Biomechanical comparison of knotless versus conventional knotted anchors in an arthroscopic cadaveric bankart model
Anil Ranawat1, Mark D. Miller2, Gehron Treme2, Paul Caldwell4, Naveen Singanamala4, Ryan Costic1, Sara Pearson4, Jon K. Sekiya3
1Orthopedics, University of Pittsburgh, Pittsburgh, PA; 2Orthopedics, University of Virginia, Charlottesville, VA; 3Orthopedics, University of
Michigan, Ann Arbor, MI; 4Orthopedics, ORV, Richmond, VA
[email protected]
Introduction: The Bankart eponym is the ‘essential lesion’ in anterior instability of the shoulder1, 2. Repair of the Bankart lesion has evolved with changing
technology, although the principle remains the same- to re-attach the capsulolabral
complex back to the glenoid rim. Open repair was at first the gold standard and
later numerous workers have shown equal results with Arthroscopic repair3-6.
Arthroscopic techniques have evolved through bioabsorbable staples7, transglenoid
repair7 and metal and bioabsorbable suture anchors3,4. In most series, staples and
transglenoid repair have been found to be inferior when compared to suture anchor
repairs, but the efficacy between arthroscopic vereus open techniques still remains
controversial6,7,8.
The newest arthroscopic technique of repairing Bankart lesions involves bioabsorbable (made of poly- L-Lactic acid) knotless suture anchors. Introduced in
2001,9 these anchors are designed to capture tissue in a double loop and embed
themselves securely in bone, creating a repair with a pull out strength markedly
improved over conventional suture anchors10. These anchors eliminate the step of
arthroscopic knot tying with its difficulties and pitfalls and are easy to deploy and
adjust, once the technique is mastered. The elimination of knots saves considerable
time that can be translated into benefits from shorter surgical and anesthesia time,
and no knot complications or slippage.
There is limited data concerning the reliability or the biomechanical behaviour
of the Bioknotless suture anchor when used for the Bankart repair. This study is an
effort to compare the biomechanical properties of a knotless and a conventional
knotted suture anchor in an arthroscopic Bankart repair model.
Materials and Methods: Eight paired matched cadaveric shoulders were used
in an in vitro biomechanical study. The Bankart lesion was created arthroscopically and fixed using either two Bioknotless suture anchors (Mitek, Depuy Westwood,
MA) or two Biosuturetak suture anchors (Arthrex, Naples, FL) with a locking
arthroscopic knot. The shoulders were tested in an Material Testing Machine
(Adelaide Testing Machine, Model TTS-25 series, Toronto, Canada). Cyclic loading was performed (10N-40 N, 100 cycles, 0.5 mm/sec, 5N preload). This was followed by an unloaded rest and then another 5N preoload followed by a load-tofailure protocol (1.25 mm/sec) with a 1000 lb Load Cell supplying cyclic creep
(mm), permanent deformation (mm), ultimate load (N), stiffness (N/m). Modes of
failure were also recorded.
Results: No significant difference were found between knot fixation
(Biosuturetak) and knotless anchors (the BioKnotless) in terms of ultimate load to
failure (mean = 125.3 vs. 96.9, p > .40), stiffness (20.9 vs19.8, p > .74), creep (2.7
vs. 1.7, p > .07), and deformation (2.5 vs. 1.9, p > .56). The modes of failure included suture-tissue interface (3 knot and 6 knotless) and anchor-bone interface (5
knot, 2 knotless). 5 specimens failed during cyclic loading of these 4 were knotless
and only 1 was knotted. There were no significant differences between pullthrough and anchor pull-out groups (p > .87 for ultimate load; p > .55 for stiffness).
There was also no significant differences in creep or deformation between pullthrough and anchor pull-out groups (p > .63 for creep, p > .96 for deformation).
Discussion: Although knotless anchor fixation appears weaker and had more
failures during cyclic loading, no statistical difference could be found. As such, clinicians performing arthroscopic shoulder stabilization can use either knotted or
knotless suture anchor techniques with equivalent biomechanical properties
according to our time-zero, cadaveric model.
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Isolated tissue fom knotted Bankart anchor repair in Material Testing Machine (Adelaide
Testing Machine, Model TTS-25 series, Toronto, Canada).
Poster No. 1534 • 54th Annual Meeting of the Orthopaedic Research Society