Microstructural and Mechanical Properties of Grafts Commonly Used for Cruciate Ligament Reconstruction

Abstract

Background: Injuries to the anterior cruciate ligament and posterior cruciate ligament are common, and often are treated with reconstruction. Limited quantitative data are available describing material properties of grafts used for reconstructions such as the bone-patellar tendon-bone (BPTB), hamstring tendon (HS), and quadriceps tendon (QT). The purpose of this study was to quantify and compare microstructural and mechanical properties of BPTB, HS, and QT grafts. Methods: Forty specimens (13 BPTB, 13 HS, and 14 QT grafts) from 24 donors were used. Specimens were subjected to preconditioning, stress relaxation, and ramp to failure. Mechanical parameters were calculated for each sample, and polarization imaging was used to evaluate the direction and strength of collagen fiber alignment during testing. Results: QT had the largest modulus values, and HS had the smallest. BPTB exhibited the least disperse collagen organization, while HS were the least strongly aligned. Microstructural properties showed more strongly aligned collagen with increasing load for all grafts. All tissues showed stress relaxation and subtle microstructural changes during the hold period. Conclusions: The mechanical and microstructural properties differed significantly among BPTB, HS, and QT grafts. QT exhibited the largest moduli and greatest strength of collagen alignment, while HS had the smallest moduli and least strongly aligned collagen. Clinical Relevance: This study identified mechanical and microstructural differences among common grafts and between these grafts and the cruciate ligaments they replace. Further research is needed to properly interpret the clinical relevance of these differences.

Donor age and sex have limited effects on the mechanical and microstructural properties of human connective tissues

“…All sample acquisition, sample preparation, mechanical and microstructural testing, and data collection were completed in previously published studies. [12][13][14][15][16][17][18] Samples of 11 different tissues were acquired from a total of 91 donors (48 females, 43 males) with an average age of 56 ± 16 years. The examined tissues, harvested from both the arm and leg (Figure 1 ).…”

“…Detailed information on the dissection techniques of each individual tissue type are included in previous publications. [12][13][14][15][16][17][18] Once harvested, all tissues underwent the same sample preparation procedure before testing. Samples were thinned on a freezing stage (Physitemp Instruments) sledge microtome (Leica 1400, Leica) to a thickness of 0.6-1.0 mm to ensure ample light penetration for collection of the QPLI data: degree of linear polarization (DoLP) and angle of polarization (AoP).…”

“…Analysis and results of mechanical and microstructural data of the 11 tissues were published previously. [12][13][14][15][16][17][18]…”

“…To determine how similar or different each T A B L E 1 Break down for each tissue type of number of male and female donors along with average age and age range ACL: anteromedial and posterolateral bundles; PCL: anterolateral and posteromedial bundles) because previous results indicated significant differences between parameter values for each subsection. [12][13][14][15][16][17][18] Results for other tissues that were split into sub-regions for testing…”

“…The current study evaluated a collection of previously published data that applied a polarized light imaging technique to measure the dynamic microstructural properties of several human soft tissues of interest, while simultaneously quantifying mechanical properties of tissues under load. [12][13][14][15][16][17][18] This new analysis sought to assess the association of age, sex, and tissue type with material properties and test the hypothesis that age and sex will significantly influence the microstructural and biomechanical properties of cadaveric connective tissues.…”