Effects of different microfracture drilling parameters on bone quality: a finite element analysis

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Regenerative medicine

Background:

• Microfracture drilling is a surgical technique to treat cartilage defects in the knee by recruiting bone marrow stem cells.
• Increasing the number of microfracture holes can enhance stem cell outflow for cartilage regeneration.
• Extensive drilling may compromise the mechanical stability of the subchondral bone.

Purpose of the Study:

• To analyze the biomechanical effects of microfracture drilling parameters on subchondral bone stability.
• To investigate the influence of drilling diameter, hole spacing, and depth on bone structure integrity.

Main Methods:

• A finite element model of a human knee joint with a femoral medial condyle cartilage defect was created.
• Microfracture holes of varying diameters (1.0-3.0 mm), depths (10-30 mm), and spacings (1.0-3.0 mm) were simulated.
• Knee joint loading conditions were applied to analyze structural stability and Von Mises stresses using Ansys software.

Main Results:

• Simulated drilling parameters did not exceed the bone's yield strength, indicating no compromise in mechanical integrity.
• Changes in drilling parameters did not negatively affect the bone structure surrounding the microfracture holes.
• The lowest average maximum Von Mises stress and stress on the holes were observed with smaller diameter drills and closer spacing.

Conclusions:

• Microfracture drilling, within the tested parameters, appears to maintain subchondral bone stability.
• Using smaller diameter drills with closer spacing maximizes stem cell recruitment potential while minimizing mechanical stress on the bone.
• This study provides valuable biomechanical data to guide microfracture drilling parameter selection for knee cartilage repair.