There is no single foot-impression technique that is right for every clinician or patient. The useful test is whether the chosen method produces a consistent, usable result. In this tutorial, Dr. Antonin Bérubé demonstrates the prone, non-weight-bearing 3D scanning workflow he uses for most patients with the Platform 3D mobile app.
The objective is repeatability
Weight-bearing scans, semi-weight-bearing scans, foam boxes, plaster casts, and direct digital scans can all lead to a good orthotic. The method matters less than the clinician's ability to reproduce the same positioning and capture process across patients and appointments. Dr. Bérubé recommends developing a technique, testing it repeatedly, reviewing the resulting orthotics, and adjusting the process until the loop is consistent.
Equipment and app setup
- Use an iPhone equipped with a front-facing TrueDepth camera. Dr. Bérubé uses an iPhone 17 Pro Max in the demonstration.
- Use the Platform 3D native mobile app, which captures depth data from the TrueDepth sensor.
- Scan with the front camera in selfie mode. Dr. Bérubé advises against using the rear LiDAR sensor for this close-range workflow because it is intended for longer scanning distances.
- Work at approximately 20 cm from the foot. In the video, the stated optimal TrueDepth range is approximately 15 to 45 cm.
The Platform 3D app is free to use for practice. An iPad with a compatible sensor can also work, but its size makes one-handed capture more difficult than an iPhone.
1. Position the patient prone
Ask the patient to lie prone with both feet extending beyond the end of the examination table. This keeps the scanning foot accessible and lets the clinician position it while holding the phone in the other hand.
Patient positioning is the part most likely to be rushed. Taking more time here reduces the need for an assistant and makes the scan easier to repeat. This position may be unsuitable or difficult for some patients, including patients whose mobility, body size, age, pain, or other limitations make prone positioning impractical. Use another impression technique when the patient cannot be positioned safely and comfortably.
2. Remove unwanted leg and pelvic torsion
Before positioning the foot, assess how freely it moves. Dr. Bérubé bends the opposite leg and adjusts the pelvis until the scanning foot hangs without residual internal rotation from the leg. The goal is a relaxed, suspended foot that can be manipulated without fighting against the patient's position.
If dorsiflexing the foot causes it to move inward or outward, reassess the patient's position and pelvic tilt. Continue adjusting until forefoot pressure produces a centered dorsiflexion movement rather than a rotational drift.
3. Find a repeatable subtalar-joint position
Palpate the ankle and subtalar region while moving the foot through small inversion and eversion movements. Dr. Bérubé then dorsiflexes the foot and looks for the position in which it stays centered instead of falling inward or outward. He describes this as his subtalar-joint neutral position.
This is a repeatability reference, not a claim that one neutral position is the scientific truth for every prescription. The practical aim is to recognize and reproduce the same position when scanning the other foot or repeating the impression later.
4. Load the forefoot without distorting it
Place the thumb distally between the second and third metatarsal heads and apply forefoot pressure while the other fingers stabilize the foot. The pressure should approximate how the forefoot broadens and deforms under load, while preserving the correction selected at the rearfoot.
Avoid dorsiflexing the toes as a routine holding strategy. In the demonstration, Dr. Bérubé explains that excessive toe dorsiflexion can create a false short-foot appearance, move the plantar soft-tissue pad distally, exaggerate the arch, and produce a shape the patient may not tolerate. Deliberate overcorrection may be appropriate in selected cases, but it should not happen accidentally during ordinary capture.
5. Keep the holding hand outside the future orthotic
Imagine the finished orthotic sitting against the plantar foot. Place the thumb and fingers outside the surface that the orthotic must cover. A hand captured over the required anatomy has to be removed from the scan later, leaving missing geometry that the designer must reconstruct or guess.
6. Set the first frame before starting
The first captured frame is the reference for the scan. Hold the phone as parallel to the plantar foot as possible at roughly 20 cm. The Platform 3D overlay helps frame the foot, and the distance indicators change from red to green when the surface is within the app's target range.
The foot should nearly fill the screen. If the entire foot fits comfortably inside one static frame, the phone is often too far away. The camera movement is what collects the heel, medial and lateral borders, and upper arch geometry.
7. Capture with a controlled cross-shaped movement
- Stabilize the foot firmly with the dominant hand.
- Hold the phone with the other hand in selfie mode.
- Start the scan with the on-screen control or the phone's volume button.
- Move the phone left and right, then up and down, forming a controlled cross-shaped path around the plantar foot.
- Capture the heel, both sides of the foot, the medial arch, and the lateral arch while keeping the foot still.
- Finish the pass in about 10 seconds.
Keep the body and the hand holding the foot stationary. Only the phone should move. Dr. Bérubé recommends learning the motion well enough to keep visual attention on the foot rather than constantly following the phone. Looking at the screen can cause the clinician's torso and stabilizing hand to drift, creating motion artefacts.
The live depth map provides a second check. Green indicates anatomy within the target capture range, while red indicates that the phone is too far away. Use the map to correct distance without slowing the scan excessively.
Common scanning errors
- Taking 20 to 30 seconds. A long scan increases the chance that the foot or holding hand will move.
- Moving too quickly. A rushed pass may capture only the plantar center and miss the heel, borders, and arch geometry needed for design.
- Scanning from too far away. Keep the foot close enough to nearly fill the frame and use the app's red and green distance feedback.
- Moving the foot while moving the phone. Stabilize the patient and the holding hand before capture.
- Dorsiflexing the toes unintentionally. This can shorten and distort the captured shape.
- Putting fingers over the orthotic-bearing surface. This blocks anatomy and forces the designer to reconstruct missing data.
- Using a mirror clip as a permanent substitute for learning the selfie-mode movement. It can help beginners see the screen, but Dr. Bérubé finds that it increases working distance and often requires an assistant.
Practice before judging the method
Holding the foot with one hand while moving the phone accurately with the other is a learned motor pattern. Do not expect the first scan to look like an experienced clinician's result. Dr. Bérubé estimates that roughly 10 to 20 practice scans are usually needed before the movement becomes comfortable and repeatable.
When another impression technique is the better choice
The prone workflow is not mandatory. If a patient cannot tolerate the position, if the clinician cannot stabilize the foot consistently, or if another technique already produces reliable outcomes, use the method that works. A clinician who obtains consistent foam-box impressions can continue using them and digitize the foam impression afterward.
The final standard is a closed feedback loop: use a defined technique, repeat it across enough cases, inspect the scan and finished orthotic, identify recurring errors, and refine the process. Consistency is more defensible than changing methods in search of a single supposedly perfect position.
Frequently asked questions
Do I need an assistant to scan a foot with the Platform 3D app?
No. In Dr. Bérubé's prone workflow, one hand stabilizes the foot and the other moves the iPhone in selfie mode. An assistant may still be useful when patient positioning or clinician mobility makes one-person capture impractical.
How far should the iPhone be from the foot?
Dr. Bérubé works at approximately 20 cm. Use the Platform 3D app's framing overlay and red-to-green distance indicators to confirm that the anatomy is within the target depth range.
How long should a 3D foot scan take?
The capture pass should take about 10 seconds. Going much slower increases motion risk, while going too fast can leave the heel, borders, or arches incomplete.
Is subtalar-joint neutral the only correct scanning position?
No. The video presents it as Dr. Bérubé's preferred repeatable reference, not as a scientifically proven universal position. Other impression methods can also produce good orthotics when used consistently.
Can I use a foam box instead of scanning the foot directly?
Yes. If foam-box impressions are reliable in your workflow, Dr. Bérubé recommends continuing to use them and scanning the foam impression afterward rather than abandoning a method that already works.