2017 ISAKOS Biennial Congress ePoster #308

 

Multi-Walled Carbon Nanotube: A New Potential Ideal Material of Synthetic Ligament Graft

Fang Wan, MD, PhD, Shanghai CHINA
Yifan Xu, PhD, Shanghai CHINA
Fang Chai, MD, Shanghai CHINA
Jia Jiang, MD, PhD, Shanghai CHINA
Huisheng Peng, Prof., Shanghai CHINA
Shiyi Chen, MD, PhD, Prof., Shanghai CHINA

Fudan University, Shanghai, Shanghai, CHINA

FDA Status Not Applicable

Summary

We successfully fabricated a brand new material for synthetic ligament graft with multi-walled carbon nanotube that had both better mechanical and biological properties than traditional PET ligament.

Abstract

Background

Current studies of synthetic ligament grafts are mainly around the material called polyethylene terephthalate (PET) that is generally used on sports medicine surgery. Despite its wide application, there are still some intrinsic weaknesses that cannot be easily compensated. Till now, the ideal material for synthetic ligament graft still remains undiscovered. In recent years, carbon nanotubes (CNTs) have been extensively explored as a functional material due to their unique one-dimensional structure and remarkable properties including their light weight, high tensile strength and large surface area. However, CNTs can only be fabricated into microscopic level in the past. Recently, we used aligned technology that can assemble multi-walled carbon nanotube (MWCNT) fibers into macroscopic level. So it became possible to fabricate a MWCNT synthetic ligament graft. Then we investigated its potential of being a new potential ideal material of synthetic ligament graft on rabbit ACL reconstruction model.

Method

The CNT fibers were dry-spun from spinnable CNT arrays with a thickness of ~250 µm synthesized by chemical vapor deposition and reported elsewhere. Multi-plied CNT fibers were bundled together with one end fixed on a motor shaft and the other at a movable block. The final MWCNT synthetic ligament for rabbit knee was 2mm in diameter and 6cm in length for ACL reconstruction procedure. Mechanical test was performed on both the CNT and the PET ligament on the same size (n=5, respectively) ex vivo. Two types of the synthetic ligament for New Zealand rabbits were prepared and sterilized by Co 60 radiation before the surgery. 24 male rabbits were randomly divided into 2 Groups. ACL reconstruction were performed on them with MWCNT synthetic ligaments (MWCNT group, n=12) and PET synthetic ligaments as control. (PET group, n=12) After opening the knee joint capsule, the native ACL was visualized and resected. The femoral tunnel and tibial tunnel were drilled at the center of the ACL remnants with 2.0mm K-wire. After suture fixation of the ligament, the wound was closed. The animals were allowed free movement and received short term antibiotics injection. They were sacrificed and the samples were harvested at 1 and 3 months after the surgery. Biomechanical pull-out tests, Micro-CT scan and histological morphology were proceeded on the samples to evaluate the graft tunnel interface and the healing progress.

Results

The maximum force of PET and MWCNT ligaments are 230.2±8.9 N and 612.8±12.3 N ex vivo respectively. All test subjects remained well-being without any loss of weight until the sacrifice. No carbon fragment is visualized in the joint space during macroscopic inspection.1 month after surgery, MWCNT group exhibited slightly higher maximum loads of 122.2 ± 5.7 N, compared with the PET control group (50.3 ± 4.5 N). Notably, the maximum load of MWCNT group was 254.4± 11.2 N at 3-month time point that is significantly higher than with the PET control group (85.3 ± 8.4 N). In morphologic analysis of histology, significant amount of new bone tissue could be observed both at the periphery and in the centre of the bone tunnel in the CNT group. Moreover, micro CT scan showed significant higher density of the bone tunnel in the MWCNT group than in the PET control group.

Conclusion

We successfully fabricated a brand new type of synthetic graft with MWCNT material that had both better mechanical and biological properties than traditional PET ligament. However, more animal and cell studies should be proceeded to confirm the safety and reliability of the CNT ligament.