Bimalleolar Equivalent Ankle Fracture-Dislocation

HPI:  Middle age male who presents with left ankle pain, swelling, and deformity s/p fall down stairs. Unable to bear weight to LLE.

Physical Exam: obvious deformity, edema, ecchymosis to L ankle. TTP over medial and lateral malleolus. Unable to flex and extend at ankle 2/2 pain. DP/PT 2+. Normal sensation to light touch to dorsal surface/plantar surface/1st web space.

IMAGING:

Diagnosis and Management:  This patient has a Weber B distal fibula fracture with medial subluxation of the tibia and disruption of the mortise joint. Combination of distal fibula fracture and likely complete disruption of deltoid ligament is a bimalleolar fracture-dislocation equivalent.  Thus, this is an UNSTABLE ANKLE!

Patient’s ankle was reduced using axial traction and inversion, placed in posterior sugar tong splint. Injury required 3 reductions, which is common due to the instability of this injury. Patient was admitted to Orthopedic Trauma service and scheduled for next day ORIF. 

Pearls: The key area to focus on imaging for this type of injury is the medial malleoulous - talar joint space (see green area on above figure). There is some debate in the orthopedic literature, but if the joint space is separated by more than 3-5mm, stress films OR treating the injury as a bimalleolar equivalent fracture/dislocation is indicated.