Oh, it is just a simple ankle sprain. It will heal fine. (Not always ! Sometimes we do not know what we should fear, often because we do not even know it exists.)
When an ankle sprain is far more than an ankle sprain.
Fracture of the Anterior Process of the Calcaneus
We have seen enough of these over our careers that we know they should be on the differential list when an ankle sprain smells fishy. This may be the most frequently missed fracture in the foot because it is not well known and the classic radiographic series often leaves this teeny tiny area poorly laid out on plain film radiographs. This focal piece of bone, has a critical attachment to the cuboid and navicular so it is critical for stability of the rear-midfoot complex and obviously for mobility of the forefoot on the mid-foot. This Bifurcate ligament (see diagram above) if left unhealed or reattached to its calcaneal base can lead to anatomic instability and serious performance and loading problems. It can be a career ending injury if it is not caught early. This fracture accounts for ~15% of all calcaneal fractures and as we mentioned, it is misdiagnosed as a more severe ankle sprain. The mechanism is a typical inversion sprain mechanism, the most common of ankle sprains, and it can have all of the other typical presentations but with this fracture as a complicating parting gift of the injury.
Do not miss this one ! When in doubt, refer it out. Don’t leave your client with an unresolving ankle sprain. If you are anxious, as for the imaging and a competent clinical exam. Tenderness over the calcaneocuboid joint that is localized approximately 1 cm inferior and 3 to 4 cm anterior to the lateral malleolus, just distal to the anterior talofibular ligament insertion is of high suspicion.
This fracture can be serious and lead to prolonged disability and as we said it can be a career ending injury. So do not take that next ankle sprain too lightly. You or your client may pay for it for a lifetime.
If you do not know it exists, you can’t make the call. So after today, after reading this short blog post, you are now officially accountable !
Shawn and Ivo
Gait guys and clinical nerds