Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Nov 18, 2015; 6(10): 821-828
Published online Nov 18, 2015. doi: 10.5312/wjo.v6.i10.821
Novel computer-assisted method for revision arthroplasty of the knee
Hanns-Edgar Hoffart, Harald Dinges, Stefan Kolbeck, Peter Ritschl, Hagen Hommel
Hanns-Edgar Hoffart, Kreisklinik Jugenheim, 64342 Seeheim-Jugenheim, Germany
Harald Dinges, Westpfalz-Klinikum, Standort II Kusel, Orthopädische Klinik, 66869 Kusel, Germany
Stefan Kolbeck, HELIOS Klinik Bad Gandersheim, 37581 Bad Gandersheim, Germany
Peter Ritschl, Orthopädisches Krankenhaus Gersthof, 1180 Vienna, Austria
Hagen Hommel, Krankenhaus Märkisches Oderland, Betriebsteil Wriezen, 16269 Wriezen, Germany
Author contributions: All authors contributed to this manuscript.
Supported by Smith and Nephew GmbH, Marl, Germany.
Institutional review board statement: Not applicable.
Institutional animal care and use committee statement: Not applicable.
Conflict-of-interest statement: Hoffart HE, Dinges H, Kolbeck S, Ritschl P and Hommel H have received fees for serving as a speaker, a consultant and an advisory board member for Smith and Nephew GmbH, Marl, Germany. This study was funded by Smith and Nephew GmbH, Marl, Germany. The sponsor had no involvement in the writing of the report or in the decision to submit the results for publication.
Data sharing statement: No patient data were used.
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: Peter Ritschl, MD, Orthopädisches Krankenhaus Gersthof, Wielemansgasse 28, 1180 Vienna, Austria. peter.ritschl@wienkav.at
Telephone: +43-1-476114300 Fax: +43-1-476111009
Received: April 9, 2015
Peer-review started: April 9, 2015
First decision: June 4, 2015
Revised: June 25, 2015
Accepted: July 29, 2015
Article in press: August 3, 2015
Published online: November 18, 2015
Abstract

AIM: To introduce the navigation system of software and instruments designed specifically for revision total knee arthroplasty (TKA).

METHODS: We present an imageless navigation system for revision TKA, with optical point and tracker identification to assess kinematic and anatomical landmarks. The system automatically positions the cutting guides with a motorized cutting unit. The cutting unit is placed on the distal femur with a femoral clamp and acts as a rigid body and the base for all femoral cuts. The surgical technique for using the navigation system for revision TKA is based on the technique used in primary TKA. However, there are some important differences. The most notable are: (1) differences in estimation of the position of the primary implant relative to the bone and the mechanical axes; (2) the specific possibilities the revision navigation software offers in terms of optimal joint level positioning; and (3) the suggested “best fit” position, in which the clock position, stem position and offset, femoral component size, and mediolateral position of the femoral component are taken into account to find the optimal femoral component position. We assessed the surgical technique, and accompanying software procedural steps, of the system, identifying any advantages or disadvantages that they present.

RESULTS: The system aims to visualize critical steps of the procedure and is intended as a tool to support the surgeon in surgical decision-making. Combining a computer-assisted cutting device with navigation makes it possible to carry out precise cuts without pinning. Furthermore, the femoral clamp provides a stable fixation mechanism for the motorized cutting unit. A stable clamp is paramount in the presence of periarticular bony defects. The system allows the position of the primary implant relative to the bone and mechanical axes to be estimated, at which point any malalignments can be corrected. It also offers an optimal joint level position for implantation, and suggests a “best fit” position, in which the clock position, stem position and offset, femoral component size, and mediolateral position of the femoral component are considered. The surgeon can therefore make decisions intraoperatively to maximise alignment and, hence, outcomes. Based on the intraoperative findings of joint stability, the surgeon can modify the preoperative plan and switch from a constrained condylar system to a hinged version, or vice versa.

CONCLUSION: The system is flexible and easy to learn and allows improvements in workflow during TKA.

Keywords: Knee, Navigation system, Revision total knee arthroplasty, Computer-assisted surgery, Surgical technique

Core tip: The obscuring of bony landmarks by the previous implant, scar formation, the loss of bone stock and ligamentous insufficiency, make revision total knee arthroplasty very demanding. Current navigation systems do not typically allow reconstruction of the anatomic joint line, which is an important factor in implant survival, or compensation for the absence of classical landmarks. We present an imageless navigation system for revision total knee arthroplasty. The system automatically positions the cutting guides with a motorized cutting unit. We assessed the surgical technique, and accompanying software procedural steps, of the system, identifying any advantages or disadvantages that they present.