P109 Sherlock Holmes in Clinical Practice: The Deduction of the Pattern and Mechanism of Injury in Ankle Fractures Using Lauge-Hansen System
Authors: Quek Fang Fang 
Published: April 2021

Abstract

Introduction
Ankle fractures are among the commonest fractures in adults and as population ages, the incidence is also increasing. It is crucial to ascertain the mechanism of injury of an ankle fracture as it determines the management plan. The diagnosis and management of ankle fractures are usually relatively straightforward but they are not always the case. Most patients are unable to recall the exact mechanism of injury due to the instantaneous nature of incident. We herein describe a case report of a patient who sustained an ankle fracture following a fall but was unable to recall the exact mechanisms of injury. This case report addresses the importance of recognising Maisonneuve fractures and how Lauge-Hansen Classification system might be useful in diagnosing and making management plans for ankle fractures.

Case Report
A 30-year-old male self-presented to the Emergency Department in a wheelchair following a fall. He tripped down the last four steps of stairs the night before, sustaining a right ankle injury as a result. He has been unable to weight-bear since. Elevation and application of ice packs have showed limited effect. Patient was unable to recall the exact mechanism of injury. On examination, the right ankle was swollen and there were bruises around the medial malleolus. Upon palpation, he complained of bony tenderness around lateral and medial malleoli. No other injury was found and patient was neurovascularly intact. A referral was made to the Orthopaedics team and further orthopaedic examinations revealed tenderness and crepitus upon palpation over the proximal fibula. Full lower leg X-rays was ordered to look for possible proximal fibula fracture. A diagnosis of closed, Maisonneuve (Weber C)/trimalleolar fracture of the right ankle was made.
A CT-scan of the right ankle was requested to determine the involvement of joint surface to aid surgical planning. Both CT-scan and ankle X-rays showed disrupted syndesmosis. Disrupted syndesmosis is most commonly associated with Weber C fractures as shown in this case. Since the fibular fracture is greater than 4.5cm away from the tibial plafond, syndesmosis fixation is required. In Maisonneuve fractures, syndesmotic screws can be used to achieve anatomical reduction and ankle stability. This patient was scheduled for an ORIF surgery.

Discussions
Based on the findings of medial and posterior malleoli fractures from the ankle X-rays, we can deduce that the patient has most likely sustained a complete Pronation-External Rotation (PER) injury. A Maisonneuve fracture was almost missed initially due to distracting injuries and not obtaining full lower leg X-rays. However, based on Lauge-Hansen Classification, we know that it is highly unlikely to have a posterior malleolus fracture (Stage 4) without any fibular fracture (Stage 3). Hence, a full-fibula X-ray was ordered to look for proximal fibula fracture and the X-rays revealed a spiral fracture at the proximal fibula (Maisonneuve fracture). The injury force was transmitted along the interosseous membrane and exited at the shaft of proximal fibula, causing a proximal fibular fracture. PER or injury sustained from an internally rotated leg on a planted foot may cause external rotation injury, resulting in a disruption of the ligaments. The syndesmosis, which provides primary support to the ankle, if disrupted, will disrupt the ankle mortise, displacing the fibula laterally, as demonstrated in this case.

Conclusion
As demonstrated in this case, some fractures, like the Maisonneuve fracture, can easily be missed. Due to distracting injuries, the chief complain in most cases of Maisonneuve fracture is severe ankle pain instead of the fracture site at proximal fibula. These fractures, if not identified early, can lead to poor prognosis. It is important to consider Maisonneuve fracture in all ankle injuries. A delayed diagnosis can lead to post-traumatic arthritis and pain, leading to loss of function. This case report addresses the importance of recognising easily missed fractures and how Lauge- Hansen Classification system is useful in aiding the diagnosis and management of ankle fracture