AcroMed

Stereolithography Cages: Life-Enhancers for Spinal Patients

With the aid of stereolithography (SL), suppliers can now build complex SL "cages" in record time and give surgeons much-needed pre-operative evaluation tools for delicate spinal disc implant surgery.

America has a nagging backache. Almost half a million people undergo surgery each year in this country to relieve back pain. Yet only 30 percent experience any relief, according to Forbes Magazine. In fact, 31 million Americans suffer from back pain at any given time, and 80 percent of us will experience it at some point during our lives, cites an article in Nation's Business. But relief may be as close as Cleveland, Ohio.

Little wonder then we should beat a path to the doors of AcroMed and Astro Model in Cleveland. This customer/vendor alliance is in the midst of FDA clinical trials that may one day give American surgeons a new spinal operative procedure to minimize surgical trauma, speed patient healing, and eliminate the need for unwanted hardware in the body. Already, thousands of patients in Europe and Japan have benefited from AcroMed's groundbreaking research.

Oftentimes, spinal discs must be replaced due to degenerative conditions, injuries, or cancer. AcroMed, a recognized global leader in surgeon-driven innovative solutions for spinal disorders, specializes in medical implants and instrumentation. Recently, AcroMed turned to stereolithography apparatus (SLA) owner, Astro Model Development, low volume manufacturer of everything from toys to CAT scanners, to solve a time crunch during a key developmental project. AcroMed's surgeon-clients needed a quick evaluation model of a complex spinal cage that could one day be destined for patient implant surgery.

"Fast stereolithography prototypes mean we can give our surgeons rapid response - up to 80-90 percent faster than machining. Also, without a true model in hand, surgeons may think they understand the drawing. With stereolithography, they know they understand it."
                               Jim Kuras, Product Development Engineer, AcroMed

No More Hardware
Spinal cages provide scaffold-type structures that create the proper growing environment for implanted bone material. Known medically as Anterior Endoscopic Thoracolumbar InterBody Fusions (AETIs), the cages are designed to replace weakened or diseased discs, enabling the surgeon to implant bone and encourage fusion of the spine. Bone tissue harvested from the patient's iliac crest, is used as fill-in to create spinal stability. Cages may eliminate the need for plates, rods or screws in the spine. Although mobility is slightly compromised, it is offset by the prospect of continued pain and dysfunction if surgical intervention is not elected.

Fast and Accurate Models
AcroMed transferred their SDRC solids file to Astro Model on a Friday. By the following Wednesday, the SL models were ready for the surgeon to use as evaluation tools in his research. Astro Model built eight iterations in SL, cutting two months out of the development time. Had the cages been machined in stainless steel, the standard approach, the process would have taken weeks for each iteration compared to the two days using SL. After converting the SDRC file to Pro/ENGINEER, Astro Model built the tiny cages, typically 7mm x 9mm x 23mm, on their SLA 250 system.

One day, the spinal cages will be injection molded in a carbon fiber composite material - similar to material in the Stealth aircraft. They will be as strong as steel but invisible to x-ray detection so the surgeon can later chart patient healing free from radiographic obstruction.

Revolutionizing Back Surgery
Spinal cages modeled in SL offer an entirely new way to perform back surgery. Typically, surgery is approached from the back of the spine, requiring the surgeon to cut muscles and tendons away from the spine, which prolongs the healing process. Because the SL cages are so small and so precise, the surgeon can enter the body laproscopically from the front of the spine with potentially far less trauma to the patient. The next time you hear a sufferer lament, "Oh, my aching back," mention that relief is in the wings in Cleveland with an enterprising team dedicated to advancing the science of spinal surgery.

Editor’s Note: It is important to emphasize that AETIs are in the early research and development phase and are not yet approved by the FDA in the United States.