Masking Burns

A man in his early 40s lay in the burn intensive care unit (ICU) at Seattle's Harborview Medical Center. He sustained burns over his face, neck and fingers, and was on life support. Although his injuries were immense, he was fortunate to have been taken to Harborview – a hospital known for their advanced techniques. The patient was scheduled for a skin graft the next day, and a special-fitting silicon soft gel burn mask needed to be prepared in order to give him the best scenario for healing.

The University Of Washington Burns/Plastics Clinic & Rehabilitation Therapies at Harborview Medical Center pioneered the technique of creating silicon gel masks that cover a patient's face to promote healing and minimize scarring. The silicon gel mask minimizes fluid from collecting under new skin grafts, a main source of preventing grafts from adhering. However, the original technique was a tedious process.

The old method of making burn masks sometimes required the patient to be anesthetized while the occupational therapist (OT) would spread an epoxy material over the patient's face. Once the epoxy is dried, plaster of Paris is poured into the mold to make a positive impression. A special silicon gel is then poured onto the positive tool to make the healing mask. This procedure could take up to six hours and required additional services from the hospital to support this technique.

In attempts to accelerate and refine the process of making burn masks, while also minimizing pain and discomfort for the patient, Harborview began working with CimMed, a company in nearby Algona, WA.

"Scanning burn patients with lasers is not new. It is currently being done in select sites around the country; however, in some situations, a patient must go to the site and this is not a feasible choice when a patient is on life support," explains Steve Kidd, president of CimMed. "In addition, these sites can be very expensive and the equipment requires a large amount of space."

What CimMed and Harborview developed is a system where the scanner goes to the patient – whether they are in the ICU or in the operating room. Kidd hopes all hospitals will eventually have their own scanners so all burn victims have access to this technology and users will simply be able to electronically send him the scanned information so they can work together to quickly make the correct mold.

The Process

Refining the process to where it is now – usable right at the patient's bedside – is the result of Kidd's driven ideas. In the past Kidd used a Polhemus portable laser – suitable for scanning a patient when there is no metal or conductive material present.

"However, we have found that the Handyscan provides a solution to scan in any condition – and in this particular case it was important to scan the patient while on life support in his bed inside the ICU," Kidd says.

So, the first step is to take the Handyscan and scan the burn victim. Once the patient has been scanned, the file is sent back to CimMed's offices in order to register what scans they are able to use and to fit them into an accurate 3D STL file – readied for the OT to decide how she wants to edit the 3D topography.

"It can take from 15 minutes up to an hour to alter the 3D STL file based on input form the OT," Kidd states. "We typically reserve five to 10 minutes to discuss topography edits with the OT."

After the modifications to the 3D tool are made on the computer and the STL file is complete, the file is moved into CNC Software's Mastercam X3 CAD/ CAM software – which is able to receive STL files into its system as an entity.

"Mastercam X3 will see this file exactly the same as a solid or as surfaces in fullshaded mode," Kidd explains. "Once imported into Mastercam, we quickly apply a toolpath to the model – within 10 minutes – and get a roughing and finishing toolpath."

The software's STL machining allows Kidd to quickly program for CNC milling on a Haas Super VF4 vertical machining center. Kidd works to keep machining time to less than one hour.

Mastercam CAD/CAM software works with any combination of solid models, surfaces and wireframe, delivering a powerful way to automatically mill and drill these parts. The Feature Based Machining module (FBM) evaluates a prismatic solid's features and automatically designs an effective machining strategy. Some of the other features include high-speed 2D machining; automatic support for closed-, open-, nested- and through-pockets and setting the right toolpath options; and selection of the appropriate tools for all operations, either from your preferred tools list or from libraries you specify.

What CimMed and Harborview developed is a system where the scanner goes to the patient.

Next up is the material. CimMed uses 45 lb tooling foam manufactured by Tacoma-WA-based General Plastics Manufacturing Co. "We work with this material because the material breaks off into chips, providing a dust-free tool ready for vacuum-forming, which also makes it very easy to clean the mill after machining," Kidd says.

Once the tool is milled in 3D, it is cut from the stock and is ready to go to the vacuum-forming machine.

Once the tool is milled in 3D, it is cut from the stock and placed directly into a vacuum-forming machine. CimMed uses Formech machines, which, according to Kidd, have the best range of machines, including a deep draw machine they use for oncology isolation masks for radiotherapy treatments. The vacuum-forming process first heats the propriety "Silon" sheet in less than 60 seconds and then forms the gel mask in less than 5 seconds.

Saving Face

At 9:00 a.m., the man in his early 40s who had sustained severe burns over his face, neck and fingers, lay on life support in the ICU. Kidd and the rest of the CimMed engineering team arrived in the ICU with their portable laser scanner. First they created a scan of the man's face and went back to their off ice where they made the 3D engineering file. Beth Costa, an OT from Harborview, met them at the office to make edits to the scan – in order to have the mask apply more pressure in one area or another, as needed for the upcoming skin graft. After the modifications to the 3D computer model were made, the STL file was sent to Mastercam X3.

By 10:30 p.m. that evening, Cimtech Inc. – another company owned by Kidd – was milling the positive tool for the mask out of General Plastics' tooling foam and the OT was there checking the progress. After vacuum-forming, the final product was delivered in less than 24 hours.

More Patients

A week after using the process on the man, a 10-year-old burn victim was scanned by the team, only this time, an online meeting was set up with the OT staff using GoToMeeting, a web-based conferencing tool. This allowed the OT to communicate with CimMed's team concerning how she wanted the mask to be edited. GoToMeeting also gives the control of the computer mouse to the parties online, making it easy for the OT staff to indicate on the 3D computer model where changes are required, accelerating the entire process.

After surgery, a patient will wear the gel mask for about two weeks until a new scan is made and a hard mask is created using clear plastic lined with silicone. Patients wear the mask for at least 23 hours per day for 12 months or longer, making a comfortable fit paramount. The simplified scanning process allows the OT staff to rescan the patient as the face becomes less swollen. In addition, the original tool can be reworked, helping keep hospital costs down.

The vacuum-forming process first heats the propriety "Silon" sheet in less than 60 seconds and then forms the gel mask in less than 5 seconds.

The product and process for creating masks can be used in different departments within a hospital – from the burn ward to the oncology unit, as well as for craniofacial helmets for children. Generally, pressure devices for burn victims are used for the face, although the neck and breast areas are other areas of consideration.

"This technology will enhance healing and reduce a hospital's non-billable hours," Kidd notes. "More importantly, it can make a significant difference in the lives of people suffering disfiguring burns or other cranio-facial conditions."

"Steve is wonderful," says Merilyn L. Moore, manager of the University of Washington's Burns/Plastic Clinic at Harborview. "Everyone at the company has a heart for helping, making them very easy to work with. It is exciting for us because they are right here in Seattle. The work, though, will make a difference to burn patients throughout the country because it is more affordable and accurate."