A Guide To Orthotic Treatment For Metatarsalgia

Start Page: 74
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Author(s): 
Jamie Yakel, DPM

What You Should Know About Lesser MPJ Instability

Lesser metatarsophalangeal (MPJ) joint instability is a common cause of metatarsalgia, specifically affecting the second MPJ. Predislocation syndrome, a term often used for this instability, is an acute, chronic or inflammatory condition that affects the MPJs, but the second MPJ is the most affected.

   While there are various intrinsic and extrinsic structures that stabilize the joint, the plantar plate is the key anatomical structure. The inflammatory process causes attenuation of the structure, which leads to dislocation. Factors such as hallux valgus, metatarsus primus elevatus, an elongated second metatarsal and a hypermobile first ray can cause an overload of the second MPJ leading to instability.

   Non-operative treatments include padding/strapping to reduce any retrograde pressure on the joint, NSAIDs, intra-articular steroid injections, orthotics and shoe modifications. When injecting steroids into the joint, rocker bottom shoe modifications are highly recommended to eliminate the propulsive phase of gait and reduce the possibility of further attenuation secondary to steroid injection. After confirming the diagnosis and identifying the etiology, one can implement the orthotic modification.

   If the etiology is an elevated first metatarsal, there are several options to address this and the goals should be to increase the ground reaction forces under the first metatarsal head and reduce lesser metatarsal overload. There are various options to achieve these objectives. These options include: a Morton’s extension; a first ray cutout with or without a reverse Morton’s extension in the second through fifth sub-metatarsals; a reverse Morton’s extension by itself; and a Cluffy wedge.

   Controlling rearfoot pronation by increasing the subtalar joint supination moment with a medial heel skive or Blake inverted pour can help stabilize the first ray. Plantarflexing the first ray while casting for orthotics is an option but is controversial to some.

Case Study: Using Orthotics For A Runner With Forefoot Pain

A 40-year-old male runner presented to the office with a two-week onset of swelling and pain in his right forefoot. He relates he had a second metatarsal stress fracture eight months ago and another one about a year before that. The patient was immobile in a surgical shoe for seven weeks before resolution of his symptoms. He enjoys running half marathons but his training has been reduced since then because of the initial stress fracture. The patient had participated in cross training via swimming and biking. He denies any change in his mileage, training surface or shoes. He also denies any acute episode of an injury.

   Clinically, the patient had a pinch callus on the right hallux but no other hyperkeratotic lesions. He had exquisite tenderness over the second metatarsal with edema around the second and third metatarsal region. Pain was also present in the second intermetatarsal space but it was not as pronounced as it was over the second metatarsal. A mild to moderate dorsal bunion was present at the first MPJ.

   The patient had approximately 40 to 45 degrees of dorsiflexion at the first MPJ on the right foot with no pain or crepitus. However, he had approximately 5 degrees of dorsiflexion with loading of the foot.His subtalar joint range of motion was normal and he had gastroc-soleus equinus. Gait evaluation demonstrated an abductory twist with early heel-off on the right side. The sock liners of his running shoes showed considerable wear under the right hallux and the lesser metatarsal area. The area under the first metatarsal showed very little wear.

   Radiographs revealed a periosteal reaction along the neck of the second metatarsal with no displacement. There was metatarsus primus elevatus of the first metatarsal with no spurring off the dorsal first MPJ and no joint space narrowing. The metatarsal parabola was normal.

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Ed Davis, DPMsays: April 15, 2012 at 9:22 am

This is an important article as a large percentage of patients with lesser metatarsal pain present with biomechanical issues such as functional equinus, hypermobile first ray, forefoot supinatus/midtarsal joint dysfunction.

It is essential to focus on the midtarsal joint as failure of the midtarsal joint to lock by maximally pronating as propulsive phase is entered is a common finding in such patients. Careful attention to forefoot posting of the orthotic device is required. The forefoot to rearfoot assessment required for orthotic design needs to include assessment with any forefoot supinatus reduced. Forefoot valgus posting and reverse Morton's extensions are commonly used. I like metatarsal elevations pressed into the shell of the orthotic devices and may supplement that with a soft extension to advance the metatarsal support beyond the distal edge of the device.

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