Indentation Depth as an Objective Supplement to Surgeon ‘Thumb Testing’ of Bone

Description

The presentation by Jacob Reeves explores the relationship between indentation depth and bone quality, specifically in the context of shoulder reconstruction surgeries. After completing a postdoctoral investigation at Exactech Inc., he highlights the need for objective measurements of bone quality to enhance implant selection. Traditional methods, like the thumb test, prove insufficiently precise, prompting the investigation into whether indentation metrics can provide a reliable correlation with bone material properties.



A handheld, spring-loaded indentor was developed to assess the impact of different tip shapes and spring energies on the indentation depth in cellular foam blocks designed to mimic bone tissue. Measurements revealed strong correlations between indentation depth and the blocks’ density, compressive stiffness, and modulus, with variations in results based on the applied energy and tool design. The study found that certain combinations of spring energy and tip shape could help distinguish between materials with similar properties effectively.



Despite some limitations—such as the use of foam blocks that may not perfectly replicate human bone tissue—Reeves concludes that the indentation method shows promise as a metric for assessing bone quality during surgeries. He emphasizes the need for further testing before implementing this technique in a clinical setting, as the indentation method is inherently destructive and should be conducted in specific areas to minimize damage.

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