Causes / typical injury mechanism: Medial malleolus fractures are a type of ankle fracture typically caused by a twisting injury with forced eversion and external rotation of the ankle joint.

Classic history and presentation: Patients present with severe ankle pain and swelling with associated difficulty ambulating.

Patient recollection of the exact motion of the foot during the injury (supination, pronation, external rotation, internal rotation) often does not reliably correlate with the injury pattern seen on imaging or in the operating room. Therefore, the initial focus should be as follows:

• Obtain a basic history (eg, whether injury occurred during a fall from a height, a sports activity, or a car crash).
• Perform a thorough physical examination, including assessment for neurovascular deficit, deformity, or soft tissue injury.
• Reduce the fracture if necessary (particularly if there is a neurovascular deficit). For more information on reduction, see ankle fracture. 
• Evaluate x-rays for stability.

In most cases, patients will present immediately after an injury. Patients will generally present with ecchymosis and swelling around the ankle (especially on the medial side but can be more diffuse) and limited ankle motion. Thorough examination of the ankle for obvious deformities around the ankle or fibula, open wounds, or soft tissue injury must be performed.

Prevalence:

• Age / Sex / Gender – Bimodal distribution, with highest incidences in young, active men (15-24 years) and older women (75-84 years).

Risk factors: Risk factors for medial malleolus fracture include obesity, smoking, younger age, male sex, and alcohol consumption. Ankle fractures are not classic osteoporotic fractures (ie, bone density is not necessarily protective).

Pathophysiology: Medial malleolus fractures are generally caused by a twisting injury to the ankle, with an outward force causing forced eversion and external rotation of the ankle joint. Distribution of fracture location is as follows: isolated malleolus fracture (70%), bimalleolar (20%), and trimalleolar (7%). Fractures may also be associated with syndesmotic injury, peroneal tendon tears, open fractures, or chondral injuries and require thorough ligamentous and soft tissue evaluation.

Grade / classification system:  There are various classification systems available to characterize medial malleolus fractures, which capture the nature of the fracture as well as the degree of ligamentous and additional bony involvement. Classification systems are as follows.

Lauge-Hansen Classification (characterizes applied force) –

• Supination-Adduction (SAD)
  • Vertical medial malleolus fracture and impaction of anteromedial distal tibia; often associated with talofibular sprain or distal fibular avulsion
• Supination-External Rotation (SER)
  • Transverse medial malleolus fracture and disruption of deltoid ligament; often associated with lateral short oblique fibula fracture, anterior or posterior tibiofibular ligament injury, and injury to the posterior malleolus (part of the tibia)
• Pronation-Abduction (PAB)
  • Transverse medial malleolus fracture and disruption of deltoid ligament; often associated with anterior tibiofibular ligament sprain and transverse comminuted fracture of the fibula above the level of the syndesmosis
• Pronation-External Rotation (PER)
  • Transverse medial malleolus fracture and disruption of deltoid ligament; often associated with anterior tibiofibular ligament injury, lateral short oblique or spiral fibula fracture, and injury to the posterior tibiofibular ligament or posterior malleolus

 Anatomic –

• Isolated medial malleolus fracture
• Bimalleolar-equivalent fracture
• Bimalleolar fracture
• Trimalleolar fracture