CU Anschutz Develops First Validated Tool to Measure Performance in Bone-Anchored Prosthesis Users after Amputation

The COLD-TUG test shows that a leg prothesis anchored to bone is faster to don and doff than a traditional socket-style prosthesis

AURORA, Colo., May 29, 2025 /PRNewswire/ -- A test developed at the University of Colorado Anschutz Medical Campus that measures both prosthetic donning time and mobility in lower-limb amputation, shows that a prosthesis anchored to bone goes on faster than a traditional socket-style prosthesis. The finding is the first to validate the test as a tool to measure performance for lower-limb amputees using bone-anchored prostheses.

The study was published recently in the Journal of Bone & Joint Surgery.

"The aim of this study was to develop and examine the reliability and validity of the Colorado Limb Donning-Timed Up and Go (COLD-TUG) test," said the study's lead author Mohamed Awad, MD, MBA, a research scientist in orthopedics at the University of Colorado School of Medicine. "This test combines the time required for donning a prosthesis with the time to complete the TUG test in lower-extremity amputees using a prosthesis."

Over the years, patients have reported that a bone-anchored limb (BAL) prosthesis, which fits directly into the bone, offers them greater physical activity, balance, sitting comfort, range of motion and donning and doffing efficiency than the traditional socket prothesis. Yet due to a lack of accurate, population-specific, performance-based testing, evidence for how this impacted quality of life remained scarce.

To find answers, CU Anschutz researchers employed the COLD-TUG mobility test, developed by a team led by Jason Stoneback, MD, associate professor of orthopedics at the CU School of Medicine and an orthopedic trauma surgeon. CU Anschutz is a global leader in BAL surgery.

"The test is simple and elegant," said Stoneback, the study's senior author. "It was developed here at CU Anschutz and it's a game changer not only because of how specific it is but also because it tests the right things. As more patients opt for BAL, health care providers around the world need validated functional outcome measures specific to BAL patients."

COLD-TUG measures the time in seconds required to put on the prosthesis, get up from a standard chair, walk about 10 feet, turn around, walk back to the chair and sit down.

The research team examined 31 patients with unilateral lower extremity amputation - 15 had a traditional socket-style prosthesis and 16 had a BAL prosthesis.

The researchers found no significant differences between the two groups in terms of baseline characteristics but did find that BAL patients could don a prosthesis significantly faster – by about 61 seconds - than those with a socket-style prosthesis.

Awad said someone with a prothesis may don and doff it up to 15 times a day and saving 61 seconds each time translates into hours over weeks and months.

"Each time they prepare to move, they save nearly a minute. If we make a calculation that we are awake for 12 hours then you are talking about hours saved over time- —time that can be spent living, not just preparing to move," he said. "This will make them more active and confident."

The test results appear to support patient testimony that a BAL prothesis offers them more mobility, stability and balance.

"We are not just capturing speed with this test," Stoneback said. "The COLD-TUG test quantifies something amputees have been experiencing for years. By measuring what is important to this population of patients we as providers can help them choose the best option for their lives."

About the University of Colorado Anschutz Medical Campus
The University of Colorado Anschutz Medical Campus is a world-class medical destination at the forefront of transformative science, medicine, education and patient care. The campus encompasses the University of Colorado health professional schools, more than 60 centers and institutes, and two nationally ranked independent hospitals - UCHealth University of Colorado Hospital and Children's Hospital Colorado - that treat more than two million adult and pediatric patients each year. Innovative, interconnected and highly collaborative, the University of Colorado Anschutz Medical Campus delivers life-changing treatments, patient care and professional training and conducts world-renowned research fueled by over $705 million in research grants. For more information, visit www.cuanschutz.edu.

Contact: David Kelly, University of Colorado Anschutz Medical Campus, [email protected]

SOURCE University of Colorado Anschutz Medical Campus