Edgerton B C, An K N, Morrey B F
Department of Orthopaedics, Mayo Clinic, Rochester, Minnesota 55905.
J Orthop Res. 1990 Nov;8(6):851-5. doi: 10.1002/jor.1100080610.
This study correlated torsional strength reduction with circular defect size in cortical bone, to define the "stress riser" and "open-section" effect of the defects. The experimental model was developed and verified. Circular defects from 10 to 60% of bone diameter were then created in paired sheep femora and the bones loaded to failure. Contrary to theory, this experimental study suggests that small defects (10%) of bone diameter cause no significant torsional strength reduction. A 20% defect caused a 34% decrease in strength, representing the "stress riser" dimension. Defects between 20 and 60% of bone diameter decreased strength linearly as a function of defect size, and thus no discrete "open section" dimension was identified. For circular defects, we were unable to demonstrate a discrete "open-section" effect at which dramatic strength reduction is observed. These data may prove to be helpful when planning surgery that involves placing defects in bone such as for infection, biopsy, and prosthesis removal. The accepted guideline to avoid defects of greater than 50% of the bone diameter may be too great. Our data reveal this 62% reduction in torque strength and 88% energy to failure exist with a 50% circular defect.
本研究将皮质骨中扭转强度降低与圆形缺损大小相关联，以定义缺损的“应力集中器”和“开口截面”效应。建立并验证了实验模型。然后在成对的绵羊股骨中制造直径为骨直径10%至60%的圆形缺损，并将骨头加载至破坏。与理论相反，本实验研究表明，骨直径10%的小缺损不会导致扭转强度显著降低。20%的缺损导致强度降低34%，代表“应力集中器”尺寸。骨直径20%至60%之间的缺损强度随缺损大小呈线性降低，因此未确定离散的“开口截面”尺寸。对于圆形缺损，我们无法证明存在观察到显著强度降低的离散“开口截面”效应。在规划涉及在骨中制造缺损的手术（如感染、活检和假体取出）时，这些数据可能会有所帮助。公认的避免缺损大于骨直径50%的指导原则可能过于严格。我们的数据显示，50%的圆形缺损会导致扭矩强度降低62%，破坏能量降低88%。
