What are the primary types of skull frontal fractures?

Primary Types of Skull Frontal Fractures

Frontal bone fractures can be classified into anterior table fractures, posterior table fractures, and combined anterior and posterior table fractures, with additional subtypes based on fracture pattern and involvement of surrounding structures. 1

Anatomical Classification

• Anterior table fractures: Involve only the outer cortical bone of the frontal sinus, representing approximately one-third of all frontal sinus fractures 1
• Posterior table fractures: Involve the thin bone separating the frontal sinus from the anterior cranial fossa, which is more delicate and easily fractured 1
• Combined anterior and posterior table fractures: Involve both tables simultaneously, representing approximately two-thirds of all frontal sinus fractures 1

Classification Based on Fracture Pattern

• Linear fractures: Simple non-displaced fracture lines 2
• Depressed fractures: Segments of bone pushed inward, causing potential increased intracranial pressure or hemorrhage 2
• Comminuted fractures: Multiple bone fragments, often requiring complex reconstruction 3
• Compound fractures: Fractures with overlying skin laceration exposing the internal cranial cavity to the external environment 2, 4
• Elevated fractures: A rare subtype where bone fragments are elevated above the normal skull contour 5

Classification Based on Vertical Trajectory and Extension

• Type 1: Frontal sinus fracture without vertical extension 6
• Type 2: Vertical fracture through the orbit without frontal sinus involvement 6
• Type 3: Vertical fracture through the frontal sinus without orbit involvement 6
• Type 4: Vertical fracture through the frontal sinus and ipsilateral orbit 6
• Type 5: Vertical fracture through the frontal sinus and contralateral or bilateral orbits 6

Classification Based on Regional Involvement

• Isolated frontal bone fractures: Limited to the frontal bone without extension 1
• Fractures with nasofrontal duct involvement: Injuries along the inferomedial aspect of the frontal sinus and anterior ethmoids, potentially causing nasofrontal duct occlusion 1
• Fractures with cribriform plate involvement: Through the medial aspect of the frontal sinus floor, potentially resulting in CSF leak or chronic sinusitis 1
• Fractures with orbital roof involvement: Through the lateral part of the frontal sinus floor 1
• Fractures with skull base extension: Penetrating into the anterior, middle, or posterior cranial fossa 6

Clinical Significance and Complications

• Vertical fractures penetrate the middle or posterior cranial fossa significantly more often than non-vertical fractures (62.2% vs. 15.7%) and have a significantly higher mortality rate (18.4% vs. 0%) 6
• Displaced posterior table fractures often indicate disruption of the underlying dura and communication between the frontal sinus and anterior cranial fossa 1
• Injuries to the nasofrontal duct can lead to potential mucocele formation and possibly osteomyelitis 1
• Fractures through the medial aspect of the frontal sinus floor may result in cerebrospinal fluid leak or chronic sinusitis 1
• Frontal bone fractures are often associated with intracranial injuries in 56-87% of cases, requiring comprehensive evaluation 1

Diagnostic Imaging

• Multidetector CT (MDCT) without contrast is the gold standard for diagnosing frontal bone fractures, providing superior delineation of osseous and soft-tissue structures 1, 7
• CT head is complementary to maxillofacial CT for complete characterization of frontal bone injuries and associated intracranial injuries 1, 7
• 3D reconstructions are particularly valuable for surgical planning and better characterization of complex fractures 1, 7

Treatment Considerations

• Surgical intervention is typically indicated for depressed fractures with >10mm depression or associated brain injury 2
• Reconstruction options include autogenous bone grafts, titanium clamps, or bone cements depending on fracture complexity 2, 3
• Frontal sinus fractures with nasofrontal duct involvement may require sinus cranialization to prevent mucocele formation 4
• Treatment approach should consider both functional and cosmetic outcomes, as frontal bone contour defects can result in marked facial deformity 2, 3