Therapeutic Advances
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Mar 18, 2017; 8(3): 221-228
Published online Mar 18, 2017. doi: 10.5312/wjo.v8.i3.221
Development of an internally braced prosthesis for total talus replacement
Markus Regauer, Mirjam Lange, Kevin Soldan, Steffen Peyerl, Sebastian Baumbach, Wolfgang Böcker, Hans Polzer
Markus Regauer, Mirjam Lange, Sebastian Baumbach, Wolfgang Böcker, Hans Polzer, Klinik für Allgemeine, Unfall und Wiederherstellungschirurgie, Klinikum der Ludwig-Maximilians-Universität München, 81377 Munich, Germany
Kevin Soldan, Steffen Peyerl, Stryker GmbH, 2545 Selzach, Switzerland
Author contributions: Regauer M had the primary idea of an internally braced prosthesis for total talus replacement, designed the research project, performed the research project including the cadaver surgery and was responsible for acquisition of data, writing the paper and design of illustrations and figures; Lange M and Baumbach S contributed relevant literature and helped to design the illustrations and figures; Soldan K and Peyerl S were responsible for the design, technical development and final production of the first prototype of the internally braced prosthesis; Böcker W and Polzer H revised the article critically for important intellectual content and were responsible for the final approval of the version to be published.
Conflict-of-interest statement: The authors report no relevant conflicts of interest. Kevin Soldan and Steffen Peyerl are employees of Stryker (Selzach, Switzerland). Markus Regauer and Hans Polzer are paid consultants of Arthrex (Naples, FL, United States).
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Markus Regauer, MD, Klinik für Allgemeine, Unfall und Wiederherstellungschirurgie, Klinikum der Ludwig-Maximilians-Universität München, Standort Großhadern, Marchioninistraße 15, 81377 Munich, Germany. markus.regauer@med.uni-muenchen.de
Telephone: +49-89-440072427 Fax: +49-89-440075424
Received: August 29, 2016
Peer-review started: September 1, 2016
First decision: September 29, 2016
Revised: December 2, 2016
Accepted: December 13, 2016
Article in press: December 14, 2016
Published online: March 18, 2017
Processing time: 200 Days and 4.6 Hours
Abstract

Total loss of talus due to trauma or avascular necrosis, for example, still remains to be a major challenge in foot and ankle surgery with severely limited treatment options. Implantation of a custom made total talar prosthesis has shown promising results so far. Most important factors for long time success are degree of congruence of articular surfaces and ligamentous stability of the ankle. Therefore, our aim was to develop an optimized custom made prosthesis for total talus replacement providing a high level of primary stability. A custom made hemiprosthesis was developed using computed tomography and magnetic resonance imaging data of the affected and contralateral talus considering the principles and technology for the development of the S.T.A.R. prosthesis (Stryker). Additionally, four eyelets for fixation of artificial ligaments were added at the correspondent footprints of the most important ligaments. Two modifications can be provided according to the clinical requirements: A tri-articular hemiprosthesis or a bi-articular hemiprosthesis combined with the tibial component of the S.T.A.R. total ankle replacement system. A feasibility study was performed using a fresh frozen human cadaver. Maximum range of motion of the ankle was measured and ligamentous stability was evaluated by use of standard X-rays after application of varus, valgus or sagittal stress with 150 N. Correct implantation of the prosthesis was technically possible via an anterior approach to the ankle and using standard instruments. Malleolar osteotomies were not required. Maximum ankle dorsiflexion and plantarflexion were measured as 22-0-28 degrees. Maximum anterior displacement of the talus was 6 mm, maximum varus tilt 3 degrees and maximum valgus tilt 2 degrees. Application of an internally braced prosthesis for total talus replacement in humans is technically feasible and might be a reasonable procedure in carefully selected cases with no better alternatives left.

Keywords: Ankle; Avascular necrosis; Total loss of talus; Prosthesis; Hemiprosthesis; InternalBrace; Talus replacement

Core tip: Implantation of a total talar prosthesis has shown promising results so far. The aim was to develop an optimized prosthesis providing a high level of primary stability. A custom made hemiprosthesis was developed using computed tomography and magnetic resonance imaging data. Four eyelets for fixation of artificial ligaments were added at the footprints of important ligaments. Correct implantation of the prosthesis in a cadaver model was possible via an anterior approach. Maximum ankle dorsiflexion and plantarflexion were measured as 22-0-28 degrees. Maximum anterior displacement of the talus was 6 mm, maximum varus tilt 3 degrees and maximum valgus tilt 2 degrees.