There are rules that have been advocated for doctors to use to determine the need for x-rays (radiographs) in the setting of a possible ankle fracture (broken ankle). The purpose for using rules is to avoid unnecessary exposure to radiation. In the wilderness, there is not likely to be an x-ray machine available. Therefore, the rules might be useful to give the rescuer (or a parent) more confidence about what clinical presentation is likely to be or not be a broken bone. This would be important in terms of deciding whether or not to allow weight-bearing, such as would occur if a victim needed to walk out under his or her own power.
In an article (Annals of Emergency Medicine 2009;54:534-540) entitled "Prospective Validation and Head-to-Head Comparison of 3 Ankle Rules in a Pediatric Population," Jocelyn Gravel, MD and colleagues looked at children aged 16 years and younger with acute ankle injuries to compare the predictive value of the Ottawa Ankle Rules, Low-Risk Exam and Malleolar Zone Algorithm with regard to a confirmed clinically important fracture.
Forty-seven of 276 study patients had a clinically important fracture. The Ottawa Ankle rules were most sensitive and identified all children with a clinically important fracture, whereas the Low-Risk Exam and the Malleolar Zone Algorithm were less sensitive. The Low-Risk Exam most often avoided an unnecessary x-ray, but it missed six important fractures.
What is a clinically significant fracture?
While this is still debated in medical circles, it is generally accepted to mean any fracture with a bone fragment greater than 3 millimeters in width. However, some argue that any broken bone in a child has the potential complication of growth deformity, so that should certainly be taken into account when recommending continued activity in the setting of a possible fracture.
What are the Ottawa Ankle Rules?
The Ottawa Ankle Rules state that x-rays are only required (because there is a chance for a fracture) if there is bony pain in the malleolar zone and any one of the following:
- bone tenderness along the distal (towards the ankle) 6 centimeters ( ) of the posterior edge of the tibia ("shinbone"), which is the larger and stronger of the two bones in the leg below the knee (the other being the fibula) and connects the knee with the ankle bones.
- pain at the tip of the medial malleolus.
- bone tenderness along the distal 6 cm of the posterior edge of the fibula, which is the bone located on the lateral (outer) side of the tibia, to which it is connected above and below. The fibula is the smaller of the two lower leg bones, and, in proportion to its length, the most slender of all the long bones.
- pain at the tip of the lateral malleolus.
- inability to bear weight both immediately and for four walking steps.
What is the Low-Risk Exam?
It is an ankle examination that yields results felt to be low risk for an ankle fracture. It is defined essentially as pain and/or tenderness with or without swelling or bruising restricted to the distal fibula, the three adjacent ankle ligaments, or both.
An ankle examination requires experience and clinical judgment. What we know from the study cited above is that correctly interpreting the Ottawa Ankle Rules will offer good insight into the presence of a fracture, but that an examination judged to be "low-risk" will on occasion miss an ankle fracture. The upshot is that these are guidelines to help the rescuer decide who might or might not have a broken bone. If I was many miles or days away from formal medical care where I could obtain an x-ray, I would use this information to help me decide how soon to allow the patient to bear weight and perhaps even the type of splint to manufacture or type of ankle wrap or taping to apply. With more confidence that I might be dealing with a sprain instead of a fracture, the show might go on. With more confidence that I might be dealing with a fracture instead of a sprain, we might be heading for home.
ankle rules image courtesy of www.bmj.com
