[00:00:00] Welcome back to another episode of AI Talks with Bone & Joint from the publishers of Bone & Joint Research. Today, we're discussing the paper 'Subluxation-induced liner adhesion and the effect of impaction to prevent liner dislocation in ceramic hip arthroplasty' published in June 2026 by M Uhler and colleagues.
Hello, I'm Lisa, here with my co-host, Brian. This paper examines critical aspects of ceramic-on-ceramic bearings and total hip arthroplasty, focusing on how subluxation-induced liner adhesion and impaction force can prevent liner dislocation.
Ceramic-on-ceramic bearings are known for their low wear and long-term clinical success. However, there's a notable complication, the risk of liner dislocation due to adhesion forces between the ceramic head and liner. This can be a significant failure mode in hip arthroplasties, impacting patient outcomes.
The aim of this study was to investigate [00:01:00] these adhesion forces and to determine whether the design of the implant and the force used to assemble them can influence the likelihood of liner dislocation.
The researchers examined two implant systems, Mathys SeleXys and DePuy Synthes Pinnacle, using two head sizes of 28 millimeters and 36 millimeters and various liner sizes. They measured adhesion forces during subluxation of the ceramic head from the liner and analyzed the forces required to fix the liner into the cup to understand how assembly forces affected the fixation strength.
They worked with three different assembly forces, 1 kN, 2 kN, and 4 kN. They observed a significant difference in adhesion forces between the Mathys SeleXys and Depuy Synthes Pinnacle bearings at the 28 millimeter head size, but not at the 36 size.
The maximum adhesion force reached was 265 N. Moreover, they found that low [00:02:00] liner impaction forces could lead to dislocation due to adhesion.
For an assembly force of 1 kN, the fixation forces were sometimes lower than the corresponding adhesion forces, which is problematic. However, when the assembly forces were increased to two kN or more, the liner fixation force always exceeded the adhesion forces, reducing the risk of dislocation.
So in essence, their conclusion was that a liner impaction force of more than two kN should be applied to prevent the risk of adhesion-related liner extractions. This has practical implications for surgical techniques.
The study also highlighted that different implant designs can significantly affect the fixation strength. Yes, and this brings us to the methods used in this study. The researchers employed a specialized setup to measure adhesion forces at varying distraction speeds and head sizes.
They also applied a standardized assembly force using a servo-hydraulic testing machine. For the adhesion tests, [00:03:00] they used bovine serum as a medium to simulate human synovial fluid. The study showed that the adhesion forces between the head and liner could be significant, especially at higher distraction speeds.
For instance, the DePuy Pinnacle system had higher adhesion forces than Mathys SeleXys across all tested velocities due to its larger equivalent radius. Indeed, and what's noteworthy is that the 36 millimeter heads showed stable adhesion forces across different velocities, suggesting that head size plays a crucial role in how these forces manifest.
This study also used a Pearson correlation to highlight the relationship between the equivalent radius and adhesion forces, finding significant correlations for the 28-millimeter head and some but not all velocities for the 36-millimeter head. The study also examined the liner fixation forces with varying assembly forces.
They [00:04:00] found that higher assembly forces led to greater liner fixation strength. DePuy systems consistently showed higher fixation forces compared to Mathys, likely due to their smaller taper angles, which improve liner retention.
Right. For example, at an assembly force of 4 kN, the DePuy system's fixation forces range from 2521 and a 1/2 N to 2672 N, which is significantly higher than the Mathys system.
It's clear that sufficient assembly force is critical, but it's also important not to exceed force limits to avoid ceramic fractures. The practical takeaway for surgeons is to ensure they apply enough force, at least 2 kN, during impaction to secure the liner properly. This study could very well influence how hip arthroplasties are performed in the future, providing a more biomechanical basis for the procedures.
Absolutely, Lisa. [00:05:00] As we conclude, let's summarize the key insights. Ceramic-on-ceramic bearings are prone to adhesion-related issues that could cause liner dislocation. Higher assembly forces significantly improve liner fixation strength, reducing this risk. This knowledge is crucial for surgeons to optimize implant success and longevity.
Be sure to check out the full paper in the June 2026 issue of Bone & Joint Research. We'll be back with another episode exploring the latest in orthopaedic research. Thanks for joining us, everyone. See you next time!
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