Impression Methods for Custom Foot Orthoses-Comparing Semi-Weight-Bearing Foam and Non-Weight-Bearing Plaster Using a Kinematic Measurement of the Medial Longitudinal Arch

INTRODUCTION: One of the goals for custom foot orthoses (CFOs) is to provide relief for pressure-sensitive areas and provide support to the joints of the foot for an optimal weight-bearing position. The most common CFO impression methods used by practitioners include plaster bandage, foam box, fiberglass, and laser-optical scanning, and are often compared by measuring foot molds created from those methods. The objective of this study is to compare the biomechanical effects of CFOs made from two common casting methods using skeletal kinematics. MATERIALS AND METHODS: The medial longitudinal arch (MLA) angle was measured for 13 participants of different foot types: five pes planus, four pes cavus, and four normally arched. Four conditions were compared: barefoot, shod, and CFOsmade from both semi-weight-bearing foam and non-weight-bearing plaster casting methods. The MLA angle was measured from three-dimensional bone models using biplane fluoroscopy images during midstance. RESULTS: Foam (P = 0.02) and plaster (P = 0.01) cast foot orthoses were significantly different from the barefoot condition, and the shod condition was significantly different from both foam (P = 0.004) and plaster (P = 0.014) cast orthoses. No statistically significant differences were found when comparing the two casting methods: non-weight-bearing plaster and semiweight-bearing foam (P = 0.170). CONCLUSIONS: Clinicians favoring one particular style of casting can feel confident, for the patient set described, that either choice will produce similar biomechanical outcomes with respect to foot kinematics.