STRESS FRACTURE

(SHIN BONE STRESS FRACTURE)


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related talks: barefoot runningshin bone fracture, shin splintsrunners knee
 

What is a Stress Fracture of the Leg (Tibia) ?

A stress fracture is a broken bone, however, unlike most broken bones that occur after a single big injury, a stress fracture occurs when many many small injuires build up over time to become painful. 

A stress fracture is an overuse injury.  A repetitve activity overwhelms our body’s ability to heal.   Whenever we go running or work out at the gym, our body experiences micro-injuries to the muscles and bone.  But after we finish working out, our body is able to repair those small injuries, and actually strengthens the bone or muscle so that it becomes more resistant for next time you work out.  This is how we become strong at the gym (when we work out, we create small muscle tears, and our body responds by repairing the muscle, and also adding more muscle fibers to prevent the micro-injuries from occuring in the future). 

The same thing occurs with bone.  Small bone cells (called osteoblasts) live within our bones, and its their job to repair our bones after daily wear and tear.  But if you go running everyday, and your body isn’t ready for that activity, these cells can be overworked, and they will be unable to keep up with the stress.  The running will create too many “micro-fractures” and your body wont keep up with repairing them.  Over time those micro-fractures will turn into normal-size fractures, and that will be painful. 

Stress fractures occur in active people.  90% of them occur in people under 30 years old.  Some studies report that up to 20% of high-performance track & field athletes will develop a stress fracture from all that running. And about 5% of military recruits will develop a stress fracture from all that marching.   Almost all of the stress fractures occur in the feet or legs because they experience all the stress of your body as you run or stomp around each day (maybe acrobats get them in their arms from walking on their hands, but its never been reported in any science journals).  About 50% of stress fractures occur in the tibia (main leg bone), about 5% occur in the fibula (the smaller leg bone), and the rest occur in the thigh bone (femur) or in one of the foot bones. 

 Some people are at increased risk for developing these injuries.  For unknown reasons, Caucasians are an increased risk, and women are at 2x increased risk.  Studies on Ballet dancers showed that eating disorders puts someone at increased risk.  However, contrary to popular belief, the shape and thickeness of someones bones, a persons weight, and the density of a person’s bones (think osteoporosis) does not have any effect on risk for developing a stress fracture. 

Stress fractures of the tibia usually occur near the knee (the proximal tibial metaphysis).  The good news is that this area has a good blood supply, so the bone can get the nutrients it needs to heal.  However, when a stress fracture develops in the middle of the tibia, doctors get concerned because these can take a very long time to heal (and sometimes they never heal at all until treated with surgery).  

How is a Stress Fracture of the Leg (Tibia) diagnosed?

People with a stress fracture will report a gradual onset of pain without any recent accident.  They typically will describe a high level of activity (run a lot or play sports) and people also report a recent increase in activity (like in early Spring after a long winter of lounging around).  50% of stress fractures occur within the first 4 weeks of a new training program.  The pain is typically worse after activity and improves with rest.  Reports of training on a hard surface, or recent changes in shoe wear, are also tip offs for a possible stress fracture.  The bone of concern is often tender to the touch, but otherwise there are few other symptoms.

The next step in diagnosis is getting x-rays.  However, only about 30% of x-rays will show signs of bony injury (like thinning, or an actual black line indicating a fracture).  Most cases of stress fracture will not appear on x-ray until a few weeks after someone first comes to the doctor complaining of pain.  If the x-ray shows a stress fracture, the diagnosis has been made and now a treatment is decided.  If the x-ray shows normal bone, many doctors, knowing that theres still a good chance that there is a “hidden” stress fracture, will order an MRI.  An MRI will detect almost 100% of stress fractures (some doctors will order a Triple-Phase Bone Scan, which is also great at detecting stress fractures, but is not as good at showing the severity of the fracture).  

How is a Stress Fracture of the Leg (Tibia) treated?

The treatment of a stress fracture depends on its severity.  Doctors consider the risk that the stress fracture will progresses to a major fracture or the risk that it simply doesn’t heal.  Since most occur because the body cannot keep up with the demands of a young athlete, treatment is usually a period of rest and limiting putting weight on the affected bone (this means using crutches).  This gives the body time to catch up and heal the bone.

Rest and limiting weight-bearing is typically tried for 2 to 4 weeks.  If the pain goes away, then a gradual return to activity can begin (but any return of pain means stopping activity and starting all over).   Full return to sport usually requires 2 to 4 months (yeah, a long time).  That doesn’t mean you have to be a couch-potato the whole time.  Low impact activity like cycling and swimming can be started early on to promote good cardio endurance.  

However, if the leg continues to be painful, the leg may be casted (like a normal complete fracture) for an additional 1 to 3 months.  The use of pharmaceutical agents, like those which treat osteoporosis (bisphosphonates and calcium supplements) have not been well studied as a treatment for stress fractures. 

 Some stress fractures have progressed to a complete fracture (or very near to a complete fracture) and cannot be treated with simple rest.  There is one particularly bad stress fracture of the mid-tibia, that shows up on MRI as a “dreaded black line”.  These stress fractures rarely heal without surgery.  Surgery involved placing a rod down the center of the tibia and placing bone graft at the fracture site to stimulate healing.  This is a worse can scenario, and is not common, however, it requires aggressive treatment when it occurs. 

What is the long term outcome?  

Most stress fracture will resolve completely after stepwise treatment.  After they heal there is always the risk of recurrence, however, precautionary steps can be taken to minimize this risk.  Effective shoe wear, training on softer surfaces, and adequate stretching are all ways to decrease this risk.

References

1) Aoki Y et al. Magnetic resonance imaging in stress fractures and shin splints. CORR 2004; 421: 260-7. full article. stress fx xr+ve periosteal rxn by 4-6 wks, mri all+ve. shin splint+ve MRI along medial posterior surface longitudinal signal. 

2) Rome K. Interventions for preventing and treating stress fractures and stress reactions of the bone of the lower limbs in young adults. Coch Data Syst Rev 2005. full article. decrease with footwear mod, no effect of calf stretch. 

3) Chang PS, Harris RM. Intramedullary nailing for chronic tibial stress fractures. A review of five cases. Am J Sports Med 1996; 24: 688-92. full article. anterior cortex poor vascularity, tension side, risk nonunion, successful rx w. imn. 

4. High-risk stress fractures: evaluation and treatment.  Boden BP, Osbahr DC. J Am Acad Orthop Surg. 2000 Nov-Dec;8(6):344-53.

5.  Characteristics of stress fractures in young athletes under 20 years.  Ohta-Fukushima M, Mutoh Y, Takasugi S, Iwata H, Ishii S. J Sports Med Phys Fitness. 2002 Jun;42(2):198-206.

6.  Low-risk stress fractures.  Boden BP, Osbahr DC, Jimenez C. Am J Sports Med. 2001 Jan-Feb;29(1):100-11.

 

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