The study was conducted with funds from the Sana Hospital Hof. Furthermore, authors want to thank Ms Hafenrichter (Serag Wiessner, Naila) for her untiring help with the experiments.

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
<ol>
	<li>Harvesting the flexor digitorum profundus
	<ol>
		<li>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.</li>
		<li>Note the age and the gender of the deceased.</li>
		<li>Using a No. 15 scalpel, place a median longitudinal incision at the index finger on the palmar side beginning from the distal phalanx distally toward the A1 pulley22 over the metacarpophalangeal joint22.</li>
		<li>Sever the A1 and A2 pulleys22 longitudinally without injuring the flexor tendons. Sever the flexor digitorum profundus22 at the level of the distal interphalangeal joint using a scalpel.</li>
		<li>Use the band of a surgical lap sponge to set the tendon under traction and retrieve the flexor digitorum profundus at the level of the A1 pulley.</li>
		<li>Make a 6 cm transversal incision on the rascetta crease22 using a No. 15 scalpel.</li>
		<li>Make another transversal incision 10 cm proximal to the rascetta.</li>
		<li>Now make a longitudinal incision at the median of the palmar side of the forearm, connecting the two aforementioned transversal incisions.</li>
		<li>Develop two opposing skin flaps at the level of the forearm fascia to expose the flexor tendons. The flexor tendons are readily identifiable under the skin.</li>
		<li>Again, use the band of a surgical lap sponge to place the flexor digitorum tendon under traction and retract the tendon proximal to the wrist.</li>
		<li>Now, sever the tendon at the musculotendinous junction for maximal tendon length by using a No. 11 scalpel.</li>
		<li>Place the tendon specimen into 500 mL of 0.9% saline solution.</li>
		<li>Repeat steps 1.1.1 to 1.1.12 for the third to fifth fingers.</li>
	</ol>
	</li>
	<li>Harvesting of the flexor digitorum superficialis
	<ol>
		<li>Sever the tendon of the flexor digitorum superficialis of the index finger proximal to the wrist at the tendino-muscular junction, where the whitish tendon changes into brownish muscle tissue.</li>
		<li>Now use the band of a surgical lap sponge to retract the tendon at the site of the A1 pulley of the index finger.</li>
		<li>Sever the vinculae22 of the tendons in the palm.</li>
		<li>Retract the flexor digitorum superficialis22 distally to the proximal interphalangeal joint.</li>
		<li>Use a No. 15 scalpel to sever the flexor digitorum superficialis at the chiasma, just at the proximal interphalangeal joint22.</li>
		<li>Place the tendon specimen into 500 mL of 0.9% saline solution.</li>
		<li>Repeat step 1.2.1 to 1.2.6 for the third to fifth fingers.</li>
	</ol>
	</li>
	<li>Harvesting of the flexor pollicis longus22
	<ol>
		<li>Use a No. 15 scalpel to make a 9 cm longitudinal median incision at the palmar side of the thumb from the distal phalanx until the A1 pulley.</li>
		<li>Incise longitudinally the A1 and A2 pulleys.</li>
		<li>Expose the flexor tendon of the thumb, and by using a No. 15 scalpel sever the tendon at its insertion over the base of the distal phalanx.</li>
		<li>Using of the band of a surgical lap sponge, retract the tendon at the level of the A1 pulley.</li>
		<li>At the surgical site proximal to the wrist, find the flexor pollicis longus tendon at the radial-most corner of the flexor compartment and retract it with a band of a surgical lap sponge.</li>
		<li>Sever the tendon at the musculotendinous junction.</li>
		<li>Place the tendon specimen into 500 mL of 0.9% saline solution.</li>
	</ol>
	</li>
</ol>
2. Transection of the tendon (Figure 1)
<ol>
	<li>Fix the tendon specimen on an expanded polystyrene plate with pins or 18 G cannulas.</li>
	<li>Transect the tendon in the middle using a scalpel with a No. 11 blade. 
	&#8203;NOTE: Do not transect the tendon twice or the length will not be sufficient for stable mounting onto the servohydraulic measuring machine.</li>
</ol>
3. Tendon repair
<ol>
	<li>Kirchmayr-Kessler two-strand core repair with the Zechner and Pennington modifications18,19 (Figure 2)
	<ol>
		<li>Use a No. 11 blade and make a 5 mm stab incision in the midline of the right-handed part of the tendon, approximately 1.5 cm from the stump (i.e., the site of the severed tendon).</li>
		<li>Through this incision insert the sharp round needle of the suture and exit at the side of the tendon on the same level toward the surgeon. This pass of the needle needs to be on the superficial plane.</li>
		<li>Now insert the needle at the surface of the tendon approximately 3 mm further to the right and dive into the deep plane.</li>
		<li>Exit at the stump and insert the needle at the exact opposite side at the left-handed part of the tendon.</li>
		<li>Emerge at the surface of the tendon, at the side nearest to the surgeon, approximately 1.8 cm from the stump.</li>
		<li>Now enter the side of the tendon 3 mm toward the stump and follow a path transversely to the tendon. Exit at the side opposite to the surgeon.</li>
		<li>Enter the surface of the tendon 3 mm further from the stump and follow a deep plane exiting at the left stump.</li>
		<li>Enter the right stump and follow a longitudinal deep plane until exiting at the surface of the tendon approximately 1.8 cm from the stump.</li>
		<li>Insert the needle at the far side of the tendon, at the level of the initial stab incision. Emerge from the stab incision.</li>
		<li>Tie a surgical knot with eight throws, alternating the direction manually23.</li>
	</ol>
	</li>
	<li>Adelaide cross-lock four-strand core repair11,19 (Figure 2)
	<ol>
		<li>Insert the needle into the left stump of the transected tendon. Follow the path of the tendon on the surgeon&#39;s side for 1.5 cm and exit at the surface of the tendon. Insert the needle 3 mm to the left and take a bite of 3 mm, exiting toward the surgeon.</li>
		<li>Insert the needle 3 mm to the right, next to the exit point of the first path and follow the tendon to the very side until the left stump. Insert the needle into the right stump in a path at the very outer part of the tendon. Exit approximately 1.5 cm to the right of the stump.</li>
		<li>Now insert the needle again at 3 mm to the right and take a grasp, exiting at the side of the tendon.</li>
		<li>Insert the needle back toward the right stump, entering approximately 3 mm to the left. Exit at the right stump and enter again into the left stump for 1.5 cm. Grasp a portion of the tendon of 3 mm with the suture and exit near the midline.</li>
		<li>Reinsert the needle 3 mm nearer to the stump and follow the direction of the tendon to the right, making sure to exit at the stump.</li>
		<li>Insert the needle into the right stump and follow the tendon fibers approximately 1.5 cm to the right. Exit at the surface.</li>
		<li>Re-enter the tendon further to the right (3 mm) and take a grasp, aiming to the far side. Insert the needle 3 mm to the left and follow the tendon exiting at the stump. Now tie a surgical knot with eight throws, alternating the direction manually.</li>
	</ol>
	</li>
	<li>M-Tang six-strand core repair11 (Figure 2)
	<ol>
		<li>Insert the needle of the loop approximately 1.5 cm from the right stump of the tendon and grasp a portion of the tendon of approximately 3 mm in size.</li>
		<li>Pass the needle through the loop and insert the needle into the surface of the tendon.</li>
		<li>Follow the path of the tendon and exit between the stumps.</li>
		<li>Reinsert the needle into the opposite stump and follow the tendon in the deep plane for 1.8 cm. Exit at the surface of the tendon.</li>
		<li>Now enter 3 mm near the stump and follow a transversal path to the far side of the tendon and exit there.</li>
		<li>Insert the needle bearing the loop 3 mm to the left, further away from the stumps. Follow the path of the tendon and exit between the stumps. Re-enter at the opposite stump and exit 1.5 cm to the right at the surface of the tendon.</li>
		<li>Cut one of the two strands arming the needle with scissors.</li>
		<li>Insert the needle and grasp a 3 mm portion of the tendon.</li>
		<li>Now manually tie a surgical knot with eight throws, alternating the direction23.</li>
		<li>Take another loop suture and perform a Tsuge suture24 by grasping a portion of the tendon of approximately 3 mm at 1.5 cm to the right.</li>
		<li>Reinsert the needle and follow the path of the tendon to the left. Exit between the stumps.</li>
		<li>Re-enter into the left stump and follow the path of the tendon for 1.5 cm. Exit at the surface of the tendon.</li>
		<li>Here, cut one of the two strands arming the needle with a pair of scissors.</li>
		<li>Reinsert the needle, grasping 3 mm of the tendon.</li>
		<li>Now manually tie a surgical knot with eight throws, alternating the direction.</li>
	</ol>
	</li>
</ol>
4. Uniaxial tensile test
<ol>
	<li>Set up the tensile testing machine
	<ol>
		<li>Mount the load cell on the upper crosshead of the standard tensile testing system using the connection system and respective bolts.</li>
		<li>Mount the specimen grips on the lower part, moving the crosshead and the load cell using the connection system and respective bolts.</li>
		<li>Switch on the control computer and open the testing software. Wait for the initialization of the tensile testing machine. Click on File &#62; Open and then choose the Zwick test program Simple Tensile Test for Fmax determination. Then click ok.</li>
		<li>Set up the current specimen grip distance by clicking on Machine &#62; Setup. Measure the specimen grip distance using a caliper and write the value in Current tool separation/Current grip to grip separation and click ok.</li>
		<li>Set up the measurement sequence by clicking Wizard. Go to Pre-test and set the grip to grip separation at the start position to 20 cm. Then, tick Pre-load and set the pre-load to 0.50 N. Go to Test parameters and set the Test speed to 300 mm/min. Click on Series Layout to finish the setup process.</li>
		<li>Click Start position to set the grip separation to the start position.</li>
	</ol>
	</li>
	<li>Mounting and testing of the repaired tendon
	<ol>
		<li>Click Force 0 in the testing software directly before the sample mounting.</li>
		<li>Transfer the repaired tendon immediately after repair to the tensile testing machine (Figure 3 and Figure 4) using forceps.</li>
		<li>Insert coarse paper between the specimen grips and the tendon to increase friction during the specimen testing. Close the specimen grips hand-tight and stress-free.</li>
		<li>Click Start to initiate the measurement sequence. The linear traction force is documented by the dedicated testing software. Document the maximum force prior to failure.</li>
		<li>Inspect the construct visually and document the sample photographically with any commercial camera. Define the mode of failure based on the subsequent classifications:
		<ol>
			<li>Slippage: The loops of the suture material slip through the tendon and the suture pulls out.</li>
			<li>Knot failure: The knot fails and unties.</li>
			<li>Break: Rupture of suture. 
			NOTE: Taking a photo of the failed specimen is just for qualitative purposes, not for a measurement, and therefore it does not have to be in a standardized way. For example, no standard light or distance.</li>
		</ol>
		</li>
		<li>Export raw data (force-displacement-data) in the form of a Table (.xls file) for graphic representation. Summarize the results in a table of values expressed in Newton (N).</li>
	</ol>
	</li>
</ol>

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The authors declare that they have no conflict of interest. There is no funding source.

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...

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 only marginal improvements could be achieved. Recently, new materials were introduced with significantly improved integral stability4,5 so that technical issues other than the failure of the suture materials came into focus, including cheese wiring and pullout6. 
Until recently, polypropylene (PPL) and polyester were widely used in flexor tendon repairs. A 4-0 USP (United States Pharmacopeia) strand of polypropylene corresponding to a diameter of 0.150-0.199 mm exhibits a linear tensile strength of less than 20 Newton (N)6,7, whereas flexor tendons of the hand can develop in vivo linear forces of up to 75 N8. After trauma and surgery, because of edema and adhesions, the resistance of the tissue advances more9. Classical techniques of tendon repair included two-strand configurations that had to be reinforced with additional epitendinous running sutures3,10. Newer polyblend polymer materials with substantially higher linear strength have brought about technical developments4; a single polyblend strand with a core of long chain ultra-high molecular weight polyethylene (UHMWPE) in combination with a braided jacket of polyester in the same diameter as PPL can withstand linear forces of up to 60 N. However, extrusion technologies can manufacture monofilamentous polymer strands exhibiting comparable mechanical properties6. 
Repair techniques have also evolved in the last decade. Two-strand tendon repair techniques have given way to more elaborate four- or six-strand configurations11,12. By the use of a looped suture13, the number of knots can be diminished. By combining newer materials with newer techniques, an initial linear strength of over 100 N can be achieved4. 
An individualized rehabilitation regimen should be advocated in any case, taking into account special patient attributes and tendon repair techniques. For instance, children and adults unable to follow complex instructions for a long time should be subjected to delayed mobilization. Less strong repairs should be mobilized by passive motion alone14,15. Otherwise, early active motion regimens should be the golden standard. 
The overall goal of this method is to evaluate a novel suture material for flexor tendon repair. To commend on the rationale of the protocol, this technique is an evolution of formerly validated protocols found in the literature4,10,12,16 as a means of assessment of suture materials under conditions that resemble clinical routine. Using a modern servohydraulic materials testing system, a traction velocity of 300 mm/min can be set resembling in vivo stress, in contrast to earlier protocols using 25-180 mm/min4,10, accounting for limitations in software and measurement equipment. This method is suitable for ex vivo studies on flexor tendon repairs, and in a wider sense for evaluation of the application of suture materials. In materials sciences, such experiments are routinely used to evaluate polymers and other classes of materials17. 
Phases of the study: The studies were performed in two phases; each was divided into two or three subsequent steps. In the first phase, a polypropylene (PPL) strand and a polytetrafluoroethylene (PTFE) strand were compared. Both 3-0 USP and 5-0 USP strands were utilized to mimic the real clinical conditions. The mechanical properties of the materials themselves were first investigated, although being medical devices, these materials have been extensively tested already. For these measurements, N = 20 strands were measured for linear tensile strength. Knotted strands were also investigated since knotting alters linear tension strength and produces a potential breaking point. The main part of the first phase was about testing the performance of the two different materials under clinical conditions. In addition, 3-0 core repairs (two-strand Kirchmayr-Kessler with the modifications of Zechner and Pennington) were performed and tested for linear strength. For an additional wing of the investigation, an epitendinous 5-0 running suture was added to the repair for additional strength18,19. 
In a subsequent phase, a comparison between three suturing materials was performed, including PPL, UHMWPE and PTFE. For all comparisons, a USP 4-0 strand was used, corresponding to a diameter of 0.18 mm. For a complete list of the materials used, refer to the Table of Materials. For the final step, an Adelaide20 or a M-Tang21 core repair was performed as described earlier.

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

polytetrafluoroethylene (ptfe) as a suture material in tendon surgery

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.

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...

Watch this Scientific Journal Video about Polytetrafluoroethylene PTFE as a Suture Material in Tendon Surgery at JoVE.com

Polytetrafluoroethylene PTFE as a Suture Material in Tendon Surgery

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.

Polytetrafluoroethylene (PTFE) as a Suture Material in Tendon Surgery

With the evolution of suture materials, there has been a change in paradigms in primary and secondary tendon repair. Improved mechanical properties allow ...

polytetrafluoroethylene-ptfe-as-a-suture-material-in-tendon-surgery

Research

JoVE Journal

Medicine

3.1K Views.  University of Erlangen Medical Center. Met dit protocol konden we de mechanische eigenschappen van een buigpeesreparatie beoordelen. Nieuwe ontwikkelingen, zoals lineaire spanningssterkte, kunnen op deze manier betrouwbaar worden geëvalueerd. Zelfs kleine verschillen kunnen worden gedetecteerd.Plaats om te beginnen een verse cadaverische bovenste ledemaat op de ontleedtafel, met de ventrale palmarzijde naar de chirurg gericht. Plaats met behulp van een scalpel nummer 15 een mediane longitudinale incisie bij de wijsvinger a...

Video: Polytetrafluoroethylene PTFE as a Suture Material in Tendon Surgery

A Strategy to Identify de Novo Mutations in Common Disorders such as Autism and Schizophrenia

There are several lines of evidence supporting the role of de novo mutations as a mechanism for common disorders, such as autism and schizophrenia. First, the de novo mutation rate in humans is relatively high, so new mutations are generated at a high frequency in the population. However, de novo mutations have not been reported in most common diseases. Mutations in genes leading to severe diseases where there is a strong negative selection against the phenotype, such as lethality in embryonic stages or reduced reproductive fitness, will not be transmitted to multiple family members, and therefore will not be detected by linkage gene mapping or association studies. The observation of very high concordance in monozygotic twins and very low concordance in dizygotic twins also strongly supports the hypothesis that a significant fraction of cases may result from new mutations. Such is the case for diseases such as autism and schizophrenia. Second, despite reduced reproductive fitness1 and extremely variable environmental factors, the incidence of some diseases is maintained worldwide at a relatively high and constant rate. This is the case for autism and schizophrenia, with an incidence of approximately 1% worldwide. Mutational load can be thought of as a balance between selection for or against a deleterious mutation and its production by de novo mutation. Lower rates of reproduction constitute a negative selection factor that should reduce the number of mutant alleles in the population, ultimately leading to decreased disease prevalence. These selective pressures tend to be of different intensity in different environments. Nonetheless, these severe mental disorders have been maintained at a constant relatively high prevalence in the worldwide population across a wide range of cultures and countries despite a strong negative selection against them2. This is not what one would predict in diseases with reduced reproductive fitness, unless there was a high new mutation rate. Finally, the effects of paternal age: there is a significantly increased risk of the disease with increasing paternal age, which could result from the age related increase in paternal de novo mutations. This is the case for autism and schizophrenia3. The male-to-female ratio of mutation rate is estimated at about 4&#x2013;6:1, presumably due to a higher number of germ-cell divisions with age in males. Therefore, one would predict that de novo mutations would more frequently come from males, particularly older males4. A high rate of new mutations may in part explain why genetic studies have so far failed to identify many genes predisposing to complexes diseases genes, such as autism and schizophrenia, and why diseases have been identified for a mere 3% of genes in the human genome. Identification for de novo mutations as a cause of a disease requires a targeted molecular approach, which includes studying parents and affected subjects. The process for determining if the genetic basis of a disease may result in part from de novo mutations and the molecular approach to establish this link will be illustrated, using autism and schizophrenia as examples.

Molecular genetic strategy for finding de novo mutations causing common disorders such as autism and schizophrenia.

There are several lines of evidence supporting the role of de novo mutations as a mechanism for common disorders, such as autism and schizophrenia. First, ...

The In ovo CAM-assay as a Xenograft Model for Sarcoma

Sarcoma is a very rare disease that is heterogeneous in nature, all hampering the development of new therapies. Sarcoma patients are ideal candidates for personalized medicine after stratification, explaining the current interest in developing a reproducible and low-cost xenotransplant model for this disease. The chick chorioallantoic membrane is a natural immunodeficient host capable of sustaining grafted tissues and cells without species-specific restrictions. In addition, it is easily accessed, manipulated and imaged using optical and fluorescence stereomicroscopy. Histology further allows detailed analysis of heterotypic cellular interactions.
This protocol describes in detail the in ovo grafting of the chorioallantoic membrane with fresh sarcoma-derived tumor tissues, their single cell suspensions, and permanent and transient fluorescently labeled established sarcoma cell lines (Saos-2 and SW1353). The chick survival rates are up to 75%. The model is used to study graft- (viability, Ki67 proliferation index, necrosis, infiltration) and host (fibroblast infiltration, vascular ingrowth) behavior. For localized grafting of single cell suspensions, ECM gel provides significant advantages over inert containment materials. The Ki67 proliferation index is related to the distance of the cells from the surface of the CAM and the duration of application on the CAM, the latter determining a time frame for the addition of therapeutic products.

The In ovo CAM-assay as a Xenograft Model for Sarcoma

The in ovo chorioallantoic membrane (CAM) is grafted with fresh sarcoma-derived tumor tissues, their single cell suspensions, and permanent and transient fluorescently labeled established sarcoma cell lines. The model is used to study graft- (viability, Ki67 proliferation index, necrosis, infiltration) and host (fibroblast infiltration, vascular ingrowth) behavior.

Sarcoma is a very rare disease that is heterogeneous in nature, all hampering the development of new therapies. Sarcoma patients are ideal candidates for ...

Wet Chemistry and Peptide Immobilization on Polytetrafluoroethylene for Improved Cell-adhesion

Endowing materials surface with cell-adhesive properties is a common strategy in biomaterial research and tissue engineering. This is particularly interesting for already approved polymers that have a long standing use in medicine because these materials are well characterized and legal issues associated with the introduction of newly synthesized polymers may be avoided. Polytetrafluoroethylene (PTFE) is one of the most frequently employed materials for the manufacturing of vascular grafts but the polymer lacks cell adhesion promoting features. Endothelialization, i.e., complete coverage of the grafts inner surface with a confluent layer of endothelial cells is regarded key to optimal performance, mainly by reducing thrombogenicity of the artificial interface.
This study investigates the growth of endothelial cells on peptide-modified PTFE and compares these results to those obtained on unmodified substrate. Coupling with the endothelial cell adhesive peptide Arg-Glu-Asp-Val (REDV) is performed via activation of the fluorin-containing polymer using the reagent sodium naphthalenide, followed by subsequent conjugation steps. Cell culture is accomplished using Human Umbilical Vein Endothelial Cells (HUVECs) and excellent cellular growth on peptide-immobilized material is demonstrated over a two-week period.

Cell-adhesiveness is key to many approaches in biomaterial research and tissue engineering. A step-by-step technique is presented using wet-chemistry for the surface modification of the important polymer PTFE with peptides.

Endowing materials surface with cell-adhesive properties is a common strategy in biomaterial research and tissue engineering. This is particularly ...

Bioengineering

Oxygen-Glucose Deprivation and Reoxygenation as an In Vitro Ischemia-Reperfusion Injury Model for Studying Blood-Brain Barrier Dysfunction

Ischemia-Reperfusion (IR) injury is known to contribute significantly to the morbidity and mortality associated with ischemic strokes. Ischemic cerebrovascular accidents account for 80% of all strokes. A common cause of IR injury is the rapid inflow of fluids following an acute/chronic occlusion of blood, nutrients, oxygen to the tissue triggering the formation of free radicals.
Ischemic stroke is followed by blood-brain barrier (BBB) dysfunction and vasogenic brain edema. Structurally, tight junctions (TJs) between the endothelial cells play an important role in maintaining the integrity of the blood-brain barrier (BBB). IR injury is an early secondary injury leading to a non-specific, inflammatory response. Oxidative and metabolic stress following inflammation triggers secondary brain damage including BBB permeability and disruption of tight junction (TJ) integrity.
Our protocol presents an in vitro example of oxygen-glucose deprivation and reoxygenation (OGD-R) on rat brain endothelial cell TJ integrity and stress fiber formation. Currently, several experimental in vivo models are used to study the effects of IR injury; however they have several limitations, such as the technical challenges in performing surgeries, gene dependent molecular influences and difficulty in studying mechanistic relationships. However, in vitro models may aid in overcoming many of those limitations. The presented protocol can be used to study the various molecular mechanisms and mechanistic relationships to provide potential therapeutic strategies. However, the results of in vitro studies may differ from standard in vivo studies and should be interpreted with caution.

Oxygen-Glucose Deprivation and Reoxygenation as an In Vitro Ischemia-Reperfusion Injury Model for Studying Blood-Brain Barrier Dysfunction

Ischemia-Reperfusion (IR) injury is associated with a high rate of morbidity and mortality. The goal of the in vitro model of oxygen-glucose deprivation and reoxygenation (OGD-R) described here is to assess the effects of ischemia reperfusion injury on a variety of cells, particularly in blood-brain barrier (BBB) endothelial cells.

Ischemia-Reperfusion (IR) injury is known to contribute significantly to the morbidity and mortality associated with ischemic strokes. Ischemic ...

A Novel Tenorrhaphy Suture Technique with Tissue Engineered Collagen Graft to Repair Large Tendon Defects

Surgical management of large tendon defects with tendon grafts is challenging, as there are a finite number of sites where donors can be readily identified and used. Currently, this gap is filled with tendon auto-, allo-, xeno-, or artificial grafts, but clinical methods to secure them are not necessarily translatable to animals because of the scale. In order to evaluate new biomaterials or study a tendon graft made up of collagen type 1, we have developed a modified suture technique to help maintain the engineered tendon in alignment with the tendon ends. Mechanical properties of these grafts are inferior to the native tendon. To incorporate engineered tendon into clinically relevant models of loaded repair, a strategy was adopted to offload the tissue engineered tendon graft and allow for the maturation and integration of the engineered tendon in vivo until a mechanically sound neo-tendon was formed. We describe this technique using incorporation of the collagen type 1 tissue engineered tendon construct.

In this paper, we present an in vitro and in situ protocol to repair a tendon gap of up to 1.5 cm by filling it with engineered collagen graft. This was performed by developing a modified suture technique to take the mechanical load until the graft matures into the host tissue.

Surgical management of large tendon defects with tendon grafts is challenging, as there are a finite number of sites where donors can be readily ...

Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons

Peripheral epitendinous sutures are believed to enhance core suture strength in tendon repair and decrease the risk of gapping between tendon ends. Here Q suture, an alternative to peripheral sutures, is presented for the use in tendon repair. Its effects on gap formation and tensile strength of the repaired tendons were compared with conventional running peripheral sutures. Three 2-strand sutures and three 4-strand sutures were used in repairing porcine tendons. The time required for performing 2Q and running sutures were recorded. The repaired tendons were subjected to a cyclic loading test, and the cycle number, during which a 2-mm gap was formed, was determined. After the cyclic loading, the gap size at the tendon ends and the ultimate strength of the repaired tendons were measured. Augmentation with the Q sutures reduced the number of tendons showing 2-mm gaps at tendon ends during cyclic loading. With addition of Q sutures 2-strand sutures significantly increased the ultimate strength of the repaired tendons and 4-strand sutures decreased the gap distance at the repair site of tendons. The time required for performing 2Q sutures was significantly less than that for running sutures. Therefore, we conclude that the Q suture is efficient in enhancing the tensile resistance and tendon repair strength and can be an alternative to conventional peripheral sutures.

Here, we present a &#8220;Q&#8221; suture technique that can be performed in tendon repair and its effects on the gap formation and tensile strength of the repaired tendons. Q suture is shown to be efficient in enhancing the tensile resistance and tendon repair strength.

Peripheral epitendinous sutures are believed to enhance core suture strength in tendon repair and decrease the risk of gapping between tendon ends. Here Q ...

Application of Straight-needle, Three-tailed, Knot-free, Peritoneal Sutures in Laparoscopic Transabdominal Preperitoneal Hernia Repair

Laparoscopic transabdominal preperitoneal hernia repair (TAPP) is one of the most widely used methods in inguinal hernia surgery. After the mesh is placed, the peritoneum must be resutured to avoid contact with the tissues and organs in the abdominal cavity. If the peritoneal suture time is too long, the operation and anesthesia time will be prolonged, increasing the burden on the patient. Moreover, improper suture methods cause serious consequences, such as intestinal obstruction and mesh infection.
The straight-needle suture method transforms the three-dimensional spatial configuration of the needle holder and the arc needle tip into a two-dimensional planar structure, which greatly reduces the difficulty of suturing. The three-tailed knot can be anchored at the beginning of the suture by its friction and button effect, which has an exact fixation effect. Thus, the suture does not easily slip, and the time to complete the suturing is shortened. Compared with the traditional suture method, the operator can suture the peritoneum more quickly, beginners can pass through the difficult learning curve faster, and skilled operators can also shorten the total operation time of TAPP to a certain extent. Thus, this suture method is extremely amenable to clinical application.

Here, we present a protocol to introduce a new peritoneal suture method. This method is called straight-needle, three-tailed, knot-free suture, and we will outline the manufacturing method and clinical application of this suture in detail.

Laparoscopic transabdominal preperitoneal hernia repair (TAPP) is one of the most widely used methods in inguinal hernia surgery. After the mesh is ...

Novel PLL-AF Suture Technique for Annulus Fibrosus Repair in Lumbar Endoscopy

A Suture Technique for Ruptured Annulus Fibrosus Following Decompression Under Percutaneous Transforaminal Endoscopic Discectomy

The suture technique for a ruptured annulus fibrosus (AF) under full-endoscopy remains challenging. Direct suturing of a ruptured annular tear after full decompression has been shown to decrease the recurrence rate of lumbar disc herniation during endoscopic surgery. Traditional suture operations under endoscopy involve only simple suturing of the ruptured AF. Due to the weak and poor quality of the AF tissue around the tear portal, using this area as needle insertion points during suturing may lead to insufficient tension and a low success rate of AF closure. Currently, there is no detailed technical illustration based on video for AF tear suturing under lumbar full-endoscopy. We innovatively propose a method of covering and suturing the AF tear by pulling up the posterior longitudinal ligament (PLL) under lumbar endoscopy and using three stitches (PLL-AF suture technique). The patient who received the novel suture technique achieved satisfactory results. Six months after the operation, lumbar MRI showed no evidence of recurrence in the outpatient clinic.

Author Spotlight: Development and Application of a Novel Suture Technique for Annular Fibrosus Repair in Percutaneous Transforaminal Endoscopic Discectomy

This protocol describes an innovative suture technique for ruptured annular fibrosus during percutaneous transforaminal endoscopic discectomy.

The suture technique for a ruptured annulus fibrosus (AF) under full-endoscopy remains challenging. Direct suturing of a ruptured annular tear after full ...

Novel Triple-Loop Technique for Suturing TFCC Injuries without Transosseous Tunnel

Injuries to the triangular fibrocartilage complex (TFCC) are the most common cause of ulnar-sided wrist pain. As deepening of the research on the function and role of the TFCC, various treatment methods have emerged. Surgical treatment is often required for TFCC injuries that do not respond to conservative therapy. Currently, suturing techniques for TFCC injuries primarily include intra-capsular and transosseous tunnel suture techniques. However, traditional intra-capsular suturing has limited effectiveness for deep tears with a foveal footprint contact, while transosseous tunnel techniques pose problems such as difficulty in locating tunnels and ulna fracture. We have developed an improved triple-loop technique for treating Palmer IB-type TFCC injuries. This technique allows for suturing of both the deep and superficial layers of the TFCC without the need for a transosseous tunnel. Clinical follow-up results show that this is a safe, effective, and simple surgical method for treating TFCC injuries. In this article, we also discussed the comparison between the triple-loop surgical approach and other commonly used surgical approaches.

The protocol presented here introduces a new surgical technique for the treatment of triangular fibrocartilage complex injuries.

Injuries to the triangular fibrocartilage complex (TFCC) are the most common cause of ulnar-sided wrist pain. As deepening of the research on the function ...

Q Suture Technique: A Suturing Technique to Reduce Gap Formation and Increase Tensile Strength in Tendon Repair

Source: Mao, W. F., et al., <a href="https://www.jove.com/v/61445">Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons.</a> J. Vis. Exp. (2020).
In this video, we demonstrate suturing techniques &#8212; core suture and Q suture &#8212; to repair the foot flexor tendon in an ex vivo porcine model. Q sutures enhance the strength of the core suture in tendon repair and decrease gapping at the tendon repair site.

Source: Mao, W. F., et al., Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons. J. Vis. Exp. (2020).
In ...

Polytetrafluoroethylene (PTFE) as a Suture Material in Tendon Surgery

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