Considerations for construction of the rearfoot and midfoot portions of a Root type custom foot orthotic have been previously reviewed. This post will review the forefoot considerations, which are the most comprehensive and complex. It has always been my opinion, which admittedly is open to debate, this is the most important function of the orthotic device, controlling compensatory and unnecessary motion in the foot during the propulsive phase of gait. Forefoot correction is also what distinguishes a custom foot orthotic from generic arch supports, which in most cases, offer little or no correction of forefoot varus/valgus forefoot deformities or control of hypermobility present due to abnormal ground reactive forces, particularly in the 1st metatarsal phalangeal joint. Increasing the propulsive power of the human foot is often the primary goal of any effective functional foot orthotic device.
The essential component of the orthotic forefoot is the post. It can either be “intrinsic” or built into the shape of the frame of the orthotic, or “extrinsic” or added as a flat, solid addition to the plantar surface of the frame. Combinations also exist primarily in cases of high degree deformities. Posts can be either varus or valgus. Intrinsic posting is generally more easily tolerated and fits well in shoes. The amount of correction built into the orthotic depends on the deformity measured during the biomechanical examination, the range of motion of the first ray and any variations in the metatarsal parabola. The default correction when no measurement is indicated on the prescription, is to “balance” the forefoot correction to perpendicular to the vertical bisection of the heel.
The next decision to be made in the forefoot construction of the orthotic device is the use of an extension. Extensions are either sulcus length or full length. Extensions are helpful for a variety of reasons, they provide extra cushioning to the plantar metatarsal head areas, and provide for placement of pads and accommodations of the forefoot. One added advantage to extensions, in my opinion, is they help keep the orthotic in proper placement within the shoe, particularly in athletic or other large volume shoes that are manufactured with a removable insole. The rigidity or flexibility of the orthotic frame is also a factor in determining the corrective ability of the orthotic device. My general rule of thumb was to typically use a more rigid orthotic for a flexible foot, conversely a more forgiving orthotic device in a more rigid foot type.
Various “bells and whistles” are available to enhance the functionality of the orthotic device. Two popular modifications are the Morton’s extension, and reverse Morton's extension. The Morton’s extension is additional padding under the 1st ray to elevated it and protect a damaged or arthritic 1st MTPJ. The reverse Morton’s extension is the opposite, removal of some of the cushioning under the 1st ray to allow the 1st metatarsal head to plantarflex and enhance the range of motion of the 1st MTPJ. One protects the 1st MTPJ, the other promotes the 1st MTPJ. A further modification of the reverse Morton’s is the “dynamic wedge” modification which adds an upward ramp (Cluffy wedge) under the Hallux to promote its dorsiflexion. Similar to the reverse Morton’s is the dancer’s pad, which will also allow more plantarflexion of the 1st metatarsal, but is more appropriately used to accommodate an already plantarflexed 1st ray or prominent sesamoid bone.
Accommodation of the lesser metatarsals may be accomplished with a metatarsal pad 2-4 which creates a transverse metatarsal arch if so desired. A metatarsal balance pad may be used to offload a prominent metatarsal head, as will a metatarsal punch or slot accommodations. Additional offloading of single or multiple metatarsal heads can be accomplished with a metatarsal bar or a foot cookie extension. These modifications can also be combined in various forms for those more creative types of practitioners. Toe crests for hammertoe deformities, as well as neuroma pads are also available for those specific conditions. Marking the desired location for pads and accommodations on the scan or impressions is highly recommended! The thickness and firmness of extension can vary based on the prescribers preference, I would recommend reviewing the various options available on the Kevin Root Medical website.
Taking the time, and making the effort to perform a comprehensive biomechanical exam, gait analysis, obtain and accurate impression of the patients foot, then writing a detailed prescription for correcting that foot with a custom foot orthotic can be a great challenge in today's practice environment of increased overhead expenses and decreased reimbursements. Hopefully, breaking down the decision making process into manageable components will allow the busy practitioner to efficiently and consistently succeed in all their lower extremity biomechanics cases.
