Pedal Stress Fractures and Orthotic Support

By: Mark N. Charrette, DC

Figure 1. Most common locations for foot stress fractures.

Figure 1. Most common location for foot stress fractures

Stress fractures are a common cause of foot pain, especially in the active population.Patients will report a dull, aching pain sensation in the foot that is often poorly localized (Fig. 1). The nagging pain increases during weightbearing and gait, and often remains for a while after use. It commonly subsides or disappears with rest overnight. The recurrence of pain with exercise and relief with rest is the most important aspect of the symptom pattern for suspicion of a stress fracture. Direct digital pressure on the bone (if it is accessible) will help to localize an area of stress reaction more specifically. Evaluation with a tuning fork probably will not significantly increase the pain.X-rays of the area may demonstrate a subtle fracture line or new bone repair (periosteal or endosteal), but often a technetium bone scan or an MRI is needed to image a stress fracture.3,4

Development of a Stress Fracture

Stress fractures result from the inability of bone to withstand repeated traumas that individually would not be sufficient to cause a fracture. Stress fractures are an “overuse” syndrome affecting bone tissue, and are caused by excessive and repetitive microtrauma. In these cases, repetitive biomechanical stress exceeds the body’s inherent capacity to repair and adapt.5

Certain activities place high levels of stress on particular bones in the foot. For instance, ballet dancers most commonly develop a stress fracture at the base of the second metatarsal,6

while a study of track and field athletes found the navicular bone most affected.7

There is a continuum from overuse to stress reaction, and eventually to stress fracture. The treating doctor must manage these conditions properly, since any delay in establishing an appropriate treatment plan will allow a progression to a true fracture of bone, which places the patient at risk for a disabling condition.8

Underlying Causes

Repetitive biomechanical stresses are often accentuated by inherent imbalances or asymmetries. An example is the increased frequency of stress fractures in the metatarsal bones of military recruits with low arches and flat feet found by Simkin.9

Inherent biomechanical imbalances often require modification of performance or equipment for complete resolution. Poor shock absorption will aggravate any tendency to overuse stress. This can result from running on unyielding surfaces or in broken-down shoes, or it may be due to biomechanical factors that interfere with normal shock absorption, such as a high arched foot.

Another complicating factor that may be involved is altered bone repair. When bone is osteopenic or osteoporotic, it is unable to respond sufficiently to even normal stresses. This condition is usually seen in postmenopausal women,10 or in female athletes with menstrual disturbances.11

Biomechanical Asymmetries

There are three common lower extremity conditions that have been found to increase the likelihood of developing pedal stress fractures. These biomechanical asymmetries can be easily identified in the Chiropractic office—a high arch, excessive pronation (with a low arch), and inequality of leg lengths. All of these conditions will respond rapidly to a well-designed orthotic support.

Figure 2. InMotion functional orthotics provides enhanced shock absorption.

Figure 2. InMotion functional orthotics provide enhanced shock absorption.

High-arched foot. The foot with a higher than normal arch (cavus foot) remains too rigid and inflexible during walking and running. This results in poor attenuation of heel-strike shock, which is then transmitted up the Kinetic Chain into the leg and hip. The person with a rigid, high-arched foot is susceptible to developing stress fractures in the sesamoids and calcaneus, and also in the femur and pelvis.8,12

This type of foot requires better flexibility (mobilization, stretching) and custom orthotics with added shock-absorbing material to dynamically support the arches and help decrease the impact at heel-strike. Foot Levelers’ InMotion® functional orthotics offers supreme shock absorption (Fig. 2).

Hyperpronation. Excessive pronation during walking and/or running may be due to either arch collapse or poor arch development. In either case, excessive torsional forces are transmitted from the overpronated foot into the leg with each step taken. The hyperpronating foot tends to develop stress fractures more frequently in the collapsed metatarsals, as well as in the tibia.13 Orthotic support for the arches that includes pronation correction at the heel and support for the medial arch will decrease the torque forces on the bones of the leg and foot.14

Short Leg. Leg length discrepancy is another inherent asymmetry that has been shown to lead to increased frequency of stress fractures. A study of Finnish military recruits who were undergoing strenuous training found that 70% of metatarsal stress fractures occurred in the longer leg, while only 10% were found in the shorter leg, and 20% in a leg of equal length.15

Although leg length asymmetry is often a normal variant, it is an inherent imbalance that subjects the bones and joints of the longer extremity to higher forces. These findings are consistent with other studies that have found that degenerative changes in the hip joint16 and lumbar spine17 occur much more frequently on the side of a longer leg. Treatment consisting of an orthotic and/or shoe build-up to reduce the discrepancy is appropriate in order to decrease the abnormal biomechanical forces developed during walking and running with asymmetrical leg lengths.18

It is very important to recognize the functional short leg, since providing a lift instead of an orthotic is likely to perpetuate or exacerbate the lower extremity asymmetries. Since there is no reliable information on the radiographs to differentiate these conditions, a clinical postural exam with lower extremity screening is the only way to make this determination. If there is any doubt, the safest approach is to fit the patient with custom-made orthotics, initially. If there is a persisting leg length inequality after wearing the orthotics for several weeks and receiving Chiropractic adjustments, a heel lift can then easily be added to the orthotic for full correction.

Treatment of Stress Fractures

Initially, rest of the affected extremity is necessary in order to allow for healing and remodeling. Bone healing does not demand complete bed rest, but rather a change and moderation of activity. Temporary cessation of the causative exercise with substitution of cross-training will prevent deconditioning of athletes. Plans to address poor training techniques should be made, including recommendations regarding the amount and frequency of training, as well as methods for achieving competitive goals with less localized stress on the affected body area.

Figure 3. Example of THERA-CISER exercise activity for foot/ankle rehab.

Figure 3. Example of THERA-CISER exercise activity for foot/ankle rehab.

Low-stress exercise programs that use controlled isotonic protocols (such as the THERA-CISER®) can provide benefits from the beginning of healing up to the achievement of previous levels of activity (Fig. 3). Most importantly, the use of custom-made orthotics that include shock absorbing materials will significantly speed recovery and prevent recurrence upon return to full activities. Properly fitted and designed orthotics can substantially reduce the abnormal forces generated by biomechanical asymmetries and poor shock absorption. The end result is a happier patient, and a more competitive athlete.

Conclusion

Pedal stress fractures are identified only with a good examination, and sometimes require advanced imaging. Very specific activity restrictions must be followed in order to allow healing and prevent continuing disability. Investigation of anatomical asymmetry or functional imbalance will help guide treatment. Most commonly, there are biomechanical abnormalities interfering with the body’s attempt to repair. In many cases, orthotic support for foot pronation or a functional short leg, along with the addition of shock-absorbing materials, is necessary. Those patients with a true anatomical leg length discrepancy will need to be supplied with the appropriate lift or shoe build-up.

References

  1. McBryde AM. Stress fractures in runners. Clin Sports Med 1985; 4:737-752.
  2. Sousa TA. Differential Diagnosis for the Chiropractor. Gaithersburg, MD: Aspen Pubs, 1997:352.
  3. Yochum TR, Rowe LJ. Essentials of Skeletal Radiology, 2nd ed. Baltimore: Williams & Wilkins, 1996:776.
  4. Steinbronn DJ, Bennett GL, Kay DB. The use of magnetic resonance imaging in the diagnosis of stress fractures of the foot and ankle: four case reports. Foot Ankle Int 1994; 15:80-83.
  5. O’Conner FG. Overuse injuries in athletes. Phys Sports Med 1992; 20:128-142.
  6. O’Malley MJ, Hamilton WG, Munyak J, DeFranco MJ. Stress fractures at the base of the second metatarsal in ballet dancers. Foot Ankle Int 1996; 17:89-94.
  7. Bennell KL, Malcolm SA, Thomas SA et al. The incidence and distribution of stress fractures in competitive track and field athletes: a twelve-month prospective study. Am J Sports Med 1996; 24:211-217.
  8. Johansson CI et al. Stress fractures of the femoral neck in athletes: the consequence of a delayed diagnosis. Am J Sports Med 1990; 18:524-528.
  9. Simkin A et al. Combined effect of foot arch structure and an orthotic device on stress fractures. Foot & Ankle 1989; 10:25-29.
  10. 10. Kaye R. Insufficiency stress fractures of the foot and ankle in postmenopausal women. Foot Ankle Int 1998; 19:221-224.
  11. 11. Brukner P, Bennell K. Stress fractures in female athletes: diagnosis, management and rehabilitation. Sports Med 1997; 24:419-429.
  12. Subotnick SI, ed. Sports Medicine of the Lower Extremity. New York: Churchill Livingstone, 1989:164.
  13. Michaud TC. Recurrent lower tibial stress fracture in a long-distance runner: a case report. Chirop Sports Med 1988; 2:78-87.
  14. Cornwall MW, McPoil TG. Footwear and foot orthotic effectiveness research: a new approach. J Orthop Sports Phys Ther 1995; 21:337-344.
  15. Friberg O. Leg length asymmetry in stress fractures: a clinical and radiographic study. J Sports Med Phys Fitness 1982; 22:485-488.
  16. Friberg O. Clinical symptoms and biomechanics of lumbar spine and hip joint in leg length inequality. Spine 1983; 8:643-651.
  17. Giles LGF, Taylor JR. Lumbar spine structural changes associated with leg length inequality. Spine 1982; 7:159-162.
  18. McCaw ST, Bates BT. Biomechanical implications of mild leg length inequality. Br J Sports Med 1991; 25:10-13.