Aneurysmal bone cyst of the calcaneus: A rare case report and review of the literature

Abstract

Introduction and importance

Aneurysmal bone cyst (ABC) is a benign lytic bone tumor of the skeletal system but locally destructive lesion of unknown origin. It often occurs in childhood and usually involves the metaphyseal region of long bones; thus, its localisation in the calcaneum remains rare; its atypical presentation in our case makes it remarkable.

Case presentation

We describe a case of a young patient who suffered from chronic heel pain, in whom the clinical examination finds swelling and pain on palpation. A complete radiological assessment was carried out, which revealed a solitary and expansive osteolytic lesion within the calcaneus. Treatment included tumor curettage and reconstruction with allograft and cement. The biopsy report was consistent with an ABC. The postoperative follow-up at 18 months was marked by a good radio-clinical evolution and no recurrence.

Clinical discussion

ABCs are benign cystic expansive tumors that are reactive, locally destructive and blood-filled, their occurrence in the calcaneus has been reported in only 1.6 % of total reported cases. Talalgia is the most frequent sign associated with swelling. Liquid-liquid level images on MRI is a pathognomonic sign of these lesions but the gold standard diagnosis remains histology. Their treatment is based on curettage - filling by grafting.

Conclusion

Curettage combined graft makes results butter and improves the quality of life.

Highlights

• •Uncomman presentation : the rarity of this localization and its atypical presentation make our case unique and need to be documented.
• •Diagnostic complexity : benign but aggressive tumor requiring early diagnosis, it also poses problems of differential diagnosis with malignant tumors.
• •Treatment Approach: the principle of overall management of cysts is the same whatever the location and is based on curettage - filling by grafting, the atypia that our case represents is the fact that this location is a bearing zone.

1. Introduction

Aneurysmal bone cyst (ABC) is a locally aggressive benign tumor that occurs in childhood and early adulthood. In more than 80 % of cases, the lesion affects patients under the age of twenty [1]. ABC accounts for approximately 1 % of all primary bone tumors. They are most commonly seen in the long bones' metaphyseal region. Only 3 % of cases have been reported in the foot, of which only 1.6 % involve the calcaneus [2].

Clinically, calcaneal ABCs behave slightly differently than those seen at other sites. They are more often symptomatic and less likely to be complicated by a pathological fracture [3,4]. An osteolytic lesion can be found on standard radiographs, and magnetic resonance imaging shows cystic formations with typical fluid levels due to blood sedimentation [5,6].

According to the literature, the majority of patients underwent surgical treatment such as curettage and grafting [3].

Because of their rarity and atypical presentation, we describe our experience managing a calcaneal primary ABC case in a 24-year-old adult, highlighting considerations specific to this location and therapeutic challenges.

This case was formulated according to the SCARE 2023 guidelines [7].

2. Case presentation

Mr. I·B, 24 years old, has BMI of 27, referred to our department for unilateral left talalgia for two years, of progressive aggravation, calmed by analgesic treatment, causing him partial functional impotence, the whole evolving in a context of conservation of the general state. He is without past medical history and he is a non-smoker patient.

On clinical examination, the patient was stable, walking pain even using crutches, with pain on palpation of the calcaneus, swelling of the hind foot and a significant reduction in the quality of life, and there was no skin signs opposite. The rest of the somatic examination was unremarkable.

Standard radiography (Fig. 1) revealed a lytic image at the inferior border of the calcaneus without trabeculation or periosteal reaction.

Fig. 1.

X-ray of the left ankle showing a lytic lesion on the lower edge of the calcaneus.

MRI showed a large lesion centered on the tuberosity of the calcaneus measuring 68*55*47 mm, relatively well-circumscribed and inhabited by multiple logettes/partitions, with several liquid-liquid levels (hematic component) (Fig. 2A). This lesion blows out the cortical bone of the calcaneus without effraction of the latter, without extraosseous tissue component (Fig. 2).

Fig. 2.

MRI of the ankle with slices (coronal and sagittal). A (T1 sequence), B (T2 sequence).

Laboratory results showed a white blood cell count of 8200, a platelet count of 378,000, an erythrocyte sedimentation rate of 8 mm/h, and a C-reactive protein level of 6 mg/L.

Based on the clinico-radiological findings, the diagnosis of a benign cystic lesion of the calcaneus, most likely ABC, was made. The patient was positioned in a lateral decubitus posture, the lateral support was placed against the pubic symphysis, first-generation cephalosporin-based antiobioprophylaxis was administered. The patient was scheduled for biopsy removal of the lesion via a retro and sub-malleolar approach.

Intraoperatively, a multilocular blood-filled cavity was noted. A wide curettage was performed with a half femoral head allograft (BioBank^R) fixed with a pin, then filled with cement. After closure, a posterior plaster splint was made (Fig. 3). The pin was removed after 60 days.

Fig. 3.

Intraoperative images: a) retro and sub-malleolar approach. b) Wide curettage of the cyst. c) Filling with allograft. d) Placement of cement.

The curetted material was sent for histological analysis which showed tumor proliferation made of regular bone trabeculae with numerous osteoclastic-like giant cells with homogeneous distribution within a fibroblastic and inflammatory stroma, and proliferation made of giant cells, fibroblasts, histiocytes and siderophages without cytonuclear atypia or mitoses with a cystic cavity and also multiple cystic cavities filled sometimes with blood and sometimes with basophilic material without a clean wall.

Complete unloading of the affected limb was recommended for six weeks and partial unloading for up to 12 weeks. The biopsy report was consistent with an ABC (Fig. 4).

Fig. 4.

Histological images of the specimen: a) Tumor proliferation made of regular bone trabeculae with numerous osteoclastic-like giant cells with homogeneous distribution within a fibroblastic and inflammatory stroma (HE×20). b) Proliferation made of giant cells, fibroblasts, histiocytes and siderophages without cytonuclear atypia or mitoses with a cystic cavity (right and bottom) (HE×20). c) Multiple cystic cavities filled sometimes with blood and sometimes with basophilic material without a clean wall (HE×20).

The post-operative recovery was straightforward; we noted the persistence of mild pain in weight bearing. After 18 months follow-up, the patient was pain free and had returned to his regular activities, there was no sign of recurrence, good integration of the grafts on the control radiograph and a satisfactory functional result (Fig. 5).

Fig. 5.

Postoperative radiological images: a) at Day 1. b) after 1 month. c) after 3 months. d) after 9 months.

3. Discussion

ABCs were first described by Jaffe and Lichtenstein in 1942; they are benign cystic expansive lesions that are reactive, locally destructive and blood-filled [1]. ABCs may occur de novo (primary ABC) or may be associated with other underlying primary bone tumors (secondary ABC), such as giant cell tumors, osteoblastomas and, most commonly, chondroblastomas of the calcaneus [6]; in our case, this is a primary ABC. To our knowledge, only 33 cases of calcaneal ABC have been reported in the literature (Table 1), our patient is added to this list to make it 34 cases. The pathogenesis of ABCs is controversial; some have been considered reactive processes resulting from a local increase in venous pressure leading to a dilated vascular bed in the involved bone and intraosseous or subperiosteal hemorrhage, thus, activating osteoclasts and inducing bone resorption and local remodeling [8]. In recent years, a novel t(X; 9) translocation (q26-q32) has been described in a robust ABC variant [9].

Table 1.

Reported cases of ABC in the literature.

References	No. of cases	Year	Mean age (years)	Sex	Treatment	Adjuvant	Recurrence
				(M/F)
Mohaidat et al. [21]	1	2019	12.8	ND	ND	ND	ND
Arif et al. [22]	1	2016	25	H	Curettage + autograft	?	No
Mahapatra et al. [23]	1	2014	21	H	Curettage + autograft + synthetic grafting	?	No
Reddy et al. [24]	4	2014	17.2	ND	ND	ND	ND
Kaplanoglu et al. [25]	1	2014	17	F	Curettage + autograft	ND	ND
Soraganvi et al. [10]	1	2011	55	H	Curettage + autograft + synthetic grafting	ND	No
Babazadeh et al. [4]	1	2011	21	H	Curettage + autograft + Allograft + Plaque	Phenol + alcool	No
Malik et al. [26]	1	2010	17	H	Curettage + autograft	ND	No
Oomen et al. [3]	3	2009	31,7	ND	2 cases: Curettage + bone graft	ND	ND
					1 case: calcanectomy
Docquier et Delloye [27]	1	2005	16,6	ND	Injection DBM + bone marrow injection	ND	ND
Gomez et al. [26]	1	1997	8	ND	ND	ND	ND
Delloye et al. [17]	1	1996	16	F	Curettage + DBM	ND	Yes
Casadei et al. [28]	10	1996	14	ND	Curettage + autograft/Allograft/	phenol	ND
					Tricalcium phosphate
Hertzanu et al. [29]	3	1984	16	ND	Partial calcanectomy + IC autograft	ND	No

ND: Not determined; DBM: demineralized bone matrix; IC: iliac crest.

ABCs represent 1 % of primary bone tumors with an incidence of no more than 0.14 per 100.000 population. There may be a slight female predominance in contrast to the gender of our case. ABC occurs at all ages, but 75–90 % of cases occur before the age of 20; it is rare after 30 years and exceptional after 50 years; Our patient is still young, which is in line with these results. It often occurs in isolation [8]. ABC can affect any part of the skeleton, but mainly the long bones (67 % of cases), the spine (15 %) and the pelvis (9 %). The metaphysis is most often involved, and the most frequently affected bones are the distal femur, tibia, humerus and fibula. Their occurrence in the calcaneus has been reported in only 1.6 % of total reported cases [3,4,10,and 11]. In our department, we have operated on several ABC located in the leg and humerus, but this location is the first, which confirms the rarity of this lesion in the calcaneus and perfectly agrees with what is found in the literature.

Clinically, they are often symptomatic. Talalgia is the most frequent sign associated with swelling. It is often chronic; an aggravation marks the evolution over months. A pathological fracture is rare because these lesions keep the cortical bone around them intact [3,10].

Radiographic findings significantly favoring ABC included a less aggressive pattern of bone destruction, a purely lytic appearance, an enlarged but intact cortex, no periosteal response and no soft tissue mass.

Standard radiographs show a lytic, expansive appearance with local aggressiveness, causing extensive destruction, and a blown and thinned cortex, but without periosteal invasion. CT and MRI allow appreciation of the cyst's dimensions, internal architecture, and the cyst's relationships. The presence of level images, which represent the interface between the sedimentary and liquid medium (liquid-liquid level images), are very typical of ABC [12]; gadolinium injection is useful because it shows the alveolar tumor structure separated by septa that enhance after injection, contrasting with a content that does not take contrast [11]. The presence of these signs: T2 tumor hypersignal (fluid component), sharp tumor borders, and peripheral border most likely points to ABC [9]. These liquid-liquid levels are not specific to ABC and can also be present in Telangiectatic Osteosarcomas, Chondroblastomas, and GCTs. Therefore, a confirmatory histopathological diagnosis is still necessary before surgery. Due to the difficulty in differentiating ABC from other benign lesions, particularly GCTs, Malawer and Vance suggested that precise radiological or histological distinction may not always be essential. Instead, treatment can be guided by the biological behavior of the lesion [13]. As our patient presented with the classic clinical and radiological signs of a benign cystic lesion, we decided to perform an excisional biopsy at the same time, since no suspicious signs were found intra-operatively.

The gold standard diagnosis remains biopsy. Primary ABCs tend to have anastomosed blood-filled ducts lined with endothelial cells [14]; those secondary to a preexisting lesion usually have additional features of their precursor. Biopsy also helps rule out other differential diagnoses (giant cell tumors, chondroblastomas, and malignancy) [3,14].

The usual management of ABC is curettage with bone filling by bone grafting (often from the iliac crest) or allograft [15]. Intraoperative bleeding can be controlled either with a tourniquet or by preoperative embolisation [16]. Low-dose radiotherapy can be used with rapid ossification but may predispose it to malignant transformation [16]. Injection of demineralised bone matrix (DBM) mixed with bone marrow aspiration into the cyst has also been described as a therapeutic option [17]. Some authors have performed a wide resection because of the local aggressiveness of the lesion and their fear of a possible recurrence after curettage; excision of the calcaneus can be compensated by transferring the Achilles tendon to the posterior aspect of the talus with intraosseous sutures [18]. Our patient did not require an Achilles tendon transfer. Calcaneal replacement surgeries are not commonly performed due to factors involving instability of the prosthesis [19]. Lange et al. have used denosumab in two patients with spinal ABCs where embolization failed, and reported healing of the lesion and regression of the neurological deficits. Denosumab is a monoclonal antibody that targets RANKL - a ligand that binds to RANK -, a protein that is essential for osteoclast function. By blocking RANKL, denosumab prevents osteoclasts from working, which helps to preserve bone mass [5].

To reduce the recurrence rate after curettage (which is in the range of 10–20 %), several physical or chemical adjuvants have been used [15]; Hussein et al. [11] used prolonged curettage with cryotherapy while Babazadeh et al. [4] and Jalan et al. [13] used phenol as a chemical adjuvant. In our case, cement (polymethylmetharcylate) was used as chemical adjuvant to immediately stabilise the resulting cavity and for its exothermic effect when the cement hardens.

ABCs generally have a favorable outcome with an overall cure rate of 90–95 %. The most frequent complication is a recurrence, usually occurring within two years after surgery [20]. In our patient, functionally, we noted the persistence of mild pain in weight bearing, with no sign of recurrence.

4. Conclusion

ABC of the calcaneus is quite rare; its diagnosis remains difficult and is based on a combination of clinical, radiological and histopathological evidence. Most cases can be effectively managed with prolonged curettage and bone grafting.

Ethical approval

The ethical committee approval was not required given the article type (case report). Ethical Approval: Not applicable.

Funding

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

Author contribution

• -The surgeon who performed this intervention is the author of this article; he is experienced in surgery for this lesion, especially on the humerus and tibia, however, this location is the first in his career: Madani Hamza: operator, study concept, data collection, writing the paper,
• -Elhassnaoui Youssef: contributor, operating aid, study design,
• -Ait Benali Hicham: contributor, revision
• -Shimi Mohammed: supervision and data validation

Guarantor

Madani Hamza.

El hassnaoui Youssef

Aitbenali Hicham.

Shimi Mohammed.

Research registration number

As this manuscript was a case report with no new medical device nor surgical techniques, not prior registration is required.

Consent for publication

The patient was operated on academic practice setting and he was informed that the data would be submitted for publication. Written informed consent was obtained. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Conflict of interest statement

The authors have no conflicts of interest to declare that are relevant to the content of this article.