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Trimal Ankle Fracture Dislocation

Case Introduction

A 56-year-old presents after a fall while walking her dog. The patient reports that her dog caused her to twist her left ankle in the opposite direction of her path as she fell. There was immediate onset of pain to the extremity with severe swelling 30 minutes later. She was unable to stand up. In the emergency department, the patient is noted to have an obvious deformity to her ankle with mild medial deviation and eversion of the foot. Her neurovascular exam was intact, and the skin was closed. She had mild tenderness over the knee joint laterally. Radiographs were obtained and the patient was diagnosed with a “trimal” or 3-part ankle fracture.

Ankle Fractures

Ankle fractures are common, with more than 250,000 annually in the United States.1 Barrett, JA, Baron, JA, Karagas, MR, Beach, ML. Fracture risk in the U.S. medicare population. J Clin Epidemiol. 1999;52(3):243–249. Malleolar fractures represent the vast majority of ankle fractures. The lateral malleolus is most commonly fractured and is seen in 55% of cases.2Elsoe F, Ostgaard SE, Larsen P. Population-based epidemiology of 9767 ankle fractures. Foot and Ankle Surgery. 2017;24(1):34–39. doi: 10.1016/j.fas.2016.11.002. Trimal fractures represent about 7 to 12% of ankle fractures.3Daly PJ, Fitzgerald RH, Jr, Melton LJ, Ilstrup DM. Epidemiology of ankle fractures in Rochester, Minnesota. Acta Orthop Scand. 1987;58:539–544. doi: 10.3109/17453678709146395 Fracture dislocations occur in approximately 21 to 36% of all ankle fractures.4Regier M, Petersen JP, Hamurcu A, Vettorazzi E, Behzadi C, Hoffmann M, Großterlinden LG, Fensky F, Klatte TO, Weiser L, Rueger JM, Spiro AS. High incidence of osteochondral lesions after open reduction and internal fixation of displaced ankle fractures: Medium-term follow-up of 100 cases. Injury. 2016 Mar;47(3):757-61. They occur more commonly in women with a biomdal distribution between ages 10-19 and over age 70.
Lateral view of a trimalleolar fracture with posterior dislocation of the talus
Lateral view of a trimalleolar fracture with posterior dislocation of the talus
Mortis view showing trimalleolar fracture with unstable joint
Mortis view showing trimalleolar fracture with unstable joint
Unilateral malleolar fractures is an isolated fracture of either the medial or lateral maleoli, typically lateral. These can be stable or unstable depending on the degree of soft tissue injuries. A stress view radiograph may further help identify instability by demonstrating widening of the ankle mortise. If a lateral talar shift is present, suspect a bimalleolar equivalent fracture where, in addition to the lateral malleolar fracture, the deltoid ligament is injured with subsequent joint instability. A bimalleolar fracture involves the fracture of the both the medial and lateral malleolus. The trimalleolar is so-termed because an additional fracture at the posterior edge of the tibia is involved. When the ankle fracture is accompanied by a high fibular fracture and disruption of the syndesmosis, it is called a Maisonneuve injury. This type of injury is often missed in the initial evaluation. 5Kalyani, Bharati & S Roberts, Craig & Giannoudis, Peter. (2010). The Maisonneuve Injury: A Comprehensive Review. Orthopedics. 33. 190-5. 10.3928/01477447-20100129-25.
Trimalleolar fracture status post reduction with splinting, lateral view
Trimalleolar fracture status post reduction with splinting, lateral view
Trimalleolar fracture status post reduction with splinting, AP view
Trimalleolar fracture status post reduction with splinting, AP view
The mechanism of injury typically involves rotational mechanisms with the external forces transmitted through the foot via the talus to the malleoli. Examples include missing a step on a curb or stairwell, or twisting injuries on a planted foot in which the primary force is acting on the ankle. Risk factors include ligamentous laxity, weak peroneal muscles, a history of ankle sprains, obesity and age. Patients are often able to describe their mechanism of injury as in the case of our patient. They will endorse pain, swelling, inability to ambulate and potentially a deformity. On physical exam, soft tissue swelling, bruising, and even skin tenting can be present. When dislocated, the deformity is typically obvious. A careful neurovascular exam should be performed.
Standard radiographs are often sufficient to make the diagnosis. Fractures of the distal tibia and fibula and any concurrent dislocation are easily seen on the anterior-posterior, lateral and mortise views. It is important to rule out any trauma mimicking a fracture dislocation such as a talus fracture or subtalar dislocation. Post reduction films should be obtained to assess for adequacy of the reduction and surgical planning. Posterior malleolar involvement can be subtle on radiographs and sometimes requires a CT to better characterize. Obtaining a CT scan is a subjective decision that can be made in consultation with your orthopedic consultant. CT scan definitely better characterizes bony lesions and can be useful for operative planning. MRI is not required but may better evaluate for soft tissue lesions, articular injuries and loose bodies.
AP view of the knee demonstrating Maisonneuve fracture
AP view of the knee demonstrating Maisonneuve fracture
Malleolar fractures are classified by the Danis-Weber (relative to the location of the fibular fracture), the AO/ATA classification systems (relative to the syndesmosis) and the Lauge-Hansen classification systems. The Lauge-Hansen classification takes into account the position of the foot at the time of the injury and the force applied to it. Supination-adduction, supination-external rotation, pronation-external rotation results in various patterns of malleolar and fibular fractures, and syndesmotic and deltoid ligaments disruption. Supination-external rotation is the most common mechanism for fracture resulting in a fracture of the distal fibula and avulsion of posterior-inferior tibiofibular ligament. While this type of mechanism may result in a Maisonneuve-type of fracture, pronation-external rotation is reported in more than half of Maisonneuve-type injuries.6Kalyani, Bharati & S Roberts, Craig & Giannoudis, Peter. (2010). The Maisonneuve Injury: A Comprehensive Review. Orthopedics. 33. 190-5. 10.3928/01477447-20100129-25.
Fluoro status post ORIF of the trimalleolar fracture
Fluoro status post ORIF of the trimalleolar fracture
In general, stable ankle fractures are managed with immobilization (splint, CAM boot), elevation, and ice therapy as tolerated. A short leg walking cast or a cast boot for 4-6 weeks might be useful. Unstable ankle fractures require a closed reduction and splinting as soon as possible to prevent tissue ischemia, articular surface damage and help with resolution of swelling. Definitive management of unstable ankle fractures (i.e. bimalleolar, bimalleolar equivalent, trimalleolar) require open reduction and internal fixation. Maisonneuve injury may require surgical management if there is true syndesmosis instability or compression of the superficial fibular nerve with subsequent motor weakness as it passes by the fracture site. Non-surgical management can be considered on a case-by-case basis with the orthopedic consultant in patients who are elderly, non-ambulatory or poor surgical candidates.
Unstable fractures and fracture-dislocations are associated with a mixed long term prognosis when managed correctly. In one study, 82% of patients reported good or excellent outcomes with a mean follow up of 2 to 6 years.7Lindsjo, U . Operative treatment of ankle fracture-dislocations: a follow-up study of 306/321 consecutive cases. Clin Orthop Relat Res. 1985(199):28–38. However, patients who are dislocated and/or require surgery are likely to have worse outcomes compared to those who do not.8Sculco, PK, Lazaro, LE, Little, MM. Dislocation is a risk factor for poor outcome after supination external rotation type ankle fractures. Arch Orthop Trauma Surg. 2016;136(1):9–15. Early reduction is associated with better outcomes.9 Payne, R, Kinmont, JC, Moalypour, SM. Initial management of closed fracture-dislocations of the ankle. Ann R Coll Surg Engl. 2004;86(3):177–181.
Post-surgical complications involve malunion, hardware loosening and infection, and post-traumatic arthrosis.10Goost, H., Wimmer, M. D., Barg, A., Kabir, K., Valderrabano, V., & Burger, C. (2014). Fractures of the ankle joint: investigation and treatment options. Deutsches Arzteblatt international, 111(21), 377–388. doi:10.3238/arztebl.2014.0377 Patients can also have soft tissue complications, with increased risk when dislocation is present, osteochondral lesions and loose bodies, and articular malreduction. Post traumatic arthritis occurs in anywhere between 14% and 63% of patients who also endorse stiffness, and chronic pain.11Regan, DK, Gould, S, Manoli, A III, Egol, KA. Outcomes over a decade after surgery for unstable ankle fracture: functional recovery seen 1 year postoperatively does not decay with time. J Orthop Trauma. 2016;30(7):e236–e241

Case Conclusion

Following the reduction and splinting, she had considerable swelling and was strictly advised to maintain elevation of the foot and non-weight-bearing status. She was discharged in stable condition. In follow up, it was determined by the orthopedic staff that initial radiographs were misleading and the patient had a bimalleolar rather than trimalleolar fracture. The patient underwent an open reduction and internal fixation of the medial and lateral malleoli 9 days later and is doing well in recovery.

3 Key Points

  1. Trimal fractures are a fairly common manifestation of ankle fractures, unstable and always require surgery
  2. They can occur from a fairly benign mechanism and are diagnosed on standard radiographs of the ankle
  3. Prognosis is mixed and many patients will go on to develop post traumatic ankle arthritis even with proper management.

Read more @ Wiki Sports Medicine: https://wikism.org/Ankle_Fracture

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