Presentation
Motor vehicle accident.
Patient Data
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There are two proximal fibular fractures involving the fibular head and proximal fibular diaphysis, as well as an avulsion of the anterior tibial eminence. A large suprapatellar effusion is also noted, with a fat/fluid level.
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The leveled suprapatellar effusion and ACL avulsion are outlined.
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The avulsion of the anteromedial tibial spine is well appreciated, with elevation of the anterior aspect of the fragment with maintenance of the posterior portion next to its parent site. This represents a "hinged appearance," indicating a type 2 avulsion of the ACL insertion. The fibular head fracture is revealed to be comminuted but minimally displaced, with minimal displacement of the proximal fibular diaphyseal fracture.
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The diagrams illustrate the hinged appearance of type 2 ACL avulsion fractures (which is elevated anteriorly but not posteriorly) as well as the proposed mechanism.
Case Discussion
Avulsions of the tibial eminence are most frequently seen in high energy trauma such as a motor vehicle accidents, and in children where bone is pliable and gives way before the ACL tears. In this case, a young man in a motor vehicle collision sets up a reasonable scenario for this injury, which is actually quite well evaluated on the plain film images in this case.
This case is courtesy of Eric White, MD, who generously shared it with me.
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