Abstract
Unicameral bone cysts (UBCs) of the calcaneus, although rare, can cause significant pain and deformity and are often missed on initial evaluation. In this case study, we present a 64-year-old male diagnosed with a calcaneal bone cyst causing pain to the right heel. Surgical intervention was deemed necessary due to persistent pain and functional impairment. The patient underwent excision of the calcaneal bone cyst via cortical windowing, curettage, application of phenol, grafting, and insertion of a fibular strut to maintain strength and stability of the calcaneus. No complications occurred and postoperative plain film radiographs confirmed adequate consolidation of bone defect with stabilization of calcaneus bone integrity. Postoperatively, the patient’s pain resolved and he was able to bear weight in stable shoe gear once again. This case presents a comprehensive approach in the treatment of unicameral bone cysts to achieve successful outcomes and prevent fracture through the subtalar joint.
Introduction
Unicameral bone cysts also known as simple bone cysts are lytic bone lesions without any periosteal reaction. Bone cysts in the calcaneus, although rare, can lead to significant pain, deformity, and functional limitations. These cysts ultimately thin and weaken the affected bone, producing mechanical fragility that can result in pathological fractures if left untreated. More so, large cysts can cause complete collapse of the subtalar joint. Treatment of calcaneal bone cysts remains largely controversial, however, all aim to resolve heel pain and consolidate cyst formation radiographically. Current surgical treatments include open curettage, bone grafting, methylprednisolone acetate injections, bone marrow injections, cyst decompression, the use of calcium sulfate, calcium phosphate and cannulated screws. Most recently, the use of denosumab, a monoclonal antibody that inhibits bone resorption has shown promising results as well. A common challenge remains the recurrence of cysts due to residual cystic cells. The use of phenol has demonstrated promising results as a sclerosant by destroying the cyst-lining cells, promoting fibrosis and closure of the cavity, and thereby reducing the risk of recurrence. Each of the treatment options have produced drawbacks such as recurrence of the cyst, inability to achieve bone healing, lack of long-term structural support and need for repeat treatment. In this article, we propose a novel approach using open cortical windowing of the calcaneus, curettage, application of phenol, and insertion of fibular strut bone graft material to treat a calcaneal bone cyst.
Case presentation
A 64-year-old male presented with a history of persistent pain localized to the right heel. The patient reported progressively worsening discomfort in the right foot, exacerbated by weight-bearing activities. Previous conservative management, including pain management with nonsteroidal anti-inflammatories and foot orthotics, had failed to provide adequate relief. Radiographs confirmed the presence of a bone defect present in the calcaneus ( Fig. 1 ). Given the persistent symptoms and risk of pathological fracture, surgical intervention was recommended.
Preoperative lateral radiograph of the right foot with a 2.99 cm x 2.46 cm osseous defect noted to the calcaneus.
Under general anesthesia, the patient was placed in a supine position, and a well-padded pneumatic tourniquet was applied to the right thigh for hemostasis. A preoperative popliteal block was administered for regional anesthesia. Once the right lower extremity was scrubbed, prepped and draped, a 5 cm longitudinal incision was made along the lateral aspect of the right heel. The incision was deepened through subcutaneous tissue, with care taken to avoid vital neurovascular structures and peroneal tendons. Intraoperative fluoroscopy was used to confirm the location of the calcaneal cyst. The periosteum over the lateral calcaneus was reflected, and a 30 mm trephine was used to create a cortical window corresponding to the size of the cyst. An osteotome was employed to carefully remove the cortical window and expose the underlying cyst cavity. Upon inspection, significant bone loss was noted within the calcaneus, with soft, yellow fluid-filled bone identified within the cavity ( Fig. 2 ). At this time no fracture lines extending through the subtalar joint were noted. A deep wound culture was obtained, and fluid and hard cancellous bone were sent for pathology. The cyst cavity was first irrigated with antibiotic solution to reduce the risk of infection, and then curettage was performed to remove irregular portions of cancellous bone. Next, phenol was applied to the cyst walls in five 30-second applications to decrease the chance of recurrence. The cyst cavity was then packed with a combination antibiotic cement and bone allograft to fill the osseous void and prevent calcaneal collapse ( Fig. 2 ). A fibular strut graft was also placed perpendicular to the weight bearing surface of the foot to provide additional structural support. The previously excised cortical window was replaced, and fluoroscopy confirmed stable re-approximation within the calcaneus. After irrigation with antibiotic solution, the incision site was closed in layers with appropriate sutures, and a sterile dressing was applied. The patient was immobilized in a posterior splint and advised to remain non-weightbearing on the right lower extremity for four weeks. After completion of this period, radiographs demonstrated osseous consolidation, and the patient was subsequently transitioned to weight bearing as tolerated in a CAM boot. The patient continued to present to clinic regularly for postoperative care following the procedure.
Intraoperative clinical images demonstrating (A) exposed calcaneal cyst cavity and (B) placement of a fibular strut allograft.
Postoperatively, the bone pathology report confirmed diagnosis of a unicameral bone cyst of the calcaneus. The patient remained free of any postoperative complications and complete resolution of pain to the right heel was noted. At three years postoperatively, radiographs demonstrated stable fixation of the fibular strut within the calcaneus with osseous consolidation and without evidence of fracture ( Fig. 3 ). The patient continues to ambulate in normal shoe gear without pain.
