Monday, September 10, 2012

The problems associated with plaster casting and the use of foam boxesfor the manufacturing of custom orthotics

Custom foot orthotics have been around for over 60 years and have historically helped patients with loadbearing joint conditions, however the "Art Form" has led to many error points.   Unfortunately, many orthotics do not adequately maximize cyclic loadbearing control of the foot on the limb, pelvis and spine due to the art form (plaster casting), and the 27 error points in the manufacturing and casting process.

A few of the error points. . .
When orthotics are manufactured from plaster casts and foam boxes, the technician has no idea as to how the foot functions. The technician is relying on the prescription by the physician or the technician for the manufacturing of the custom device, however critical elements relative to static and dynamic biomechanical conditions are completely unknown to the technician at the time of manufacturing.

Some of these error point include;
  • Proper alignment of the rear foot and midfoot joints by palpation
  • Applying adequate thickness of plaster on the feet. If the plaster is not thick enough it will create distortion.
  • Making sure that the plaster has dried properly. If the Plaster is not completely dried it can become distorted leading to error.
  • Making sure that the patient has not moved their feet after the slipper cast is been applied.
  • Making sure that the technician or physician properly removes the cast without distorting the neutral position of the foot. Improper removal of the slipper cast can create distortion.
  • Allowing the negative casts to dry thoroughly prior to shipping.
  • Proper protection of the negative cast during shipping to the laboratory. This is necessary to ensure that the plaster caster not get broken during the shipping process by common carrier.
  • Making sure that the prescription form is properly documented relative to the patient's diagnosis and Baturro request.
  • Once the negative cast is received by the production laboratory, it is critical that the negative cast be balanced with the heel vertical at 90°. If this is not done adequately and there's error in this vertical bisection process, there can be significant error in the manufacturing of the orthotic device.
  • Next, it is important to make sure that the plaster that is poured into the slipper cast is of the right consistency of water to plaster. If there's too much water in the plaster, it can cause the negative cast to collapse thereby losing correction.
  • Next, it is important to make sure that the technician does not put too much plaster fill in the arch. If there's too much plaster fill this will also reduce controllability of the device on the foot.
  • Next, the plastic that is heated in the convection oven must be heated at the right temperature for the right time. So that the plastic is pliable and not too soft and not too rigid for thermal pressing. If the plastic is not heated properly this can cause distortion and weakening of the plastic over the positive mold.
  • It is also vital that the bladder suctioning be of proper negative pressure so that the bladder that molds the heated plastic onto the positive shell brings the plastic down exactly to the surface of the plantar aspect of the positive mold so that there's adequate correction of the device. If bladder pressure is too weak then they'll be gapping between the plastic and the mold leading to further error.
  • There are also a series of errors relative to the rough grinding and final grinding of the orthotic shell.
  • Errors on the medial and lateral side of the distal orthotic is also critical to supporting vital 1st Ray stability as well as other structures of the foot. If the shell is cut to narrow than the first ray and primary propulsive areas of the foot will fail to be supported.
  • Heel cup depth is also a critical factor in the manufacturing of the orthotic. If the heel cup is too shallow, particularly for men, this can effectively interfere with rear foot control.
  • Proper rear foot posting is critical for the locking and unlocking of the sub taylor joint against the mid tarsal joints of the foot. If there is not a proper posting correction, it could interfere with functional control of the rear foot on the midfoot thereby leaving the orthotic more vulnerable to error.
  • Understanding what type of orthotic is going be placed in the proper footwear. If the wrong orthotic is improperly matched to the footwear, this can cause binding of the orthotic and loss of biomechanical control. An example would be manufacturing an oxford orthotic to fit into a style shoe. Style orthotics are generally low bulk orthotics made specifically for style footwear.
Advancements
Advancements in 3-D weight-bearing kinematic imaging have dramatically improved the accuracy of manufacturing process of corrective devices. 3DO imaging does not rely on neutral joint positioning, (Art Form), but rather it relies on the assessment of seven unique static and dynamic areas of physics;

  1. Mass displacement analysis
  2. Motion analysis
  3. Body balance in all three body planes
  4. Pressure analysis, both linear and sheer pressures
  5. Symmetry
  6. Gait Analysis
  7. Three dimensional plantar surfacing

3DO imaging (3-D weight-bearing kinematic imaging), is a new state-of-the-art static and dynamic imaging process that accurately identifies complex to simple cyclic load conditions affecting the foot, lower leg, knee, hip, pelvis and spine. Sophisticated imaging software properly identifies the neutral joint position of the rear foot (Sub Talar Joint), midfoot, (mid tarsal joints) and the first ray (navicular, medial cuniform, 1st metatarsal, hallux) which is a primary propulsive part of the foot.

3DO imaging relies on precise three-dimensional geometry in order to provide the anatomy deformity to the necessary correction required.

Technicians have software where they are are allowed to see the static and dynamic forces affecting the patient's cyclic load conditions in real time,(just what the physician sees). This is a critically important element in new imaging technology providing the technician with functional data relative to the patient's biomechanical and ergonomic conditions. It is as if the technician is standing right next to the doctor during the examination process. When the technician can see exactly what the doctor sees then he is able to perform the manufacturing process with greater degrees of accuracy.

Reducing the multiple areas of error in the data acquisition to manufacturing process improves dramatically the success rate of these devices on the patient's medical conditions. As a result we have developed a new product called a Bioengineerd Device as opposed to an orthotic that meets higher calibration and precision requirements of limb function.

To learn more about 3DO imaging technology and manufacturing advancements please go to the following websites;
 
Older Plaster Methods of Manufacturing - Full of Errors 



 
 
3DO - 3D Weight Bearing Kinematic Imaging to Manufacturing
Accuracy and Reliability  
 
 
 
 
 
 
 
 


 714-669-9600
 
 
 
 

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