Arthroscopic knot tying

Terminology

General knot tying principles
The knots
    Non sliding knots
            Revo knot
            Square knot

    Sliding knots
            Duncan loop / hangmans loop - (non locking)
            Nicky's knot
            Field knot
            Giant knot
            SMC knot
            Roeder knot
            Weston knot
            Taut-line hitch
            Buntline hitch
            Tennessee slider

    Modified Mason Allen
 

Terminology

• Suture limbs - free ends of a suture available to be tied.

• Turn - number of twists in a given throw.

• Throw - specific step or layer of the knot.

• Post (limb or strand) - suture limb around which you make a loop.

• Wrapping or loop limb (or strand) - portion of the suture limb that one makes a loop around the post.

• Slack -loose configuration of loop or compound loop, which slides in around the post.

• Half-hitch knot - single turn around the post limb making a loop. It can be both used in sliding or nonsliding conditions.

• Slipknot - formed by sliding the loop strand on the post strand.

• Square throw- simple two throws, which makes a square knot, with each throw having one turn. When tying a square knot, the strands are pulled down in a line, perpendicular to the axis of the knot.

• Reverse slippage (loop security) - knot loosening after placement of the slipknot or first throw half-hitch. Since the knot pusher must be removed to allow passing of further locking hitches, during this stage the slipknot or hitch tend to loosen slightly before final locking.

General Knot-tying Principles:

1. Have only one pair of sutures inside an operative cannula when knot tying, park the additional sutures through an accessory cannula outside the working portal.

2. Place the cannula tip as close as possible to the area being tied,  to minimize soft tissue interposition and suture limb tangling.

3. Maintain tension in the first loop to prevent reverse slippage. Loop security is as important as knot security. Consider a self-locking knot.

4. Pass the knot pusher down one post of the suture through the cannula to make sure the posts (or limbs) of the suture are not tangled and are free of tissue ( consider using double hole knot pusher). Once the suture is untwisted as the pusher is withdrawn, get your assistant to place a finger between the parallel suture limbs. This keeps the suture limbs from re-twisting.

5. Ensure the suture slides freely.

6. Place a “single-hole” knot pusher on the post strand and a mosquito clip onto the end of the limb to “identify” it as the “post”. (Technique varies dependent on the type of knot pusher used). Pass the knot pusher down the cannula again to check the pusher is on the “post” and to double-check for any soft tissue or twists in the suture.

7. The tissues to be tied should be relaxed. Tension on the tissues can be decreased by internally or externally rotating, or abducting or adducting the shoulder to relax the tissues or place traction sutures.

8. Tie the knot and advance it into the joint. Each time the “post strand” is changed, place the knot pusher and mosquito clip on it, to identify the “new” post.

9. Every time the “post” is switched, run the knot pusher down the “new” post to check for twists or soft tissue. (This is an important step and can prevent complications with seating the half-hitch throws).

10. Never tie all loops of your knot around the same post. The best method is alternating post with reversing throws with more than three additional half hitches, regardless of the type of suture material.

11. Use a sliding knot whenever possible.

12. Use a suture anchor with good sliding capability, remember the anchor eyelet orientation.

13. The screw hole made for anchors should be funnel shaped

The knots

Knots can be divided into sliding and nonsliding.

Sliding knots can be further classified into:

• Lockable - theoretically prevent reverse slippage and maintain loop security.

• Nonlockable - require additional locking half-hitches.

In a simple knot, the first throw invariably slips when the knot pusher is withdrawn to place the second throw, locking knots prevent this.

Locking knots may be further divided into: proximal locking, distal locking or middle locking.
Distal locking  prevents knot slippage better than proximal locking, but is difficult to lock when tension in the knot loop is high.

Proximal locking knots can easily be locked under the desired loop tension, but can also easily lose tension during additional locking half-hitches.

Middle-locking knots (SMC) prevents knot slippage maintaining loop security, like distal locking and can also easily be locked like proximal locking knots, even with high loop tension.

Non sliding knots

Revo knot

The Revo knot is a non sliding knot consisting of multiple half hitches made by alternating the post and direction of half hitches.

	Underhand knot is thrown around the post and with the knot pusher on the post strand, the half-hitch is pushed down the post with alternating tension on each strand until the half-hitch is tightened on the tissue.
	Back off the knot pusher while still holding tension on the post strand and throw another underhand half-hitch and similarly push it into the joint until the knot is seated.
	Again, maintaining tension on the post strand, an overhand half hitch is thrown around the post and “walked” down into place.
	This knot is then further tensioned by “past-pointing”, (relax the loop strand and push the knot pusher past the knot on the loop strand and then apply tension to both strands while holding the pusher past the knot. This further tensions the knot). The knot pusher is then switched to the other suture limb, i.e. the “new” post and an underhand half hitch is placed and tensioned.
	The post is again changed and an overhand half hitch is placed and walked down the post and tensioned again by “past-pointing”. The tails of the suture are then cut 3-4mm from the knot.

Alternatively, the half hitches may be “pulled” into the joint by placing the knot pusher on the loop strand “ahead” of the loop to drag it down the post. This allows you to tighten the knot in the joint by “past-pointing”. The above steps are repeated, but by “pulling” instead of pushing. ( This is somewhat easier and smoother than “pushing” the knots down and can help “protect” the suture from breakage if it has become frayed).

Square knot

Square knots are difficult to tie arthroscopically. If tension is applied asymmetrically to the limbs the knot converts to two non-identical half hitches, and once the knot seats it is very difficult to tension. However, this made easier by using mechanical spreader types of knot pusher/tiers.

Place an overhand loop around the post strand and place a single hole knot pusher on the loop limb and pull the loop limb into the joint by passing the knot pusher beyond the loop, holding it in that location and applying tension on the free end of the loop strand to pull the first loop into position. Snug it down by keeping the knot pusher beyond the knot on one side and apply tension on the post limb. Inspect the knot to confirm that it is not a half hitch, and if desired the knot may be clamped from an alternative portal to maintain tension.

Back the knot pusher up the loop suture and pass an underhand loop around the same post and advance it into the joint as above using the knot pusher still on the loop suture. Seat the knot by moving the knot pusher to the post suture and passing it beyond the knot again applying tension to tighten and secure. Additional loops can be applied if needed.
 

Sliding knots

When tying a sliding knot, make the post strand as short as possible and the loop strand as long as possible. (As the knot slides down the post entering the joint, you end up with two fairly even suture limbs.)

Place the knot pusher and mosquito clip on the post strand. The sliding knot is tied around the post strand, tightened, and pushed down into the joint.

Duncan Loop, Hangmans or Fishermans knot

Several variations exist

			Ensure there are no twists or soft tissue entanglements and that the suture slides freely. Begin with two uneven, parallel sutures and grasp them between the thumb and index finger. Throw three to four successive loops around the post with the first around your thumb. Alternatively, make a loop in the loop strand and pinch this between your thumb and index finger followed by the successive 3-4 loops around both the post and loop strand. Then pass the tail of the loop strand up through the loop of suture around your thumb (or pinched between your thumb and index finger) and pull on the two sides of the loop strand to tighten the knot and snug it down tightly. Push the knot into the joint with the knot pusher while pulling on the post strand. Maintain tension on the post and then place the first half hitch on the same post strand. Change the post and place an opposite throw half hitch. Alternate the post and direction of throws to give a total of three to four half hitches to prevent slippage of the sliding knot.

Nicky's knot

SMC knot

	Thread the knot pusher on the post strand (held in the left hand) and place a clamp on the post. Pass the knot pusher into the joint to ensure that there are no twists or obstructing of soft tissue. Arrange the suture so that the original post suture is short.
	Pinch the two strands together between the thumb and index finger, crossing the loop strand over the post.
	Pass the loop suture under and then over both strands.
	Pass the loop strand under the post strand between the two sutures and over the top of the post strand in a direction away from the pinching fingers. There will be a triangular interval formed between the two previous loops over the post strand.
	Feed the free end of the loop strand from bottom to top through this interval under the post strand. A locking loop is created.
	Release the thumb and index finger and place the left index finger into the locking loop from bottom to top to keep it open. Remove all slack with the index finger in place to avoid tightening the locking loop prematurely.
	Pull on the post strand and use the knot pusher to guide the knot down to the tissue. Do not pull on the loop strand until the knot is seated. Maintain tension on the post strand and back off the knot pusher to assess the knot.
	Once satisfied that the knot is well seated, tighten the locking loop by pulling on the loop strand while maintaining pressure on the knot with the knot pusher. The locking loop will slide over the knot pusher and secure the knot by the internal locking mechanism. For further security, an underhand half-hitch is worked down the post suture. An overhand half hitch is next placed on the post and worked down into position onto the knot stack.

Roeder knot

Begin with two uneven, parallel limbs. Throw the first loop around the post strand only, the second loop around both limbs, and the third loop only around the post strand, passing the tail of the loop limb between the two parallel strands, between the second and third loops. The knot is again seated and tensioned and pushed into the joint. This is again secured with a series of half hitches alternating direction of throws and utilizing post switching.
Modified Roeder Knot:
The Roeder knot has been modified in several ways. One way is to add an extra loop around both sutures and again passing the tail between the parallel strands, between the third and fourth strands.

The Lieurance modification is to tie the standard Roeder knot, but after passing the tail between the second and third loops, the tail is then brought back up and through the initial loop and pulled into the joint without pre-tensioning the knot. This provides a “self-locking” knot which is secured with alternating half hitches.

Lieurance-Modified Roeder Knot:
Begin with two uneven, parallel limbs. The short is the “post” and the longer limb is the “loop strand”. Throw the first loop around the post strand only, the second loop around both limbs, and the third loop only around the post strand, passing the tail of the loop limb between the two parallel strands, between the second and third loops. The tail is then brought back up and down through the initial loop. This is then “loosely” tightened, making sure not to pull on the “loop strand” as this will “lock” the knot. This is then pulled into the joint without pre-tensioning the knot. The knot pusher is pushed down on the “post” strand. The “post” strand is then pulled on while pushing down on the knot. With the knot pusher firmly against the knot, the “loop” strand is then pulled, locking the knot. This provides a “self-locking” knot, which does not “back-up” when tension is relaxed on the post. This is then secured with alternating half hitches.

Buntline hitch

	Pull suture ends to form a short post and a long leg. Hold the short strand between your thumb and index finger.
	Loop the long leg around your index finger and under both suture limbs.
	Loop the long limb around and under both limbs a second time.
	Pass the long limb through the first loop made by your index finger.
	Tighten both limbs of the suture. The short limb will become longer than the original long limb.
	Switch posts, loop a surgeon’s double half-hitch behind the knot.
	Slide the surgeon’s half-hitch to the buntline hitch knot.
	Secure the knot by pulling on the shortest limb.

Dines knot

Lafosse Knot

Modified taught line hitch

Tenesee slider

The Tennessee slider is essentially another modification of the Roeder knot. To tie the Tennessee slider, the sutures are again made uneven and parallel. The loop strand is thrown around both the post and loop strand one time and then around the post strand only and is brought up between the parallel limbs between the first and second loops. This is tensioned and pushed into the joint and again backed up by a series of four alternating half hitches with post switching.
 

French knot

Tarbuck knot

Scaffold knot

Modified Mason allen

	The entrance stitch is begun from the edge of the tendon exiting on its superior surface.
	A throw is then made horizontally from the superior to the inferior surface of the tissue.
	The needle is then passed from the inferior to superior surface of the tissue medial to the horizontal stitch.
	The suture is finally passed over the top of the horizontal throw, creating a cruciate configuration.
	This final manoeuvre serves to lock the suture within the tendon, creating superior pull-out strength.

References

Arthroscopic Knot Tying; Seung-Ho Kim, MD, PhD; Jae Chul Yoo, MD; Techniques in Shoulder & Elbow Surgery 4(2):35–43, 2003

Failure characteristics of various arthroscopically tied knots; RK Lieurance, Daniel S. Pflaster, Douglas Abbott, Wesley M. Nottage; Clin orth and related research; 408:311–318, 2003

www.arthroscopy.co.uk

Page created by: Lee Van Rensburg

Last updated: 11/09/2015