Lower Extremity Cast
Short Leg Cast (Walking Vs. Non-walking)
Materials Needed. A 3-inch or 4-inch stockinette, 3-inch and 4-inch cast padding, cast material, with or without foot stand/stockinette loop trick.
Technique. The patient can be sitting, prone, or supine with the hip and knee bent to 90 degrees. If sitting, the patient can rest the forefoot on a foot stand to control equinus and inversion. The ankle should be in a neutral position without equinus, and the base of the second metatarsal should line up with the tibial crest. Ensure use of the appropriate size stockinette depending on the size of the patient. The length of the stockinette could be from the tip of the toes to the mid-patella; alternatively, a cuff of stockinette could be used. Cut the stockinette along the anterior ankle creases to avoid wrinkles, which can cause skin irritation.
Start with applying cast padding snugly over the stockinette with four layers of cast padding at the tips of the toes and the metatarsal heads and proximally to the tibial tubercle. Ensure that all bony prominences including the calcaneus, medial and lateral malleoli, and fibular head are padded adequately. Wrap cast material from the tips of the toes up proximally to the tibial tubercle using moderate tension and ensuring 50% overlap as well. Maintain neutral ankle position during application of cast padding and cast material to avoid causing creases in the cast and possible skin irritation. After applying three to four layers of cast material, fold the stockinette ends over, and apply one final layer of cast material. Reinforce any weak areas as deemed necessary. Proceed with molding the cast by creating a flat Achilles border and applying a proximal tibial medial and lateral mold to prevent slippage (Figure 9). Trim the distal edge of the cast to allow for exposure of the toes as needed.
Walking Cast. Provide the patient with a cast shoe after the cast has dried and solidified.
Indications. A short leg cast is indicated for the last stage of treatment for tibial fractures, ankle fractures, some distal tibial fractures, talar, hindfoot, midfoot, and some metatarsal fractures.
Long Leg Cast
Materials Needed. A 3-inch or 4-inch stockinette, a 3-inch and 4-inch cast padding, and cast material.
Technique. The patient can be sitting or supine. A long leg cast extends from the metatarsal heads to the midproximal third of the thigh. The below knee component is exactly the same as the short leg cast described above. There are two additional advantages that long leg casts can offer compared to short leg casts: the ability to control rotation of the tibia and the ability to control weight bearing, with the knee in a slightly bent position. The position of the knee should have flexion to 20 degrees, and the ankle is in a neutral position. Confirm adequate fracture reduction, angulation, and rotation. The base of the second metatarsal should line up with the tibial crest and the midpatella ensuring that the patella is not internally or externally rotated.
Ensure the use of an appropriately sized stockinette depending on the size of the patient. Stockinette length could be from tip of the toes to the proximal thigh; alternatively, a cuff of the stockinette can be used. Cut the stockinette along anterior ankle creases and popliteal fossa to avoid wrinkles, which can cause skin irritation. Start with applying cast padding snugly over the stockinette with 50% overlap from the metatarsal heads and proximally to the proximal third of the thigh. Ensure that all bony prominences including the calcaneus, medial and lateral malleoli, fibular head, and patella are padded adequately. Wrap cast material from the tips of the toes up proximally to the thigh using moderate tension and ensuring 50% overlap as well. It is important to limit motion of the ankle and knee during application of the cast padding and material to limit crease formation, which can lead to skin irritation. After applying three to four layers, fold the stockinette ends over, and apply one final layer of cast material. Reinforce any weak areas as deemed necessary. Proceed with molding the cast by creating a flat Achilles border, flat anterior thigh, and anterior tibial mold to prevent skin irritation, and a supracondylar (medial and lateral thigh) mold to prevent slippage. Three-point molding might be necessary depending on the fracture pattern. Trim the distal edge of the cast to allow exposure of the toes. All toes must be visible at the end of cast application to allow for assessment of neurovascular function after fracture reduction and cast application.
Indications. A long leg cast is indicated for distal femoral and femoral supracondylar fractures, tibial tubercle fractures, tibial plateau fractures if a brace is not indicated, and, most commonly, tibial shaft and ankle fractures.
Sarmiento or Patellar Tendon Bearing (PTB) Cast
Materials Needed. A 3-inch or 4-inch stockinette, four rolls of 3-inch and 4-inch cast padding, cast material, with or without a cast stand.
Technique. A PTB cast is a modified short leg cast that extends proximally to include the upper pole of the patella with a firm molding of the medial flare of the tibia, the patellar tendon, and the popliteal space. It is shaped like a triangle at the proximal end of the tibia allowing for a "fracture-suspending" effect. This mechanism helps unload the fracture, reducing the forces transmitted through the tibial shaft with weight bearing. This cast often is used as a transition for partially healed fractures for which weight bearing is encouraged to stimulate osteogenesis, but additional support remains necessary to avoid refracture. Additional advantages that this cast can offer compared to a short leg cast are rotational stability of the tibia and ankle, as well as the ability to range the knee to avoid stiffness of the joint.
Indications. Sarmiento or PTB casts usually are applied as a stage of treatment for tibial fractures and sometimes as initial treatment for stable fractures in the distal half of the tibia.
Wedging The Cast
In case of persistent fracture malalignment after the cast is applied, cast wedging is a valuable technique that can be used instead of exchanging the entire cast. Cast wedging involves cutting the cast 300 degrees out of 360 degrees circumferentially at the level of the fracture with a cast saw, spreading the cast to correcting the fracture angulation, adding a spacer, and reinforcing the cut portion with new cast material (Figure 10).
(A and B) Cast wedge. The fiberglass should be wrapped over wedged area to reinforce as needed.
To determine the size of the wedge, the angulation at the fracture is measured by using a plain radiograph. A line is drawn perpendicular to the apex of the fracture and the malalignment angle is then measured off of this perpendicular line. We then measure the distance between the malalignment angle and the perpendicular line at the level of the skin, which will equal the size of the wedge. Accounting for magnification change is critical based on the radiology software. The wedge is placed opposite to the apex of the deformity. For example, the wedge would be placed volarly in the cast for an apex dorsal deformity. If there is significant pain after wedging, the wedge size may have to be reduced or additional valving of the cast may be necessary. It is also important to monitor for signs and symptoms of compartment syndrome and to instruct parents on these signs.
Curr Orthop Pract. 2020;31(3):277-287. © 2020 Lippincott Williams & Wilkins