Can Orthotics Address The Faulty Biomechanics Of Metatarsalgia?

Author(s): 
Guest Clinical Editor: Bruce Williams, DPM

   Metatarsalgia is one of the more commonly seen complaints in any podiatry practice. Common treatments for the disorder include ice, removable metatarsal pads, antiinflammatories, injected steroids and physical therapy. While such treatments often completely resolve an acute bout of metatarsalgia, they often do nothing to remedy the true underlying biomechanical causes of the problem.

   To correct the faulty foot biomechanics, DPMs rely on custom foot orthotics. Unfortunately, the devices are often no different than what one prescribes for any other foot disorder with the addition of a forefoot extension to “accommodate” the painful metatarsal head. This is a reasonable modification to any foot orthotic device but it is often unnecessary or does not address the true cause of the problem. Often, one needs to focus on areas of dysfunction within the foot and away from the primary area of pain.

   Q: In your opinion, what sagittal plane foot function problems predominantly contribute to metatarsalgia?

   A: Generally, Bruce Williams, DPM, always assesses the ankle joint for non-weightbearing range of motion and compares both ankles at the same time. One ankle often has much less range of dorsiflexion than the other ankle. Dr. Williams says this is often associated with limb shortness on the limited side and can also contribute to increased forefoot pressures due to the impending equinus deformity.

   Stanley Beekman, DPM, says ankle equinus contributes to metatarsalgia as it reduces midstance and lengthens the propulsive phase, which increases forefoot forces. Equinus may also cause extensor substitution, which decreases digital flexion and increases metatarsal pressures, notes Dr. Beekman.

   Metatarsus primus elevatus often contributes to lesser metatarsal pain, according to Jamie Yakel, DPM. When the first metatarsal head does not receive its share of ground reaction forces, Dr. Yakel says the forces must be transferred and one subsequently develops pathology under the second and possibly the third metatarsal heads.

   When Dr. Yakel uses his in-shoe pressure system to evaluate a patient with an elevated first metatarsal and/or functional hallux limitus, he says peak pressures do arise under the second and third metatarsal heads. As he explains, the center of pressure (CoP) trajectory is usually lateral to the midline. Once one addresses the functional hallux limitus, Dr. Yakel notes the trajectory becomes more midline and pressures decrease. Accordingly, the patient’s symptoms dissipate.

   Dr. Williams will also examine the patient for functional hallux limitus and determine how far proximal and plantar the first ray is sensitive to dorsiflexory forces. If clinicians load the first metatarsal head and attempt to dorsiflex the hallux, they will usually see a limitation in motion in patients with functional hallux limitus, according to Dr. Williams. However, he notes if one continues this dorsiflexory force proximally under the first metatarsal, the functional limitation often will continue all the way to the first metatarsal base.

    “If one addresses the foot from a viewpoint of sagittal plane function (i.e., facilitating motion in the metatarsophalangeal joints, the ankle joint and at heel contact), one can alleviate metatarsalgia very consistently and easily, and can often do so without a bulky forefoot extension,” contends Dr. Williams.

   Q: What orthotic modifications do you regularly use to treat metatarsalgia?

   A: When treating sub-second metatarsal capsulitis, if the cause is an elevated first metatarsal, Dr. Yakel adds a Morton’s extension, a metatarsal pad and an accommodative pad. If the sub-second metatarsal pain is secondary to functional hallux limitus, he provides a generous first ray cutout along with a reverse Morton’s extension for metatarsals three to five.

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great article!

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