Episode 38: Biomechanical Analysis of All-Suture Suture Anchor Fixation Compared With Conventional Suture Anchors and Interference Screws for Biceps Tenodesis

Podcast Hartzler Frank biceps biomech (Completed 08/26/19)
Transcript by Rev.com
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Rob Hartzler : Welcome to The Arthroscopy Association’s Arthroscopy Journal podcast. The
views expressed in this podcast do not necessarily represent the views of The
Arthroscopy Association, or the Arthroscopy Journal. Greetings, this is Rob
Hartzler from TSAOG Orthopedics in San Antonio. Today on the podcast, we
have the honor of hearing from Dr. Rachel Frank, assistant professor of
Orthopedic Surgery and a Sports Medicine Specialist at the University of
Colorado. Dr. Frank, welcome to the podcast.
Rachel Frank: Thanks so much for having me, appreciate the opportunity.
Rob Hartzler : Today we're going to be discussing your article from the June, 2019 issue of the
journal entitled Biomechanical Analysis of All-Suture Suture Anchor Fixation
Compared With Conventional Suture Anchors and Interference Screws for
Biceps Tenodesis. So Dr. Frank, how'd you get interested in this topic?
Rachel Frank: Well, first and foremost, I’d just like to thank and acknowledge the co-authors
on this paper, especially our research fellows, and my co-fellows and the faculty
that helps with this. You know, this is a common area of discussion amongst
shoulder surgeons and sports medicine specialists. And I think at every meeting
that we go to, we hear debate and discussion on the best technique for biceps
tenodesis, and there still is no consensus. And so, we got interested in this topic
essentially due to the fact that multiple different attendings during my
fellowship use different techniques for biceps tenodesis fixation, and essentially
each one would argue that their technique is superior. And so, we really just
wanted to see from a lab perspective which technique would be superior, if one
in fact would be. And so, that formed the baseline and the interest in doing this
study.
Rob Hartzler : And you specifically set up this study to investigate the risk of torsional fracture
with the different techniques. Was there any sort of clinical concern that had
come up? This study was done while you were a fellow at Rush, any clinical
indication for that?
Rachel Frank: You know, it's something that we always worry about, and we always discuss,
and I think comes up at meetings quite often, especially when discussing larger
fixation constructs such as the interference screw. And I was fortunate during
my fellowship and residency at Rush, I didn't see any of these, but it was always
this thought that if you're drilling eccentrically, or if it's an overhead athlete or a
volleyball athlete and they place their arm in a position of provocation, will they
be at risk for fracture with a bigger implant, or a bigger drill hole? So I think it's
the theoretic clinical risk, certainly there's been reports of fracture in the
literature. During my time at Rush, I didn't see any of these, but that's certainly
provided some of the emphasis for wanting to study this topic in more detail
than what was previously studied.
Podcast Hartzler Frank biceps biomech (Completed 08/26/19)
Transcript by Rev.com
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Rob Hartzler : How about these all-suture suture anchors? So what's the potential benefit of
using that type of fixation construct, that's a newer device that we have
available for this type of fixation of the biceps?
Rachel Frank: Absolutely. I think that also was of interest for this study. So not only looking at
torsional strength of screws, or torsional risks for fracture for screws, but
looking at different constructs in all-suture suture anchors are developed by ...
or are produced by a variety of different companies. And I think that they are
appealing to surgeons, not only for biceps tenodesis, but for labral repairs, and
for other areas of fixation throughout the shoulder, and other joints simply due
to the fact that there's ... that it's just a suture material. And so there's no
plastic, there's no metal, and the drill hole is much smaller. So I think the idea of
learning about these materials, and about this type of fixation construct in
determining the biomechanical properties was very much of interest to us,
because of the small and really minimally invasive nature of this type of fixation
device.
Rob Hartzler : Yeah, so it was a 1.9 millimeter, it looked like, drill hole for the all-suture suture
anchor or versus a 2.9 millimeter drill hole for the conventional suture anchor,
and then an 8 millimeter hole for the interference screw, is that right?
Rachel Frank: Exactly right. And so, that theoretic risk of creating a stress riser in the proximal
humerus with a bigger implant such as the interference screw when you're
drilling a bigger hole, even if you're slightly off center or eccentric with a smaller
suture anchor, that risk in theory goes down. And so, the attractiveness of using
a smaller implant then goes up.
Rob Hartzler : So tell us what you found in the lab testing these subpectoral biceps tenodesis
constructs.
Rachel Frank: Well, I think the biggest take home from this study and very similar to other
studies is that all of these devices provide excellent fixation for biceps tenodesis,
and so that's the biggest take home. There's really no superiority of one
construct versus another when it comes to all biomechanical properties. We did
find some nuances, so in particular the conventional interference screw, was
better with regard to tendon elongation at maximal load, but we also noted that
in the cyclical loading phase, which occurred before the failure loading phase
that some of the implants, or excuse me, some of the constructs with the
conventional interference screw actually failed even before they got a chance to
go to pull to failure loading. And so that was an interesting finding for us.
Rachel Frank: We also found that the torsional testing resulted in some spiral fractures with
the constructs using the interference grew, and actually 100% of those implants
... or excuse me, 100% of those specimens, and we did not see any of those
types of failure mechanisms with the conventional suture anchor or the allsuture
suture anchor.
Podcast Hartzler Frank biceps biomech (Completed 08/26/19)
Transcript by Rev.com
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Rachel Frank: And so the take homes from this for our team were that any of these constructs
can work biomechanically at time equals zero. The clinical healing factors that
come into play obviously were not tested in this time equals zero biomechanical
lab study. But we were able to get some good data on torsional properties, and
in particular torsional testing of those interference screws resulted in more
fractures.
Rachel Frank: And so, this potentially tells us that we can use smaller implants and achieve the
same biomechanical properties, again at time equals zero, potentially with less
risk of fracture. And so for us, the clinical translation of this, this potentially for
our high risk torsional athletes such as overhead throwers, we may be able to
consider a smaller implant with equal biomechanical properties, and less risk of
catastrophic failure.
Rob Hartzler : The thing that really raised my eyebrows was, as you mentioned in the
interference screw fixation group, three out of the seven specimens failed
during cyclic testing, by tearing at the screw tendon interface. I mean, that's a
significantly high rate of tearing at that junction in my mind, what'd you think
about that?
Rachel Frank: Yeah, that was definitely curious for us too. I think that a lot of that potentially is
due to the fact that this is a cadaveric study. And so, when we're physically
screwing in the tendon with the screw into the proximal humerus, you can
certainly see some potential fraying of the tendon that may lead to early failure,
especially during cyclical loading. I think that's one part of a cadaveric study
that's really difficult to translate to real life, and a lot of that is because in real
life that patients are much younger with better tendon quality. And while we
tried to control for that by selecting specific cadaveric criteria, you can't always
control for that, and understand the quality of the tendon before you start
doing the experiment. And so, that was interesting for us, but I think is probably
more of a lab or statistical finding than clinically relevant just given the nature of
cadaveric shoulders.
Rob Hartzler : I've actually largely moved away from high in the groove, proximal tenodesis
using interference screw fixation, and gone to an onlay technique, because I
observed that happening with the arthroscope a lot, that the screw was cutting
into the tendon substance, and that oftentimes it was relying on the whip stitch
with the anchor being more like a suture anchor type of a fixation mechanism.
Thoughts on that? Is that ... do you think that visualizing it arthroscopically you
observe that more readily than in open surgery, or is it just that as you said, it's
cadaveric tissue and we shouldn't worry about the screw cutting into the
tendon issue in younger and healthier patients?
Rachel Frank: I think in this case, it's probably more of a cadaveric issue, although I do always
worry about that. And after having done this study, and a couple other biceps
tenodesis studies in the lab, it is interesting to see how much that tendon either
wraps around the screw as you're screwing it in, or tends to fray a bit, a little bit
Podcast Hartzler Frank biceps biomech (Completed 08/26/19)
Transcript by Rev.com
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like a frayed rope. I've actually ... I've gravitated toward using an onlay fixation
construct with a suture anchor, as well. I do that in a subpec technique, and I'm
very biased by my training, as I trained primarily with surgeons who did this in a
subpec technique, but again with a of different implants including interference
screws as well as suture anchors.
Rachel Frank: And I think this study did give me some more confidence to be able to use the
suture anchor as opposed to an interference screw, but I think with experienced
hands, any of these techniques can work. I think when you talk about doing this
arthroscopically versus through a mini open approach, that debate we can talk
about, I think for the next 10 podcasts that you do, and I think that there's likely
no clinical difference, and I think the literature supports that. Although all of us
have, I think some different biases with regard to arthroscopic versus a mini
open approach.
Rob Hartzler : Yeah, definitely. And but it does seem like in the interference group, if it doesn't
tear, it doesn't have as much elongation as the suture anchor groups.
Rachel Frank: Yeah, exactly. And that's ... when you're talking about especially those higher
demand patients who, not necessarily overhead throwers, but lifters, or
patients who you know are going to place some demand potentially earlier on in
their recovery process. I think that's where the interference screw may be most
advantageous, because you're going to get less of that elongation early on. That
being said, the first six weeks are critical for tendon healing into the bone, or
onto the bone regardless. And so, regardless of my fixation technique, whether I
choose to use a screw or a suture anchor, I do try to limit my patients with
regards to early and aggressive therapy just to let that healing process occur.
But I think if you were going to have that patient who might want to move a
little bit more aggressively, the screw construct may be better for that at least
based on this data.
Rob Hartzler : So you basically rehab them the same whether you use a suture anchor or the
interference screw, but maybe high demand, lean towards the screw or
untrustworthy patients?
Rachel Frank: So in those higher demand patients, I think a screw can be helpful, but in my
practice I've gravitated towards using a suture anchor. In some of these
patients, I'll actually use two suture anchors in a staggered fashion to avoid
creating a stress riser, but I don't know of any clinical data to necessarily
support that. I think that in itself is a study worth doing comparing one versus
two suture anchors potentially compared to a conventional interference screw,
and that may provide some additional data to help us figure out what is the best
construct, especially in high demand athletes.
Rob Hartzler : So do you use a conventional suture anchor at this point or an all-suture suture
anchor?
Podcast Hartzler Frank biceps biomech (Completed 08/26/19)
Transcript by Rev.com
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Rachel Frank: I've moved to using an all-suture suture anchor.
Rob Hartzler : Okay, nice. But does this convince you that this small ... that the smaller hole was worth making the jump for?
Rachel Frank: I think so. I mean, this data really helped provide me some evidence that,
biomechanically at least and there's some other studies to support this, the allsuture
suture anchors are adequate. I think with less risk and equal
biomechanical properties, for me, that gives me some more confidence using
this implant. I also again feel, especially in the teaching environment, that if the
drill hole is a little off center, which of course we're aiming for perfectly
centered in the groove, but if it's a little bit off center, I'm less concerned about
creating a stress riser with a hole that's less than two millimeters.
Rob Hartzler : Excellent. Any closing thoughts?
Rachel Frank: You know, I think again, I think this was a really nice study, and I want to
acknowledge all of the work done by our team at Rush, when I was there, and
especially by the research fellows and my co-fellows and the faculty. I hope that
the take homes from this for anyone listening, or anyone reading the article, are
that you can really get biceps tenodesis done in a variety of ways, with a variety
of implants and again, biomechanical findings don't necessarily correlate to
clinical findings, but I think in this case, we can take home the following points:
Number one, both interference screw and suture anchor constructs are
acceptable. Number two, interference screw constructs may provide an
increased strength at time equals zero with regard to tendon elongation, but
also may provide an increased risk for fracture. And so you've got to weigh the
risks and benefits in your hands for your patients.
Rob Hartzler : This article from the June, 2019 issue of The Journal entitled “Biomechanical
Analysis of All-Suture Suture Anchor Fixation Compared With Conventional
Suture Anchors and Interference Screws for Biceps Tenodesis” can be found on
the Arthroscopy Journal's website at arthroscopyjournal.org.