This report details a study on the crucial role of graft materials in enhancing the structural stability of a medial opening wedge high tibial osteotomy (MOWHTO). The research investigated the biomechanical impact of using different graft types compared to leaving the osteotomy gap unfilled, providing important insights for surgical best practice. The findings suggest that the inclusion of graft materials significantly improves the static strength of the construct, which is essential for successful bone healing and long-term stability.
Study Design and Key Findings
The study used 15 artificial tibiae, a standard model known for its biomechanical similarity to human bone, to simulate a 10mm biplanar MOWHTO. The specimens were divided into three groups:
- Synthetic Group: Osteotomies were filled with synthetic wedges.
- Allograft Group: Osteotomies were filled with allograft bone wedges.
- Control Group: The osteotomy gap was left unfilled.
All tibiae were fixed with an Activmotion 2 plate and subjected to a static compression test until the construct failed. The results were conclusive:
- Improved Strength: Both the synthetic and allograft groups demonstrated significantly higher ultimate load capacities compared to the control group, which had the lowest failure load (4.5kN). This confirms that any graft material provides superior strength and support to the osteotomy site than leaving it empty.
- Enhanced Stiffness: The use of graft materials resulted in greater stiffness across the osteotomy. Notably, the allograft wedges showed a more balanced stiffness across both the medial and lateral sides of the tibial head, suggesting a more physiologically consistent response to loading. This balance is critical for preventing stress concentration and potential complications.
- Reduced Displacement: The inclusion of a graft was shown to minimise displacement and valgus malrotation of the tibial head under load, highlighting its role in maintaining the integrity of the correction.
The Clinical Importance of Static Strength
The ability of an osteotomy construct to withstand immediate postoperative forces is known as its static strength. This study reinforces that a graft acts as a structural buttress, sharing the load with the fixation plate and providing a more stable environment for healing. While leaving the gap unfilled with a modern locking plate is a viable option for small corrections, this research suggests that for larger osteotomies, a graft is a powerful tool to enhance stability.
These findings have direct clinical implications, guiding surgeons on when and how to use graft materials to optimise surgical outcomes. By providing greater structural support from day one, grafts can help facilitate a more predictable healing process, potentially leading to faster patient recovery and a lower risk of complications.
Professor Wilson’s Comments
“This is another great study that we carried out, exploring different types of graft materials that could be used to fill the gap during opening wedge osteotomy surgery.
Our findings confirmed what experience has consistently shown over the years — bone remains the best graft material of all. Despite two decades of innovation and experimentation with synthetic substitutes and so-called “exciting new materials,” none have truly replicated the biological and mechanical properties of real bone.
While these synthetic substitutes often promise osteointegration and bone-forming potential, in reality, they are expensive, slow to incorporate, and can persist indefinitely — sometimes even causing long-term complications.
In summary: bone is still the gold standard. Nothing heals like bone!”
For an in-depth look at the complete findings and methodology, the full research paper is available for your perusal.
Sources used in report overview:
- https://pubmed.ncbi.nlm.nih.gov/30923931/
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6439028/
- https://www.researchgate.net/publication/286488537_Is_Bone_Grafting_Necessary_in_Opening_Wedge_High_Tibial_Osteotomy_A_Meta-Analysis_of_Radiological_Outcomes
