Using The A.C.T.™ Casting Pillow
Inconsistencies of casting techniques provide the greatest challenge in any fabrication lab as impression methods. Modifying the casts to estimate the weight-bearing foot’s arch height, length, and width is subjective at best. Extensive discussion and debate have been ongoing over the years with no ultimate solution on making foot casting consistent, whether using a plaster slipper cast, wax, or foam impression tray. Simply “loading” the lateral column during casting does not effectively create a functional or comfortable foot model. Foam impression boxes, while allowing a load to be placed manually on the midfoot, do not overcome the problem of inconsistency due to practitioner techniques. Common complaints of foot orthotics being intolerable or ineffective due to improper “interpretation” of the plaster model are eliminated by creating a weight-bearing foot impression. Utilizing The A.C.T.® impression pillow provides an accurate, reproducible, and consistent plantar foot topography regardless of technician technique.
The A.C.T.® Casting Pillow is designed to create an accurate and reproducible model of the foot. The unique pillow shape and density allow the uncompensated foot to be suspended while maintaining neutral subtalar joint alignment as it bears the load. This produces a foot model that requires little, if any, modification in the lab.
The pillow contours and slow-recovery foam allow the rear foot and mid-foot to be suspended, effectively enveloping the foot without the potential for ground reactive forces to cause distortion. The memory foam material gently compresses the soft tissue at the heel and mid-foot while the forefoot splays naturally, as it does under normal load. With the subtalar joint in neutral, the thinner memory foam layer under the ball of the foot and toe area will capture the forefoot plane as neutral unless there is a rigid forefoot varus or valgus.
The A.C.T® pillows are designed as a single-component slow-recovery foam with a smooth, durable exterior surface. The pillow surface can be cleaned with soap and water, disinfectant spray, or brushed. Plaster, STS® socks, and thermal moldable mediums will not stick to the surface.
It is generally accepted that during the contact phase of the gait cycle, the subtalar joint passes through neutral alignment twice. It occurs first just after the heel strike as the ball of the foot comes into contact with the ground and as the mid-tarsal joint begins to pronate to absorb shock. The second time the subtalar joint passes through neutral is just before toe-off as the mid-tarsal joint events, and the foot becomes a rigid lever for propulsion.
In casting with the A.C.T.® Casting Pillow, the plantar foot shape is captured in the latter subtalar neutral position. The ankle is dorsiflexed approximately 17 to 22 degrees, the subtalar joint is maintained in a neutral position, and the load is placed on the foot. Depending on practitioner requirements, the foot can be in partial weight-bearing while seated or a full or semi-weight-bearing position while standing.
- Full and semi-weight bearing casting methods are achieved with the patient standing and bearing load on the foot to be cast. The most common technique is to have the patient stand on the A.C.T.® Casting Pillow with even weight on both feet (considered semi-weight bearing) during the curing or cooling period. This is the most accurate and reproducible casting technique. Assuming consistency in the distribution of patient weight, subtalar alignment, and pillow density, the resultant impressions will be the same regardless of the practitioner or casting medium (material). Impressions are taken one foot at a time, not entirely to load the foot during the curing/cooling process.
- The seated or partial weight-bearing casting method is best used when compromising weight-bearing and non-weight-bearing impressions is desired. This will produce a slightly “higher” arch profile. This is sometimes indicated for cases of extreme pes planus or use with obese patients when patient weight makes subtalar alignment challenging to maintain. This technique is also advisable when working with patients who are unsteady while standing.
A.C.T.™ Pillow Applications:
The A.C.T.™ Casting Pillows are designed for various casting materials and orthotic devices. A.C.T.™ pillows can be used to make impressions for functional foot orthotic fabrication, direct molded shoe inserts, full contact diabetic inlays, custom molded shoes, and AFOs. Materials that can be used include plaster, thermal cork, STS® casting socks, and direct moldable thermoplastics.
For improved control, the A.C.T™ Impression Stand is designed to simplify the casting process and provide diagnostic information (see A.C.T™ Impression Stand description below). Please reference specific instructions for materials and applications.
Using Thermal moldable A.C.T® Impression Cores
Step 1: Preheat oven to 300° F.
Step 2: Select the appropriate core size.
- Medium: up to Women’s size 9 or Men’s size 8.
- Large: Women’s size 9.5 or Men’s size 8.5 and larger.
Step 3: Place one impression core in the oven and heat for 60 to 70 seconds or until soft and pliable.
Step 4: Locate the heated core under the patient’s foot on the A.C.T.® pillow and manipulate it to subtalar neutral.
Step 5: Allow the cork to cool under the foot for at least 60 seconds or until firm.
Using Plaster Slipper Casts and STS® Socks
Cover the A.C.T. Impression Pillow with a plastic bag. Prepare slipper cast or STS® sock as usual. With the patient in either a standing or seated position, place the foot on the molding pillow, as shown, with the ball of the foot at the transition and the heel centered in the back. Align the subtalar joint to neutral and allow the material to harden.
The A.C.T.® pillows are designed as a single component of slow-recovery memory foam with durable outer skin. This allows for easy material release and cleaning. The surface should be disinfected with spray after each use. The surface can be cleaned with mild soap and water. Do not use solvents of any kind on the pillows.
The pillow is designed for use with heated materials; however, excessive heat may damage the surface. Do not directly place materials heated to over 300° F onto the pillow. The pillows can only be used with materials heated to over 300° F with an insulating layer of heat-dissipating material underneath.
Using the A.C.T.™ Impression Stand:
The A.C.T.™ Impression Stand is uniquely designed to simplify molding using the A.C.T.™ pillows. Once the subtalar joint has been aligned, the knee cups hold the patient in position for hands-free molding/casting. The plumb bobs identify the alignment of the knee over the metatarsals, providing both a reference point and a diagnostic tool.
Step 1: Have the patient step onto the pillows, locating the feet in the appropriate position with the ball of the foot at the transition and the heel centered in the back.
Step 2: Loosen the knobs on the sides of the crossbar and position the bar slightly below the plane of the knees.
Step 3: Loosen the knee cup knobs, center the cups to the patient’s knees, and retighten. Have the patient bend their knees to fit securely into the cups. Grasp the subtalar joint with one hand and the knee cup knob with the other. Loosen the knob and slide the knee cup medially and laterally while feeling for subtalar alignment. Once alignment is achieved, tighten the knee cup knob. Repeat for the other foot.
Step 4: Suspend the plumb bobs and check alignment. The plumb bob should be located between the first and third toes, generally over the second. A lack of symmetry may suggest that subtalar alignment should be rechecked or that a leg length discrepancy or other anomaly needs to be explored.
Step 5: Place molding/casting medium under one foot at a time and allow to cool/cure. Repeat for the other foot.