评价人体软骨拉伸性能的数字散斑相关分析

Digital speckle correlation method: a technique to evaluate the tensile property of articular cartilage

目的 建立数字散斑相关分析(DSCM)测量人体软骨拉伸性能的新技术和应用方法。方法 选取因股骨颈骨折而行置换术的股骨头软骨(52岁男性,老年对照者),因骨肉瘤行截肢术(16岁女性,年轻对照者)的胫骨平台和晚发性脊柱骨骺发育不良伴进行性关节病(SEDT-PA)患者(19岁女性)行置换术的股骨头软骨。切取10 mm×4 mm大小全层软骨,应用数字散斑相关分析测量软骨拉伸力学性能,分析在U场和V场方向的变化程度。结果 SEDT-PA患者的软骨表面凸凹不平,变形起伏加大;而两种对照软骨标本变形均匀。老年对照、年轻对照和SEDT-PA的软骨标本在3.3 N载荷级差下的平均应变分别为3800με、8800με和9500με,拉伸弹性模量(E)分别为227.23MPa、89.59 MPa和127.25MPa。老年对照和SEDT-PA患者的软骨标本在沿X方向拉伸移动20个像素点的U方向位移场像素点差异有显著意义(0.101±0.022 vs 0.220±0.053,P=0.023);而沿Y方向拉伸20个像素点的V方向位移场像素点,三者之间差异均有显著意义(0.055±0.018,0.196±0.057 vs 0.658±0.144)。结论 数字散斑相关分析能测定相应的软骨标本的拉伸性能变化,能将因年龄和病变所致的拉伸性能改变区别开来。SEDT-PA患者的关节软骨拉伸功能下降是导致软骨病变的主要原因。

Objective To establish a new technique for evaluation of the tensile property of articular cartilage using digital speckle correlation method ( DSCM) . Methods Three specimens of whole layer articular cartilage of the size of 10 mm × 4 mm were prepared from the cartilage of head of femur replaced from a 52-year-old male suffering from fracture of neck of femur ( old control) , the amputated tibia plateau of a 16-year-old female suffering from osteosarcoma ( young control) , and the cartilage of head of femur of a 19-year-old female suffering from spondyloepiphyseal dysplasia tarda with progressive arthropathy ( SEDT-PA) and then underwent DSCM in U and V fields. Results The specimens of the 2 controls showed a smooth surface of cartilage and homologous deformation while the specimen of the SEDT-PA patient showed a rough surface of cartilage and deformation with increased undulation. Under a changed loading of 3. 3 N the values of average strain of cartilage were 3800, 8800, and 9500 με, and the values of tensile elastic modularity were 227.23, 89.59, and 127.25 MPa respectively for the old control, young control, and SEDT-PA patient. The numbers of pixel in U field after 20 pixels were moved in the X direction were significantly different between the old control subject and the SEDT-PA patient (0. 101 ± 0. 022 vs 0. 220 ± 0. 053, P = 0. 023). The numbers of pixel in V field after 20 pixels were moved in the Y direction were significantly different among the old control subject and the SEDT-PA patient. Differences were also significant among the three kinds of cartilage (0. 055 ± 0. 018,0. 196 ± 0. 057 vs 0. 658 ± 0. 144, both P < 0. 05). Conclusion DSCM is a reliable technique to measure the tensile property of articular cartilage, especially for evaluation of small specimens. SEDT-PA is characterized by a dramatic decrease of tensile property, causing destruction and loss of the articular cartilage.