Patellar resection during total knee arthroplasty: effect on bone strain and fracture risk

  • D. T. T. Lie
  • N. Gloria
  • A. A. Amis
  • B. P. H. Lee
  • S. J. Yeo
  • S. M. Chou


Patellae in small knees, or after severe patellar erosion, may be vulnerable to fracture after resection during arthroplasty. The patellar remnant may be thin, while the polyethylene component has a standard thickness. Anterior patellar bone strain was measured in cadaver knees loaded via the quadriceps, from 0 to 90° flexion, with the patella intact, and after resections to 16, 13 and 11 mm thick and replacement by an 8-mm-thick polyethylene component. Strain increased significantly with knee flexion with constant 500 N quadriceps tension. Resection caused significant changes from intact values in knee flexion and extension and no significant effect at 30° flexion. In flexion, bending caused the anterior surface to become more convex, with high tensile bone strains. In extension, resection caused negative anterior strains, representing bending in the opposite direction, with large tensile strains on the cut posterior surface. For normal activities, such as rising from a chair (1.8 kN quadriceps tension) the patella appears safe against fracture with a minimal resection to 16 mm thick. An eroded patella resected to 11 mm thickness may be at risk of fracture with that loading.


Patella Prosthesis Fracture Bone strain Stress analysis 



We thank Mr. Robert Ng for his technical help with this work, and Zimmer Inc. for providing the prosthesis and instruments. Professor Amis was supported as a Visiting Professor by the Nanyang Technological University, Singapore. This project was funded by an educational research grant from the Singapore General Hospital.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • D. T. T. Lie
    • 1
  • N. Gloria
    • 1
  • A. A. Amis
    • 2
    • 3
  • B. P. H. Lee
    • 1
  • S. J. Yeo
    • 1
  • S. M. Chou
    • 2
  1. 1.Department of Orthopaedic SurgerySingapore General HospitalSingapore
  2. 2.Mechanical and Production Engineering DepartmentNanyang Technological UniversitySingapore
  3. 3.Biomechanics Section, Mechanical Engineering DepartmentImperial CollegeLondonUK

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