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Jul 28

Written by: Larry Huppin, DPM
7/28/2010 1:32 PM

When you prescribe a custom foot orthosis, do you always know what you are getting from your lab?

Not long ago it was clear that if you ordered a custom orthosis you were getting a truly custom orthosis. You sent in a plaster cast and the lab made a plaster positive cast, modified it as prescribed and then heat molded a material to create an orthosis on top of that cast. The resulting orthosis was clearly custom made for a specific patient.

Orthotic fabrication has changed dramatically over the past two decades. More likely than not, a plaster positive will no longer be produced when you send a negative cast to your orthotic lab. Instead, the corrections that were previously performed to create a plaster positive are now done on a CAD / CAM computer system. The same corrections can be performed on the computer as were done in plaster and then a positive cast can be milled on which the orthosis is produced; or the orthosis can be milled directly. This technology has allowed many orthosis labs to provide their clients (and your patients) with the same quality orthoses while keeping costs under control.

This technology has also allowed the creation of a type of orthosis known as a “library system orthosis” (LSOs). Library systems allow a lab to scan a negative cast and then choose the orthotic shape from a “library” of predetermined shapes stored in the computer. A library may consist of a dozen or several hundred different orthotic shapes. They are not really custom orthoses, but more of an enhanced prefab.

Ethical orthotic labs inform their clients if they use library systems and charge less for them than they would for custom orthoses. Unfortunately, some labs use LSOs to fill prescriptions for custom orthoses without making this information clear to their clients. This has great potential to lead to a reduction in positive clinical outcomes. In fact a recent article comparing the effect of custom orthoses and semi-custom orthoses (LSOs) on second metatarsal strain showed custom orthoses decreased 2nd metatarsal bone strains and strain rates more effectively than semi-custom orthotics (1).

It is imperative that every orthotic practitioner be aware of how their orthoses are manufactured. In particular, if you are ordering a custom orthosis, you must ensure that your lab is truly manufacturing a custom orthosis and is not using a library system. In future blogs we will review how to evaluate an orthosis to confirm that you have received what you prescribed.

(1) Meardon SA, Edwards WB, Ward E, et al: Effects of Custom and Semi-Custom Foot Orthotics on Second Metatarsal Bone Strain during Dynamic Gait Simulation. Foot Ankle Int, 30(10):998-1004, 2009.


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