Intrinsic Adjustments - Machined EVA
- Konrad Job
This page explains all relevant features on the Intrinsic Adjustments page of LaserCAM Prescribe for Machined EVA prescription.
Overview
- 1 Overview
- 1.1 Navigation
- 1.2 Page Layout
- 2 Page Fields
- 2.1 Plantar Fascia Accommodation (PFA)
- 2.2 Medial Arch Fill
- 2.3 Lateral Arch Fill
- 2.4 Medial RF Posting
- 2.5 Lateral RF Posting
- 2.6 Ramp
- 2.7 Heel Cup
- 2.8 Intrinsic Heel Lift
- 2.9 Metatarsal Wedge
- 2.10 Skive
- 3 Support
Navigation
Click Intrinsic Adjustments from the menu to access this page in LaserCAM Prescribe.
Page Layout
Page Fields
Plantar Fascia Accommodation (PFA)
A Plantar Fascia Accommodation (PFA), sometimes referred to as a Plantar Fascia Groove, is an accommodation at a specified depth (mm) in the top surface of the orthosis shaped according to a Curved, Straight or Scan style selection.
It is highly recommended that all prescriptions consider the accommodation of the plantar fascia. Not including an accommodation for the plantar fascia can result in patient discomfort.
The specified depth is measured prior to surface smoothing and is subject to minor variability.
Default Value | Minimum Value | Maximum Value | Default Selection | Available Selections |
|---|---|---|---|---|
0mm | 0mm | 8mm | Curved | Curved |
Straight | ||||
Scan |
Curved
Adjustment Origin | Adjustment Insertion |
|---|---|
Medial calcaneal tubercle | Inline with 1st metatarsal ~10mm proximal to 1st MPJ |
Straight
Adjustment Origin | Adjustment Insertion |
|---|---|
Medial calcaneal tubercle | Inline with 1st metatarsal ~10mm proximal to 1st MPJ |
Scan
A Scan style selection will indicate to technicians that a marking has been made on the plantar fascia prior to 3D scanning, or has been indicated using the Make Drawing tool.
This is the most accurate method of Plantar Fascia Accommodation prescription.
Adjustment Origin | Adjustment Insertion |
|---|---|
As per marking | As per marking |
Medial Arch Fill
Medial Arch Fill represents a percentage based adjustment to the height of the orthosis within the area of application.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0% | -50% | 50% |
Area of Application
Positive Percentage
A positive percentage represents an increase in the height of the orthosis in the area of application. For example, if the medial arch height is measured at 30mm then a value of 10% will result in a total height of ~33mm.
In traditional orthosis terms a positive value can be though of as removing plaster from the positive cast.
Negative Percentage
A negative percentage represents a decrease in the height of the orthosis in the area of application. For example, if the medial arch height is measured at 30mm then a value of -10% will result in a total height of ~27mm.
In traditional orthosis terms a negative value can be though of as adding plaster to the positive cast.
Lateral Arch Fill
Lateral Arch Fill represents a percentage based adjustment to the height of the orthosis within the area of application.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0% | -50% | 50% |
Area of Application
Positive Percentage
A positive percentage represents an increase in the height of the orthosis in the area of application. For example, if the lateral arch height is measured at 10mm then a value of 10% will result in a total height of ~11mm.
In traditional orthosis terms a positive value can be though of as removing plaster from the positive cast.
Negative Percentage
A negative percentage represents a decrease in the height of the orthosis in the area of application. For example, if the lateral arch height is measured at 10mm then a value of -10% will result in a total height of ~9mm.
In traditional orthosis terms a negative value can be though of as adding plaster to the positive cast.
Medial RF Posting
Medial RF Posting, sometimes referred to as a Medial Heel Wedge, represents an intrinsic addition of material at a specified angle within the area of application.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0° | -20° | 20° |
Area of Application
Positive Degree
A positive degree will commonly apply a supination moment to the subtalar joint within the area of application. This adjustment will result in an application of force that is medial to a normal subtalar joint axis.
In traditional orthosis terms this is similar to inverting an extrinsic rearfoot post, however this is applied internally.
Negative Degree
A negative degree will commonly apply a pronation moment to the subtalar joint within the area of application. This is sometimes requested when a positive degree of Lateral RF Posting is deemed a contraindication due to orthosis fit, or other reasons.
Applying a negative value for Medial RF Posting will result in a lower medial heel cup height.
Lateral RF Posting
Lateral RF Posting, sometimes referred to as a Lateral Heel Wedge represents an intrinsic addition of material at a specified angle within the area of application.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0° | -20° | 20° |
Area of Application
Positive Degree
A positive degree will commonly apply a pronation moment to the subtalar joint within the area of application. This adjustment will result in an application of force that is lateral to a normal subtalar joint axis.
In traditional orthosis terms this is similar to everting an extrinsic rearfoot post, however this is applied internally.
Negative Degree
A negative degree will commonly apply a supination moment to the subtalar joint within the area of application. This is sometimes requested when a positive degree of Medial RF Posting is deemed a contraindication due to orthosis fit, or other reasons.
Applying a negative value for Lateral RF Posting will result in a lower lateral heel cup height.
Users will often match negative and positive values to twist the rearfoot into a more everted or inverted position.
Ramp
Inversion Ramp
An Inversion Ramp is an intrinsically applied medial wedge applied within the area of application.
Default Value | Minimum Value | Maximum Value | Default Selection | Available Selections |
|---|---|---|---|---|
0° | 0° | 45° | Full Length, Full Width | Full Length, Full Width |
Full Length, Half Width | ||||
Sulcus Length, Full Width | ||||
Sulcus Length, Half Width | ||||
3/4 Length, Full Width | ||||
3/4 Length, Half Width | ||||
Forefoot Only, Full Width | ||||
Forefoot Only, Half Width |
Area of Application
This area of application can be easily modified during computer-aided design. The best practice is to mark the required area of application directly on the foot prior to 3D colour scanning or plaster casting. If this is not possible, then you can simply draw a diagram using the Make Drawing tool.
Eversion Ramp
An Eversion Ramp is an intrinsically applied lateral wedge applied within the area of application.
Default Value | Minimum Value | Maximum Value | Default Selection | Available Selections |
|---|---|---|---|---|
0° | 0° | 45° | Full Length, Full Width | Full Length, Full Width |
Full Length, Half Width | ||||
Sulcus Length, Full Width | ||||
Sulcus Length, Half Width | ||||
3/4 Length, Full Width | ||||
3/4 Length, Half Width | ||||
Forefoot Only, Full Width | ||||
Forefoot Only, Half Width |
Area of Application
This area of application can be easily modified during computer-aided design. The best practice is to mark the required area of application directly on the foot prior to 3D colour scanning or plaster casting. If this is not possible, then you can simply draw a diagram using the Make Drawing tool.
Heel Cup
The Heel Cup adjustment allows a user to increase or decrease the internal width of the heel, while also having a minor effect on heel cup height.
It is not recommended that this adjustment be used to increase heel height. This is better suited for narrowing, or widening the internal heel cup. If you would like to increase heel height we recommend reading about the Orthosis Width (US Foot Size) prescription variables on the Shoe Fitting page of LaserCAM Prescribe.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0% | -50% | 50% |
Area of Application
Positive Percentage
A positive percentage represents a decrease in the internal diameter of the heel cup and an increase in the height of the heel cup within the area of application.
You should consider the other variables being intrinsically added to the rearfoot, as well as top cover thickness. These can have a negative impact on orthosis fitting clinically.
Negative Percentage
A negative percentage represents an increase in the internal diameter of the heel cup and a decrease in the height of the heel cup within the area of application.
A negative value can help to allow for fat pad expansion during weight bearing, however this will lower heel cup height.
Intrinsic Heel Lift
The Intrinsic Heel Lift adjustment applies a lift specified in millimetres within the area of application. The peak thickness is at the most proximal point of the area of application.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0mm | -30mm | 30mm |
Area of Application
This area of application can be easily modified during computer-aided design. The best practice is to mark the required area of application directly on the foot prior to 3D colour scanning or plaster casting. If this is not possible, then you can simply draw a diagram using the Make Drawing tool.
Positive Value
A positive value represents an increase in heel height that is tapered from the proximal edge to the distal edge of the area of application.
Negative Value
A negative value represents a decrease in heel height that is tapered from the proximal edge to the distal edge of the area of application.
A negative value is rarely prescribed, however can result in a completely flat heel if required.
Metatarsal Wedge
The Metatarsal Wedge adjustment applies a lateral or medial forefoot wedge within the area of application.
Default Value | Minimum Value | Maximum Value |
|---|---|---|
0° | -45° (medial metatarsal wedge) | 45° (lateral metatarsal wedge) |
Area of Application
This area of application can be easily modified during computer-aided design. The best practice is to mark the required area of application directly on the foot prior to 3D colour scanning or plaster casting. If this is not possible, then you can simply draw a diagram using the Make Drawing tool.
Positive Degree
A positive degree results in a lateral wedge applied within the area of application.
Negative Degree
A negative degree results in a medial wedge applied within the area of application.
Skive
We recommend that you read the published works of Kevin Kirby to understand relevant theory prior to requesting this adjustment. We have used these works to inform how we recommend the application the Skive adjustment in a computer-aided design environment.
K. Kirby (1989), Rotational equilibrium across the subtalar joint axis, JAPMA
A Skive is an adjustment that is achieved by orientating a flat plane relative to the aligned 3D foot scan during computer-aided design. This plane is orientated in relation to a marked subtalar joint axis, or at a specific angle, and pushed through the 3D foot scan at a specified depth.
Default Value | Minimum Value | Maximum Value | |
|---|---|---|---|
Depth | 0mm | 0mm | 10mm |
Angle (°) | 0° | -90° (lateral skive) | 90° (medial skive) |
There are two methods of prescribing a Skive. Please use the method available to you depending on your 3D scan hardware.
Prescription Variable | STJ Axis Method (Recommended Method) | Depth/Degree Method |
|---|---|---|
Angle (°) | Not required | Required |
Depth (mm) | Required | Required |
3D Scan Type | Colour 3D Scan Only | Any 3D Scan |
STJ Axis Method
Recommended Method
This method is only possible when using colour 3D scan formats such as VRML.
The image below shows the orientation of the adjustment relative to the subtalar joint axis marked on the 3D scan (represented by the yellow line).
Using the STJ Axis Method the only variable required is the Skive Depth.
Skive Angle is not required as the orientation of the skive plane is based upon the marked subtalar joint axis.
Depth/Degree Method
The Depth/Degree Method allows a user to enter a specific Skive Depth and Skive Angle.
Skive Depth
The Skive Depth directly effects the magnitude of supination or pronation moment applied to the subtalar joint.
Skive Angle
The Skive Angle defines the frontal plane orientation of the skive plane. If the subtalar join axis is medially deviated then the Skive Angle should increase to ensure a supination moment is being applied to the subtalar joint.
The Skive Angle does not need to be specified when using the STJ Axis Method.
Inclination Angle
The Inclination Angle defines the sagittal plane orientation of the skive plane. The default value is set to Maximum Inclination, which is considered generally appropriate. Specific values may be requested.
Default Selection | Available Selections |
|---|---|
Maintain Maximum Inclination | Maintain Maximum Inclination |
Zero Degree Inclination | |
Specific Inclination (°) |
Maintain Maximum Inclination
The image below shows a Skive with the Maximum Inclination of the skive plane.
Additional information regarding Inclination Angle can be found in the following article: