W C Kim

U.S. Department of Veterans Affairs, Washington, Washington, D.C., United States

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Publications (6)8.5 Total impact

  • T Q Lee, S L Barnett, W C Kim
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    ABSTRACT: To test the stability and strength of tibial trays fixed with cortical screws and tibial trays fixed with cancellous screws under axial and anterior-posterior shear loading conditions. Five matched human fresh frozen cadaver knees without prior pathology were used as paired specimens for comparison of cortical to cancellous screw fixation of tibial trays. Current cementless fixation of tibial trays in total knee arthroplasty is obtained by using a combination of stems, keels, posts, pegs, and screws. To date there has been no study comparing isolated cortical and cancellous screw fixation in cementless arthroplasty. An Instron machine and a video digitizing system were used to examine tibial tray lift-off, subsidence, and anterior-posterior load to failure at the bone-implant interface in five matched pairs of knees and compare the difference between cancellous and cortical screw fixation. Non-destructive cyclic testing showed a significant difference between the two types of screws for tibial tray subsidence with cancellous fixation greater than cortical (P < 0.05), but not for lift-off (P > 0.05). Load to failure testing in anterior-posterior direction did not result in a significant difference between the two types of screws for initial stiffness and ultimate load (P > 0.05), but did result in a significant difference of energy absorbed to failure (P < 0.01). The difference in amount of subsidence between cortical and cancellous fixation could possibly be due to microfractures of the underlying trabecular bone with cancellous fixation. Neither screw type was able to completely fix the tibial tray to bone and prevent micromotion. Although the load at failure for anterior-posterior shear was similar for the two screw types, the energy absorbed was greater for the cortical screws which may be a result of additional strength provided by the cortical bone surrounding the screw.
    Clinical Biomechanics 05/1999; 14(4):258-64. · 1.87 Impact Factor
  • T Q Lee, M I Danto, W C Kim
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    ABSTRACT: Synthetic femurs were used to assess the initial bone-implant interface stability of three total hip systems: Wright Medical Technology's Infinity smooth trochanteric module (S-TM), Infinity porous-coated trochanteric module (PC-TM), and Johnson and Johnson S-ROM with a porous surface. The hips were implanted into synthetic femurs, rigidly fixed, and subjected to internal rotation and cyclic, axial compressive loads. The results showed that all three implants achieved good initial implant stability and would be expected to permit bone ingrowth. The porous-coated implants showed greater initial implant stability with less axial micromotion compared with the smooth implants. This finding suggests that surface texture plays a role in initial stability of uncemented prostheses if the bone behaves similar to the material used in this study.
    Orthopedics 09/1998; 21(8):885-8. · 1.05 Impact Factor
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    ABSTRACT: Five matched pairs of fresh human femurs were used to quantitatively assess the structural integrity of the implanted Wright Medical Technology modular Infinity hip and the Osteonics single-piece Omnifit hip. The results showed that neither bone implant system was able to recreate the femoral anteversion of the intact femur (p < 0.05). Although the micromotion at the bone-implant interface was well within the limits of achieving bone ingrowth, the axial micromotion was greater for the Infinity hip than for the Omnifit hip (p < 0.05), but the rotational micromotion did not show a significant difference between the two bone implant systems (p > 0.5). The anterior proximal femur deformation patterns were similar for both the two bone implant systems and intact femurs. However, the medial proximal femur deformation patterns showed that the Infinity hip-implanted femur was more similar to the intact femur than the Osteonics Omnifit hip-implanted femur.
    Journal of Biomedical Materials Research 03/1998; 39(4):516-23.
  • T Q Lee, W C Kim
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    ABSTRACT: Thirty-six patellae were used to geometrically assess anatomically based patellar resection criteria for total knee arthroplasty. The plane of resection was defined in the coronal plane by three distinct anatomic landmarks on the undersurface of the patella: the medial and lateral edges of the quadriceps tendon insertion and the lateral edge of the patellar ligament insertion. The depth of the resection plane is defined by the anatomic landmark points approximately 1 mm posterior to the posterior aspect of the superior and inferior ligament insertions. Following resection, the resected patellae were geometrically characterized using two dimensional rectangular Cartesian coordinate system. The anatomically based patellar resection yielded a simple, consistent, and reliable method for patellar resection for total knee arthroplasty. The proportionate geometric characteristics of both the remaining anterior piece and the resected posterior piece were remarkably uniform. Following resection, the remaining patellar thickness was 65.6+/-5.3% (mean+/-SD) of the original thickness. The maximum width to height ratio of the resected surface was approximately 1:1. The thickness to diameter ratio of the resected portion of the patella was approximately 1:5. The apex of the patella was slightly off to the medial-distal quadrant from the geometric center of the resected surface. The results of this study indicate that anatomically based patellar resection criteria may help reduce the surgical variations associated with patellar resurfacing in total knee arthroplasties with dome-shaped prostheses.
    The American journal of knee surgery 02/1998; 11(3):161-5.
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    ABSTRACT: Patellofemoral joint kinematics, contact areas, and contact pressures were measured concomitantly before and after total knee arthroplasty in 10 fresh frozen human cadaver knees using an Instron machine, a custom patellofemoral joint testing jig, axial bone markers, a continuous video digitizing system, and Fuji pressure sensitive film. The implant used in this study was the Kirschner Performance Knee System with an all polyethylene, domed patellar component. For all tests, the patella was aligned in its anatomically neutral position. Patellofemoral joint contact areas decreased as much as 19-fold after total knee arthroplasty. Mean patellofemoral joint contact pressures increased as much as 32-fold, and peak patellofemoral joint contact pressures increased as much as 22-fold after total knee arthroplasty. No statistically significant differences between preoperative and postoperative specimens were observed with respect to the patellofemoral, patellotibial, or patellar tilt angles from 30 degrees to 120 degrees knee flexion. Thus, the elevated patellofemoral joint contact pressures observed after total knee arthroplasty in vitro are not a primary consequence of iatrogenically altered patellofemoral kinematics.
    Clinical Orthopaedics and Related Research 08/1997; · 2.79 Impact Factor
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    ABSTRACT: Patellofemoral contact pressures resulting from fixed rotational deformities of the femur were studied in human cadaver knees. The increase in the degree of fixed rotational deformities of the femur results in a nonlinear increase in patellofemoral contact pressures on the contralateral facets of the patella (i.e., external rotational deformity resulted in a contact pressure increase on the medial facet, and internal rotational deformity resulted in a contact pressure increase on the lateral facet of the patella). With the initial isometric tension of 200 N in the quadriceps tendon for 30 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion, the peak contact pressure showed no significant differences between the medial and lateral facets of the patella in its anatomic position. At 20 degrees of rotational deformity of the femur, only a slight increase was noted for the tension in the quadriceps tendon and the patellofemoral contact pressures on the contralateral facets of the patella. However, at 30 degrees rotational deformity of the femur, both the external and internal rotational deformity of the femur showed a significant increase in the tension of the quadriceps tendon and the patellofemoral contact pressures on contralateral facets of the patella. The greatest increase in patellofemoral contact pressures was observed at 30 degrees and 60 degrees knee flexion for both the external and internal rotational deformity of the femur. The external rotational deformity of the femur for all knee flexion angles showed significantly higher peak patellofemoral contact pressure increases on the medial facet of the patella as compared with the lateral patellofemoral contact pressure increase resulting from internal rotational deformity of the femur.
    Clinical Orthopaedics and Related Research 06/1994; · 2.79 Impact Factor

Publication Stats

83 Citations
8.50 Total Impact Points

Institutions

  • 1999
    • U.S. Department of Veterans Affairs
      Washington, Washington, D.C., United States
  • 1998
    • University of California, Irvine
      • Department of Orthopedic Surgery
      Irvine, CA, United States
  • 1994
    • Long Beach Memorial Medical Center
      Long Beach, California, United States