Efficacy of Lesion Specific Portals in Endoscopic Treatment of Calcaneal Bone Cyst: A Case Report and Literature Review

Abstract

Background: Calcaneal bone cysts rarely occur and most of them are known to be benign. Among them, simple bone cysts (SBCs) third most commonly occur in the calcaneus and of the many surgical treatment options, endoscopic curettage is recently gaining popularity among surgeons due to its advantages of minimal invasiveness and optimal visualization. As for portal placement for endoscopy, two lateral portals are considered a standard technique, but no rationale has been established for SBCs with abnormal geometry. This case report suggests an SBC with secondary aneurysmal change located outside the Ward's triangle, as well as an appropriate endoscopic approach. Case Presentation: An 18-year-old male high school student presented with a main complaint of pain at the hind foot level for the past one year, without significant improvement from conservative treatment. An endoscopic curettage through the lesion specific two posterior portals and bone graft using allogeneic cancellous bone were performed. SBC with a secondary aneurysmal bone cyst was diagnosed on pathology. At a one-year follow-up, the patient was painless and had returned to his regular activities. Physical and radiographic examinations revealed that the lesion was completely healed without any evidence of recurrence. Conclusion: For calcaneal bone cysts located at the posterior aspect of the calcaneus, eccentrically medial and abnormally long anterior-posteriorly, we suggest an endoscopic procedure using lesion specific portals such as two posterior portals.

Keywords: benign bone tumors; calcaneal bone cysts; endoscopic curettage; portal.

Figure 1

Preoperative radiographs of the calcaneus. (A) axial and (B) lateral view.

Figure 2

Preoperative computed tomography (CT) scans of the left foot (A) sagittal and (B) axial views show lytic mass lesion, 4.6 × 2.4 × 4.4 cm in dimension, localized postero-medially, leading to the cortical bone thinning, containing calcified lesions without signs of stress fracture.

Figure 3

Preoperative magnetic resonance imaging (MRI) scans axial view shows a cystic mass lesion in the posteromedial part of the calcaneus medullary cavity. (A) T1W intermediate, (B) T2W heterogeneously high signal intensity multi-lobulated cystic structure. (C) Contrast enhanced image shows a peripherally enhanced mass with fluid-fluid level formation.

Figure 4

Intraoperative aspiration of the cyst. The patient is in a prone position. The black asterisk (*) marks the calcaneus.

Figure 5

Portal placement. The first guide wire inserted from the most thinned wall of the posteromedial aspect of the cyst (arrowhead) toward the center (asterisk). The second guidewire inserted through posterolateral aspect of the cyst, forming a right angle with first guidewire.

Figure 6

Intraoperative image showing the posterolateral viewing portal (PL) and the posteromedial working portal (PM).

Figure 7

Endoscopic view showing (A) the inner septum in the cyst and (B) the cavity after resection of the bony septum. (C) After curettage of the inner surface of the calcaneal cyst.

Figure 8

Impaction of the allogenic cancellous bone chips through the portals.

Figure 9

Histologic features of the obtained specimen. (A): Cystic wall containing ossification along the fibrous wall (Hematoxylin-eosin stained (H-E); magnification, ×40). (B) Fibrous exudate in the wall (H-E; magnification, ×40). (C) Hemosiderin pigment in the wall (H-E; magnification, ×40). (D) Focal giant cell reaction due to Aneurysmal bone cystic change (H-E; magnification, ×100).

Figure 10

Postoperative one year (A) axial and (B) lateral view of the calcaneus.

Figure 11

Comparison of the accessible area for debridement (dotted area) upon the portal placement. Working on the lateral portal (A) provides limited motion for the suction shaver because of the thick cyst wall. Accessed from the posterior portal (B), the suction shaver is more mobile because of the thin cyst wall, allowing a larger area for debridement.