Quantification of soft tissue artefact in motion analysis by combining 3D fluoroscopy and stereophotogrammetry: a study on two subjects.

BACKGROUND Soft tissue artefact is the most invalidating source of error in human motion analysis using optoelectronic stereophotogrammetry. It is caused by the erroneous assumption that markers attached to the skin surface are rigidly connected to the underlying bones. The quantification of this artefact in three dimensions and the knowledge of how it propagates to relevant joint angles is necessary for the interpretation of gait analysis data. METHODS Two subjects, treated by total knee replacement, underwent data acquisition simultaneously with fluoroscopy and stereophotogrammetry during stair climbing, step up/down, sit-to-stand/stand-to-sit, and extension against gravity. The reference 3D kinematics of the femur and tibia was reconstructed from fluoroscopy-based tracking of the relevant prosthesis components. Soft tissue artefact was quantified as the motion of a grid of retro-reflecting makers attached to the thigh and shank with respect to the underlying bones, tracked by optoelectronic stereophotogrammetry. The propagation of soft tissue artefact to knee rotations was also calculated. FINDINGS The standard deviation of skin marker trajectory in the corresponding prosthesis-embedded anatomical frame was found up to 31 mm for the thigh and up to 21 mm for the shank. The ab/adduction and internal/external rotation angles were the most affected by soft tissue artefact propagation, with root mean square errors up to 192% and 117% of the corresponding range, respectively. INTERPRETATIONS In both the analysed subjects the proximal thigh showed the largest soft tissue artefact. This is subject- and task-specific. However, larger artefact does not necessarily produce larger propagated error on knee rotations. Propagated errors were extremely critical on ab/adduction and internal/external rotation. These large errors can nullify the usefulness of these variables in the clinical interpretation of gait analysis.

[1]  G K Cole,et al.  Application of the joint coordinate system to three-dimensional joint attitude and movement representation: a standardization proposal. , 1993, Journal of biomechanical engineering.

[2]  A Leardini,et al.  Position and orientation in space of bones during movement: anatomical frame definition and determination. , 1995, Clinical biomechanics.

[3]  K Manal,et al.  Knee moment profiles during walking: errors due to soft tissue movement of the shank and the influence of the reference coordinate system. , 2002, Gait & posture.

[4]  M. Sati,et al.  Quantitative assessment of skin-bone movement at the knee , 1996 .

[5]  B. Nigg,et al.  Tibiofemoral and tibiocalcaneal motion during walking: external vs. skeletal markers , 1997 .

[6]  K. Manal,et al.  Comparison of surface mounted markers and attachment methods in estimating tibial rotations during walking: an in vivo study. , 2000, Gait & posture.

[7]  P R Cavanagh,et al.  Three-dimensional kinematics of the human knee during walking. , 1992, Journal of biomechanics.

[8]  Alberto Leardini,et al.  Validation of the Interval Deformation Technique for Compensating Soft Tissue Artefact in Human Motion Analysis , 2003, IS4TH.

[9]  A Leardini,et al.  Position and orientation in space of bones during movement: experimental artefacts. , 1996, Clinical biomechanics.

[10]  T. Kepple,et al.  Surface movement errors in shank kinematics and knee kinetics during gait , 1997 .

[11]  B. Maslen,et al.  Radiographic study of skin displacement errors in the foot and ankle during standing. , 1994, Clinical biomechanics.

[12]  A. Leardini,et al.  Data management in gait analysis for clinical applications. , 1998, Clinical biomechanics.

[13]  R. Mann,et al.  A comparison of lower-extremity skeletal kinematics measured using skin- and pin-mounted markers , 1997 .

[14]  S.A. Banks,et al.  Accurate measurement of three-dimensional knee replacement kinematics using single-plane fluoroscopy , 1996, IEEE Transactions on Biomedical Engineering.

[15]  T P Andriacchi,et al.  Studies of human locomotion: past, present and future. , 2000, Journal of biomechanics.

[16]  E S Grood,et al.  A joint coordinate system for the clinical description of three-dimensional motions: application to the knee. , 1983, Journal of biomechanical engineering.

[17]  C. Ranawat,et al.  Total condylar knee replacment: preliminary report. , 1976, Clinical orthopaedics and related research.

[18]  A. S. Levens,et al.  Transverse rotation of the segments of the lower extremity in locomotion. , 1948, The Journal of bone and joint surgery. American volume.

[19]  I Söderkvist,et al.  Determining the movements of the skeleton using well-configured markers. , 1993, Journal of biomechanics.

[20]  R. Brand,et al.  Prediction of hip joint centre location from external landmarks , 1989 .

[21]  Dan Karlsson,et al.  The relative skin movement of the foot: a 2-D roentgen photogrammetry study. , 1998, Clinical biomechanics.

[22]  A. J. van den Bogert,et al.  Effect of skin movement on the analysis of skeletal knee joint motion during running. , 1997, Journal of biomechanics.

[23]  M. Lafortune,et al.  The use of intra-cortical pins to measure the motion of the knee joint during walking , 1985 .

[24]  Paul J. Besl,et al.  A Method for Registration of 3-D Shapes , 1992, IEEE Trans. Pattern Anal. Mach. Intell..

[25]  E. Gronenschild,et al.  The accuracy and reproducibility of a global method to correct for geometric image distortion in the x-ray imaging chain. , 1997, Medical physics.