Dorsal cortex line is more reliable than transepicondylar axis for rotation in revision total knee arthroplasty with severe bone loss

Listen to Simon and Amy discuss the paper 'Dorsal cortex line is more reliable than transepicondylar axis for rotation in revision total knee arthroplasty with severe bone loss' published in the December 2024 issue of Bone & Joint Open.

Click here to read the paper.

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Transcript

[00:00:00] Welcome back to another episode of AI Talks with Bone and Joint brought to you by the publishers of Bone and Joint Open. Today we're discussing the paper 'Dorsal cortex line is more reliable than transepicondylar axis for rotation and revision total knee arthroplasty with severe bone loss' published in December 2024 by M. Saltzman, E. Kropp, R. Prill, M. N. Ramadanov, M. Adriani, and R. Becker. 

I'm Simon, and I'm joined by my co-host, Amy. 

Thank you, Simon. I'm quite keen on today's topic because it's both highly technical and incredibly pertinent for orthopaedic surgeons managing complex knee arthroplasties. Let's get started, shall we? Can you give us a bit of background on the importance of this study?

Certainly, Amy. Traditionally, the surgical transepicondylar axis, or sTEA, has been used to determine femoral component rotation in total knee arthroplasty. It's a well established [00:01:00] landmark, but requires intact medial and lateral epicondyles, which can be problematic in cases of severe bone loss, where these epicondyles are often compromised.

Indeed, Simon. Severe bone loss can occur for various reasons, such as periprosthetic fractures, septic or aseptic loosening of the prosthesis, or even tumor-related surgeries. In such cases, identifying a reliable landmark for femoral component rotation becomes quite tricky. Precisely. This is where the dorsal cortex line, or DCL, comes in.

The researchers aimed to determine if the DCL could be a more reliable landmark compared to the sTEA, especially in scenarios of significant bone loss. They analyzed 75 CT scans, defining the DCL as a tangent to the dorsal femoral cortex. located 75 millimeters above the joint line. It's worth noting that these CT scans were measured independently by three experienced [00:02:00] surgeons and the study demonstrated excellent intra- and inter-rater reliability for the DCL. The mean external rotation of the DCL relative to the sTEA was about 9.47 degrees. 

Yes, the reliability was quite impressive. The intraclass correlation coefficient, or ICC, range from 0.80 to 0.99, indicating very good to excellent reliability. This suggests that the DCL can be a consistent landmark for surgeons, even when traditional landmarks are not feasible.

A key takeaway for clinical practice is that the DCL offers a reliable alternative for femoral component rotation in revision TKA. However, they did note some outliers in the study with about 17% of measurements showing deviations greater than four degrees. These outliers highlight that while the DCL is generally reliable, surgeons need to be cautious and ensure proper tracking of the femoral component throughout the knee's [00:03:00] range of motion before finalizing its position.

Another interesting point is the DCL's potential independence from femoral notching. Given that it is located higher along the dorsal cortex, 75 millimeters above the joint line, it can be measured even when significant notching of the ventral femur is present. 

Exactly, this makes the DCL particularly useful in cases of severe bone loss, periprosthetic fractures, or when the entire distal femur is being replaced. It provides a new method to achieve accurate rotational alignment in these challenging scenarios. 

So, to summarize, this study suggests that the DCL could serve as a valuable landmark for femoral component rotation and revision TKA with severe bone loss. It's been shown to be reliable and reproducible with excellent intra- and inter-rater consistency. However, surgeons should remain mindful of the potential for outliers. 

Precisely Amy, the [00:04:00] DCL offers a new and reliable alternative to the sTEA in challenging revision TKA cases. It's a promising development, though as always, surgical judgment and intraoperative verification are crucial. 

That's it for today's episode. We hope you found this discussion on the DCL and its implications for knee arthroplasty just as fascinating as we did. Thank you for tuning in to AI Talks with Bone & Joint. 

Thank you for listening, everyone. Goodbye.