Early Indicators of Bone Loss After Hip Replacement Discovered

Hip replacements relieve pain and restore mobility for hundreds of thousands of patients in the United States each year, but of the more than 400,000 hip replacements performed in the U.S. annually, about 10 percent will fail within 10 to 15 years. One main cause of this failure — which results in a need for a second hip replacement surgery (known as a revision surgery) — is the destruction of bone tissue around the replacement joint, a condition called osteolysis, which may cause the joint to loosen.
Now a research team at Rush University Medical Center has identified a pair of biomarkers that indicate which patients are likely to develop osteolysis.
The discovery could lead to tests that would enable surgeons to identify those patients in advance and adjust post-operative monitoring routines for them. It even might lead to treatments to prevent osteolysis in these patients.
“We are hopeful that early biomarkers for implant loosening will alert surgeons to be especially vigilant in their follow-up of at-risk patients and may eventually lead to treatments delaying or avoiding the need for revision surgery,” said the paper’s senior author D. Rick Sumner, PhD, chairperson of the Department of Cell & Molecular Medicine in Rush Medical College and the Mary Lou Bell McGrew Presidential Professor for Medical Research.
With the U.S. population aging, many individuals remaining very active late in life and others becoming heavier, hip replacements are projected to increase by 174 percent by 2030, with a projected 137 percent increase in the number of hip revision surgeries to fix or replace the failed implant over the same time period.
“We need to find effective strategies to handle this demand. These joints need to last, if possible, for the rest of a patient’s life,” said Joshua Jacobs, MD, a co-investigator on the study. Jacobs is Rush University’s vice provost for research and the William A. Hark, MD/Susanne G. Swift Professor and chairperson of the Rush Department of Orthopedic Surgery.
For their study, Sumner and his colleagues took what he calls “a candidate protein approach.” They drew on a previous review of medical literature they had conducted, which identified 40 possible biomarkers of future osteolysis development.
They divided the markers into four groups based on their likelihood to predict osteolysis and focused on the two groups that were most likely. The researchers winnowed the field of candidate proteins by eliminating markers found in blood rather than urine and those for which tests weren’t readily available.

Two combined biomarkers provided strongest indication of risk
Ultimately they tested for the presence of seven biomarkers and compared findings to the medical history of the patients – 16 of whom eventually had developed osteolysis. A biostatisican on the team then conducted an analysis to determine which combinations of the biomarkers correlated most with the osteolysis development.
“We looked at each marker independently, but none of them worked that well by themselves. Then he looked at panels of markers,” Sumner explained. “When we did that, we found we got a much better discrimination between patients that developed osteolysis and those that did not.”
The analysis found that a higher than normal levels of the connective tissue protein alpha CTX (a marker for bone resorption) and the immune response protein interleukin 6 (a marker of inflammation) were highly accurate in identifying patients at risk for osteolysis. The combination was detectable in patients up to six years before they were diagnosed with osteolysis.

Rush University
www.rush.edu/news/press-releases/early-indicators-bone-loss-after-hip-replacement-discovered