foot in the desired alignment . Plaster casting allows a lot of control and flexibility in making the negative cast .
Advanced casting techniques are commonly used that mimic what occurs with intrinsic posting . An example of this is pressing the medial calcaneus with the fleshy part of the palm while the plaster is drying , thus mimicking the Kirby Skive technique in rear foot intrinsic posting . Clinicians will commonly add pressure to the forefoot to obtain a tripod with the first , fifth and heel when the client has a flexible forefoot varus .
Plaster casts are either a full-length slipper cast that covers the toes and will hold plaster to do a manual positive cast or a three-quarter slipper cast that is not as deep and does not include the toes . The three-quarter slipper cast is often done when a cast laser scanner is going to be used to make a computergenerated positive cast or shell . To achieve good and workable casts , training and time for the clinician are required .
Advantages of plaster casting :
• Easy to manipulate the subtalar joint into a neutral position .
• Can load the lateral column and neutralize longitudinal axis to provide good mid-foot and forefoot stability .
• Good visual confirmation of foot position .
Disadvantages of plaster casting :
• Need to modify positive model of cast to compensate for soft tissue expansion during weight bearing .
• Requires water and creates a mess .
• Can be time consuming .
Common errors :
• Poor positioning of the subtalar joint : either too much pronation or too much supination .
• Insufficient or excessive loading of the lateral column .
• Allowing the metatarsal heads to elevate ( and the toes to sag ), which distorts the position of the first ray .
Plaster sock casting
The plaster sock medium is very similar in pros and cons to plaster casting . The plaster sock is one unit where the clinician matches the client ’ s foot size to the sock size . During the drying process , the plaster sock heats up and requires a plastic bag to act as a barrier between the foot and the cast . A plastic tube is inserted in the dorsal aspect of the foot and acts as a vacuum , taking away any air pockets .
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Current Pedorthics March | April 2012 13