A simple series of urine tests could be the key to identifying hip implant patients who are likely to suffer bone problems, according to new research from Chicago’s Rush University Medical Center.
Researchers Predict Osteolysis In Hip Implant Patients With Remarkable Accuracy
In a new study published in the Journal of Orthopaedic Research, Dr. D. Rick Sumner and colleagues describe the results of their search for illuminating urinary markers, which could help us diagnose osteolysis, a disorder in which the bone tissue degrades over time, up to 6 years earlier than current diagnostic methods.
To perform their study, the researchers analyzed 24-hour urine samples from 26 patients, 16 of whom ultimately developed osteolysis. Each patient provided a sample prior to receiving their hip implant, then continued giving samples on an annual basis.
Urinary Biomarkers Hold Key To Prediction
The researchers were looking for biomarkers, substances present in the body that accompany disease or infection. In particular, the study authors were searching for biomarkers of osteolysis, the common form of bone tissue degradation that often results in implant failure and subsequent revision procedures.
Seven candidate biomarkers were measured, but two in particular stood out, the authors write. A marker called ?-CTX, which indicates the rate at which bone cells break down to release calcium into the blood, predicted the development of osteolysis with “moderate accuracy,” ScienceDaily reports. But taken together with IL-G, a marker of inflammation, the screening test became remarkable.
Using the presence of these two biomarkers as a clue, the researchers were able to predict that several patients would develop osteolysis nearly 6 years before the disorder was diagnosed through imaging tests. All told, the researchers were able to predict the development of osteolysis using these two biomarkers 94.1% of the time.
Are Osteolysis Biomarkers Sign Of “Genetic Risk”?
“Perhaps even more intriguing,” according to study senior author Dr. D. Rick Sumner, was that the two biomarkers were found to be elevated even prior to initial implantation in patients who eventually developed osteolysis. The result, Dr. Sumner says, “support[s] the concept that other researchers have proposed of genetic risk factors for loosening.” In short, patients who have elevated levels of IL-G and ?-CTX could be at-risk for osteolysis even before receiving their hip implants.
“We are hopeful,” Dr. Sumner added, “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.”
Osteolysis & Hip Implant Failure
Osteolysis is fairly common in hip replacement patients. According to authors in The Journal of Bone and Joint Surgery, the condition is usually caused by the hip implant itself, as “particulate debris” from the implant wears away and collects in surrounding soft tissues.
Over time, cyst-like lesions (referred to as “pseudotumors”) develop around the hip replacement, ultimately eating away at the bone and leading in many cases to implant loosening and failure. Adding to the problem, osteolysis around a hip implant can complicate revision surgery; substantial bone loss makes it more difficult to remove and replace the implant.
High Risk: Metal-On-Metal Implants
The risk for osteolysis appears highest in patients with metal-on-metal implants, which are most likely to result in corrosion and particulate debris. In fact, tens of thousands of implant patients have filed product liability lawsuits over the issue, accusing hip implant manufacturers from Stryker and Depuy Synthes to Smith and Nephew of failing to warn the public about these risks.