Testing of Hip Implants

The hip joint consists of the femur and the pelvis. Diseases can make it necessary to replace parts of or the entire hip joint with an implant. 
Embedding device_hip joint endoprotheses_ISO7206 (5)

Fatigue Tests on Hip Endoprotheses to ISO 7206 and ASTM F2068 (H2)

The Zwick Amsler HC Compact servo-hydraulic testing machine is used to simulate dynamic loadings on a hip prosthesis stem in accordance with the relevant standards, ISO 7206-4, ISO 7206-6, ISO 7206-8 and ASTM F2068. Use of the appropriate embedding device enables the mechanical conditions specified in the standard, such as the orientation of the hip joint prosthesis to the test load or the embedding height, together with the angle of load application, to be defined with accuracy. 

On the one hand, dynamic loading on the hip endoprosthesis stem while walking with an implant that is already loosening is simulated in order to check the stem life expectancy. On the other hand, alternating loading is applied to the neck region of the prosthesis, which is clinically well-anchored. Zwick software allows you to run user-friendly progressive load tests (Locati tests).

These tests can be implemented under physiological environmental conditions (for example, temperature-conditioned saline solution) with the use of the Zwick temperature conditioning vessel. This enables you to perform a corrosion test to ASTM F1875, which tests a modular junction's resistance to crevice corrosion and fretting corrosion under dynamic load.

Zwick's hip endoprotheses fulfills the requirements of ISO 7206 Implants for surgery - Partial and total hip joint prostheses.

Determination of endurance properties of stemmed femoral components

A minimum of six hip endoprosthesis stems must withstand 5 million load cycles with a maximum load of 2300 N and a minimum load of 300 N.

  • Number of cycles: 5 million (6 specimens)
  • Test frequency: up to 30 Hz
  • Load (ASTM F2068-03; ISO 7206-8): Fo: 2300 N; Fu: 300 N

Determination of endurance properties of head and neck region of stemmed femoral components

A minimum of six hip endoprosthesis stems must withstand 10 million load cycles at a load of 5.34 kN (R=0.1).

  • Number of cycles: 10 million (6 specimens)
  • Test frequency: up to 30 Hz
  • Load (ASTM F2068-03): Fo: 5340 N; Fu: 534 N

Endurance performance of stemmed femoral components with application of torsion

  • A precision-manufactured embedding device is used to embed the stem, ensuring exact orientation of the implant to the test loads.
  • Head and foot flange assembly for simple and durable installation, taking into consideration the necessary degrees of freedom for the test.

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Lever out test

Lever-out testing on hip joint pairings

Torsion testing_artificial_hip joints_test platform

Torsion Tests on Artificial Ball Joints

Artificial hip joints must withstand both compressive loads and torsion loads. To determine the optimum materials and alloys, these are tested with a special testing machine,

consisting of a 20-kN Zwick materials testing machine plus a 500-Nm torsion drive.

The artificial hip joint (here made of metal) is rotated on a support unit (torsion loading) and compression loading is applied at the same time. This tests materials and alloys best suited for artificial hip joints.

  • ISO 7206-9:1994 (Determination of resistance to torque of head fixation of stemmed femoral components)
  • Characterization of the resistance of a hip joint head to torques in normal in-vivo use
  • Makes it possible to develop a better anchor between the two components
  • Application of a static compression preload, the transverse torque then increases until the head turns
  • Static biaxial testing machine (20 kN) with 500-Nm torque motor
Artificial bones

Testing of the Anchoring of a Hip Endoprosthesis

Hip endoprostheses can be anchored in the femur with or without the use of bone cement. In addition to fatigue tests on the prosthesis itself, the strength of the fastening in the bone must also be tested. For this, an endoprosthesis is anchored in natural or artificial bone, the load axis is adjusted by means of a clamping fixture and the entire test device is clamped in an AllroundLine Z020 testing machine. During the cyclic loading, loads can be measured, together with any micro-movements between prosthesis and bone.

Customized implants – Zwick delivers innovate testing technology to Karl Landsteiner University of Health Sciences

Technology always greatly impacts medicine. This is due to demographic changes and the associated socioeconomic challenges to the health care system. Innovations through customization in medical technology are necessary to maintain the current high standard. Musculoskeletal diseases such as osteoporosis or osteoarthritis are among the top five diseases in old age.
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