Lucent Calcaneal Lesions: Differential Diagnosis

Pseudocyst of the Calcaneus

• Normal variant in the anterior calcaneus.
• Trabecular pattern visible, no cortical expansion.
• Incidental finding, no risk of fracture.

Simple Bone Cyst

• Fluid-filled cavity, centrally located.
• Well-defined, thin sclerotic border.
• Risk of fracture, may show fallen fragment sign.

Intraosseous Lipoma

• Fat-containing lesion, may calcify over time.
• Lucent with central fat density, thin sclerotic rim.
• Confirmed by CT/MRI, may show dystrophic calcifications.

Ankle Fracture

This case fits into both the Weber C classification and the Lauge-Hansen Pronation-External Rotation classification. The fracture pattern includes:

• Suprasyndesmotic distal fibular fracture
• Medial malleolar avulsion
• Posterior malleolar fracture

These injuries indicate a significant disruption of the ankle mortise and syndesmosis, necessitating surgical fixation. For a comprehensive review, refer to the Radiology Assistant’s articles on ankle fractures—undeniably top-notch and worth the read for any MSK enthusiast.

Calcaneal Lipoma

The lucent lesion in the calcaneus shows peripheral fat with some internal calcifications. The differential for a lucent calcaneal lesion includes:

1. Calcaneal Lipoma (confirmed by fat presence)
2. Calcaneal Pseudocyst
3. Simple Bone Cyst

An intriguing paper by some of my mentors (Powell et al.) at Mayo Clinic proposed a mechanism where a calcaneal lipoma develops within a pre-existing intraosseous ganglion cyst. This study, titled Intraosseous "Lipoma" of the Calcaneus Developing in an Intraosseous Ganglion Cyst, showed gradual peripheral fat deposition within a lesion over a 4-year period, and some companion cases demonstrating a similar process. The peripheral fat deposition in the case at hand raises the question of something similar going on, with the lesion potentially evolving into a more completely fat-filled lesion over time.

1. Howe BM, Powell GM, Ringler MD, Turner III NS, Broski SM. Intraosseous “Lipoma” of the Calcaneus Developing in an Intraosseous Ganglion Cyst. Journal of Radiology Case Reports. 2018;12(12). doi:https://doi.org/10.3941/jrcr.v12i12.3263
2. The Radiology Assistant : Weber and Lauge-Hansen Classification. radiologyassistant.nl. https://radiologyassistant.nl/musculoskeletal/ankle/weber-and-lauge-hansen-classification

Lucent Calcaneal Lesions: Differential Diagnosis

Pseudocyst of the Calcaneus

• Normal variant in the anterior calcaneus.
• Trabecular pattern visible, no cortical expansion.
• Incidental finding, no risk of fracture.

Simple Bone Cyst

• Fluid-filled cavity, centrally located.
• Well-defined, thin sclerotic border.
• Risk of fracture, may show fallen fragment sign.

Intraosseous Lipoma

• Fat-containing lesion, may calcify over time.
• Lucent with central fat density, thin sclerotic rim.
• Confirmed by CT/MRI, may show dystrophic calcifications.

Calcaneal pseudocyst

Calcaneal pseudocyst

• A benign “don't touch” lesion
• Due to a decrease in bony trabeculae from an absence of stress
• Calcaneal bone cysts and intraosseous lipomas occur in the same location
• Because of the relative lack of stress placed in this part of the calcaneus, they rarely fracture and should be left alone

Lucent Calcaneal Lesions: Differential Diagnosis

Pseudocyst of the Calcaneus

• Normal variant in the anterior calcaneus.
• Trabecular pattern visible, no cortical expansion.
• Incidental finding, no risk of fracture.

Simple Bone Cyst

• Fluid-filled cavity, centrally located.
• Well-defined, thin sclerotic border.
• Risk of fracture, may show fallen fragment sign.

Intraosseous Lipoma

• Fat-containing lesion, may calcify over time.
• Lucent with central fat density, thin sclerotic rim.
• Confirmed by CT/MRI, may show dystrophic calcifications.

Calcaneal intraosseous lipoma