Third generation medially-congruent TKA better reproduce knee kinematics when compared to posterior-stabilized designs
ESSKA Academy. Indelli P. Nov 8, 2019; 284366; epEKA-24 Topic: Biomechanics
Prof. Pier Indelli
Prof. Pier Indelli
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Third generation medially-congruent TKA better reproduce knee kinematics when compared to posterior-stabilized designs

ePoster - epEKA-24

Topic: TKA

Indelli P.F.1, Leonardi E.1, Ghirardelli S.1, Giuntoli M.2
1Stanford University, Orthopedic Surgery, Palo Alto, United States, 2Universita' degli Studi di Pisa, Orthopaedic Surgery, Pisa, Italy

We compared parameters of kinematics during normal gait of TKA patients having either a third-generation posterior-stabilized (PS) TKA design or a medially-congruent (MC) design from the same manufacturer with a matched group of healthy controls. The hypothesis was that the kinematic of MC TKAs would more closely resembles that of healthy controls than PS TKAs during gait.
Ten TKAs (5 PS and 5 MC) were matched by gender, age, BMI and operating surgeon to 10 healthy controls. A normal contralateral knee was an inclusive criteria in the TKA group.
Post-operative 3D knee kinematic analysis, performed using a multi-camera optoelectronic system and a force platform embedded in a 10-m walkway was compared between PS TKA patients, MC TKA patients and healthy controls.
Postoperative inclusion criteria in both TKA groups were obtaining a high score according to the WOMAC (< 43), KOOS (>80) and Forgotten Joint Scores (>75). Patients in both groups were matched by age, sex and BMI. All patients had full extension and at least 125°of knee flexion.
The kinematic of the knee was calculated using the peak knee adduction (KAM) and knee flexion moments (KFM) and the knee rotational moment (KRM) (t-tests edited).
The MC TKA group showed significant knee kinematic differences compared to the PS TKA in the knee flexion angle at heelstrike (MC 3.1°; PS 8.0°p< 0.05), in the knee adduction angle during the gait cycle (MC 1.8°; PS 3.1°p< 0.05) and in the knee rotational moment (MC 0.9 % BWHt; PS 0.6 % BWHt p< 0.05); the PS TKA group showed an higher peak KFM (3.78% BW Ht) than the MC group (2.34% BW Ht) (n.s.).
Compared to normal knees, TKAs had less late stance peak extension moments compared to controls (p< 0.05), less rotation at heel strike compared to controls (p< 0.05), greater 2ndpeak knee adduction moment compared to controls (p< 0.05) and greater peak Knee Adduction Angle during swing phase than controls (p< 0.05). When compared to the contralateral knee in the same patient, TKA knees showed a smaller mid-stance knee flexion angle (n.s.) and were more externally-rotated during swing compared to their contralateral (p=0.02).
This study showed that modern TKA systems fail to reproduce the normal knee kinematics: the lack of full extension during stance, the absence of the “screw-home mechanism”, the increased medio-lateral instability (KAM) still represent major differences: the knee kinematics of MC TKAs more closely resembled that of normal healthy controls than PS TKAs.
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