Working Diagnosis:
Non-displaced medial malleolus fracture

Treatment:
Patient was placed in a short leg cast and made non-weight bearing on crutches for 3 weeks. At follow-up, he continued to have focal swelling of his ankle, though it was improved. Point of care ultrasound revealed a well circumscribed area of swelling with mixed echogenicity, consistent with a resolving hematoma Case Photo #5 Case Photo #6 . Repeat X-rays showed appropriate healing. He was placed in a walking boot for another 3 weeks.

Outcome:
Patient started physical therapy, and transitioned out of the walking boot into a lace-up ankle brace. He was subsequently lost to follow-up.

Author's Comments:
In this case of an occult medial malleolus fracture, diagnosis was delayed due to normal initial imaging and the fact that the patient had improved and returned to football. If not treated in a timely manner, this fracture had potential for displacement and need for surgery, given its extension into the articular surface of the tibia. This case highlights the need for a careful physical exam, and consideration of further imaging if bony tenderness persists with "simple" ankle sprains. The presence of a focal hematoma should alert to the possibility of an underlying fracture. Ultrasound can be beneficial in characterizing swelling and detecting an occult fracture.

Editor's Comments:
Isolated medial malleolar are less common and account for roughly 7% of all ankle fractures. More commonly, they occur in combination with lateral malleolar fractures. The Muller classification has traditionally been used to characterized: Type A – avulsion fracture, Type B – fracture between the tip and the plafond, Type C – fracture at level of plafond, and Type D – fracture extending obliquing from plafond. Stable fractures with less than 2mm displacement maybe treated non-operatively with a non-weightbearing short leg cast for 6 weeks. Unstable fractures or those with greater than 2 mm displacement should undergo surgical treatment. MRI maybe useful to assess concomitate ligament injuries. Weight bearing CT can be used to assess stability.
This case emphasizes the importance of repeating radiographs if occult fracture is suspected. After the initial inflammatory phase, the next phase in fracture healing involves resorbing the necrotic tissue at the ends of the bone. As much as 1-2 mm of tissue maybe resorb, making fracture lines more distinguishable on radiographs 5-10 days after the injury.

References:
Carter TH, Duckworth AD, White TO. Medial malleolar fractures: current treatment concepts. Bone Joint J. 2019 May;101-B(5):512-521. doi: 10.1302/0301-620x.101B5.BJJ-2019-0070. PMID: 31038989.

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