Mastering a good Negative Foot modeling technique is probably one of the most important steps in the process of creating good foot orthoses.  But what is the best technique, based on the best evidence available?
If we take into account that you want to have the best control over the forefoot to rearfoot relationship, results from a study done in ‘89 by McPoil et al indicated that a reliable forefoot to rearfoot alignment can be obtained using either the supine or prone method but not with the semi weight-bearing method.  This line of thought was confirmed again in ‘02 by Laughton et al, where they concluded that non weight-bearing plaster casting may be preferable to partial-weight-bearing foam impressions, and partial-weight-bearing and non weight-bearing laser scanning.  Important to keep in mind is, when taking your negative foot model non weight bearing, is that the contact area , foot length, foot width, and rearfoot width significantly decreases.  This was examined by Tsung et al in ‘03.   According to Chuter et al in ‘03, the inter-rater reliability in capturing the same amount of forefoot to rear-foot is low among clinicians.  Trotter et al repeated a same sort of study in 2008 and concluded that the intrarater is high, bus the inter-rater is low and that ’a specific foam box technique’ would be more accurate than the ‘golden standard – plaster casting’ but the study itself could be biased…

For the fellow interested in this subject check out Podiatry-Arena 

and for some comfort and piece of mind a quote:

‘I am sure that as long one understands the principles of negative casting, orthosis manufacture, and foot and lower extremity biomechanics, nearly any technique which captures a three-dimensional impression of the plantar foot can be used to make effective and therapeutic custom foot orthoses’
Kevin Kirby, 2006 

(1)McPoil TG, Schuit D, Knecht HG.Comparison of three methods used to obtain a neutral plaster foot impression. Phys Ther. 1989 Jun;69(6):448-52.
(2)Laughton C, McClay Davis I, Williams DSA comparison of four methods of obtaining a negative impression of the foot.  J Am Podiatr Med Assoc. 2002 May;92(5):261-8.
(3)Tsung BY, Zhang M, Fan YB, Boone DA.Quantitative comparison of plantar foot shapes under different weight-bearing conditions. J Rehabil Res Dev. 2003 Nov-Dec;40(6):517-26.
(4)Chuter V, Payne C, Miller K. Variability of neutral-position casting of the foot. J Am Podiatr Med Assoc. 2003 Jan-Feb;93(1):1-5
(5)Trotter LC, Pierrynowski MR. Ability of foot care professionals to cast feet using the nonweightbearing plaster and the gait-referenced foam casting techniques. J Am Podiatr Med Assoc. 2008 Jan-Feb;98(1):14-8