Hipp J A, Katz G, Hayes W C
Department of Orthopaedic Surgery, Charles A. Dana Research Institute, Beth Israel Hospital, Boston, MA 02215.
Invest Radiol. 1991 Nov;26(11):934-8. doi: 10.1097/00004424-199111000-00003.
The structural consequences of bone density changes associated with lytic metastatic lesions were investigated using an experimental model of regular, lytic metastatic lesions in bone. Circular holes were drilled in the mid-diaphyseal cortex of paired adult canine femora. The region around the defect was demineralized in one bone of each pair with 0.8 N HCl. Specimens were tested to failure in four-point bending. Defect size was determined from conventional planar radiographs as the maximum apparent defect diameter divided by the periosteal diameter. Demineralization resulted in irregular defect geometries, which increased the maximum defect dimension 33% to 57% with respect to the original drill hole diameter. Demineralization resulted in additional strength reductions beyond those expected from the original drill hole alone. Despite the irregular demineralization patterns observed, strength reductions were in close agreement with those predicted from data for regular, nondemineralized holes (r2 = 0.93). The results demonstrate that irregular diaphyseal defect borders may not require more complex fracture risk predictors than can be determined from analytic and experimental studies of regular defect geometries. Our results also demonstrate that errors of over 100% can occur when measuring diaphyseal defect size from radiographs that are not optimally aligned with respect to the defect.
利用骨中规则溶骨性转移瘤的实验模型，研究了与溶骨性转移瘤相关的骨密度变化的结构后果。在成对的成年犬股骨骨干中段皮质上钻出圆形孔。每对骨头中的一根骨头，其缺损周围区域用0.8N盐酸进行脱矿处理。标本进行四点弯曲试验直至破坏。根据传统的平面X线片确定缺损大小，即最大表观缺损直径除以骨膜直径。脱矿导致缺损几何形状不规则，相对于原始钻孔直径，最大缺损尺寸增加了33%至57%。脱矿导致的强度降低超出了仅由原始钻孔预期的强度降低。尽管观察到脱矿模式不规则，但强度降低与根据规则、未脱矿孔的数据预测的结果密切一致（r2 = 0.93）。结果表明，与根据规则缺损几何形状的分析和实验研究确定的骨折风险预测指标相比，不规则的骨干缺损边界可能不需要更复杂的指标。我们的结果还表明，当从与缺损未最佳对齐的X线片测量骨干缺损大小时，可能会出现超过100%的误差。
