Knee biomechanics after replacement surgery (Kbars): kinematic and electromyographic comparison of posterior-stabilised, cruciate-retaining and medial-pivot designs during locomotion

David Parker*, Aaron Beach, Gianmarco Regazzola, Richard Verheul

*Corresponding author for this work

Research output: Contribution to journalMeeting abstractpeer-review

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Introduction & Aims: Despite the promising clinical outcomes of the medial-pivot knee design reported to-date, fundamental questions regarding the in-vivo functional behaviour of the implant remain. The purpose of this study was to determine whether the tibiofemoral motion and electromyographic activity of the knee extensors and flexors differs in patients with a medial pivot implant, compared to those with cruciate-retaining or posterior-stabilised designs, during locomotion.

Methods: A cohort of patients (n = 54) that had undergone TKA a minimum of 12 months prior were split into 3 even groups (n = 18) based on implant type: medial-pivot (MP), posterior-stabilised (PS) and cruciate-retaining (CR). Knee kinematics were measured with a high-speed optoelectronic motion capture system (200Hz, Vicon Bonita/Nexus, USA) and surface electromyography with wireless sensors (Delsys Trigno, USA) of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris and medial hamstrings. Patients performed a step-ascent task onto an 18cm high block, and locomotion on a treadmill at a self-selected comfortable, and 30% faster walking speeds. Kinematic data were normalized to 0-100% of the weight acceptance phase for the step-ascent task (contralateral toe-off to contact), and the terminal swing phase for the locomotion task (87-100% of the gait cycle). Medians with 95% confidence intervals were generated for each dependent variable to allow for between-group comparisons. EMG signal amplitude for the step ascent task was expressed relative to an MVIC (%).

Results: In the step task, there was a significantly greater tibial rotation in the MP (11.7°, 9.1 – 13.8) and PS (10.5°, 8.3 – 11.2) groups, compared with the CR (7.4°, 5 – 9.2) group (both p<0.01); there was no difference between MP and PS groups. This difference was not apparent in each of the locomotion tasks. Interestingly, all groups produced a median internal rotation, which contradicted the screw-home mechanism. The MP knees displayed significantly (P<0.01) greater knee extensor activation (rectus femoris muscle) to achieve the step-ascent than the PS group.

Conclusion: These findings suggest that patients with either knee implant types are not strictly limited to producing the traditional screw-home mechanism, as previously reported. The present findings also suggest that the MP design does not necessarily encourage greater range of rotational movement during locomotion.
Original languageEnglish
Pages (from-to)12-13
Number of pages2
JournalAsia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology
Publication statusPublished - Jul 2018
Externally publishedYes
EventAsia-Pacific Knee, Arthroscopy and Sports Medicine Society (APKASS) Congress 2018 - Sydney, Australia
Duration: 31 May 20182 Jun 2018

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Copyright 2018. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


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