TTU Home COE Home Mechanical Engineering Orthopaedic Biomechanics Laboratory Projects Quantified Structure-Function

Quantified structure-function relationship for human anterior cruciate ligament

There can be many variables that affect the tensile properties of human ACL. Knowledge of these variables is needed to better understand the tensile behavior of the ACL. The magnitude of the relationship between the variables and the tensile properties is needed to standardize the results before analyzing the results. From an engineering point of view, the size (length, area and volume), composition, and internal structure of the specimen should be the only three factors that affect the structural properties. It is necessary to understand the relationship between the ultrastructure and tensile properties of the ACL in order to understand the mechanical behavior of the tissue.

Measuring ACL fibril Diameter Using Software

 

The purpose of this study was to investigate the existence of sex-based differences in the ultrastructural characteristics of the human anterior cruciate ligament (ACL) as the underlying cause of differences in the structural and mechanical properties between sexes. The ACL of six male and six female cadaveric donors were randomly chosen from a pool of ten male and ten female ACLs that had previously been tested for their structural and mechanical properties. Eighteen tissue samples from the distal, proximal, and middle sections of the anteromedial and posterolateral bundles were analyzed by transmission electron microscopy. Female ACLs exhibited both lower fibril concentration and lower percent area occupied by collagen fibrils (p<0.05) as compared to males. There was also a difference in the fibril diameters (p<0.05); donor, age, height, body mass, and body mass index contributed significantly to this difference. In females, ACL stiffness and modulus of elasticity were highly correlated to fibril concentration (r = 0.96 and 0.97 respectively), and in males ACL failure load and strength were highly correlated to percent area occupied by collagen (r = 0.96 and 0.96 respectively). These differences in ultrastructure may underlie differences in ACL properties between sexes.       a) Distal, F                               b) Middle, F                            c) Proximal, F       d) Distal, M                             e) Middle, M                           f) Proximal, M Figure 1. Sample distal, middle, and proximal cut micrographs (all @ 30,000X) of the female (a, b, c) and male (d, e, f) ACLs.