Effectively addressing spinal problems requires viewing the musculoskeletal structure as a series of interrelated components, with the feet as its foundation. Pedal imbalance can lead to postural imbalance, which in turn can negatively affect the entire body.
In seven out of 10 cases of back pain, postural fatigue and spinal strain are frequent causes of discomfort.1 The stress often can be traced to altered foot biomechanics that lead to pelvic and spinal distortion.2 Custom-made, flexible orthotics are useful in correcting abnormal biomechanics in the lower extremities and in enhancing the effectiveness of chiropractic care.
Risky Moves
The spine is one link in a biomechanical kinetic chain, where movement at one joint influences movement at other joints in the chain,3 extending from the feet to the spine. Locomotion demonstrates the complexities of biokinetic interaction and the risk of imbalance or structural deficiency that leaves the spine vulnerable to destructive torque, bending and shearing stresses.4-6
Locomotion is comprised of two phases: stance, when the foot bears weight; and swing, when no weight is borne. When the foot hits the ground, changes occur that can have detrimental effects if pedal imbalance is present.
The stance phase is divided into three subphases:
- Contact. A natural inward rotation of the subtalar joint produces pronation. The tibia rotates internally, with the femur moving slightly.
- Midstance. Forefoot loading occurs as the foot supinates, accompanied by external rotation of the tibia and femur while the knee unflexes.
- Propulsion. For toeing-off, the foot remains in supination and leg bones rotate externally.
Biomechanical Consequences
If pronation is maintained into the midstance phase of gait, the tibia and femur will remain in the inward rotational configuration. This places the patellofemoral complex in immediate jeopardy - the structure that is the most frequent source of knee disorders.7
Rotation of the lower extremity transmits to the pelvis, causing an inward hip rotation commonly associated with myofascial back pain.8 Inward rotation of the femur brings the greater trochanter forward and outward, stretching the piriformis muscle. The sacrum may be pulled into a subluxated anterior and inferior position.2
The gluteus maximus muscle contracts to compensate for the downward and forward pelvic tilt. The innominate at its iliac portion rotates to the posterior, producing a typical pelvic distortion. The sacrum's anteroinferior position causes the L5 vertebral body to gravitate and rotate toward the low side, initiating structural scoliosis.2 Excessive pronation results in abnormal firing of muscles and inaccurate proprioceptive nerve impulses. This also interferes with the toe-off phase, resulting in less efficient propulsion.
Correcting Postural Imbalance
When the gait is affected by excessive pronation the pelvis and spine must compensate. The specific way in which each patient adapts to abnormal support from the lower limbs is very individualized. This explains why patients often notice so many areas of improvement when their pronation is corrected with orthotic support.
Flexible, custom-made orthotics help to enhance biomechanics of the lower extremity and modify minor deficits that inhibit the integrity of the pedal foundation.9 Orthotic therapy seeks to control - not restrict - motion within the pedal structure, particularly of the subtalar joint.10 Restricted subtalar joint pronation affects the knees, hips and back.11 Also, custom-made orthotics can improve back pain caused by walking with an abnormal gait and poor toe-off.12
Balance and Orthotics
Postural instability is a direct result of imbalance in the pedal foundation. As the arch rolls inward, the tibia twists, the knee strains, the femur rotates and spinal curves are affected. Custom-made, flexible orthotics address problems of pedal imbalance and related postural instability. When used as an adjunct to chiropractic care, orthotics enhance postural stability and protect the integrity of musculoskeletal structures.
References
- Brunarski DJ. Chiropractic biomechanical evaluations: validity in myofascial low back pain. JMPT 1982;5(4):155-161.
- Schafer RC. Clinical Biomechanics: Musculoskeletal Actions and Reactions. Baltimore: Williams & Wilkins; 1983.
- Gross MD, Davlin LB, Evanski PL. Effectiveness of orthotic shoe inserts in the long-distance runner. American Journal of Sports Medicine 1991;19(4):409-444.
- Farfan HF. Muscular mechanisms of the lumbar spine and the position of power and efficiency. Orthop Clin North Am 1975;6(1):135-144.
- Cappozzo A. Compressive loads in the lumbar vertebral column during normal level walking. J Orthop Res 1984;1(3):292-301.
- Adams MA, Hutton WC. Mechanical factors in the etioogy of low back pain. Orthopedics 1982;5(11): 1461-1465.
- Foot Levelers Educational Division. Clinical Chiropractic Biomechanics. Roanoke: Foot Levelers, Inc., 1984.
- Greenawalt MH. Spinal Pelvic Stabilization, 4th ed. Roanoke: Foot Levelers, Inc., 1990.
- Steindler A. Kinesiology of the Human Body Under Normal and Pathological Conditions, 3rd Ed. Springfield: Charles C. Thomas, 1970.
- Christensen KD. Orthotics: do they really help a chiropractic patient? ACA Journal 1990;27(4):63-71.
- Gastwirth KD, et al. Electrodynographic study of foot functions in shoes of varying heel heights. J Am Podiatr Med Assoc 1990;81(9):463-472.
- Dananberg HJ, Giuliani M. Chronic low-back pain and its response to custom-made foot orthoses. J Am Podiatr Med Assoc 1999;89:109-117.
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