Biomechanical Properties of Small-Size Hamstring Autografts

Abstract

To evaluate small-size hamstring (HS) autografts for biomechanical properties and determine a threshold diameter necessary for appropriate reconstruction. Methods In a controlled laboratory setting, biomechanical testing was performed upon 15 hamstring autografts. The grafts were divided into three groups by diameter, with five grafts each at diameter sizes of 6, 7, and 8 mm. Testing of the specimens was performed using an MTS 858 (Materials Testing System, Eden Prairie, MN). We determined load to failure by looking at the maximum load as well as the stiffness of the graft. Statistical analysis was performed via analysis of variance (ANOVA) testing with Tukey's post-hoc test and P-values set at 0.05. Results There was a significant difference in ultimate tensile strength for the different size grafts: 1990 +/-302.42 N for 6 mm grafts (n=5), 2179 +/-685.36 N for the 7 mm grafts (n=5), and 3074 +/-781 N for 8 mm grafts (n=5). This was statistically significant for the group overall (p=0.039), as well as between the 6 mm and 8 mm grafts (p=0.044). Graft stiffness for the 6 mm grafts was 317 +/-85 N (n=5), 288.6 +/-66 for 7 mm grafts (n=5), and 428.053 +/-83 for 8 mm grafts (n=5). This achieved statistical significance for the group overall (p =0.037) as well as between the 8 mm and 7 mm grafts. Conclusions The biomechanical data presented here demonstrate that graft diameter is highly correlated with ultimate tensile strength and stiffness. Clinical relevance When viewing this biomechanical data in conjunction with prior clinical data, consideration should be given for the supplementation of an HS autograft as the size decreases below 8 mm.

Plastic and elastic biomechanical properties of anterior cruciate ligament autografts

“…The samples were tested using a load frame (Instron 5944, Instron, Canton, MA, USA) (Fig. 1 ), first preloaded to 10 N to remove any slack in the system and cycled ten times from 50 to 250 N at a rate of 1 mm/s to remove any viscoelastic effects during testing [ 18 , 19 ]. The grafts were loaded to failure at 100 N/s.…”

The Correlation Between Graft Size and Graft Failure in Hamstring Autograft Anterior Cruciate Ligament Reconstruction

“…Moreover, surgical experience and magnetic resonance imaging (MRI) studies show significant discrepancies in hamstring size among the population [ 10 , 11 ]. Some biomechanical studies suggest that larger graft sizes are more beneficial as they account for potential strength reduction during graft healing [ 12 ]. Previous studies have also shown that smaller graft sizes are correlated with an increased risk of failure in these patients [ 12 , 13 ].…”

“…Some biomechanical studies suggest that larger graft sizes are more beneficial as they account for potential strength reduction during graft healing [ 12 ]. Previous studies have also shown that smaller graft sizes are correlated with an increased risk of failure in these patients [ 12 , 13 ]. Other studies have also shown that younger age may be associated with graft failure.…”

No Deficits in Functional Outcomes of the Contralateral Limb Are Seen When the Hamstring Is Harvested for Augmentation of Small Diameter Ipsilateral Hamstring Autograft

“… 2 Advantages to the use of hamstring (HS) autograft in comparison with other autograft choices include decreased levels postoperative knee pain, absence of violation to the extensor mechanism, and greater graft tensile strength. 2 , 3 , 4 , 5 However, one notable limitation to the use of HS autografts for ACLR is unpredictable graft sizes, which can range from 6 to 9 mm. 4 , 6 , 7 Although certain patient-specific demographics and cross-sectional measurements on magnetic resonance imaging may be used to help predict legs that will yield a HS autograft diameter less than 8 mm, grafts not exceeding this threshold have been demonstrated to be associated with an increased risk of failure of ACLR.…”