Paige Little is an expert on using state-of-the-art imaging technology to understand ideal body position and support for enhancing the quality of sleep. It’s the kind of research used to improve beds for the home. But in 2018, Little was contacted by a consultant who asked for something more serious. Could she design a customized, patient-specific surgical mattress for a 10-year-old about to undergo spinal surgery?
The patient had Morquio syndrome, a disorder that causes skeletal abnormalities and neuromuscular scoliosis. She would need to lie safely on her stomach and the front of her body for the duration of the surgery.
“Intraoperative patient position is always a critical factor in spinal surgery, particularly in the case of prone patient positioning, where the anatomy and physiology of the torso is such that additional pressure may have adverse effects on the cardiopulmonary system as well as causing skin and muscle necrosis,” Little said. “Optimal patient positioning for spine surgery is vital for surgical success and the minimization of complications intra and postoperatively.”
Little, an associate professor at the school of mechanical, medical, and process engineering at Queensland University of Technology, is up to the challenge. Using an innovative digital workflow involving 3D surface scanning, 3D simulation and computer-aided design (CAD), she successfully created a customized theater mattress with the patient’s specific body-contour requirements. The operation was a success, and the surgical team praised the mattress and its positive impact on patient outcome.
Patient-specific design
Little’s goal was to create a customized mattress to hold the patient safely and reduce possible skin damage during the surgery procedure. By using digital simulation tools and CAD, she was able to create a patient-specific surgical mattress that fit the contours of the patient’s body. This made it easier for the surgeon to relieve load bearing on prominent anatomical features during the surgery because the support surface was tailored to the patient’s anatomy for the lengthy procedure.
“The design process is based in CAD, and for many of the mattresses I have designed, I use Solidworks to create the mattress contours,” Little said. “We have recently explored the use of CNC machining to create the surface contours in the polyurethane foam, and with high spindle speeds it is possible to machine this foam using standard tooling. The machining is very successful with well-defined surface contours, and relatively little post-process cleaning is needed to remove dust waste. The foams do not require freezing to machine them. They also do not release toxic fumes or particulate matter.”
Topographic scanning of the entire patient was required to create a mattress contour. “The contour is not a replica of the patient’s anatomy, but rather is custom-designed using the topographic scan as a basis,” Little said. “The design process cannot be parameterized—the design is created for each patient using CAD methods to alleviate pressure on the skin surface over areas that are delicate, or regions of the anatomy that cannot bear load for long periods of time. For some corrective surgeries, the patient may be lying stationary for many hours.”
Manufacture is currently a manual, just-in-time process. The process may benefit from CNC machining or robotic manufacturing, especially for mattress contours that are for large or tall individuals or have deep cutouts and/or overhangs.
Sealy of Australia then manufactured the final mattress product. Technicians used the 3D model to hand-cut and piece together multiple layers of soft hypo-allergenic foam to conform exactly to the patient’s anatomy.
The custom mattress is effectively contoured to the patient’s anterior anatomy during surgery. Intraoperative monitoring indicated the patient was not under undue cardiovascular strain over the course of the operation “and she successfully remained in the prone position for the entire eight-hour operation,” Little said. “Immediately postoperatively, there was no evidence of excessive interface pressure between the patient and the support, suggesting the custom-fit mattress successfully distributed the patient’s body weight, alleviating regions of excessive pressure.”
Moving Forward
Since the first use of the surgical mattress, Little has designed 11 other supportive mattresses for pediatric patients with unique anatomies requiring support during surgery—all with successful results.
The next step is to continue showcasing the mattresses to a broader clinical audience so other patients can benefit from the use of customized body supports during surgery. “Their surgical teams will also gain confidence in reducing the risks of complications due to extended periods of weight-bearing in patients with unique conditions,” Little said.
The digital workflow she used to design the mattresses can also be applied to the design and advanced manufacturing of other custom-fit devices to assist in treatment and/or rehabilitation of patients. “These same techniques—3D topographic scanning, 3D simulation, and CAD methods—can be applied to the design of customized corrective/rehabilitation orthoses,” Little said, “or to the custom design of supports for radiation therapy to ensure the patient is positioned in a repeatable position between treatment appointments.”
