Compostable splint can be reshaped multiple times as patient heals

A newly developed medical splint can be repeatedly reshaped as the patient recovers from a bone injury and can be composted when it is no longer needed. The device is made from a PLA-based biopolymer formulated by the Fraunhofer Institute for Applied Polymer Research IAP (Potsdam, Germany) and was developed by injection molder Nölle Kunststofftechnik GmbH (Meschede, Germany).

PLA-based splint

Conventionally designed splints cannot be adjusted as the healing process runs its course, creating complications and discomfort as the swelling subsides. Also, they are not biodegradable, creating up to 150 metric tons of waste per year, notes Fraunhofer IAP.

The Recast immobilization concept developed by Nölle Kunststofftechnik uses variously sized pre-shaped splints made from biodegradable PLA. The splints are heated to between 55° and 65°C. The temperature of the splints is then reduced to a minimum, explained Fraunhofer IAP. The now formable plastic is molded to fit the corresponding part of the body. This process takes about five minutes. If further adjustments are necessary, the hardened splint can simply be reheated.

"We wanted to find a way for [practitioners] to care for their patients more quickly, cleanly and, above all, on a more individual basis,” explained Anselm Gröning, Managing Director of Nölle Kunststofftechnik. “For patients, we wanted to create a splint that would be significantly more comfortable and lighter. At the same time, it was important for us to use a plastic that is biodegradable, affordable and non-toxic," said Gröning.

Nölle Kunststofftechnik worked closely with materials scientists at Fraunhofer IAP to develop a material that could meet a set of complex requirements. “It had to remain formable for only one-half to three minutes and then become hard and stable at body temperature,” explained Helmut Remde, head of the Processing Technology Center at Fraunhofer IAP. “It also had to be possible to readjust the shape several times," added Remde.

PLA perfectly fit the bill for this application because of a property that often is a major disadvantage in other uses—the polymer starts to soften at around 58°C. “The low thermal softening point of PLA is a great advantage when used [to manufacture] an orthopedic splint," said Remde. “This means that the product can be shaped repeatedly and quickly by heating it.” Fraunhofer IAP researchers combined PLA with suitable fillers and developed a formulation that met all customer-specified requirements. They also ensured that the material could be produced in sufficient quantities to meet demand.

Using PLA also allowed the manufacturer to achieve sustainability goals. The Recast splints biodegrade in industrial composting systems, an 80% waste reduction compared with conventional splints that are incinerated or sent to landfills, according to the injection molding company. An additional “20% of the plastic waste could also be saved through the possibility of reuse," added Gröning.

The Recast splints also feature a fleece padding made of PLA and viscose to enhance patient comfort. The padding, which is also biodegradable, was developed in collaboration with the Saxon Textile Research Institute in Chemnitz, Germany.

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