Polytetrafluoroethylene (PTFE) as a Suture Material in Tendon Surgery

Summary

The present protocol illustrates a method for assessing the biophysical properties of tendon repairs ex vivo. A polytetrafluoroethylene (PTFE) suture material was evaluated by this method and compared to other materials under different conditions.

Abstract

With the evolution of suture materials, there has been a change in paradigms in primary and secondary tendon repair. Improved mechanical properties allow more aggressive rehabilitation and earlier recovery. However, for the repair to hold against higher mechanical demands, more advanced suturing and knotting techniques must be assessed in combination with those materials. In this protocol, the use of polytetrafluoroethylene (PTFE) as a suture material in combination with different repair techniques was investigated. In the first part of the protocol, both linear tension strength and elongation of knotted against not-knotted strands of three different materials used in flexor tendon repair were evaluated. The three different materials are polypropylene (PPL), ultra-high molecular weight polyethylene with a braided jacket of polyester (UHMWPE), and polytetrafluoroethylene (PTFE). In the next part (ex vivo experiments with cadaveric flexor tendons), the behavior of PTFE using different suture techniques was assessed and compared with PPL and UHMWPE.

This experiment is comprised of four steps: harvesting of the flexor tendons from fresh cadaveric hands, transection of the tendons in a standardized manner, tendon repair by four different techniques, mounting, and measurement of the tendon repairs on a standard linear dynamometer. The UHMWPE and PTFE showed comparable mechanical properties and were significantly superior to PPL in terms of linear traction strength. Repairs with four- and six-strand techniques proved stronger than two-strand techniques. Handling and knotting of PTFE are a challenge due to very low surface friction but fastening of the four- or six-strand repair is comparatively easy to achieve. Surgeons routinely use PTFE suture material in cardiovascular surgery and breast surgery. The PTFE strands are suitable for use in tendon surgery, providing a robust tendon repair so that early active motion regimens for rehabilitation can be applied.

Introduction

The treatment of flexor tendon injuries of the hand has been an issue of controversy for over half a century. Until the 1960s, the anatomical area between the middle phalanx and the proximal palm was named "no man's land", to express that attempts of primary tendon reconstruction in this area were futile, producing very poor results¹. However, in the 1960s, the issue of primary tendon repair was revisited by introducing new concepts for rehabilitation². In the 1970s, with advances in neurosciences, new concepts of early rehabilitation could be developed, including dynamic splints³, but thereafter ....

Protocol

This article does not contain any studies with human participants or animals performed by any of the authors. The use of the human material was in full compliance with the university policy for use of cadavers and recognizable body parts, Institute of Anatomy, University of Erlangen.

1. Harvest the flexor tendons

1. Harvesting the flexor digitorum profundus
   1. Place a fresh cadaveric upper limb on the dissecting table with the ventral-palmar side facing the surgeon. Use a standard hand fixation device to keep the phalanges in the extension.
   2. Note the age and the gender of the deceased.

Results

Tendon repairs: When a two-strand Kirchmayr-Kessler technique was used alone, there was a high rate of slippage with repairs reaching a linear strength of approximately 30 N (Figure 2 and Figure 5A)⁵. In vivo, the tendon of the flexor digitorum profundus can develop linear traction of up to 75 N⁸. Under post-traumatic conditions, this value can be even higher due to friction, swelling, and.......

Discussion

In this line of experiments, a PTFE strand was evaluated as suturing material for flexor tendon repair. The protocol reproduces conditions that are like the in vivo situation in all but two aspects. First, the loads applied in vivo are repetitive, so a cyclically repeated type of loading might be better suitable. Second, over the first 6 weeks postoperatively, the significant shift from biomechanics toward biology as tendon healing progresses, which is a process that cannot be adequately addressed under.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Chirobloc	AMT AROMANDO Medizintechnik GmbH	CBM	Hand Fixation
Cutfix Disposable scalpel	B. Braun Medical Inc, Germany	5518040	Safety one use blade
Coarse paper/ Aluminium Oxide Rhynalox	Indasa	440008	abrasive with a grit size of ISO P60
Fiberloop 4-0	Arthrex GmbH	AR-7229-20	Ultra-high molecular weight polyethylene with a braided jacket of polyester 4-0
G20 cannula Sterican	B Braun	4657519	100 Pcs package
Isotonic Saline 0.9% Bottlepack 500 mL	Serag Wiessner GmbH	002476	Saline 500 mL
KAP-S Force Transducer	A.S.T. – Angewandte System Technik GmbH	AK8002	Load cell
Metzenbaum Scissors (one way, 14 cm)	Hartmann	9910846
Screw grips, Type 8133, Fmax 1 kN	ZwickRoell GmbH & Co. KG,	316264
Seralene 3-0	Serag Wiessner GmbH	LO203413	Polypropylene Strand 3-0
Seralene 4-0	Serag Wiessner GmbH	LO151713	Polypropylene Strand 4--0
Seralene 5-0	Serag  Wiessner GmbH	LO103413	Polypropylene Strand 5-0
Seramon 3-0	Serag Wiessner GmbH	MEO201714	Polytetrafluoroethylene 3-0
Seramon 4-0	Serag Wiessner GmbH	MEO151714	Polytetrafluoroethylene 4-0
Seramon 5-0	Serag Wiessner GmbH	MEO103414	Polytetrafluoroethylene 5-0
testXpert III testing software (Components following)	ZwickRoell GmbH & Co. KG, Ulm, Germany	See following points for components	testing software
Results Editor	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035615
Layout Editor	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035617
Report Editor	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035620
Export Editor	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035618
Organization Editor	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035614
Virtual testing machine VTM	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035522
Language swapping	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035622
Upload/download	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035957
Traceability	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035624
Extended control mode	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035959
Video Capturing	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035575
Plus testControl II	ZwickRoell GmbH & Co. KG, Ulm, Germany	1033655
Temperature control	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035623
HBM connection	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035532
National Instruments connection	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035524
Video Capturing multiCamera I	ZwickRoell GmbH & Co. KG, Ulm, Germany	1035574
Video Capturing multiCamera II	ZwickRoell GmbH & Co. KG, Ulm, Germany	1033653
Measuring system related measuring uncertainty to CWA 15261-2	ZwickRoell GmbH & Co. KG, Ulm, Germany	1053260
Zwick Z050 TN servohydraulic materials testing system	ZwickRoell GmbH & Co. KG, Ulm, Germany	58993	servohydraulic materials testing system