Inside Insights On Orthotic Modifications

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Addressing Range Of Motion Issues At The First MPJ: How The Kinetic Wedge Can Help

   Justin Wernick, DPM, says one of the most common podiatric dilemmas is identifying when to expedite the range of motion at the first metatarsophalangeal joint (MPJ) or when to block range of motion. In the clinical assessment, he says it is important to determine the off-weightbearing range of motion of the hallux. The demand in gait for dorsiflexion of the hallux is 55 to 85 degrees. Dr. Wernick says this is determined by the amount of knee flexion, usually 35 degrees and plantarflexion, which is approximately 25 degrees.

   Knowing the length of an individual’s step is very important in this assessment. The longer the step length, the more demand there is for dorsiflexion at the metatarsophalangeal joint, according to Dr. Wernick. He notes that if an individual walks with a rapid cadence or is involved with sports, there will be a greater demand for dorsiflexion. If the range of motion is at least 20 degrees or greater, Dr. Wernick will attempt to expedite motion by:

   • supinating the subtalar joint;
   • maintaining the medial architecture of the foot; and
   • using a Kinetic Wedge™ forefoot modification.

   Dr. Wernick notes the wedge is designed to promote the plantarflexion-eversion motion of the first ray via the wedge’s shape (wider medially) and its density (softer under the head).

   The wedge’s proximal angle is designed to act as does the first ray axis, says Dr. Wernick, and the distal angle compliments the axis of the hallux. By controlling the rearfoot, he can restore the contour of the arch and increase the plantarflexion angle of the first ray. Combining these efforts with the Kinetic Wedge will increase motion at the first MPJ, notes Dr. Wernick.

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   These expert panelists share their most commonly used orthotic modifications as well as insights on using highly inverted orthoses and the lateral Kirby skive.

Q: What are the most common orthotic modifications that you prescribe and why?

   A: Joseph D’Amico, DPM, most commonly employs a deepened heel seat at a standard size of between ¾ inches and 1 inch. He says a deepened heel seat enhances rearfoot control via better seating and positioning of the calcaneus. Dr. D’Amico notes this is particularly effective and critical in orthoses designed for patients with proximal plantar fasciitis, especially when the point of maximum tenderness is inferior. Dr. D’Amico cites Richard O. Schuster, DPM, who said in the treatment of heel pain, no heel seat is ever too deep.

   Richard Blake, DPM, commonly uses deep heel cups. These are normally 23 to 25 mm high medial and/or lateral, and he says they provide greater pronation/ supination control.

   In contrast, a high medial heel cup is helpful for Justin Wernick, DPM. He says DPMs often use a deep heel cup to control eversion of the calcaneus associated with subtalar pronation. However, he notes a deep heel cup/seat will occupy a great deal of room in the posterior part of the shoe, leading to difficulties with fit.

    “By using just an elevation of the medial border of the heel cup, we can resist eversion of the calcaneus in the shoe and reduce the bulk,” says Dr. Wernick.

   Both Dr. D’Amico and Dr. Blake commonly use metatarsal pads. Dr. D’Amico uses PPT® (Langer), noting that its closed cell foam resists deformation even after years of use. He prescribes a metatarsal pad for patients with a “dropped” transverse metatarsal arch, metatarsalgia or neuromas.

   Dr. D’Amico also employs metatarsal pads if he does not believe the amount of forefoot posting that he can place in the shoe will achieve the desired correction. Additionally, he uses a pad if there is increased pressure on metatarsals two, three and four as evidenced on computer assisted gait analysis. Dr. D’Amico notes metatarsal pads have been effective in the elderly to encourage plantarflexion of the digital segments, thereby improving stability and propulsion.

   Dr. Blake uses the metatarsal pads to relieve soreness distally. Likewise, he will use accommodative forefoot extensions to relieve areas of soreness directly by placing weight laterally, medially or both.

   Dr. Wernick commonly uses a forefoot extension to the sulcus. He notes that fabricating a functional device that extends to the cut lines will result in a slimmer device. However, in these situations, Dr. Wernick says the device tends to slide in the shoe, generally in a medial direction. Adding an extension of 1/6 inch or 1/8 inch of material can seat the orthotic and resist its migration, according to Dr. Wernick. He says this modification also adds some cushioning to the plantar surface of the metatarsal heads and will not take up any additional room in the shoe.

   Michael Burns, DPM, and Dr. D’Amico frequently use an extended forefoot posting. Dr. Burns says this modification permits him to maintain some “frontal plane control” of the foot after the heel leaves the ground during the propulsive phase of gait. Furthermore, the posting is particularly useful with rigid forefoot valgus, reducing the propulsive phase “over-supination” that might otherwise occur. He uses extended forefoot posting whenever the forefoot frontal plane variation exceeds 5 degrees and for all athletes who need any forefoot posting.

   Dr. D’Amico reserves extended forefoot posting for orthoses for athletic footwear. However, he will regularly prescribe this extended posting arrangement in the elderly to improve stability. He says the forefoot post extension should extend to the sulcus and be feathered distally. The material is butadiene rubber of varying durometer measurements to meet the weight and functional requirements of the patient, according to Dr. D’Amico.

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