prescription writing for orthoses

prescription writing for orthoses

instruction to laboratory describing the underlying foot/limb pathology, type of orthotic required to achieve correction, materials to be used in manufacture and degree of correction to be achieved by means of intrinsic or extrinsic posting and other adaptations (see Table 1 and Table 2)
Table 1: Types of posts that may be added to functional orthoses
Post typeRationale
Forefoot postsPost (extrinsic/intrinsic/combination of both) to improve medial-column stability; posting degree/type is dictated by angle between plantar aspects of forefoot and heel, available ranges of motion and level of control sought
Extrinsic posts are added to the undersurface of the distal part of the orthotic shell, in effect 'bringing the ground up to the foot' and allowing foot to function in its natural orientation to ground and lower limb, whilst accommodating/resolving symptoms of the biomechanical problem
Intrinsic posts are added to the cast of the foot to allow the orthosis, made to the adapted cast, to alter the angulation of the medial column in relation to the ground surface. An intrinsically posted orthotic allows the forefoot to come down toward the ground surface during gait and resolves the biomechanical problem by modifying foot function
Bar postPost (2-5 mm thick) added to the underside of distal part of orthotic to create greater lateral column stability
Rearfoot postsExtrinsic rearfoot post; post dimension is dictated by the angle between calcaneal bisection and midline of lower leg, and the level of control sought
Blake post aligns distal edge of forefoot to parallel with undersurface of extrinsic rearfoot post, imposing considerable rearfoot control

Note: Functional orthoses are made to casts of the foot in subtalar neutral (i.e. point in the gait cycle when the midtarsal area is at its most stable).

Table 2: Adaptations to orthoses
AdaptationRationale
First metatarsal cutoutA section of the orthotic shell is cut away proximal to the head of the first MTPJ to provide adequate space for sesamoid function and facilitate sagittal-plane motion
Low firstA groove (2-5mm deep) is skived into the upper surface of the orthotic immediately beneath the shaft of the first metatarsal to accommodate a plantarflexed first ray
First ray cutoutA section of the orthotic shell is cut away from beneath the first ray to facilitate first-ray movement
Fascial grooveA groove skived out of the shell in the area that lies immediately beneath the plantar fascia, to accommodate a tight plantar fascia or prominent flexor hallucis longus tendon
Flange outAn extension at the medial border of the orthotic to provide additional support for the MLA area, especially for cases of posterior tibial dysfunction
Morton's extensionA distal extension beyond the first MTPJ to limit movement at the first MTPJ and transfer load to the IPJ of the hallux
Lateral clipAn extension to the lateral side of the heel cup to control the rearfoot motion associated with excess pronation
Heel (Kirby) skiveAn addition to the medial or lateral side of the heel cup
Heel raiseAdditional height added to the plantar area of the heel cup to compensate for a mild leg length discrepancy
Pegasus rockerA rocker added to the proximal heel area in order to increase sagittal-plane motion at the ankle joint

MTPJ, metatarsophalangeal joint; MLA, medial longitudinal arch; IPJ, interphalangeal joint.

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