The effect of metaphyseal holes and interposition material on the longitudinal growth stimulation of long bones in a rabbit model

Listen to Simon and Amy discuss the paper 'The effect of metaphyseal holes and interposition material on the longitudinal growth stimulation of long bones in a rabbit model' published in the March 2025 issue of Bone & Joint Research.

Click here to read the paper.

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Transcript

[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, 'The effect of metaphyseal holes and interposition material on the longitudinal growth stimulation of long bones in a rabbit model', published in March 2025 by BK Park and colleagues. I am Simon and I'm joined by my co-host Amy.

Hello, Simon, I'm quite excited about today's episode. Let's dive in!

The main motivation behind this research was to understand what influences overgrowth of the tibia, particularly from the metaphyseal hole, created during anterior cruciate ligament, ACL reconstruction in skeletally immature patients. It's a specific issue with considerable consequences.

Exactly Simon. Sometimes skeletally immature patients experience overgrowth leading to length discrepancies or valgus deformities of the tibia after ACL reconstruction. The idea was to study this phenomenon using a rabbit model and see how the location of the [00:01:00] metaphyseal hole and the type of interposition material used, influenced growth stimulation.

Indeed, the researchers used 38 skeletally immature male New Zealand white rabbits for their experiments. They created metaphyseal holes at varying distances from the physis on the left proximal tibia, and try different materials to fill these holes. Then they tested key distances of 5, 10, and 15 millimeters using bone wax, whilst also leaving some holes unfilled or filling them with Tisseel.

The outcomes were fascinating. They discovered that a hole created 10 millimeters distal to the physis and filled with bone wax, significantly stimulated longitudinal growth compared to the control group. Conversely, holes filled with Tisseel or left unfilled did not show significant growth stimulation.

Additionally, radiological and histological analysis showed that overgrowth was more pronounced in the groups with holes drilled at 5 and 10 millimeters distal to the physis compared to the sham group. However, there was no significant difference when the hole was 15 millimeters away.[00:02:00] 

Indeed. Another significant observation was the valgus deformities present in all groups with drilled metaphyseal holes regardless of distance or material used. This suggests that simply creating a metaphyseal hole can lead to angular deformities in the tibia.

The conclusion from this appears to be twofold. First, in procedures like ACL reconstruction or physeal bar excision, one could optimize the location of the metaphyseal hole around 10 millimeters from the physis and using bone wax to stimulate growth or mitigate overgrowth. Second, these results highlight the importance of considering potential angular deformities.

I'm also intrigued by the study's scope. It looked not just at overgrowth, but also at the dynamics of healing and the implications of different interposition materials. For instance, the inert nature of the bone wax helped maintain prolonged growth stimulation while Tisseel didn't have the same effect.

It's a nuanced area of study and understanding the mechanisms behind growth stimulation via [00:03:00] microinstability and hyperaemia provides insights into how these physiological changes occur. The findings could lead to improved surgical techniques that take growth and structural integrity into account.

Indeed, Simon. This research paves the way for further studies potentially with larger animal models to bridge the gap between these findings and human clinical applications. There's plenty of room to explore the long-term effects and implications for paediatric orthopaedics.

Quite so. To summarize, today's discussion covered a significant study on how creating metaphyseal holes and using specific interposition materials can stimulate longitudinal bone growth in rabbits. These findings have intriguing implications for surgical practices in skeletally immature patients.

Well put, Simon. We hope our listeners found this episode as fascinating as we did. Remember to check out the full paper in the March 2025 issue of Bone & Joint Research for a deeper dive into this study.

Thank you for tuning in everyone. Be sure to join us next time for more of [00:04:00] the latest orthopaedic research.

Goodbye for now.