Quantitative Analysis of the Weakening Effect of Cortical Windows in Non-Osteoporotic and Osteoporotic Proximal Femurs

Abstract

Introduction: Cortical windows in the proximal femur are used in musculoskeletal tumor surgery for both biopsy and curettage purposes. This study aimed to evaluate the effect of cortical windows on the weakening of the proximal femur under axial and rotational loading using finite element analysis and determine the safe widths, levels, and axial positions. Methods: The proximal femurs of a healthy 37-year-old male and an osteoporotic 76-year-old female were 3D modeled using computed tomography scans. A total of 192 different models were created with 225 mm-long oblong windows with widths of 10, 12.5, 15, and 17.5 mm at 8 different levels and 3 different axial locations. Each model was tested for axial and rotational loading up to failure point. Results: The safe maximum width for all levels and both bones was found to be 10 mm (p0.05). Conclusion: The study quantitatively shows that keeping the width of the cortical window below 15 mm and proximal to the lesser trochanter is an important factor in keeping the fracture risk low during biopsy procedures. Additionally, anterolateral or posterolateral placement of cortical windows does not offer any biomechanical advantages. The findings of this study can help clinicians to avoid iatrogenic fractures during biopsy and curettage procedures.

Keywords

• femur
• finite element analysis
• biomechanics
• bone biopsy