@article{NedopilShekharHowelletal.2021,
  author    = {Nedopil, Alexander J. and Shekhar, Adithya and Howell, Stephen M. and Hull, Maury L.},
  title     = {An insert with less than spherical medial conformity causes a loss of passive internal rotation after calipered kinematically aligned TKA},
  series = {Archives of Orthopaedic and Trauma Surgery},
  volume    = {141},
  journal   = {Archives of Orthopaedic and Trauma Surgery},
  number    = {12},
  issn      = {1434-3916},
  doi       = {10.1007/s00402-021-04054-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-266710},
  pages     = {2287-2294},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}