2015 ISAKOS Biennial Congress ePoster #1336

Biomechanical Comparison of Allograft Tendons for Ligament Reconstruction

Jeremiah Palmer, MD, Baltimore, MD UNITED STATES
Joseph Russell, BS, College Park, MD UNITED STATES
Jason Alan Grieshober, MD, Manhattan Beach, CA UNITED STATES
Abigail Iacangelo, BS, College Park, MD UNITED STATES
Benjamin Ellison, BS, College Park, MD UNITED STATES
Hyunchul Kim, MS, Baltimore, MD UNITED STATES
R Frank Henn, MD, Baltimore, MD UNITED STATES
Adam Hsieh, PhD, College Park, MD UNITED STATES
Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA

FDA Status Not Applicable

Summary: Tibialis anterior, tibialis posterior, and peroneus longus soft-tissue allografts exhibit similar structural characteristics when standardized by looped diameter and likely may be used interchangeably.

Abstract:

Background

Ligament reconstruction about the knee is one of the most commonly performed orthopaedic procedures, with over 440,000 in the United States in 2013. Allograft tendons are used in increasing numbers, and recent meta-analyses have demonstrated no significant differences in outcomes when comparing allograft and autograft in anterior cruciate ligament reconstruction. Graft availability and increased costs are potential disadvantages to using allograft, but identifying additional adequate allograft donor sites could help minimize both problems. The aim of this study is to compare the biomechanical properties of three soft-tissue allografts: tibialis anterior (TA), tibialis posterior (TP), and peroneus longus (PL). We hypothesize that these allografts will exhibit similar characteristics when standardized by looped diameter, allowing them to be used interchangeably for ligament reconstructions.

Methods

A total of 141 TA, TP, and PL allograft tendons (n=47 each) were tested. All tissues were donated by RTI Surgical, Inc. and had undergone sterilization via BioCleanse® processing. Each specimen had a looped diameter of 9.0 to 9.5 mm as measured using a standard pull-through gauge. Sample sizes were calculated to detect practical differences with a power of 90% and confidence of 95%. Prior to testing, specimens were thawed and rehydrated. Thickness and width of each strand was measured using a digital caliper and used to calculate the cross-sectional area (CSA). Specimens were then placed into a cryogrip fixture attached to an MTS testing system. A warm water jacket surrounded the gage length to maintain body temperature. Each specimen was pre-tensioned and underwent a protocol to simulate stretch, cyclic loading, and load to failure. Outcome measures included the modulus of elasticity (E) in the linear portion of the ramp load phase, ultimate tensile force (UTF), maximal elongation at failure, ultimate tensile stress (UTS), and ultimate tensile strain (UT?). One-way ANOVA and Tukey post-hoc tests were used for statistical comparisons with significance levels of a = 0.05.

Results

TA, TP, and PL tendons exhibited similar UTF (2,367±652 N, 2,427±697 N, and 2,685±683 N, respectively), maximal elongation (7.67±2.83 mm, 7.08±1.99 mm, and 7.62±2.72 mm), and UT? (0.219±0.081, 0.203±0.057, and 0.218±0.078). PL tendons exhibited significantly greater UTS (54.19±16.96 MPa) compared to both TA and TP (43.58±16.55 MPa and 43.41±14.61 MPa). PL tendons had significantly higher E (500.51±179.87 MPa) compared to TP (416±138.02 MPa) but were similar to TA (426.03±159.62 MPa). These differences appeared to stem from a significantly smaller CSA in PL tendons (51.38±9.74 mm2) compared to TA (57.01±12.08 mm2) and TP (57.89±11.18 mm2).

Conclusions

TA and TP tendons exhibited similar characteristics, implying direct substitution is possible without any biomechanical consequences. The PL group was structurally similar with no difference in maximal elongation and UTF, but had significantly smaller CSA, higher UTS (versus TA and TP) and higher E (versus TP). The smaller CSA (despite similar looped diameter) may have been due to the more fan-like shape of the graft as opposed to the more cylindrical TA and TP grafts.