肩膝关节软骨组织结构差异相关的生物力学实验研究

Biomechanics study on the joint cartilage structural differences between shoulder and knee

摘要:

目的探讨肩膝关节软骨结构差异相关的生物力学特点。 方法选取6例人体尸体肩膝关节软骨样本，通过苏木精-伊红染色、甲苯胺蓝染色、番红固绿染色等组织学染色方法，观察肩膝关节软骨细胞的排列、软骨层厚度、蛋白多糖及胶原纤维的分布；通过关节软骨静态压痕、疲劳等生物力学实验方法，检测关节软骨应力-应变关系、弹性模量、应力最大值、应力平衡值及最大应力减少量等生物力学参数。 结果肩关节与膝关节软骨在细胞形态、基质成分及排列方式上存在显著差异。膝关节软骨比肩关节软骨厚，分层明显，细胞密度高，异染性更明显。膝关节软骨中的蛋白多糖丰富，胶原纤维更为密集。相反，肩关节软骨较薄、无明显分层、细胞分布稀疏、异染性较少、蛋白多糖含量较少，胶原纤维分布均匀且密度低。疲劳前，肩关节软骨的应力最大值大于膝关节[2.428±0.759) N vs (1.853±0.871) N，P=0.004]；肩关节软骨的应力平衡值大于膝关节[(0.923±0.247) N vs (0.646±0.330) N，P<0.001];肩关节软骨与膝关节软骨的弹性模量差异无统计学意义[中位数14.469(10.637，16.592) Pa vs 11.459(8.543，15.001) Pa，P=0.086]。疲劳后，肩关节软骨的应力最大值大于膝关节[(2.081±0.624) N vs(1.540±0.685) N，P<0.001];肩关节软骨的应力平衡值大于膝关节[(0.870±0.223) N vs (0.596±0.292) N，P<0.001];肩关节软骨与膝关节软骨的弹性模量差异无统计学意义[(15.451±4.517) Pa vs (13.363±6.350) Pa，P=0.117]。 结论膝关节软骨在细胞密度和基质成分上更加丰富，而肩关节软骨则在承受负荷时表现出更高的应力值。在弹性范围内，肩关节的弹性模量提升幅度低于膝关节，且疲劳负荷会增加软骨组织的弹性模量。这些差异可能与两种关节在功能和负荷条件上的不同需求密切相关。

Abstract:

ObjectiveTo explore the biomechanical characteristics related to structural differences in joint cartilage between shoulder and knee. MethodsSix joint cartilage samples from human cadavers(shoulder and knee) were selected. The arrangement of chondrocytes, cartilage thickness, distribution of proteoglycans and collagen fibers were observed with histological staining methods such as hematoxylin and eosin(H-E), toluidine blue, and safranin O-fast green-staining. The biomechanical parameters(stress-strain relationship, elastic modulus, peak force, equilibrium force, and maximum stress reduction) were measured via static indentation and dynamic fatigue testing. ResultsSignificant differences in cell morphology, matrix composition, and chondrocyte arrangement were observed between shoulder and knee cartilage. Knee cartilage was thicker than shoulder cartilage, with distinct stratification, higher cell density, and more pronounced heterogeneous staining. Knee cartilage demonstrated higher proteoglycan content, and exhibited a denser collagen fiber network. In contrast, shoulder cartilage was thinner, lacked distinct stratification, exhibited sparse cell distribution, weaker staining intensity, lower proteoglycan content, and evenly distributed but low-density collagen fibers. Pre-fatigue, shoulder cartilage showed higher peak force [(2.428±0.759) N vs (1.853±0.871) N, P=0.004] and equilibrium force [(0.923±0.247) N vs (0.646±0.330) N, P<0.001] when compared to knee cartilage. No significant differences was found in elastic modulus [median 14.469(10.637，16.592) Pa vs 11.459(8.543，15.001) Pa, P=0.086]. Post-fatigue, the shoulder cartilage retained higher peak force [(2.081±0.624) N vs (1.540±0.685) N, P<0.001] and equilibrium force [(0.870±0.223) N vs (0.596±0.292) N, P<0.001]. There was no significant differences in elastic modulus between the shoulder and knee cartilage [(15.451±4.517) Pa vs (13.363±6.350) Pa, P=0.117]. ConclusionKnee cartilage exhibits higher cell density and matrix complexity, shoulder cartilage demonstrates superior load-bearing capacity with higher stress values. Within the elastic range, the elevation of elastic modulus in shoulder cartilage is lower than knee, and fatigue loading elevates the elastic modulus of both tissues. These differences may be closely related to the distinct functional and loading requirements of the two types of joints.