Basic Science
Biomechanical analysis of conventional anchor revision after all-suture anchor pullout: a human cadaveric shoulder model

https://doi.org/10.1016/j.jse.2019.04.053Get rights and content

Hypothesis and background

The possibility of implanting a conventional anchor at the pullout site following all-suture anchor failure was evaluated in a biomechanical cadaveric model. The hypothesis of the study was that anchor revision would yield equal biomechanical properties.

Methods

Ten human humeri were obtained, and bone density was determined via computed tomography. After all-suture anchor (n = 5) and conventional 4.5-mm anchor (n = 5) insertion, biomechanical testing was conducted. Following all-suture anchor pullout, a conventional 5.5-mm anchor was inserted at the exact site of pullout (n = 5) and biomechanical testing was reinitiated. Testing was conducted using an initial preload of 20 N, followed by an unlimited cyclic protocol, with a stepwise increasing force of 0.05 N for each cycle at a rate of 1 Hz until system failure. The number of cycles, maximum load to failure, stiffness, displacement, and failure mode, as well as macroscopic observation at the failure site including diameter, shape, and cortical destruction, were registered.

Results

The defect following all-suture pullout showed a mean diameter of 4 mm, and conventional revision was possible in each sample. There was no significant difference between the initial all-suture anchor implantation and the conventional anchor implantation or the conventional revision following all-suture failure regarding mean pullout strength, stiffness, displacement, or total number of cycles until failure.

Conclusion

Conventional anchor revision at the exact same site where all-suture anchor pullout occurred is possible and exhibits similar biomechanical properties.

Section snippets

Methods

A biomechanical investigation was performed, and a total of 10 human humeral bones (5 matched pairs) were collected from donors aged between 50 and 73 years. Each specimen was scanned using a 16-row computed tomography scanner (Brilliance 16 CT; Philips Healthcare, Hamburg, Germany) with a solid calibration phantom (Bone Density Calibration Phantom; QRM, Möhrendorf, Germany) to determine the volumetric bone mineral density in terms of calcium hydroxyapatite (in milligrams per cubic centimeter)

Results

Determination of volumetric bone mineral density revealed similar values in both groups (126 ± 25 mg/cm3 in ASA/revision group [n = 5] and 127 ± 30 mg/cm3 [n = 5] in 4.5-mm conventional anchor group; P = .81). Revision with the 5.5-mm conventional anchor system at the previous drilling site worked without fail; thus, biomechanical testing was possible in all specimens. All tested anchors failed via anchor pullout during biomechanical testing.

Biomechanical comparison of all 3 tested anchor types

Discussion

This study demonstrates that implantation of a 5.5-mm conventional anchor at the exact site where ASA pullout occurred is possible and provides similar biomechanical properties. Anchor pullout, while not being the most common failure mechanism following rotator cuff repair, is a critical problem in suture anchors, which can lead to rotator cuff instability.20, 21, 22 Whereas conventional anchors are concentrically shaped and their corresponding cortical implantation hole matches the largest

Conclusion

This study demonstrates that there is no difference in load to failure between ASAs and conventional anchors. Furthermore, if pullout of an ASA occurs, adequate fixation can be achieved with a 5.5-mm anchor placed at the exact location of pullout without compromising ultimate fixation.

Disclaimer

ConMed provided the anchors used in this study. The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

References (23)

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Approval of the institutional review board was obtained from the Ethical Review Committee (Hamburg, Germany; study no. WF-27/17).

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