cad-cam orthoses

cad-cam orthoses

; computer-aided design and manufacture of bespoke functional orthoses digitized data (of the dimensions of the neutral cast, modified by computer program to incorporate prescribed postings, expansions and accommodations) is used to mill the orthotic directly from a block of polypropylene (see Table 1)
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).