Refixation of Osteochondral Fractures by an Ultrasound-Activated Pin System – An Ovine In Vivo Examination Using CT and Scanning Electron Microscope

Neumann H1, Schulz A.P2, 3, Breer S1, Unger A2, Kienast B*, 1, 3
1 Department of Traumatology, Orthopaedics and Sports Medicine, BG Trauma Centre Hamburg, Germany
2 Department of Biomechatronics and Academic Orthopaedics, University of Schleswig-Holstein, Campus Luebeck, Germany
3 Department of Traumatology, Orthopaedics& Reconstructive Surgery, University of Schleswig-Holstein, Campus Luebeck, Germany

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© Neumann et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the BG Trauma Centre Hamburg, Bergedorfer Str. 10, 21033 Hamburg, Germany; Tel: +49-40-7306-2241; Fax: +49-40-41466969; E-mail:



Osteochondral injuries, if not treated appropriately, often lead to severe osteoarthritis of the affected joint. Without refixation of the osteochondral fragment, human cartilage only repairs these defects imperfectly. All existing refixation systems for chondral defects have disadvantages, for instance bad MRI quality in the postoperative follow-up or low anchoring forces. To address the problem of reduced stability in resorbable implants, ultrasound-activated pins were developed. By ultrasound-activated melting of the tip of these implants a higher anchoring is assumed. Aim of the study was to investigate, if ultrasound-activated pins can provide a secure refixation of osteochondral fractures comparing to conventional screw and conventional, resorbable pin osteosynthesis. CT scans and scanning electron microscopy should proovegood refixation results with no further tissue damage by the melting of the ultrasound-activated pins in comparison to conventional osteosynthesis.


Femoral osteochondral fragments in sheep were refixated with ultrasound-activated pins (SonicPin™), Ethipins® and screws (Asnis™). The quality of the refixated fragments was examined after three month of full weight bearing by CT scans and scanning electron microscopy of the cartilage surface.


The CT examination found almost no statistically significant difference in the quality of refixation between the three different implants used. Concerning the CT morphology, ultrasound-activated pins demonstrated at least the same quality in refixation of osteochondral fragments as conventional resorbable pins or screws. The scanning electron microscopy showed no major surface damage by the three implants, especially any postulated cartilage damage induced by the heat of the ultrasound-activated pin. The screws protruded above the cartilage surface, which may affect the opposingtibial surface.


Using CT scans and scanning electron microscopy, the SonicPin™, the Ethipin® and screws were at least equivalent in refixation quality of osteochondral fragments.

Keywords: Bioresorbable implant, CT, osteochondral fracture, scanning electron microscope, sheep study, ultrasound-activated pin. .