@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}
}
@article{NedopilDelmanHowelletal.2021,
  author    = {Nedopil, Alexander J. and Delman, Connor and Howell, Stephen M. and Hull, Maury L.},
  title     = {Restoring the patient's pre-arthritic posterior slope is the correct target for maximizing internal tibial rotation when implanting a PCL retaining TKA with calipered kinematic alignment},
  series = {Journal of Personalized Medicine},
  volume    = {11},
  journal   = {Journal of Personalized Medicine},
  number    = {6},
  issn      = {2075-4426},
  doi       = {10.3390/jpm11060516},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240996},
  year      = {2021},
  abstract  = {Introduction: The calipered kinematically-aligned (KA) total knee arthroplasty (TKA) strives to restore the patient's individual pre-arthritic (i.e., native) posterior tibial slope when retaining the posterior cruciate ligament (PCL). Deviations from the patient's individual pre-arthritic posterior slope tighten and slacken the PCL in flexion that drives tibial rotation, and such a change might compromise passive internal tibial rotation and coupled patellofemoral kinematics. Methods: Twenty-one patients were treated with a calipered KA TKA and a PCL retaining implant with a medial ball-in-socket and a lateral flat articular insert conformity that mimics the native (i.e., healthy) knee. The slope of the tibial resection was set parallel to the medial joint line by adjusting the plane of an angel wing inserted in the tibial guide. Three trial inserts that matched and deviated 2°> and 2°< from the patient's pre-arthritic slope were 3D printed with goniometric markings. The goniometer measured the orientation of the tibia (i.e., trial insert) relative to the femoral component. Results: There was no difference between the radiographic preoperative and postoperative tibial slope (0.7 ± 3.2°, NS). From extension to 90° flexion, the mean passive internal tibial rotation with the pre-arthritic slope insert of 19° was greater than the 15° for the 2°> slope (p < 0.000), and 15° for the 2°< slope (p < 0.000). Discussion: When performing a calipered KA TKA with PCL retention, the correct target for setting the tibial component is the patient's individual pre-arthritic slope within a tolerance of ±2°, as this target resulted in a 15-19° range of internal tibial rotation that is comparable to the 15-18° range reported for the native knee from extension to 90° flexion.},
  language  = {en}
}