A clear understanding of the mechanism of injury is important not only for diagnosis of the ankle injury, it is important for considering the probability of associated injuries. Knowing the direction and magnitude of the forces applied allows a reasonable prediction of which structure are likely to be affected. The examination and investigation can then be focussed in rapidly.
What follows is a general approach to ankle injury which provides rapid identification of injury and therefore management with a high degree of sensitivity and specificity.
Ankle dislocation is an orthopaedic emergency. Do not delay for X-ray prior to reduction of the joint.
Keep in mind the Talus is wedge shaped, this will aid in remembering how to reduce an ankle dislocation.
The Talus can dislocate in 5 ways - medially, laterally, anterior, posterior and complete or total dislocation (talus is dislocated from the ankle, subtaler and talonavicular joints).
Mid foot and hind foot injuries are common with ankle injuries. Apply the Ottawa foot rules and if positive add a foot X-ray to the investigations. Especially consider peroneal tendon injuries, base of 5th MT fractures, anterior process of calcaneous fractures, and talonavicular joint injuries.
The Ottawa ankle rules allow triage of patients into those whom may be Xrayed prior to medical review. Whilst the Ottawa ankle rules have 95% sensitivity in ruling out significant ankle fractures, clinical consideration may be given to X-ray in high risk cases and those whom have distracting injuries.
A high ankle sprain, or syndesmosis injury is much less common than a low ankle sprain. It therefore can be easily missed. The stability of the distal Tibiofibula joint is crucial to the ability to walk and run and it is therefore important not to miss this injury.
A high ankle sprain may be part of a Maisonneuve fracture or a complication of a webber C fracture, it may indicate syndesmosis instability and therefore a risk of late severe OA of the ankle, or it may be a relatively minor injury simply requiring protection for a few weeks.
Pain above the joint line should alert the clinician to the possibility of this injury.
Ligament examination requires testing each ligament individually. In elite athletes and recurrent injury consider POCUS or formal USS.
The anterior draw test assesses instability as a result of injury to the ATFL. You are looking for anterior translation of the talus with respect to the tibia in the sagittal plane.
The talar tilt test is used to assess CFL.
When the anterior draw test is positive and the tilt test is negative, then it is a grade 2 sprain. If both the anterior draw test and the tilt test are positive then it is a grade 3 sprain.
Understanding the grade of ligament injury is helpful to efficiently manage the acute presentations. The table below is modified from Malliaropoulos et al.
Think of grade 1 as ligament inflammation, grade 2 as ligament stretch, and grade 3 as ligament tear.
| Grade | Appearance | Examination |
|---|---|---|
| 1 | Mild swelling, little or no ecchymosis, point tenderess over the ligament, minimal restriction of movement. | No laxity on stability testing. |
| 2 | localised swelling, ecchymosis, haemorrhage(often anterolateral). In the actue setting may be indistinguishable from a grade 3 injury. | No or minimal laxity on stability testing but may be unreliable in the first few days. In lateral injury the anterior draw test may be positive with an end point and tilt test negative. |
| 3a | complete disruption of the liagment complex, diffuse swelling, ecchymosis often extending bilateral and to the heel. Tenderness over the anterior capsule. | Decrease in ROM > 10', oedema > 2cm, stress xray normal. |
| 3b | same as 3a | ROM decrease >10', oedema > 2cm, >3mm difference in distance between the posterior articular surface of the tibia to the nearest point of talus on radiographic comparison between the uninjured and injured ankle |
In clinical practice it is rare to undertake the textbook examination of a joint or any other system. The examination is informed by the history and constrained by the realities of practice - particularly time.
The ankle is a ring in both the AP and saggital planes.
When this ring structure is kept in mind it is then easy to remember the ligamentous anatomy which holds the ring together. The naming convention is usually big bit - little bit - ligament. For example tibiofibula ligament, or if there is more than one of them anterior talofibula ligament and posterior talofibula ligament.
The ankle is a complex piece of anatomy. Understanding the anatomy is best done functionally. The ankle is often thought of as a complex mortice and tennon joint. However it is probably more useful to think of it more like a dynamic dove tail joint. The Talus is wedge shaped in both the saggital and AP planes. As the ankle moves, the wedges rotate into the joint to lock it into place in the plane where most force will be experienced. To prevent the wedge from just pushing the joint apart the ankle is constructed as a ring structure in those planes.
The ankle is a ring in both the AP and saggital planes.
When this ring structure is kept in mind it is then easy to remember the ligamentous anatomy which holds the ring together. The naming convention is usually big bit - little bit - ligament. For example tibiofibula ligament, or if there is more than one of them anterior talofibula ligament and posterior talofibula ligament.
Ankle injuries are common in both adults and children, with the highest incidences of serious injury in young athletes and elderly females.
The mechanism is crucial to determining the likely injury pattern and therefore the appropriate investigation and management.
The diagnosis and therefore management decision can usually be made by a combination of mechanism, examination and plain X-ray.
The soft tissue anatomy is complex and the radiological findings may be difficult to interpret, so seek advice if there is no bony injury and the patient remains non weight bearing.
Associated foot and knee injuries are common.
The outcome depends upon recognising the specific injury and managing appropriately.
Luck is what happens when preparation meets opportunity