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Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 267 - 267
1 May 2009
Marcacci M Nofrini L Bignozzi S Iacono F Zaffagnini S Lo Presti M Di Martino A
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Aims: In Revision Total Knee Arthroplasty (RTKA), bone deficiencies and lack of anatomical references make it difficult to understand the normal knee kinematic and adequately plan the intervention. To our knowledge there are no data about computer assisted navigation system specifically developed for RTKA in the literature and existing navigated techniques for RTKA use navigation systems developed for primary TKA. A new computer assisted technique for RTKA is presented.

Methods: This technique is based on the use of a navigation system, RTKANav consisting of an optical localizer, a dedicated software and some navigated tools specifically done for RTKA. The system doesn’t use medical images, and patient anatomy model is represented with dots and lines corresponding to acquired landmarks, providing the surgeon with the main references for the intervention monitored in real-time. During the most critical steps of the intervention (soft tissue balancing and the consequent choice of implant size, and joint line height restoration), the system provide the surgeon with graphical and numerical tools to improve the surgical outcome. Several criteria to set each degree of freedom of prosthetic components are considered and compared, and even if some required landmarks can not be identified, the system is always able suggest an intervention plan. The surgeon is provided with tools to analyze and modify the proposed plan, and to reproduce it on the patient.

Results: Till now the presented technique was used on five patients by an expert surgeon. Qualitative results, collected after the intervention through a questionnaire on surgeon feelings, in order to assess the functionality, user friendliness and the data visualization criteria implemented were very satisfying. System reliability was assessed intraoperatively analyzing joint line height, limb alignment and knee stability using trial components: based on his experience, the surgeon checked some acceptable components combination and compared the corresponding outcome with the one provided by the implant planned by the system. In three out five cases the suggested implant was considered the best by the surgeon, while in one case he decided to change the tibial insert of one size because of knee instability and in another case he changed the tibial component of one size because the planned one was too small. Final limb alignment evaluated with postoperative x-rays, was satisfactory in all cases.

Conclusions: Presented navigation system showed early promising results providing the surgeon with intraoperative quantitative and qualitative information on the main surgical parameters, useful to achieve a satisfactory prosthesis implant. Moreover this system use anatomical patient specific landmarks acquired after prosthesys removal, while navigation systems developed for primary TKA use both reference taken from preoperative x-rays and anatomical references acquired on metal component to be removed. Therefore in this case the operation planning is based on rough anatomical landmarks that do not reflect patients original anatomy.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_III | Pages 428 - 428
1 Oct 2006
Marcacci M Nofrini L Iacono F Zaffagnini S
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A computer assisted technique for TKA Revision is presented. It is based on the use of a navigation system, RTKANav consisting of anl optical localizer, a dedicated software specifically done for TKA revision and some navigated tools developed for this application.

The system doesn’t use any patient model derived from medical images, but on the system interface patient anatomy model is represented with dots and lines corresponding to acquired landmarks and data derived from them. These data describe the main anatomical features and provide the surgeon with the main references for the intervention; angles between the mechanical axes can be controlled and monitored at any time.

Even if during acquisition phase some specific points can not be identified, since for each prosthetic component several criteria to set each degree of freedom are considered and compared, the system is always able suggest an intervention plan.

The system provides the surgeon with tools to analyse and modify the proposed plan, and to reproduce it on the patient.

Navigated technique validation is under development. Till now it was used on two patients by an expert surgeon. Computer guidance showed early promising results providing the surgeon with useful indications achieve a satisfactory prosthesis implant.