts include curettage saucerization, resection, radiotherapy, cryotherapy and vascular occlusion. Nevertheless, there is no consensus among the treating physicians regarding how these methods should be used. As a result of this there are quite contradictory reports regarding results and complications[8]. Recurrence rate in young children with cysts classified as active or aggressive according to Campanacci et al1 after curettage and bone grafting can be as high as 100%[3].
Resection of the lesion offers low recurrence rate[2], but can be mutilating leading occasionally in loss of function. A combination of curettage and cryosurgery has been employed by some authors that reported local control after the first treatment in 82% of the patients[6].
Radiotherapy can result in radiation induced sarcomas and can cause radiation injury to a nearby physis[2].

4A
4B
Figure 4A. Anteroposterior plain radiograph of the right shoulder at the latest follow up visit, 48 weeks post operatively. Complete healing of the lesion.
B. Close up view.

On the other hand there are published reports recently with encouraging data with saucerization of bone cysts with recurrence rates near zero[2-4,6]. Saucerization consists of excision of the subperiosteal new bone with its attached cyst contents and curettage of the remaining cortical bone. The only prerequisite for the above procedure is the presence of a normal strut of cortical bone that maintains length, shape and stability. Aneurysmal bone cysts of the clavicle represent 3% of the reported cases[9]. Two patients in the literature were treated with resection of the lesion with part of the clavicle with no recurrence[7,9]. One patient was treated with saucerization and instillation of autologous bone marrow4, with healing of the lesion after one session. Another patient was treated with curettage and bone grafting. There is no comment regarding control of the disease in this patient[3].
We elected to perform saucerization with augmentation with autologous iliac crest bone grafting since there was a strut of normal cortex at the bottom of the cavity. We felt that the literature at that point supported this option. The published results of saucerization and bone marrow injection were not available at that time. The latter would probably be our current preference should we had to treat a patient with a similar lesion. Our patient responded nicely to this form of treatment and we feel that his case enriches the existing data regarding treating options of an aneurysmal bone cyst in a young patient.

REFERENCES
1. Campanacci M., Capanna R., Picci P. Unicameral and Aneurysmal bone cysts. Clin Orthop. 1986; 204, 25-36.
2. Cole W.G., et al. Treatment of Aneurysmal Bone Cysts in Childhood. J Pediatr Orthop. 1986; 6, 326-329.
3. Freiberg A.A., et al. Aneurysmal Bone Cysts in Young Children. J Pediatr Orthop. 1994.
4. Hemmadi S.S., Cole W.G. Treatment of aneurysmal bone cysts with saucerization and bone marrow injection in children. J Pediatr Orthop. 1999; 19, 4, 540-542.
5. Leithner A., et al. Aneurysmal bone cyst. A population based epidemiological study and literature review. Clin Orthop. 1999; 363, 176-179.
6. Marcove R., et al. The treatment of aneurysmal bone cyst. Clin Orthop. 1995; 311, 157-163.
7. Pointu J., et al. Aneurysmal cyst of the clavicle: an uncommon lesion and a difficult diagnosis [Article in French]. Sem Hop. 1982; 58, 18, 1141-1143.
8. Tillman B., et al. Aneurysmal bone cyst: an analysis of ninety-five cases. Mayo Clin Proc. 1968; 42, 478-495.
9. Vedantam R., Crawford A.H., et al. Aneurysmal Bone Cyst of the Clavicle in a Child. Br J Clin Pract. 1996; 50, 8, 474-476.

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