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Creating a Low Profile Anchor to Eliminate High Profile Suture Knots
Jason L. Green, BS1, Mario Padelli Chee, BS2, Fangqi Gu, BS3, Jane Hung, BS2, Alissa Ebong, BS3, Mohamed Ibrahim, MD4, Jeremy Martinez, BS5, Richard Glisson, BS6, Sabino Zani, Jr., MD7, Ken Gall, Ph.D.8, Howard Levinson, MD9.
1Duke University School of Medicine, Durham, NC, USA, 2Duke University Pratt School of Engineering, Durham, NC, USA, 3Duke University Department of Biomedical Engineering, Durham, NC, USA, 4Division of Plastic and Reconstructive Surgery, Department of Surgery, Duke University School of Medicine, Durham, NC, USA, 5Duke University, Durham, NC, USA, 6Department of Orthopedic Surgery, Duke University Hospital, Durham, NC, USA, 7Department of Surgery, Duke University Hospital, Durham, NC, USA, 8Duke University Department of Mechanical Engineering and Materials Science, Durham, NC, USA, 9Division of Plastic and Reconstructive Surgery, Department of Surgery, Duke University Hospital, Durham, NC, USA.

Purpose
Large sutures, such as mesh suture or tape suture, are used in hernia and tendon repair and have shown enhanced mechanical performance compared to smaller suture. However, a limitation to the use of large suture is knot size. Large sutures produce high profile knots that are susceptible to palpability, infection, and increased foreign body response. The goal of this study was to use 3D printing to develop an anchoring device to replace suture knots. The device was designed to be low profile and to have superior mechanical performance to a knot.
Methods
Flat, cylindrical anchor prototypes were iteratively created using 3-D design software (SolidWorks®) (Figure 1-A) and 3D printed from a Carbon3D printer using liquid polymer resin. After testing multiple iterations of the device, we settled on a male component with four horizontal posts that integrate into opposing holes of a female component. The posts were placed through pores of a hernia mesh, providing multiple fixation points. Each post was designed with a distal element to serve as a locking mechanism when approximated to the female component.
The profile of the anchor was compared to that of a large suture knot (mesh extension, 1cm diameter, 4 throws). Next, monotonic tensile testing of the anchor vs. a knot control in a silicone gel model was performed using an Instron (Figure 1-C) in accordance with ASTM D5034. Failure load and mode of failure were recorded and compared. This was followed by cyclic tensile testing of the anchor and knot control at a range of 10 to 20N (maximum physiologic force on the abdomen is 16N/cm2) at 1Hz for 200 cycles, then pull to failure at a rate of 300mm/min. Cycles until failure, failure load, and mode of failure were recorded.
Results
The profile of the suture anchor (27.5mm2) was ~50% smaller than the large suture knot (50 mm2) (Figure 1-B). During monotonic tensile testing, the anchor had a significantly greater failure load (58 ± 11N) in comparison to the knot control (31 ± 13N) (P< .05). The most common modes of failure were anchor fracture (post breakage) and suture tearing for knot failure. During cyclic tensile testing, the anchor’s failure load (56 ± 8N) was significantly higher than the knot control (30N ± 8N) (P< .05). The most common modes of failure were anchor fracture and knot sliding through the suture tract. The anchor consistently sustained 200 cycles while the knot failed at an average of 134 cycles.
Conclusions
The anchoring device is lower profile than a knot and demonstrates superior mechanical performance. The anchor experiences a significantly greater load at failure in both monotonic and cyclic testing. Additionally, it consistently sustains 200 load cycles, indicating durability. Future efforts will focus on minimizing the anchor profile, creating an anchor applicator for open and laparoscopic applications, and modifying the post mechanism for translation to other suture types.


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