A drop tower for controlled impact testing of biological tissues

Leanne V. Burgin, Richard Malcolm Aspden

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


Impact damage, in particular to tissues such as articular cartilage, is a recognised source of morbidity. To understand better the clinical outcomes, it is important to know the mechanics of the damage sustained and the biological response of cells to rapidly applied forces and subsequent tissue disruption. An instrumented drop tower has been designed to enable controlled impact loads to be applied to small samples of biological materials. Impact severity can be controlled by using impactors of different masses and various drop heights. Force and deceleration at impact are recorded at 50,000 samples s(-1) by a force transducer under the sample and an accelerometer on the impactor. Repeatability was tested on rubber washers and coefficients of variation were found to be better than 8% for dynamic stiffness, 3.4% for stress and 4.3% for strain. Initial tests on isolated biopsies of articular cartilage showed that at an initial strain rate of 916 s(-1), the peak dynamic modulus of human femoral head cartilage was 59 MPa, and for a bovine biopsy the initial strain rate and corresponding peak dynamic modulus were 3380 s(-1) and 130 Wa, respectively. The equipment described is capable of applying an impact load to small biopsies of tissue with a defined energy and velocity and measuring deformation and load at high rates of loading.

Original languageEnglish
Pages (from-to)525-530
Number of pages6
JournalMedical Engineering & Physics
Issue number4
Early online date27 Jul 2006
Publication statusPublished - May 2007


  • impact
  • articular cartilage
  • mechanical properties
  • drop tower
  • mechanical testing
  • articular-cartilage
  • joint fluid
  • knee-joint
  • inhibitor
  • fragments
  • injury
  • model


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