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Simulation of in vivo dynamics during robot assisted joint movement.

Bobrowitsch E, Lorenz A, Wülker N, Walter C - Biomed Eng Online (2014)

Bottom Line: Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures.Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively.This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Biomechanics Laboratory, University Hospital Tübingen, 72076 Tübingen, Germany. Evgenij.Bobrowitsch@med.uni-tuebingen.de.

ABSTRACT

Background: Robots are very useful tools in orthopedic research. They can provide force/torque controlled specimen motion with high repeatability and precision. A method to analyze dissipative energy outcome in an entire joint was developed in our group. In a previous study, a sheep knee was flexed while axial load remained constant during the measurement of dissipated energy. We intend to apply this method for the investigation of osteoarthritis. Additionally, the method should be improved by simulation of in vivo knee dynamics. Thus, a new biomechanical testing tool will be developed for analyzing in vitro joint properties after different treatments.

Methods: Discretization of passive knee flexion was used to construct a complex flexion movement by a robot and simulate altering axial load similar to in vivo sheep knee dynamics described in a previous experimental study.

Results: The robot applied an in vivo like axial force profile with high reproducibility during the corresponding knee flexion (total standard deviation of 0.025 body weight (BW)). A total residual error between the in vivo and simulated axial force was 0.16 BW. Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures. Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively.

Conclusions: We developed and evaluated an algorithm for the robotic simulation of complex in vivo joint dynamics using a joint specimen. This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

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Related in: MedlinePlus

Influence of flexion velocities above the 10°/s limit. (A) Knee flexion angle curves and (B) axial contact force curves were measured during the simulation of the gait cycle with three different target velocity profiles with maximal target velocity of 10 (black), 15 (gray dashed) and 20 (gray)°/s.
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Fig5: Influence of flexion velocities above the 10°/s limit. (A) Knee flexion angle curves and (B) axial contact force curves were measured during the simulation of the gait cycle with three different target velocity profiles with maximal target velocity of 10 (black), 15 (gray dashed) and 20 (gray)°/s.

Mentions: The limitation of the flexion velocity to 10°/s, which had an impact during the swing phase of the gait cycle, caused a left shift of flexion angle curves after 50% of the gait cycle (Figure 5A). In contrast, the axial contact force curves showed a small left shift while all target values were closely passed (Figure 5B).Figure 4


Simulation of in vivo dynamics during robot assisted joint movement.

Bobrowitsch E, Lorenz A, Wülker N, Walter C - Biomed Eng Online (2014)

Influence of flexion velocities above the 10°/s limit. (A) Knee flexion angle curves and (B) axial contact force curves were measured during the simulation of the gait cycle with three different target velocity profiles with maximal target velocity of 10 (black), 15 (gray dashed) and 20 (gray)°/s.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4279817&req=5

Fig5: Influence of flexion velocities above the 10°/s limit. (A) Knee flexion angle curves and (B) axial contact force curves were measured during the simulation of the gait cycle with three different target velocity profiles with maximal target velocity of 10 (black), 15 (gray dashed) and 20 (gray)°/s.
Mentions: The limitation of the flexion velocity to 10°/s, which had an impact during the swing phase of the gait cycle, caused a left shift of flexion angle curves after 50% of the gait cycle (Figure 5A). In contrast, the axial contact force curves showed a small left shift while all target values were closely passed (Figure 5B).Figure 4

Bottom Line: Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures.Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively.This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Biomechanics Laboratory, University Hospital Tübingen, 72076 Tübingen, Germany. Evgenij.Bobrowitsch@med.uni-tuebingen.de.

ABSTRACT

Background: Robots are very useful tools in orthopedic research. They can provide force/torque controlled specimen motion with high repeatability and precision. A method to analyze dissipative energy outcome in an entire joint was developed in our group. In a previous study, a sheep knee was flexed while axial load remained constant during the measurement of dissipated energy. We intend to apply this method for the investigation of osteoarthritis. Additionally, the method should be improved by simulation of in vivo knee dynamics. Thus, a new biomechanical testing tool will be developed for analyzing in vitro joint properties after different treatments.

Methods: Discretization of passive knee flexion was used to construct a complex flexion movement by a robot and simulate altering axial load similar to in vivo sheep knee dynamics described in a previous experimental study.

Results: The robot applied an in vivo like axial force profile with high reproducibility during the corresponding knee flexion (total standard deviation of 0.025 body weight (BW)). A total residual error between the in vivo and simulated axial force was 0.16 BW. Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures. Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively.

Conclusions: We developed and evaluated an algorithm for the robotic simulation of complex in vivo joint dynamics using a joint specimen. This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

Show MeSH
Related in: MedlinePlus