Measuring Device Could Raise Hip Operation Success Rate

State-of-the-art measuring techniques, similar to those used in making aerospace components fit together precisely, could improve success rates for hip replacement surgery.

Researchers at the U.S. National Institute of Standards and Technology (NIST; Gaithersburg, MD, USA) are working to improve calibrations and operating room testing of the computer-assisted orthopedic surgery (CAOS) tracking instruments surgeons use to plan the delicate, highly complex operation. The researchers have built a lightweight device called a "phantom” that resembles the artificial socket, ball, and femur substitutes that surgeons use to replace the joint and bone in hip operations, based on a calibrated XY coordinate frame. They then drilled tiny holes at precisely measured intervals into the phantom and made cuts at precisely measured angles, favored by surgeons for CAOS operations.

Because the precise coordinates of the mechanical ball and socket joint center of rotation have been measured, manufacturers of CAOS tracking sensors can use the phantom to test the accuracy of their measuring instruments. Surgeons also should be able to test the accuracy of their CAOS devices, just before making their first incision, to measure ball and socket joint center of rotation coordinates, angles for cuts into the bone, and places for the insertion of screws.

To be completely successful, CAOS hip replacement surgery must take into account tiny human skeletal differences. Imprecise measurements, which could result from conditions seemingly unrelated to the surgery, such as operation room noise or temperature, can lead to poor positioning of implants, leaving some former patients with discomfort during walking, and in rarer cases, a need to redo the operation.


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U.S. National Institute of Standards and Technology