Difference in implant design affects midflexion rotational laxity in cruciate-retaining total knee arthroplasty: a computer navigation study

Takashi Tsuda; Kazunori Hino; Tatsuhiko Kutsuna; Kunihiko Watamori; Tomofumi Kinoshita; Masaki Takao

doi:10.1186/s40634-023-00652-6

Difference in implant design affects midflexion rotational laxity in cruciate-retaining total knee arthroplasty: a computer navigation study

J Exp Orthop. 2023 Aug 21;10(1):85. doi: 10.1186/s40634-023-00652-6.

Authors

Takashi Tsuda¹, Kazunori Hino², Tatsuhiko Kutsuna¹, Kunihiko Watamori³, Tomofumi Kinoshita¹, Masaki Takao¹

Affiliations

¹ Department of Bone and Joint Surgery, Ehime University, Graduate School of Medicine, Shitsukawa, Toon City, Ehime, 791-0295, Japan.
² Department of Joint Reconstruction, Ehime University, Graduate School of Medicine, Shitsukawa, Toon City, Ehime, 791-0295, Japan. ehukne@gmail.com.
³ Department of Joint Reconstruction, Ehime University, Graduate School of Medicine, Shitsukawa, Toon City, Ehime, 791-0295, Japan.

Abstract

Purpose: This study aimed to compare midflexion rotational laxity between two different design concept models of cruciate-retaining total knee arthroplasty: symmetrical surface design of neutral joint line obliquity and asymmetrical surface design of varus joint line obliquity.

Methods: Sixty-three knees that underwent cruciate-retaining total knee arthroplasty were evaluated. Manual maximum passive rotational stress without acceleration was applied to the knees under navigation monitoring. Pre-operative and post-operative internal and external rotational angles were measured at 30°, 45°, 60°, and 90° knee flexion.

Results: The post-operative internal rotational laxity was significantly increased compared with pre-operative levels at 30°, 45°, 60°, and 90° flexion among all subjects (mean 9.7° vs 11.1°, 10.6° vs 11.6°, 11.2° vs 12.9°, and 13.2° vs 14.9°; p = 0.01, 0.04, 0.001, and 0.008, respectively). The post-operative external rotational laxity was significantly decreased compared to pre-operative levels at 30°, 45°, 60°, and 90° flexion among all subjects (mean 10.8° vs 6.8°, 12.5° vs 9.4°, 12.8° vs 10.0°, and 11.3° vs 9.5°; p < 0.0001, < 0.0001, < 0.0001, and 0.0008, respectively). The post-operative total rotational laxity significantly decreased, compared with pre-operative levels, at 30° and 45° flexion among all subjects (mean 20.4° vs 17.9°, and 23.1° vs 21.1°; p = 0.002 and 0.04, respectively). The post-operative total rotational laxity was significantly smaller in asymmetrically designed total knee arthroplasty than in symmetrically designed total knee arthroplasty at 30°, 45°, and 60° flexion (mean 19.3° vs 15.8°, 22.8° vs 18.7°, and 24.4° vs 20.8°; p = 0.03, 0.03, and 0.02, respectively), whereas no significant difference was observed at 90° flexion.

Conclusion: Compared to symmetrical surface design, asymmetrical surface design resulted in lower rotational laxity at the midflexion range in cruciate-retaining total knee arthroplasty.

Level of evidence: III.

Keywords: Cruciate-retaining; Design of implants; Midflexion laxity; Navigation system; Rotational laxity; Total knee arthroplasty.