Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Aug 3;12(8):1274.
doi: 10.3390/jpm12081274.

A TKA Insert with A Lateral Flat Articular Surface Maximizes External and Internal Tibial Orientations without Anterior Lift-Off Relative to Low- and Ultracongruent Surfaces

Alexander J Nedopil  1 , Stephen M Howell  2 , Maury L Hull  2   3   4
Affiliations

A TKA Insert with A Lateral Flat Articular Surface Maximizes External and Internal Tibial Orientations without Anterior Lift-Off Relative to Low- and Ultracongruent Surfaces

Alexander J Nedopil et al. J Pers Med. .

Abstract

Background: In total knee arthroplasty (TKA), inserts can have different levels of medial and lateral congruency determined by the acuteness of the upslopes of the anterior and posterior articular surfaces. The present study evaluated an insert with different levels of lateral congruency and a medial ball-in-socket congruency to test the hypothesis that a lateral flat (F) insert maximizes external tibial orientation at extension and internal orientation at 90° flexion and lowers the incidence of anterior lift-off relative to low-congruent (LC) and ultracongruent (UC) lateral inserts. Methods: Two surgeons treated 23 patients with unrestricted caliper-verified kinematic alignment (KA) and posterior cruciate ligament (PCL) retention. They randomly trialed inserts with a medial radial dial that functioned as a built-in goniometer by measuring the tibial orientation relative to a sagittal line on the femoral trial component. Anterior lift-off of the insert from the baseplate indicated PCL tightness. Results: The F insert’s mean of 9° of external tibial orientation was higher than that of the LC (5°, p < 0.0001) and UC inserts (2°, p < 0.0001). The −13° of internal tibial orientation at 90° flexion was higher than that of the LC (−9°, p < 0.0001) and UC inserts (−7°, p < 0.0001). The 0% incidence of anterior lift-off was less than that of the LC (26%) and UC inserts (57%) (p < 0.0001). Conclusions: Surgeons and implant manufacturers should know that adding congruency to the lateral articular surface limits external tibial orientation in extension and internal tibial orientation at 90° flexion and overtightens the PCL. These rotational limitations and flexion space tightness can adversely affect patellofemoral tracking and knee flexion.

Keywords: PCL retention; congruency congruency; implant design; kinematic alignment; total knee arthroplasty.

PubMed Disclaimer

Conflict of interest statement

One author is the inventor of the insert goniometer and is a consultant of the implant manufacturer (Medacta).

Figures

Figure 1
Figure 1
Schematics showing poses of the trial insert goniometer (top row) and the measurement of 0° external orientation or screw-home movement in extension and 15° internal tibial orientation at 90° flexion (cyan circles) relative to a laser etched sagittal line (black) on the femoral component (bottom row) (GMK Sphere, Medacta).
Figure 2
Figure 2
Schematics show the sagittal profiles of flat (F), low-congruent (LC), and ultracongruent (UC) lateral inserts relative to the femoral component with the knee in extension (top row) and at 90° flexion (bottom row).
Figure 3
Figure 3
Box plot showing external tibial orientation in flexion for the three insert congruencies. Congruencies not connected by the same letters were significantly different.
Figure 4
Figure 4
Box plot showing internal tibial orientation in 90° flexion for three insert congruencies. Congruencies not connected by the same letters were significantly different.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Putame G., Terzini M., Rivera F., Kebbach M., Bader R., Bignardi C. Kinematics and kinetics comparison of ultra-congruent versus medial-pivot designs for total knee arthroplasty by multibody analysis. Sci. Rep. 2022;12:3052. doi: 10.1038/s41598-022-06909-x. - DOI - PMC - PubMed
    1. Freeman M.A.R., Pinskerova V. The Movement of the Knee Studied by Magnetic Resonance Imaging. Clin. Orthop. Relat. Res. 2003;410:35–43. doi: 10.1097/01.blo.0000063598.67412.0d. - DOI - PubMed
    1. Freeman M., Pinskerova V. The movement of the normal tibio-femoral joint. J. Biomech. 2005;38:197–208. doi: 10.1016/j.jbiomech.2004.02.006. - DOI - PubMed
    1. Pinskerova V., Samuelson K.M., Stammers J., Maruthainar K., Sosna A., Freeman M.A.R. The knee in full flexion. J. Bone Jt. Surgery. Br. Vol. 2009;91:830–834. doi: 10.1302/0301-620X.91B6.22319. - DOI - PubMed
    1. French S.R., Munir S., Brighton R. A Single Surgeon Series Comparing the Outcomes of a Cruciate Retaining and Medially Stabilized Total Knee Arthroplasty Using Kinematic Alignment Principles. J. Arthroplast. 2020;35:422–428. doi: 10.1016/j.arth.2019.09.021. - DOI - PubMed