Regional mechanical properties of human patellar tendon allografts

Very little is known regarding regional biomechanical properties of patellar tendon allografts. Ten human bone-tendon-bone (BTB) patellar grafts were separated into equal thirds and underwent cyclic and failure testing. Grafts were non-irradiated and processed using proprietary sterilization methods. The central third was the thickest region (4.9 +/- A 0.4 mm) compared to the medial and lateral (p < 0.05). The lateral third was the longest region (58.8 +/- A 8.8 mm) compared to the medial (47.9 +/- A 8.5 mm) and central (47.2 +/- A 8.8 mm) portions (p < 0.05). Cyclic testing demonstrated no regional differences with respect to elongation (n.s.) and creep strain (n.s.). Failure testing demonstrated increased maximum load and stiffness in the central region (1,680 +/- A 418 N and 278 +/- A 67 N/mm, respectively) as compared to the medial (1,033 +/- A 214 N, p < 0.002, 201 +/- A 37 N/mm, p < 0.03) and lateral thirds (908 +/- A 412 N, p < 0.03, 173 +/- A 66 N/mm, p < 0.002). Elongation at maximum load did not vary between regions. Central region maximum stress (41.0 +/- A 12.5 MPa) was greater than that of the medial third (28.1 +/- A 3.6 MPa, p < 0.02), with strain at maximum stress larger in the central third (0.21 +/- A 0.03) compared to lateral (0.16 +/- A 0.03, p < 0.01). The central third of a non-irradiated, human bone-patellar tendon-bone construct is thicker and biomechanically superior to the medial and lateral regions in most respects. These findings reinforce the use of the central third of a patellar tendon allograft in anterior cruciate ligament reconstruction. Further investigations are required to determine whether the decreased biomechanical properties of the medial and lateral third of the BTB construct negatively influence the mechanical function of hemi-BTB grafts.