Noyes and Grood tested ACL bone-ligament-bone specimens from 28 humans (ages 16–86) and 25 rhesus monkeys to failure under high strain-rate conditions. The study asked whether discrepancies between human and animal ACL strength data were explained by donor age, disuse, or testing variables. All specimens were pulled to failure at physiologic strain rates to isolate true ligament material properties from bony insertion effects.
ACL biomechanics data published before 1976 systematically underestimated ligament strength because almost all cadaveric donors were elderly — a population in which bony avulsion, not ligament failure, is the dominant failure mode.
When you select a graft or evaluate a prosthesis for ACL reconstruction, the relevant benchmark is 1730 N (young adult ligamentous failure), not the 620–626 N figures from prior aged-cadaver series. A construct that meets only the older threshold leaves significant margin unaccounted for in an active patient.
This paper also explains why testing conditions matter: slow strain rates and aged or immobilized specimens shift failure to bone avulsion, making the ligament appear weaker than it truly is. High strain-rate testing on young donors is required to capture real ligament material properties.
The clinical corollary: bone loss at the ligament insertion. Whether from age, disuse, or osteopenia. Is the variable that determines whether a knee fails by ligament midsubstance tear or bony avulsion fracture. In older or osteopenic patients, the insertion site, not the ligament collagen, is the limiting structure.
Noyes and Grood tested ACL bone-ligament-bone specimens from 28 humans (ages 16–86) and 25 rhesus monkeys to failure under high strain-rate conditions. The study asked whether discrepancies between human and animal ACL strength data were explained by donor age, disuse, or testing variables. All specimens were pulled to failure at physiologic strain rates to isolate true ligament material properties from bony insertion effects.
ACL biomechanics data published before 1976 systematically underestimated ligament strength because almost all cadaveric donors were elderly — a population in which bony avulsion, not ligament failure, is the dominant failure mode.
When you select a graft or evaluate a prosthesis for ACL reconstruction, the relevant benchmark is 1730 N (young adult ligamentous failure), not the 620–626 N figures from prior aged-cadaver series. A construct that meets only the older threshold leaves significant margin unaccounted for in an active patient.
This paper also explains why testing conditions matter: slow strain rates and aged or immobilized specimens shift failure to bone avulsion, making the ligament appear weaker than it truly is. High strain-rate testing on young donors is required to capture real ligament material properties.
The clinical corollary: bone loss at the ligament insertion. Whether from age, disuse, or osteopenia. Is the variable that determines whether a knee fails by ligament midsubstance tear or bony avulsion fracture. In older or osteopenic patients, the insertion site, not the ligament collagen, is the limiting structure.