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Grip and Arm Position
Note: The plaster splints will normally be applied at this point but only after the following positioning steps have first been completed in a dry run to confirm that the proper casting position can be achieved.
- With your casting hand (ie. right foot, left hand), grasp the 4th and 5th metatarsal heads and move the STJ through the neutral position several times while keeping the MTJ fully pronated. Pronate the STJ back to the neutral position. Pronating the STJ back into the neutral position helps ensure that the MTJ remains fully pronated. (see figure 6)
- Using the back of your opposite hand, support the plantar surface of the foot in the medial arch as you re-grip the foot with your casting hand. Place the palmar surface of your thumb in the sulcus and grasp the proximal aspect of the 4th and 5th phalanges between your thumb and your 2nd metacarpophalangeal joint. Extend or hyper-extend your thumb to minimize your thumb impression in the sulcus. Your thumb impression in the sulcus should not extend medial to the 4th met head. Do not flex the distal phalanx of your thumb, as this can cause increased pressure in the central metatarsal area and can alter the plane of the metatarsal heads. (see figure 7)
- Gently lift the foot and simultaneously rotate your palm towards the floor. Your palm should face in the direction of the floor but it should not parallel the floor. Your palm and forearm should parallel the angle of the sulcus. Lift the foot only enough to slightly un-weight the lower leg on the leg rest. This will provide ample force to fully pronate the MTJ provided the patient is sufficiently relaxed (see fig. 6). Do not lift the lower leg off of the leg rest of the casting chair. Doing so can cause practitioner fatigue and increases the dorsiflexion force acting on the foot which may move the STJ out of the neutral position in some patients.
- Your wrist and fingers should be in a rectus position and your forearm should describe a common plane from your elbow through the tips of your fingers, like a perfectly flat salute (see figure 7). The height of your elbow will be determined by the angle of the sulcus since your forearm should be parallel to angle of the sulcus. You should be very comfortable and it should require minimal effort to hold the foot during the casting process. If you are not comfortable or find casting fatiguing, it is likely that either you or the patient are not properly positioned. You should never need to squeeze the toes forcefully in order to hold onto the foot. If you feel like you need to squeeze the toes or if you feel that the foot is slipping, your grip is likely incorrect. Verify that your palm (salute) is facing the floor and that your thumb is extended or hyper extended.
- The frontal plane of the practitioner’s body should parallel the plantar plane of the forefoot when the MTJ is in a fully pronated position. Standing or sitting parallel to the plane of the forefoot enables the forefoot to easily be positioned so that the MTJ is fully pronated (ie. everted to the end range of motion). Make sure you are as close to the foot as possible so it is not necessary to lean forward. If you lean forward during casting it will be uncomfortable and fatiguing and creates a tendency to pull the patient’s forefoot towards you, which can easily cause inadvertent MTJ supination (ie. forefoot plantarflexion and adduction).
- Apply a very slight abduction force to the forefoot to confirm that the MTJ is fully pronated in the transverse plane. If the MTJ is fully pronated, then the entire foot will abduct. If the MTJ is not fully pronated, the forefoot will abduct relative to the rearfoot. Cast the foot with the forefoot fully abducted. If the patient has a large amount of transverse plane motion available at the MTJ or has a highly abducted forefoot to rearfoot relationship, it may be necessary to lightly grasp the medial and lateral aspect of the heel above the weightbearing surface with the opposite hand, in order to maintain a forefoot abduction force while the plaster sets. If it is necessary to grasp the heel, use as little force as possible and remain above the plantar weightbearing surface to avoid any distortion of the plantar surface of the cast that might adversely affect the orthosis.
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