TY  - JOUR
A1  - Nedopil, Alexander J.
A1  - Shekhar, Adithya
A1  - Howell, Stephen M.
A1  - Hull, Maury L.
T1  - An insert with less than spherical medial conformity causes a loss of passive internal rotation after calipered kinematically aligned TKA
T2  - Archives of Orthopaedic and Trauma Surgery
N2  - Introduction
In total knee arthroplasty (TKA), the level of conformity, a medial stabilized (MS) implant, needs to restore native (i.e., healthy) knee kinematics without over-tensioning the flexion space when the surgeon chooses to retain the posterior cruciate ligament (PCL) is unknown. Whether an insert with a medial ball-in-socket conformity and lateral flat surface like the native knee or a less than spherical medial conformity restores higher and closer to native internal tibial rotation without anterior lift-off, an over-tension indicator, when implanted with calipered kinematic alignment (KA), is unknown.
Methods and Materials
Two surgeons treated 21 patients with calipered KA and a PCL retaining MS implant. Validated verification checks that restore native tibial compartment forces in passive flexion without release of healthy ligaments were used to select the optimal insert thickness. A goniometer etched onto trial inserts with the ball-in-socket and the less than spherical medial conformity measured the tibial rotation relative to the femoral component at extension and 90° and 120° flexion. The surgeon recorded the incidence of anterior lift-off of the insert.
Results
The insert with the medial ball-in-socket and lateral flat surface restored more internal tibial rotation than the one with less than spherical medial conformity, with mean values of 19° vs. 17° from extension to 90° flexion (p < 0.01), and 23° vs. 20°-120° flexion (p < 0.002), respectively. There was no anterior lift-off of the insert at 90° and 120° flexion.
Conclusion
An MS insert with a medial ball-in-socket and lateral flat surface that matches the native knee's spherical conformity restores native tibial internal rotation when implanted with calipered KA and PCL retention without over-tensioning the flexion space.
KW  - calipered
KW  - medial stabilized
KW  - spherical
KW  - conforming
KW  - insert
KW  - rotation
KW  - total knee arthroplasty
KW  - total knee replacement
KW  - kinematic alignment
Y1  - 2021
UR  - https://opus.bibliothek.uni-wuerzburg.de/frontdoor/index/index/docId/26671
UR  - https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-266710
SN  - 1434-3916
VL  - 141
IS  - 12
ER  -