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3D Technology Improves Surgical Implants and Procedures

Crisco’s team then imported the digital wrist models into SolidWorks CAD software for additional fine-tuning. The final CAD data was then output to a rapid prototyping machine, to create physical models of the wrist. These extremely accurate models were within two degrees of rotation and 0.2mm of dimension, and preserved the bone orientation of each wrist position.

Brown Medical researchers also used the digital models to create 3D animations of wrist movement with the help of proprietary mathematical algorithms to fill in the gaps between scanned positions. The animations helped the researchers see, three dimensionally, how the relations between wrist positions play out in real life.

Based on the animations, Crisco has found that wrist motion and function were more complicated than previous theories indicated. Descriptions of wrist motion at the time suggested that the eight wrist bones move as three columns or two rows. Instead, Crisco discovered that each bone has a separate pattern of motion that is associated with each unique direction of wrist motion. (See Exhibits 2 and 3.)

Exhibit 2: NURBS surface models of the human wrist bones in flexed (blue) and extended (gray) positions.

NURBS surface models of the human wrist bones in flexed (blue) and extended (gray) positions.

Exhibit 3: NURBS surface model of human wrist in neutral position, as if looking at top of the hand. Neutral wrist positions were used as comparison for the wrist models created through a complete range of motion.

NURBS surface model of human wrist in neutral position, as if looking at top of the hand. Neutral wrist positions were used as comparison for the wrist models created through a complete range of motion.

The team studied injured wrists as well as healthy ones to determine if diagnosis and treatment methods could be improved. They examined soft tissue injuries, such as scapholunate ligament tears, which are often the consequence of a fall on an outstretched hand. At the time, evaluations of ligament tears used x-rays to examine the gap between the scaphoid and lunate bones. If the gap between is wider than expected, a ligament tear is the most probable diagnosis.

“Our current findings indicate that altered 3D bone motion of the wrist – rather than x-rays – is a better indicator of ligament injuries,” says Crisco.

Better Understanding of Implant Wear

 In 2006, Dr. B.J. Fregly, assistant professor in the Department of Mechanical and Aerospace Engineering (MAE) at the University of Florida, was quoted as saying, “More engineering analysis goes into the washing machine in your home than into the artificial knee joints implanted in people.”

He set out to change that, taking technologies traditionally used for virtual prototyping of mechanical systems and extending them to more complex and variable biomechanical systems. His toolbox for studying and predicting joint contact stresses and motions in artificial and natural knees included dynamic modeling and simulation, parallel processing, image processing of CT and MRI data, 3D modeling from Geomagic, video-based motion capture and fluoroscopic imaging.

To utilize all these technologies, Fregly collaborated with Drs. Greg Sawyer and Rafi Haftka of the university’s MAE department and Dr. Scott Banks of the Biomotion Foundation in West Palm Beach, Florida. (See Exhibit 4.)

Exhibit 4: (Foreground) Complete knee assembled in Geomagic Studio, overlaying a fluoroscopic image of the knee. The lab can calculate the 3D relative motion of the artificial knee components through image matching. (Background) Fluoroscopy is used to measure detailed knee joint motion. Reflective markers on the patient’s skin and clothing capture gross movement.

(Foreground) Complete knee assembled in Geomagic Studio, overlaying a fluoroscopic image of the knee. The lab can calculate the 3D relative motion of the artificial knee components through image matching. (Background) Fluoroscopy is used to measure detailed knee joint motion. Reflective markers on the patient’s skin and clothing capture gross movement.

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