Stress Fracture of the Foot

A stress fracture is a localized area of bone damage where the cells that comprise the bone have become damaged due to repeated forces. The forces effect is cumulative, creating a circumstance where the speed with which the body produces bone-building cells, osteoblasts, is less than the bone-reducing, or osteoclastic, activity. Next to stress fractures of the lower tibia (shin bone), the stress fracture of the foot is the second most common location for this type of injury, accounting for approximately 25% of all such fractures.

The most common location among the 26 bones of the foot and ankle for a stress fracture are the five metatarsal bones, the structures that are the skeletal connection between the tarsal bone (ankle) and the toes on each foot. The second and third metatarsals are the most common bones of the foot to sustain a stress fracture; the fifth metatarsal (the bone connecting the ankle to the little toe) is the least common location for a stress facture of the foot.

There are number of factors that inevitably lead to the creation of a stress fracture of the foot in an athlete. Stress fractures of the foot occur slightly more often in female athletes than in males, a fact that is attributable to the difference in the shapes of male versus female athletes. The proportionately wider pelvis and shorter femur and tibia in a female athlete lead to a proportionately different distribution of forces throughout the female musculoskeletal structure. For both men and women, there is often more than one risk factor operating to produce the fracture, many of which are tied to the concepts of either overuse or repetitive motion.

Sports that involve repetitive motions such as running (particularly on hard surfaces) and jumping, or training on angled surfaces, where the force of each foot strike is distributed unevenly, are a leading contributing factor in the cause of stress fractures in the foot. Similarly, when the athlete has suddenly increased either training intensity or training volume, or when the athlete embarks on a running or training program that is too vigorous for the current level of fitness, the foot is the recipient of forces to which it is unsuited.

Physiological and nutritional factors also play a role in the formation of these fractures. When the athlete has a previously undetermined dietary mineral deficiency (calcium, vitamin D, or phosphorus) that has created a corresponding bone density deficit, the bone becomes more vulnerable to injury. Structural imbalances such as unequal leg length will result in forces being generated when the athlete's foot strikes the ground. Footwear that is inappropriate to the foot strike motion of the athlete will accentuate all structural deficiencies present in the lower

limbs of the athlete. An example is the wearing of a running shoe that is suited to a runner whose foot pronates (the ankle rolls inward) on impact, when the foot of the runner in fact supinates (rolls outward) on impact. This footwear will improperly absorb the forces and may permit the force of impact to be excessively directed into the foot.

Athletes with poor flexibility tend to be more susceptible to stress fractures of the foot because their bodies do not move as fluidly or as responsively as those athletes who possess a greater range of motion in the joints.

From a psychological perspective, athletes with a strong desire to reach or exceed their training objectives, the so-called type A personality, often fall victim to stress fractures. These athletes are the most likely individuals to return to training too quickly after an injury, or to excessive training intensity. These circumstances often do not permit a previously injured metatarsal bone to heal properly, resulting in a recurrent stress fracture of the foot.

Stress fractures of the foot are first noticeable through the development of a sharp, almost debilitating pain at the location of the fracture. A stress fracture will often not reveal itself while the person is at rest, but only in the course of the sports activity that caused the fracture. A regular x ray will often not reveal the location of the injury; a nuclear bone scan will almost always reveal the location of the fracture. Magnetic resonance imaging (MRI) is another technology that will usually reveal the location of the fracture.

The treatment of a stress fracture of the foot is similar to that sustained at any other bone: rest and a complete cessation of the sport for a period of at least six to eight weeks. The RICE (rest/ice/compression/elevation) treatment is also often recommended, as are the use of nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation. In more extreme cases, the foot may be placed in a cast for approximately six weeks.

The preventative measures to reduce the risk of recurrence of this injury to the foot are primarily a very gradual return to training, with careful attention paid to the elimination of the stress fracture risk factors noted. High level young athletes, who move from sport to sport throughout the year, are especially vulnerable to stress fracture, because the young athlete is not provided with a period of rest and general down time from high level training.

SEE ALSO Bone, ligaments, tendons; Lower leg injuries; Musculoskeletal injuries; Recurrent stress fractures.