Hip Replacement Study Earns Resident Poster Award

At the conference, which took place March 10-14 in San Diego, Listopadzki presented research describing the use of CT imaging with implant movement analysis to better detect aseptic loosening of prostheses following hip replacement surgery.  

Poster awards at the conference were given for various subspecialities. Listopadzki’s award was in the adult hip reconstruction subspeciality, and winners were chosen by a group of researchers and surgeons who reviewed poster submissions. His poster was titled “CT Using Implant Movement Analysis Software Identifies Clinically Stable Total Hip Prostheses in Patients with Painful Total Hip Replacements.”   

Hip replacement surgery can be necessary to relieve pain from arthritis, injury, and other causes. “While hip replacements are some of the most successful and commonly performed orthopaedic surgeries, there are still complications to deal with,” Listopadzki says. For example, the hip implant can become unstable, which, in the absence of infection, is known as aseptic loosening.

Hip implants contain a coating that encourages the bone to grow into it after it’s been inserted, Listopadzki says. But for reasons not fully known, the bone does not ingrow sufficiently for some patients, resulting in loosening. “Sometimes it can be hard to figure out that that’s the problem. People can have pain after surgery for all sorts of reasons,” Listopadzki says.

To look for aseptic loosening, health care teams will typically take and analyze X-rays to see if the bone is not as thick around the implant as expected or if it has changed positions, Listopadzki notes. Spotting the problem on X-rays can be challenging, however.

So, Listopadzki and his colleagues evaluated the use of CT imaging with implant movement analysis as an additional tool to check for implant loosening. “The goal of our study was to compare the analysis of plain X-rays versus the analysis of this new CT imaging software in a group of patients,” Listopadzki says. The objective was to see which technique could more accurately detect loosening and stability. 

To evaluate, CT scans were taken with the hip in two different positions. “You then look at those CTs and you might be able to see that between the two stressed positions there’s been some tiny amount of movement of the implant,” Listopadzki says.

The software then creates overlays of the bone and implant and can measure precise sub-millimeters of movement. More than 0.5 millimeters of movement was considered loose.

The study involved 80 patients with painful hip prostheses. Comparing X-rays to CT scans with implant movement analysis from these patients revealed both agreement and disagreement in terms of detecting loosening or stability.

Both X-rays and CT scans indicated agreement that 66 of the patients had stable prostheses and eight patients had loose implants. X-rays from six of the patients, however, showed loosening, while CT scans from those same six indicated stability.

Follow-up evaluations of these six patients revealed that all of their implants were stable, meaning the CT scan analysis, not the X-ray analysis, was correct. 

CT scanning is routinely obtained following hip pain. While the CT implant movement analysis software is widely attainable, it’s been more commonly used in Europe, Listopadzki says, as the company that developed the technology is based in Sweden.

As a technique that can be easily implemented, the CT imaging with implant movement analysis could be a helpful addition to using X-rays to detect hip prostheses loosening, Listopadzki adds.

The research and findings that Listopadzki shared at the conference have since been published online in April in the Journal of Arthroplasty.   

Study co-authors are K. Keely Boyle, MD, and Scott R. Nodzo, MD, both current University of Texas Southwestern Medical Center faculty members and former Jacobs School faculty, whom Listopadzki says helped mentor him and provided key input.

Listopadzki says he’s been interested in orthopaedics since he first helped out and scrubbed in an operating room one summer during college. Now, he's pursuing a joint-replacement fellowship, continuing to do work that he says is very gratifying.

“A lot of the work involves restoring someone’s abilities to use their extremities, and that is extremely gratifying.”