Successful treatment of your patients with custom foot orthoses is directly related to the accuracy of the impressions that you have obtained. The particular technique, be it plaster cast, foam box or digital scan is a secondary consideration, the accurate depiction of the complete anatomy of the foot in the desired configuration must be attained. There is only so much the lab can do to compensate for a poor quality cast or impression. Neutral position casting for foot orthoses is the preferred method used to capture the foot in its most anatomically optimal alignment, ensuring proper biomechanical function when fabricating custom orthoses. This technique is widely used in podiatry and orthotic device manufacturing.
A key component to gaining consistent accuracy in your casting technique is similar to many other learned physical activities in life, be it sports, hobbies, technical work, or even surgical skills, practice, practice, practice. Ask for volunteers to practice on, see if you can adequately reproduce your results repeatedly. Learn to evaluate your impressions, do they line up with examination findings? Are you consistent with both the left and right casts? Mastering whatever technique for orthotic impressions you prefer will pay off in no time at all. Less adjusting, replacing of improper devices, less complaints and more compliance with your patients will be the natural consequence.
Steps for Neutral Position Casting:
1. Patient Preparation:
- The patient is positioned either prone (face down), supine with the leg extended or seated with the foot hanging freely or supported.
2. Identifying Subtalar Neutral:
- The practitioner palpates the talonavicular joint or medial and lateral talar head to find the neutral position of the subtalar joint (STJ)—the point where the talar head is evenly palpable on both sides. If the patient is prone then have them rotate on their hip to allow the foot to point directly downward toward the floor
- The midtarsal joint is also stabilized to prevent excessive forefoot motion. The thumb is placed in the sulcus of the 4th and 5th toes, taking care not to dorsiflex the toes, or push straight under the 4th metatarsal head to fully lock the midtarsal joint
3. Casting Techniques:
There are several methods for capturing the foot in neutral:
Digital Scanning
- A non-contact scanner (Foot ID Pro) captures the foot’s shape while the practitioner holds it in neutral.
- Provides high precision and eliminates mess from plaster.
Plaster Casting (Most Traditional Method)
- Non-weight-bearing methods are preferred to avoid deformation.
- A plaster bandage is applied to the foot and molded carefully while maintaining the subtalar joint in neutral.
- Once the plaster sets, it is removed and sent to a lab for orthotic fabrication.
B. Foam Box Impression
- The patient presses the foot into a foam box while the practitioner guides the foot into a neutral position.
- This method is quicker but may be less precise than plaster.
4. Verification and Fabrication:
- The cast or scan is checked for accuracy.
- A prescription is created for corrections based on the patient's needs. Areas of interest may be marked on the impressions, such as bony prominences of locations of various pads or dells
Let us enter the wayback machine and review videos made By Dr. Richard Blake and Kevin Rosenblum demonstrating neutral position casting using plaster splints. Enjoy!
