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Published on: September 2, 2025
Age-related differences in hamstring tendon used as autograft in reconstructive anterior cruciate ligament surgery
Dorit Naot1, Ally J Choi2, Matthew Street2
1Department of Medicine, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand. d.naot@auckland.ac.nz.
Insights
Younger hamstring tendons are stiffer, potentially leading to poorer outcomes in anterior cruciate ligament (ACL) reconstructions. Age-related gene expression differences in tendons may explain this increased re-rupture risk in younger patients.
Area of Science:
- Orthopedic surgery
- Biomedical engineering
- Molecular biology
Background:
- Hamstring tendons are common autografts for anterior cruciate ligament (ACL) reconstruction.
- Younger patients experience worse outcomes and higher re-rupture rates after ACL surgery.
Purpose of the Study:
- To investigate age-related differences in hamstring tendon properties.
- To compare tendon samples from donors aged 20 years or younger with those from older donors.
Main Methods:
- Biomechanical testing of tendon samples.
- Electron microscopy for collagen fibril structure analysis.
- Microarray analysis for gene expression profiling.
Main Results:
- Younger tendons exhibited higher stiffness (Young's modulus) than older tendons.
- No significant difference in collagen fibril diameter was observed between age groups.
- 162 genes were differentially expressed, with notable changes in adhesion, migration, and inflammation pathways.
Conclusions:
- Hamstring tendons from younger individuals are stiffer and show distinct gene expression profiles compared to older donors.
- These age-related variations may contribute to poorer graft performance and increased re-rupture risk in younger ACL reconstruction patients.
Purpose:
The hamstring tendon is the most commonly used autograft material in reconstructive surgeries of anterior cruciate ligament (ACL) tears. Younger patients have worse surgical outcomes, with a higher risk of re-rupture. We hypothesized that age-related changes in hamstring tendon properties affect the tendon's propensity to rupture when used as an autograft in ACL reconstructions. The purpose of this study was to compare hamstring tendon samples obtained from people aged 20 years or younger to samples obtained from older people.
Methods:
Superfluous hamstring tendon material was collected from 13 young donors (aged 16-20 years) and 17 older donors undergoing ACL reconstructive surgery. Sections of the tendon samples were used for biomechanical testing, structural analysis of collagen fibrils by electron microscopy, and global analysis of gene expression by microarrays.
Results:
We found that tendon samples from the older group had lower Young's modulus than the younger group (P = 0.015), whereas the stress to failure was similar in the two groups. We found no difference in the average diameter of collagen fibrils between the two groups. Microarray analysis identified 162 differentially expressed genes (fold change ≥ 1.5, P < 0.05), with overrepresentation of several biological processes, including regulation of adhesion, migration, inflammation, and differentiation (fold enrichment > 2.0, false discovery rate P < 0.05).
Conclusion:
The hamstring tendon from younger people has higher stiffness than tendon from older people, and the profile of gene expression in tendon varies with age. These differences may negatively affect the performance of the hamstring tendon in ACL reconstructions in younger people.
