On Thin Ice
Monday March 2, 2009
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“Anecdotally there is a belief that we’re seeing more overuse leading to stress fractures because of an increase in sports athletics in general and a rise in specialized athletes,” says Mark Paterno, PT, MS, MBA, SCS, ATC, coordinator of orthopedic and sports physical therapy at the Sports Medicine Biodynamic Center at Cincinnati Children’s Hospital Medical Center.
The boom in organized sports for children began decades ago, and now close to 40% of children ages 9 to 13 participate in an organized sport in the U.S., according to the Centers for Disease Control and Prevention. Additionally, some 7.2 million high school students participated in high school sports in 2005 to 2006, the CDC reports.
Painful, hard-to-diagnose stress fractures are showing up routinely in these young athletes, especially in children who focus intensely on one sport year-round. Although clinical studies of stress fractures in adolescent competitive athletes are few in number, one recent study at the University of Heidelberg in Germany showed a disturbing trend: Of the 19 children with 21 stress fractures studied, seven did not have a satisfactory outcome, perhaps in part due to their immature skeletal systems.
One theory suggests that the bones may be more susceptible to stress fractures because osteoblastic activity lags behind osteoclastic activity when there is an increase in exercise, whether starting a new exercise program or increasing the exercise intensity of an existing program.
Repetitive shearing, compressive, or rotational forces with sports that require running and jumping can result in bony microfractures that may merge or spread into a larger, symptomatic stress fracture.
The other prevailing theory suggests that forceful, repeated stress on a bone at its muscular insertions results in a localized deformation of the bone beyond its tolerance.
Stress fractures typically present as a dull, localized pain that worsens with weight bearing and exercise. Unfortunately, many stress fractures do not immediately show up on plain X-rays, although some may be detected on a follow-up X-ray in as many as two to 10 weeks post injury.
“[A stress fracture] may be found only by palpation at the point of maximum tenderness, percussion, and special tests to rule out more common injuries or overuses,” says Kevin McHorse, PT, SCS, Cert. MDT, Board Certified Specialist in Sports Physical Therapy, at Central Texas Pediatric Orthopedics and Scoliosis Surgery in Austin.
“In most cases, the pain and dysfunction from the stress fracture will slow the athlete enough that they get evaluated before further damage takes place.”
Paterno suggests additional tests, such as bone scans and MRIs, are helpful to detect an occult stress fracture. “If the patient is training at high levels and complains of shin pain for a few weeks, for example, it’s routine to have more tests done to give you a better diagnosis,” he notes.
Tibial stress fractures are the most common, especially in the proximal anterior tibia, accounting for half of all stress fractures in children. These are seen most frequently in young athletes doing a lot of distance training such as cross country runners and track athletes.
One in four stress fractures occur in the metatarsals, specifically the distal second, third, and sometimes fifth metatarsals, from forces associated with sprinting and cutting sports.
One in five lower extremity stress fractures in children affect the fibula, particularly the distal one-third. These fractures occur in jumping sports such as basketball and volleyball, McHorse says. “All of these usually occur with increased activity in highly competitive athletes,” he says. “Stress fractures to the neck of the femur are also concerning, but not as common.” Other risks for stress fractures are a rapid increase in a sports training program, running on irregular surfaces, and using shoes that do not support adequately or fit well.
In general, girls tend to be at a slightly higher risk for stress fractures than boys, McHorse says. “This appears to result from adolescent female athletes not taking in enough calories to meet the caloric demands of their athletic endeavors,” he says. “This is often as a consequence of body image issues, and contributes to the development of amenorrhea and suboptimal bone health.”
Consultation with a nutritionist or endocrinologist is a good idea to ward off fracture recurrence in this cohort.
“A walking boot is a nice alternative to having a cast,” he says. “When they come out of the boot, we work with them on range of motion exercises with the ankle and knee, core strengthening, and non-weight bearing exercises in the pool.” It’s important to emphasize a slow return to sports so children do not re-injure themselves, McHorse says. The latest statistics support this slow approach, as approximately 60% of those who have a stress fracture have had one before.
“I feel it is critical to outline this process for the patient and family, as the nature of [children’s] sports is to go back to full speed as quickly as possible, since they are usually pain free after recovery,” he says.
One sign the child may be taking on too much loading or physical stress is pain at the injury site, Warden says. Because of this, the child athlete needs to be educated about staying within certain pain levels, he says.
“Once an athlete has been asymptomatic for three consecutive days, we like to start them on a progressive loading program,” Warden says. “This initially starts with a 30-minute walk on the first day.”
If patients experience less than a two-out-of-ten level of pain both during and after this walk, they can progress the next day to a nine-minute walk with a one-minute slow jog, repeated three times, he says. If the pain level remains low, patients can progress the next day to an eight-minute walk with a two-minute slow jog repeated three times, and so on.
But if pain levels increase above a two-out-of-ten level, the athlete should go back to the previous level in the program. For tibial stress fractures, this progressive loading program may be performed while wearing a pneumatic leg brace.
“By using a graduated loading program that is strictly guided by pain to manage low-risk stress fractures, the athlete and clinician can facilitate recovery while being relatively confident the pathology is not progressing,” Warden says.
Athletes can maintain their fitness while healing by doing exercises such as cycling, deep water running, or working out on exercise equipment, as long as they are pain free.
“However, running on a softer and less even surface hastens muscle fatigue, potentially leading to increased bone loading.” Excessively soft surfaces can predispose athletes to soft tissue sprains and strains.
Paterno recommends using the new absorbent running tracks whenever available, and otherwise trying to avoid hard asphalt and concrete tracks.
But Warden notes that even more important than the surface itself is to be sure the athlete is introduced slowly to a new surface during a number of weeks, so his or her body can adapt to it.
Proper footwear is very important for reducing the risk of stress fractures, Paterno says. “The curve of the bottom of the shoe will tell you whether that shoe is better for a high arch or flat foot,” he says. “If a shoe matches the foot better, you are less at risk for a stress fracture.”
Supportive arches also can be recommended to patients, he continues, advising that competitive athletes can be fitted at a specialized sports shoe store, or by a PT who is also a certified pedorthist.
Overall, children today have a fine line to walk in terms of bone development and activity to avoid both overuse and underuse, Warden says. “We have found that exercise that loads the skeleton during growth is very important to optimize bone mass and, particularly, size,” he says. “This increases the ability of the skeleton to resist fatigue and protects against the development of a stress fracture.”
But both ends of the loading spectrum need to be avoided, he continues. “This includes too little exercise resulting in the development of suboptimal bone health, and too much exercise, which is relevant to developing overuse injuries such as stress fractures,” he says. “How much is too much is entirely dependent upon an individual athlete’s internal make-up and their training progression.”
Teresa McUsic is a medical writer for the Gannett Healthcare Group. To comment, e-mail pteditor@gannetthg.com.
