Ankle fractures are a very common entity in musculoskeletal radiology (and for many a weekend warrior). Two main classification systems are used to group the various ankle fractures: the Weber and the Lauge-Hansen (LH) classification schema. While Weber is much easier to apply, LH is the standard used by radiologists and orthopedic surgeons as it offers a higher level of detail about the mechanism of injury. However, the main drawback is... it's confusing! However, misery loves company as the quote below from an ortho resident shows that the orthopods also find it confusing:
For whatever reason, I have a difficult time wrapping my head around the Lauge-Hansen (LH) ankle fracture classification. The Weber classification is a little more straightforward, but doesn't impart as much information about the injury as the LH classification. I'm going to go through ankle fractures like I did with pelvic fractures and hopefully, in attempting to understand the LH classification, impart some knowledge on everyone else. As usual, I'm stealing my images from the AAOS Comprehensive Orthopaedic Review. Information is borrowed from this text and the Handbook of Fractures.
To begin, let's take a quick look at the anatomy of the ankle joint (picture below). The ankle is made up of articulations between the tibia, fibula and talus. The joint is maintained by a variety of ligaments. On the lateral side, the anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament and the inferior transverse ligament help to prevent eversion of the ankle. The lateral collateral ligaments of the ankle (anterior/posterior tibilfibular ligaments, calcaneofibular ligaments) help to prevent inversion and anterior translation of the fibula. Medially, the strong deltoid ligament, which has a short and thick deep layer covered by a more superficial layer help to resist inversion of the foot.To see the rest of the post which attempts to clarify the situation a bit, including the anatomy and fracture diagrams, check out the post on the blog Bone Broke? Me Fix!
The challenge for the radiologist is a little different from the orthopedist, who is more concerned about treatment. From the plain x-ray, the radiologist has to infer which type of injury has occurred. The following framework applies to the most common categories but is not all inclusive. Remember: in an ankle fracture x-ray, is the fibula fractured?
- Yes: Is the fracture above the tib-fib syndesmosis, or at/below it?
- High: If there is only a medial malleolus fracture, this is a pronation-external rotation type III; if there is a medial and posterior malleolus fracture, this is a P-ER type IV.
- At/Below: If there is a posterior malleolus fracture also, this is a supination-external rotation type III; if there is only a medial malleolus fracture also, this is a S-ER type IV.
- No: Is there a medial malleolus fracture?
- Yes: This is a P-ER type II or III fracture.
- No: This is a S-ER type I fracture (anterior tib-fib ligament sprain)
Like anything, getting used to this classification scheme takes practice. Review ankle fracture studies several times until it becomes comfortable.