Plaster of Paris Casting
Important points highlighted during the Plaster of Paris casting demo include:
- Raising the contralateral hip of the foot the Podiatrist intends to cast by placing the opposite foot across the hamstring of the leg being cast,
- this allows the casting foot to fall into subtalar neutral as long as the knee is in the frontal plane,
- lock the mid-tarsal joint, or position the foot as required,
- a single piece of plaster of Paris [doubled over] will be used to cast patient from big toe to little toe,
- a strip of double plaster is folded once to increase the strength and reduce the depth of the cast,
- the cast in the demo is not a full cast, only to metatarsal for the purpose of scanning the cast using CAD/CAM,
- use warm water to ensure cast sets quickly,
- when casting make sure to capture a good representation of the anatomy to ensure the orthotic can sufficiently alter moments of force when worn by the patient,
- consider MOMENTS OF FORCE! “kinetics rather than kinematics”,
- keep foot at 90 degrees relative to the leg,
- lock mid-tarsal joint,
- take your time to ensure you capture the best impression of the foot as possible,
- TOP TIP: once the cast is removed from the patient’s foot, place it in a microwave and cook on full heat for 1 minute to ensure the cast is completely set.
Foam Box Impression
- Ensure the patient is completely relaxed,
- the Podiatrist will create the foam impression, NOT the patient.
- hip at 90 degrees, knee at 90 degrees and ankle at 90 degrees: “90, 90, 90”,
- Here the Podiatrist is pushing the foot down, not the knee.
- right hand on top of patient’s foot to maintain subtalar neutral position and to stabilize the hind foot to mid-foot,
- push down on the lateral border of the foot to create a lateral force that locks the mid-tarsal joint.
- create impression by entering the foot into the from the lateral side of the foot.
- place the toes down into the foam,
- plantar flex the first ray,
- make sure to load the foot evenly when entering the foam,
- remove the foot from the foam box to inspect the impression
- TIP: inspect the plantar level of the fifth ray and the heel – these should both be at an equal depth in the foam.
3D Structure Sensor Scanning using iPad
- The same concept applies as the Plaster of Paris cast, placing the non scanned foot in a contralateral hip position to allow the foot to be scanned to fall into a subtalar neutral position,
- make sure the knee is in the frontal plane,
- it is difficult to ensure all the metatarsal heads are on the same plane [we are working on an apparatus to achieve this]
- with foot and ankle at 90 degrees [patient has to hold this which can create an artificial forefoot supinatus by firing EHL and TA],
- some Podiatrists prefer to scan the POP or foam impressions after achieving the position they desire.
- launch the AOMSTOT application on the iPad,
- on the app, enter the patient’s second name to create a new patient record, choose left or right foot depending on which foot is about to be scanned,
- place the iPad roughly 2 feet away from the plantar aspect of the foot,
- make sure the foot is within the rectangular box visible on-screen,
- you will see the application scanning the foot data, building up the data as the iPad moves around the patient’s foot.
- move the iPad slowly around the foot to build the 3D model!!!
- did we say move the iPad slowly, yes? Well, we’re saying it again, move the scanner slowly to ensure you capture as accurate a scan as possible.
- move on to the second foot,
- or press ‘save’, this adds the scan to an email as an attachment which can easily be sent to the lab for manufacture.