Department of Orthopaedic Surgery
Stellenbosch University

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Plaster Casts and Splints

Functional Braces

The principle of these is that a well fitting plaster cast is applied and the patient uses the extremity ie walks on a the cast. Muscle action and the intermittent axial compression stimulates bony union.

Femoral Cast Braces

Cast braces enjoyed a considerable vogue during the 1970s for the management of femoral fractures and fractures of the tibial plateau. After preliminary treatment by traction, the cast brace is applied when the fracture is "stable and firm."
In essence, a long-leg cast is applied over a long "Stockinette" stocking, with the upper end molded to the shape of a quadrilateral socket, or a plastic socket is incorporated in the cast.
Another name for the femoral brace is a "Box Plaster" A full leg cast is applied and molded in a right angled "box" form to prevent rotation. It bears weight on the ischial region. Box plasters are only suitable from the mid femoral shaft downwards. A hinge may be worked into the plaster and the knee left free.
Box Plaster for Femoral #
Cast Brace
Well molded into ischial region - rubber walking heel

All functional braces need the fracture to be stable ie partially united. It is not a suitable method for the fresh fracture.

The Patellar Tendon Bearing Cast

At Tygerberg hospital tibial fractures are initially treated for about 6 weeks in a full length POP then Patellar Tendon Cast (PTB) is applied. The PTB is not suitable for proximal tibial fractures, but is a good conservative method of treating stable tibial fractures from the middle third downwards. The principle of tibial PTB casting is the same as for the femoral cast brace. A well fitting below knee cast is applied and molded between the gastrocnemius heads. The actual weight is born on the patellar tendon region anteriorly. A rubber heel is applied and the patient is encouraged to weight-bear on the plaster.

Technique of PTB casts

PTB cast
A PTB Cast
Well molded between the gastroc. heads - bears weight on the patellar area
Patellar tendon-bearing (PTB) casts were devised by Sarmiento to immobilize fractures of the tibial shaft and at the same time allow the knee to bend. This type of cast must be applied with care over minimal padding and is applied in segments. In applying the upper portion of the cast, the knee should be flexed to a right angle and the cast molded flat over the upper calf to give a triangular cross section. The cast is molded anteriorly around the patella, and an indentation is made over the patellar tendon. The cast is trimmed to look like a PTB prosthesis, and it is most important to trim the cast like a wingback chair around the femoral condyles to prevent rotation of the proximal tibia on weight bearing
Consider using a PTB plaster, especially if a tibial fracture is taking longer than expected to unite.