Comprehensive Assessment of the Musculoskeletal System
Condition: Total Knee Arthroplasty
Study type: Observational

Summary: 
      The objective of this research is to synchronously assess in vivo loading data of the knee
      joint, tibio-femoral 3D kinematics by means of automated video-fluoroscopy, whole leg
      kinematics by means of skin markers, ground reaction forces, as well as muscle activity
      patterns in 4 to 6 subjects with instrumented total knee arthroplasty (TKA) during dynamic
      functional activities of daily life. The comprehensive in vivo dataset will provide unique
      information to evaluate the relationship between the kinematics, respectively the alignment
      of the TKA, and the resulting loading of the implant in vivo.

      The whole data package will be made available for download on a public database, such that it
      can be utilized for the testing and improvement of TKA designs as well as for the validation
      and improvement of musculoskeletal modelling by researchers around the world.
    

Detailed description: 
      STUDY SUBJECTS:

      4-6 subjects with an instrumented TKA, that has been implanted within the study
      "Kniemessprothese: Belastungsmessung bei Patienten mittels einer instrumentierten
      Knie-Endoprothese" (EA4/069/06) approved and conducted at the Charité- Universitätsmedizin in
      Berlin, Germany, will be involved in this project. This instrumented prosthesis was implanted
      in 9 subjects with osteoarthritis.

      DATA ACQUISITION:

      The testing will be performed at the Institute for Biomechanics at the ETH Zurich. The
      kinematic and kinetic measurements include video-fluoroscopic tibio-femoral 3D implant
      motion; whole leg motion capture based on skin markers as well as ground reaction forces.
      Simultaneously the joint loading is assessed by means of the instrumented TKA and a telemetry
      unit for transmitting the strain gage signals. In all subjects, muscle activity is
      additionally simultaneously assessed using surface electromyography (EMG). The electrodes are
      placed onto the skin at the sites of eight muscles in the lower limbs. At the beginning of
      the test session, the maximal voluntary contraction will be assessed by means of the EMG
      electrodes, performing the following four motion tasks:

        -  One legged standing and lifting the heel to stand on tiptoe.

        -  Extension of the knee joint against a load by means of a strap around the lower leg just
           above the ankle. (Subject is sitting on a bench, lower legs are hanging down).

        -  Flexion of the knee joint against a load by means of a strap around the lower leg just
           above the ankle. (Subject is sitting on a bench, lower legs are hanging down).

        -  Dorsiflexion of the ankle against a manual resistant force of the investigator. (Subject
           is sitting on a bench, lower legs are hanging down).

      To familiarize the subjects with the dynamic data acquisition protocol, six test trials will
      be conducted that just include the motion capture system (motion capture trials, each
      performed twice). This is followed by the main test procedure, which will consist of two
      static (static trials) and three dynamic trials (dynamic trials) assessed simultaneously by
      the video-fluoroscopy, the motion capture systems the force plates, as well as the
      instrumented TKA. During the dynamic trials the fluoroscopic measurement unit mounted on an
      automated trolley will move along the subject and capture the motion of the knee in question.

      Motion capture trials:

        -  Standing trial in an anatomic upright position

        -  Calibration motion (Standing in upright position, followed by free movement of legs and
           arms)

        -  Four basic motion tasks to define functional estimated joint axis, respectively centers:
           dorsiplantarflexion motion of the ankle, inversion/eversion motion of the ankle,
           flexion/extension motion of the knee, hip circumduction (List et al., 2012b)

      Static trials:

        -  Standing trial in an anatomic upright position captured from the side.

        -  Standing trial in an anatomic upright position captured from an angle of 45°.

      Dynamic trials:

      For each of the following activities the subjects has to perform five valid gait cycles or
      repetitions respectively. A trial is considered valid, when the knee is in the field of view
      of the image intensifier during the whole cycle and the force plate got hit for level gait,
      walking downhill and stair descent.

        -  Level gait

        -  Stair descent a two steps staircase

        -  Downhill walking a 10° inclined slope

        -  Sit down and stand up from a chair

        -  Squatting

      For documentation, all dynamic trials will additionally be captured by two video cameras. All
      anonymized data will be made available for download on a public database.
    

Observational model: Case-Only
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Patients after total knee replacement surgery from the Charité- Universitätsmedizin in
        Berlin, Germany
      
Keywords: In vivo knee joint kinematics; In vivo knee joint loading; Video-fluoroscopy; Instrumented implants; Optical motion capture; Ground reaction forces; Electromyography