Turning Motion Into Data

High Tech Equipment Measures Surgical Outcomes
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Apr 11, 2008

There are three Duke specialists in hip replacement using three different approaches to the surgery: posterior, direct lateral, and modified anterior lateral -- or back, side and front. Each involves cutting different muscles.

Until now, follow-up studies of how well each approach works have been based solely on patient satisfaction surveys. But Duke's 10-year-old Michael Krzyzewski Human Performance Lab -- the K-Lab -- is adding some sophisticated measurement to the survey data.

"We’re looking at what the numbers say in addition to what the patients say," says K-Lab director Robin Queen, PhD. "It’s a novel concept to combine biomechanics with clinical outcomes," Queen says.

While wearing an array of reflective markers on outsides of their knees, ankles, and hips, post-surgical patients are asked to perform simple exercises, such as climbing a step, walking across the room, or standing up from a seated position. Eight cameras around the room capture the movement from the markers and feed computers that create digital representations of the motion of their joints, making the patient into a stick figure.

In this study, for which Queen serves as the principal investigator, patients who have undergone hip surgery will be examined to determine whether they have returned to walking normally. Their movement will be compared to that of a control group measured in the K-Lab. Members of the control group have been chosen to match the age, weight, gender and other characteristics of the group that has undergone surgery.

Initially, Queen’s group is looking at patients post-surgery. Eventually the team will examine the gait and movement of patients before surgery in order to compare movement before the operations and at several milestones afterward.

The same idea drives studies of hip resurfacing. Patients who have undergone either hip replacement or hip resurfacing will be compared to healthy patients in a control group, with researchers examining such the mechanics of the hip joint's motion.

A similar study is evaluating ankle replacements. And as the K-Lab builds databases of human movement, they could be applied to future studies as well.

The K-Lab also plays a vital role in collecting movement data on patients who have osteoarthritis of the knee in an attempt to understand how the disease alters movement patterns.

"We’re looking at gait mechanics as a functional outcome following a clinical intervention of weight loss and pain management," says Queen.

This work is part of a larger NIH-funded Program Project Grant directed by Farshid Guilak, PhD, who heads Duke’s Orthopedic Bioengineering Lab.

This article was excerpted from DukeMed Magazine.