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. 2021 Jul 10;8(1):50.
doi: 10.1186/s40634-021-00361-y.

Assessment of paradoxical anterior translation in a CR total knee prosthesis coupling dynamic RSA and FE techniques

Agostino Igor Mirulla  1   2 , Laura Bragonzoni  3 , Stefano Zaffagnini  2   4 , Tommaso Ingrassia  1 , Raffaele Zinno  5 , Bernardo Innocenti  6
Affiliations

Assessment of paradoxical anterior translation in a CR total knee prosthesis coupling dynamic RSA and FE techniques

Agostino Igor Mirulla et al. J Exp Orthop. .

Abstract

Purpose: The study aims were to assess the kinematic data, Internal-External (IE) rotation, and Antero-Posterior (AP) translation of the contact points between the femoral condyles and polyethylene insert and to develop a combined dynamic RSA-FE (Radiostereometric - Finite Element) model that gives results congruent with the literature.

Methods: A cohort of 15 patients who underwent cemented cruciate-retaining highly congruent mobile-bearing total knee arthroplasty were analyzed during a sit-to-stand motor task. The kinematical data from Dynamic RSA were used as input for a patient-specific FE model to calculate condylar contact points between the femoral component and polyethylene insert.

Results: The femoral component showed an overall range about 4 mm of AP translation during the whole motor task, and the majority of the movement was after 40° of flexion. Concerning the IE rotation, the femoral component started from an externally rotate position (- 6.7 ± 10°) at 80° of flexion and performed an internal rotation during the entire motor task. The overall range of the IE rotation was 8.2°.

Conclusions: During the sit to stand, a slight anterior translation from 40° to 0° of flexion of the femoral component with respect to polyethylene insert, which could represent a paradoxical anterior translation. Despite a paradoxical anterior femoral translation was detected, the implants were found to be stable. Dynamic RSA and FE combined technique could provide information about prosthetic component's stress and strain distribution and the influence of the different designs during the movement.

Keywords: Dynamic RSA; FE analysis; Kinematics; Mobile bearing; TKA.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Mesh of femoral component and boxes
Fig. 2
Fig. 2
Initial relative position between the femoral component and the boxes
Fig. 3
Fig. 3
Total knee arthroplasty Anterior-Posterior translation (mean and standard deviation)
Fig. 4
Fig. 4
Total knee arthroplasty Internal-External rotation (mean and standard deviation)
Fig. 5
Fig. 5
Normalized Anterior-Posterior translation of the medial and lateral condyles
Fig. 6
Fig. 6
Normalized Anterior-Posterior translation of the femoral compartment
See this image and copyright information in PMC

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