High risk vs low risk stress fractures
Author: By Steve “The Footman” Manning Founder of intraini
Not all stress fractures are equal. Low risk stress fractures are much more common, but they heal quicker and have much fewer complications. High risk stress fractures in comparison are at risk of non-union and delayed healing and are much more likely to develop into a complete fracture.
How common are stress fractures?
More than a third of distance runners will experience a bone stress injury. Stress Fractures are thought to make up around 20% of injuries in runners.
The most common stress fractures are in the forefoot (Metatarsals) and the leg bones (Tibia and Fibula). Less often are stress fractures in the midfoot and heel (Tarsals), the thigh bone (Femur), the kneecap (Patella) and even in the big toe (Hallux).
Why do you get a stress fracture?
Bone stress injuries are usually the result of repetitive chronic overuse. When you stress your body at a level to which it is unaccustomed, the tissue response is to adapt and remodel so that the body is better able to cope with the same stress in the future. In your bones, this triggers special cells called osteoclasts to go in and eat away the bone so that other cells called osteoblasts can then lay down new stronger bone with a higher bone density and alignment towards the direction of the force.
This process takes around five to six weeks to occur. If the stress increases or continues without recovery weeks, then the result is that you are stressing a bone that is weaker while it is remodelling.
That is why stress fractures usually occur around 6 weeks after there has been an increase or change in training. It is also possible to have a stress fracture from a single traumatic like a sprain, fall or contusion but that is rarer.
We can often make a clinical diagnosis of a stress fracture from history and palpation. If the patient is just willing to do the time, then we can review it before they return to running. If it is not clear and the patient has a race, they want to do then we will refer for an MRI. There is an MRI classification system for bone stress injuries that classify by the depth of the swelling and findings on T2 and T1 images. If the fracture has not healed in the normal time, then we will suspect a high-risk fracture
and refer to an MRI immediately. All stress fractures in someone with low bone density or osteoporosis should be considered to be high risk.
What is a high risk stress fracture?
The location of the stress fracture determines the risk classification. When weight bearing different bones or parts of bones undergo either compression or tension.
Compression forces are much more likely to lead to a stress fracture especially in long bones. In the Tibia the distal half of the medial or inside border undergoes compression during weight bearing so that is where most of the tibial stress fractures occur. The front or anterior border experiences tension with normal weight bearing. For this reason, normal weight bearing pushes the medial border stress fracture edges together encouraging healing while the anterior border stress fracture is pulled apart leading to non-union.
The same thing occurs in the metatarsal bones which make up the front part of the arch. On normal weight bearing the top of the bone has compression and the bottom of the bone has tension. The vast majority of metatarsal stress fractures occur in the midshaft area. The treatment for these common low risk fractures is to cease running and jumping activities. Normal weight bearing with walking will help the healing process so the use of a boot is not indicated. Long periods in a boot will lead to a loss of bone density, delayed healing and a much longer return to sport.
However, if the stress fracture is in the base of the second metatarsal then this is a high risk fracture. Normal weight bearing will prevent the union of the fracture and a boot is critical to healing despite the loss of bone density. In some cases even a boot may not be enough and surgery will be required to have a resolution of the fracture. A recent study found that low running mileage was a factor linked to a greater risk of a high risk fracture in the base of the second metatarsal.
Some bones like the navicular, fifth metatarsal and femur are always high risk fractures. They require a reduction of weight bearing for an extended period with either a boot or crutches.
The size of the bone determines the duration of the recovery time. Metatarsals take the least amount of time - between 4 and 6 weeks off running. The Tibia and the Calcaneus will take 6 to 8 weeks and the femur will be 12 weeks. If the fracture is at a high risk location, then the recovery period should be at the high end of the range and may take even longer.
Stress fractures are an injury that needs you to stop running. You can do any activity which does not hurt but be careful of not getting another injury from your cross training. Only high risk fractures should be immobilised. There are no treatments or exercises that have been shown to make any
significant difference in your recovery time. However, maintaining some non-running activity will help your return to running.
Once you have recovered you should get a review of your training and a return to running training plan. It also might be worthwhile to investigate other contributing factors like your foot structure and biomechanics, your running shoes and your diet.
At the Intraining Running Injury Clinic, we can help you diagnose your running injuries and create a treatment plan. We are running coaches as well as being Podiatrists or Physios. We have extensive experience in helping runners get back on the road as soon as possible.