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
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Suture limbs - free ends of a suture
available to be tied.
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Turn - number of twists in a given
throw.
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Throw - specific step or layer of the
knot.
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Post (limb or strand) - suture limb
around which you make a loop.
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Wrapping or loop limb (or strand) -
portion of the suture limb that one makes a loop around the post.
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Slack -loose configuration of loop or
compound loop, which slides in around the post.
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Half-hitch knot - single turn around
the post limb making a loop. It can be both used in sliding or nonsliding
conditions.
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Slipknot - formed by sliding the loop
strand on the post strand.
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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.
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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.
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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.
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Place the cannula tip as close as
possible to the area being tied, to minimize soft tissue interposition and
suture limb tangling.
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Maintain tension in the first loop to
prevent reverse slippage. Loop security is as important as knot security.
Consider a self-locking knot.
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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.
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Ensure the suture slides freely.
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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.
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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.
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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.
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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).
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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.
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Use a sliding knot whenever possible.
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Use a suture anchor with good sliding
capability, remember the anchor eyelet orientation.
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The screw hole made for anchors
should be funnel shaped
Knots can be divided into sliding and nonsliding.
Sliding knots can be further
classified into:
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.
Conditions |
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Knots |
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Nonsliding |
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Revo (Snyder knot) |
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Half hitch with post switch and reverse throws |
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Square knot |
Arthroscopically difficult |
Sliding |
Non locking |
Modified Duncan loop |
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Modified hangman's loop |
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Locking |
Nicky's knot |
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Field knot |
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Giant knot |
Self locking |
SMC knot |
Self locking, middle |
Roeder knot |
Distal locking |
Weston knot |
Distal locking |
Taut-line hitch |
Proximal locking |
Buntline hitch |
Proximal locking |
Tennessee slider |
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Non sliding knots
The Revo knot is a non sliding knot
consisting of multiple half hitches made by alternating the post and direction
of half hitches.
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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.
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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.
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Again, maintaining
tension on the post strand, an overhand half hitch is thrown around the post
and “walked” down into place.
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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.
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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.
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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 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.
Modified Duncan loop - (non
locking)
Modified hangman's loop - (non
locking)
Nicky's knot
Field knot
Giant knot
SMC knot
Roeder knot
Weston knot
Taut-line hitch
Buntline hitch
Tennessee slider
Duncan Loop,
Hangmans or Fishermans knot
Several variations exist
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Ensure there are no twists or
soft tissue entanglements and that the suture slides freely.
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Begin with two uneven, parallel
sutures and grasp them between the thumb and index finger.
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Throw three to four successive loops
around the post with the first around your thumb.
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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.
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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.
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Push the knot into the joint with the
knot pusher while pulling on the post strand.
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Maintain tension on the
post and then place the first half hitch on the same post strand.
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Change the post and place an
opposite throw half hitch.
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Alternate the post and direction of
throws to give a total of three to four half hitches to prevent slippage of the
sliding knot.
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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.
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Pull suture ends to form a short post and a long leg. Hold
the short strand between your thumb and index finger. |
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Loop the long leg around your index finger and under both
suture limbs. |
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Loop the long limb around and under both limbs a second
time. |
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Pass the long limb through the first loop made by your index
finger. |
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Tighten both limbs of the suture. The short limb will become
longer than the original long limb. |
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Switch posts, loop a surgeon’s double half-hitch behind the
knot. |
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Slide the surgeon’s half-hitch to the
buntline hitch knot. |
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Secure the knot by pulling on the shortest limb. |
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.
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The entrance stitch is begun from the edge of the tendon
exiting on its superior surface. |
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A
throw is then made horizontally from the superior to the inferior surface of
the tissue.
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The needle is then passed from the inferior to superior
surface of the tissue medial to the horizontal stitch. |
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The suture is finally passed over the top of the horizontal
throw, creating a cruciate configuration. |
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This final manoeuvre serves to lock the suture
within the tendon, creating superior pull-out strength. |
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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
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