Primary calcaneal aneurysmal bone cyst in a 5-year-old treated with serial polidocanol sclerotherapy: a case report

INTRODUCTION

Pediatric primary ABC in calcaneus is an extremely rare occurrence. To our knowledge, till date less than 50 cases of calcaneal ABC have been reported in the literature.^1,7-12 The age of the youngest reported calcaneal ABC was 8 years who was observed without treatment.² Most of the literature reported curettage with bone grafting to treat calcaneal ABCs. ABC accounts for approximately 1% of all primary bone tumors, of which only 3% of cases have been reported in the foot, of which only 1.6% involve the calcaneus.¹

Calcaneal ABC’s are more often symptomatic and less likely to be complicated by a pathological fracture.^3,4 There is paucity of literature, regarding sclerosant injection of pediatric calcaneus ABC, though it is a less morbid procedure than other treatment options like curettage with or without bone grafting, cementing of the cavity, reconstructive surgery etc.⁵ Because of their rarity and atypical presentation, we report a 5-year-old with extensive calcaneal ABC managed with serial polidocanol sclerotherapy and outline dose rationale, technique, and one-year outcomes.

The guardians of the patient were informed that data concerning the case would be submitted for publication and they agreed and gave consent for it.

CASE REPORT

A 5 years old female child, with a body weight of 15 kg, came to our department with left heel pain for 2 months. It was of progressive aggravation, relieved by analgesic treatment, hampering her day-to-day activities. On clinical examination, she was having pain while walking, firm on palpation and swelling of the heel region. Standard radiograph showed osteolytic lesion engaging the whole calcaneus without periosteal reaction (Figure 1). MRI showed a large lesion of the calcaneus, volume measured 11.9 cm³, relatively well-circumscribed and inhabited by multiple partitions, with several fluid-fluid levels (Figure 2 A-C). Based on clinico-radiological data, differentials were made, of which ABC was first in the list. MRI showed liquid-liquid levels, but not specific to ABC and can also be present in telangiectatic osteosarcomas, chondroblastomas, and GCTs. That's why a HPE diagnosis is still necessary before surgery. The patient was then scheduled for surgery for a biopsy. During biopsy Jamshidi needle was introduced under C-arm guidance (Figure 3), and aspiration revealed blood (Figure 4). HPE showed presence of blood-filled cystic spaces separated by cellular septa containing fibroblasts, giant cells and woven bone formation (Figure 5). Based on the clinico-radiological and histopathology report it was diagnosed as primary ABC of the calcaneus. We planned for Sclerosant injection of the tumor. Dose of the sclerosant (Polidocanol) was first tried to determine with the help of the volume of tumor, but it would have been a large dose of sclerosant, so decided to go with another dosing system. Dose was determined by bodyweight of the patient (2-4 mg/kg).^5,6 We percutaneously put J. Needle in the bone, then attach a 3 way connector with the J needle, and attach polidocanol and normal saline with 2 ports. We mixed both the liquids for the next 1-2 minutes and then injected it into the bone (Figure 6) and kept the needle for 10 minutes. As the patient was 15 kg, so 15×4 mg=60 mg. One vial of polidocanol consists of 2 ml or 60 mg of polidocanol, so we gave 2 ml or 60 mg of polidocanol injection 4 times over a period of 9 months. In the postoperative period we gave below knee slab for 2 weeks, and strict non-weight bearing for the same duration. No adverse reactions noted during the sclerosant injection therapy like local skin necrosis, neurovascular events, infection, hypersensitivity etc.

There were signs of healing after each injection on X-rays which were taken approximately 6 weeks post injection. Calcaneus gradually became firm to hard after each injection and pain was also reducing sequentially. After the 4^th injection the calcaneus became hard and the patient was completely painless. After the 4^th injection, it was seen that it is now in stage 1 modified Neer classification of radiologic healing status which states cyst filled with new bone and small radiolucent area (<1 cm).

No sign of recurrence is seen over 1 year after the 4th injection, like no lytic and expansile area in bone, soap bubble appearance, bony destruction, involvement of soft tissue, periosteal reaction and there were no clinical signs for recurrence also like pain, swelling etc. (Figure 7-D). As there was no sign of recurrence, further imaging like CT or MRI was not done.

DISCUSSION

In our department of pediatric orthopedics, we have operated on several ABCs on different locations of bone, but never encountered one in the calcaneus, which supports paucity of literature regarding it. As we discussed earlier, less than 50 cases of primary calcaneus ABC were reported till date, a very small portion of them was treated with sclerosant injection, and the rest were treated with extended curettage and bone grafting.^1,7-12 As our patient was a 5 year old female child and almost the entire calcaneus was affected by a cyst resulting in a thin wall, we tried a less morbid procedure which was sclerosant injection. Polidocanol is a widely used sclerosant agent which is used in treatment of ABC nowadays. Its mechanism of action primarily revolves around its ability to cause endothelial damage, leading to vein sclerosis and eventual obliteration of the targeted vascular structures. The surfactant action of polidocanol leads to the denaturation of proteins and lipids in the cell membrane. This denaturation process causes cell membrane damage and loss of cellular integrity. The endothelial cells, being particularly sensitive to such damage, begin to swell and rupture, leading to cell death. Then it forms blood clots and then it turns into fibrosis over time. The concentration we use is also important to treat ABCs.

After 4 sequential injections of polidocanol, the patient was fit, no signs of recurrence or any adverse effect after giving polidocanol was noted. In our patient there was no sign of recurrence even after 1 year of completing the last injection.

Limitations of this study being it is a single case; absence of standardized outcomes; no cross-sectional imaging post treatment and short follow-up.

CONCLUSION

Primary aneurysmal bone cysts of the calcaneus are extremely rare in early childhood. This case highlights successful management of a large, thin-walled calcaneal ABC using serial polidocanol sclerosant injection, avoiding the morbidity of curettage and grafting. At one-year follow-up, the patient demonstrated radiographic healing and full resolution of symptoms without recurrence. Larger studies are needed to establish optimal dosing protocols and long-term outcomes.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not Required

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