Biomechanical Analysis of Patellar Tendon Allografts as a Function of Donor Age

Abstract

We evaluated the biomechanical properties of patellar tendon allografts from donors aged 18 to 55 years. Bone-patellar tendon-bone complexes were harvested from acceptable donors and processed. Fat and soft tissue were removed, and the tendons were sectioned lengthwise leaving the central third. Area measurements were taken, and mechanical testing was performed. Specimens were pulled to failure at a rate of 10% of the initial length per second. The force at failure, tensile stress, modulus of elasticity, and percent elongation were determined for each specimen. There was no significant correlation (P > 0.05) between age and any of the mechanical properties. Load at failure ranged from 2110 to 4650 N, with a mean of 3424 N. Regression analysis showed slightly decreasing tensile stress with increasing age, but the correlation was not significant. It appears that patellar tendon allografts from donors up to age 55 have similar mechanical properties.

Advanced glycation end-products diminish tendon collagen fiber sliding

“…This echoes previous studies investigating the effects of AGEs in tendon Danielsen and Andreassen, 1988;Reddy et al, 2002;Reddy, 2004;Fessel et al, 2012). However, these findings contradict reports of altered elastic properties in studies on the mechanical properties of aged animal tendons (Vogel, 1978;Dressler et al, 2002;Goh et al, 2008) and on human patellar tendons explants (Blevins et al, 1994;Flahiff et al, 1995;Lewis and Shaw, 1997;Hansen et al, 2010). Such conflicting results clearly suggest that either numerous competing factors can affect tendon stiffness/modulus in the aging process: changes in cross sectional area, age-related differences in water and type-1 collagen content (Couppé et al, 2009), and/or an increase in type V collagen (Magnusson et al, 2008), among others.…”

“…These changes correlate to clinically relevant loss of tissue function (Abate et al, 2011;Fox et al, 2011), increased susceptibility to damage and injury (Dressler et al, 2002), and reduced potential for healing (Bedi et al, 2010). While age-related changes in tendon tissue have been associated with increased stiffness and higher failure, a concurrent age-associated loss of tendon mechanical integrity has been reported for both animals (Vogel, 1978;Dressler et al, 2002;Goh et al, 2008) and humans (Blevins et al, 1994;Flahiff et al, 1995;Lewis and Shaw, 1997;Hansen et al, 2010).…”

Age-related changes in the biomechanics of healing patellar tendon

“…Others have studied the effects of aging on tendon properties in dogs and humans. They found no significant differences in some of the biomechanical properties of tendons with aging (Flahiff et al, 1995;Hubbard and Soutas-Little, 1984;Haut et al, 1992). In our previous study we also found increased amounts of type V collagen and decreased fibril diameters in the patellar tendons.…”

In vitro comparison of tension and stiffness between hamstring tendon and patella tendon grafts

“…For the patella tendon grafts, decreasing the age of the specimens by 40 years could have increased the stiffness by 17 to 50%. 13,24,25 The data indicates that the stiffness decreases following reconstruction for both types of graft, although not as dramatically as the tension. For the current study, and for a previous study focused on dual strand hamstring tendon grafts, 12 relaxation decreased hamstring tendon graft stiffness by approximately 20% from the value at 15 min following application of initial tension.…”