Is there significant variation in the material properties of four different allografts implanted for ACL reconstruction

Abstract

The aims of our study were to: (1) determine if there are differences in the material properties of tendon obtained from implanted tibialis anterior, achilles, bone-patella- bone and tibialis posterior allografts; (2) determine the variability in material properties between the implanted specimens. A total of 60 specimens were collected from fresh frozen allografts implanted at ACL reconstruction. Specimens collected included 15 tibialis anterior, 15 tibialis posterior, 15 achilles and 15 bone-patella-bone tendons. Each specimen was mounted in a custom made cryogrip. The mounted specimens were loaded onto a MTS Testline servo-hydraulic testing machine in a uni-axial tensile test configuration. Specimens were subjected to a strain rate of 5% per second until the ultimate tensile stress (UTS), failure strain and high strain modulus was calculated for each specimen after being normalized for specimen dimensions. Individual material properties were tested using one way analysis of variance (ANOVA) and post hoc Tukey's B test with a P value of <0.05 considered significant. Homogeneity of variance was assessed using the Levene's test. As a result, no significant difference was found between all four grafts with regards to UTS, failure strain or high strain linear modulus. The UTS was plotted against the modulus demonstrating a linear relationship which is typical of soft tissues. Significant variability in the results were observed. In conclusion, there was no significant statistical difference between the material properties of the four tendon allografts tested. But significant variability in results was observed within groups and between groups, which may provide one explanation for the range of results in allograft ACL reconstruction reported in the literature.

Deformation behavior of the iliotibial tract under different states of fixation

“…To consider the cross-sectional areas as rectangular may compromise the measurements [1,24]. Our setup with digital scan resulted in a low standard deviation, as compared to similar tests of Shim et al [37] or Penn et al [35] ( Table 2). The low standard deviation may be interpreted as another result of minimizing material slippage at the specimen-clamp interface.…”

“…However, freezing the specimens for storage does not alter the YM in the defrosted state [36]. Another approach is to investigate bone-specimen-bone allografts [17,35,37,38]: Bone-specimen-bone allografts do not reflect the YM of the specimen solely, because specimens such as the tract insert to the bone via fiber cartilage [14,39]. Shim et al obtained YM values of allografts with a low standard deviation for the transverse ligament of the atlas (294.24 ± 13.97 N/mm 2 [37]).…”

“…Uniaxial material testing is capable of measuring the specimen in total, thus it is severely limited by material slippage. To avoid slippage, one approach is freezing the specimens to the clamps [17,[33][34][35]. The YM is known to be temperaturedependent which has to be taken into account when applying cryo-clamping [26].…”

Fabrication and properties of acellular porcine anulus fibrosus for tissue engineering in spine surgery

“…Due to the anatomy and lamellar architecture of AF, it is difficult to examine variation in mechanical properties by tensile testing as it can be undertaken like a tendon. We thus designed a bone-AF-bone specimen, to examine the differences in the mechanical properties before and after decellularization by tensile testing, using a testing protocol based on work by Woo et al and Penn et al [ 19 , 20 ]. Two parallel bone-AF-bone specimens were obtained from the same level disc and adjacent vertebrae with a width of 5 mm, depth of 8 mm, and bone stump length of approximately 15 mm (Figure 1 A).…”

How Variable Are Achilles Allografts Used for Anterior Cruciate Ligament Reconstruction? A Biomechanical Study

“…48 Despite the popular use of allografts, there is a paucity of data regarding variability in biomechanical properties of processed allografts that are used intraoperatively. 34,52 A study of Achilles allografts by Penn and colleagues 34 showed significant variability in material properties in nonirradiated Achilles allograft. However, to the best of our knowledge, no prior studies have examined the variation in the material properties of low-dose irradiated Achilles allograft used in the operating room for ACLR.…”