4D X-ray imaging enhances diagnosis of shoulder instability

“We combine high-precision X-ray videos from two perspectives and use them to reconstruct a four-dimensional motion analysis – in other words, a 3D image while the shoulder is moving,” explains Aiyangar. 

The shoulder is the most flexible joint in the human body and therefore prone to dislocation. Although only about two percent of people experience shoulder dislocation in their lifetime, many return for additional care due to recurring instability or dissatisfaction with treatment outcomes. 

“This is particularly problematic with surgical procedures – up to two thirds of patients who have undergone surgery dislocate their shoulder again and come back to seek help. This shows that there is great potential for optimization in diagnostics and treatment planning,” Aiyangar states. 

Currently, shoulder stability is assessed through manual testing by physicians and physiotherapists, with accuracy depending heavily on individual expertise. The new dynamic imaging method provides objective, quantifiable data to assess joint stability and guide treatment decisions. 

“This avoids unnecessary surgical interventions or does not unnecessarily delay sensible ones, thus enabling individually optimized therapy,” Aiyangar adds. 

The system used is a biplanar radiographic imaging setup (DBRI) at sitem-insel in Bern, developed in cooperation with Empa and Inselspital Bern. Test subjects perform controlled shoulder movements while synchronized X-ray images capture the motion. Additional CT scans help reconstruct precise 3D bone models with anatomical reference points. Tracking software then determines joint positions, and an optimization algorithm calculates the motion path. 

This approach captures not only gross movements but also fine rolling and sliding actions of the shoulder joint, with a precision of 0.1 to 0.5 millimeters. 

“This is a decisive step forward, because conventional motion sensors with infrared cameras and markers on the skin are inaccurate by 20 to 40 millimeters – far too imprecise to reliably detect instabilities,” says Aiyangar. 

Next, Empa and Inselspital will conduct a study with about 40 patients suffering from untreated shoulder instability. Participants will undergo imaging before and after targeted muscle training. Musculoskeletal models will help analyze the complex interactions of joints, muscles, and forces. 

The long-term goal is to develop force-controlled kinematic models that enable personalized diagnostics without relying on radiation-based imaging, offering a safer and more comprehensive clinical tool for managing shoulder instability. 

MEDICA-tradefair.com; Source: Empa