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A Novel Approach for Dynamic Testing of Total Hip Dislocation under Physiological Conditions.

Herrmann S, Kluess D, Kaehler M, Grawe R, Rachholz R, Souffrant R, Zierath J, Bader R, Woernle C - PLoS ONE (2015)

Bottom Line: The outcomes for a normal sitting down and standing up maneuver revealed good agreement in trend and magnitude compared with in vivo measured hip joint forces.Reducing body mass did not influence impingement-free range of motion and dislocation behavior; however, higher resisting torques were observed under higher loads.Based on the presented data, it can be concluded that the HiL test system is able to reproduce comparable joint dynamics as present in THR patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedics, University Medicine Rostock, Rostock, Germany.

ABSTRACT
Constant high rates of dislocation-related complications of total hip replacements (THRs) show that contributing factors like implant position and design, soft tissue condition and dynamics of physiological motions have not yet been fully understood. As in vivo measurements of excessive motions are not possible due to ethical objections, a comprehensive approach is proposed which is capable of testing THR stability under dynamic, reproducible and physiological conditions. The approach is based on a hardware-in-the-loop (HiL) simulation where a robotic physical setup interacts with a computational musculoskeletal model based on inverse dynamics. A major objective of this work was the validation of the HiL test system against in vivo data derived from patients with instrumented THRs. Moreover, the impact of certain test conditions, such as joint lubrication, implant position, load level in terms of body mass and removal of muscle structures, was evaluated within several HiL simulations. The outcomes for a normal sitting down and standing up maneuver revealed good agreement in trend and magnitude compared with in vivo measured hip joint forces. For a deep maneuver with femoral adduction, lubrication was shown to cause less friction torques than under dry conditions. Similarly, it could be demonstrated that less cup anteversion and inclination lead to earlier impingement in flexion motion including pelvic tilt for selected combinations of cup and stem positions. Reducing body mass did not influence impingement-free range of motion and dislocation behavior; however, higher resisting torques were observed under higher loads. Muscle removal emulating a posterior surgical approach indicated alterations in THR loading and the instability process in contrast to a reference case with intact musculature. Based on the presented data, it can be concluded that the HiL test system is able to reproduce comparable joint dynamics as present in THR patients.

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Related in: MedlinePlus

Impact of friction under dry and lubricated conditions on HiL-simulated THR load situation for a deep seating-to-rising motion cycle.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Absolute value of predicted reaction force /fr/. b Absolute value of measured resisting torque /τf/.
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pone.0145798.g005: Impact of friction under dry and lubricated conditions on HiL-simulated THR load situation for a deep seating-to-rising motion cycle.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Absolute value of predicted reaction force /fr/. b Absolute value of measured resisting torque /τf/.

Mentions: For both friction conditions (parameter sets ② and ③), the absolute value of the resisting torque (Fig 5b) was roughly proportional to the absolute value of the joint force (Fig 5a). The brief sharp drops of the resisting torque were caused by changes of the direction of the flexion angle under high load during seating-to-rising. Joint lubrication reduced the absolute value of friction torque over the whole motion cycle (Fig 5b).


A Novel Approach for Dynamic Testing of Total Hip Dislocation under Physiological Conditions.

Herrmann S, Kluess D, Kaehler M, Grawe R, Rachholz R, Souffrant R, Zierath J, Bader R, Woernle C - PLoS ONE (2015)

Impact of friction under dry and lubricated conditions on HiL-simulated THR load situation for a deep seating-to-rising motion cycle.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Absolute value of predicted reaction force /fr/. b Absolute value of measured resisting torque /τf/.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4696831&req=5

pone.0145798.g005: Impact of friction under dry and lubricated conditions on HiL-simulated THR load situation for a deep seating-to-rising motion cycle.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Absolute value of predicted reaction force /fr/. b Absolute value of measured resisting torque /τf/.
Mentions: For both friction conditions (parameter sets ② and ③), the absolute value of the resisting torque (Fig 5b) was roughly proportional to the absolute value of the joint force (Fig 5a). The brief sharp drops of the resisting torque were caused by changes of the direction of the flexion angle under high load during seating-to-rising. Joint lubrication reduced the absolute value of friction torque over the whole motion cycle (Fig 5b).

Bottom Line: The outcomes for a normal sitting down and standing up maneuver revealed good agreement in trend and magnitude compared with in vivo measured hip joint forces.Reducing body mass did not influence impingement-free range of motion and dislocation behavior; however, higher resisting torques were observed under higher loads.Based on the presented data, it can be concluded that the HiL test system is able to reproduce comparable joint dynamics as present in THR patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedics, University Medicine Rostock, Rostock, Germany.

ABSTRACT
Constant high rates of dislocation-related complications of total hip replacements (THRs) show that contributing factors like implant position and design, soft tissue condition and dynamics of physiological motions have not yet been fully understood. As in vivo measurements of excessive motions are not possible due to ethical objections, a comprehensive approach is proposed which is capable of testing THR stability under dynamic, reproducible and physiological conditions. The approach is based on a hardware-in-the-loop (HiL) simulation where a robotic physical setup interacts with a computational musculoskeletal model based on inverse dynamics. A major objective of this work was the validation of the HiL test system against in vivo data derived from patients with instrumented THRs. Moreover, the impact of certain test conditions, such as joint lubrication, implant position, load level in terms of body mass and removal of muscle structures, was evaluated within several HiL simulations. The outcomes for a normal sitting down and standing up maneuver revealed good agreement in trend and magnitude compared with in vivo measured hip joint forces. For a deep maneuver with femoral adduction, lubrication was shown to cause less friction torques than under dry conditions. Similarly, it could be demonstrated that less cup anteversion and inclination lead to earlier impingement in flexion motion including pelvic tilt for selected combinations of cup and stem positions. Reducing body mass did not influence impingement-free range of motion and dislocation behavior; however, higher resisting torques were observed under higher loads. Muscle removal emulating a posterior surgical approach indicated alterations in THR loading and the instability process in contrast to a reference case with intact musculature. Based on the presented data, it can be concluded that the HiL test system is able to reproduce comparable joint dynamics as present in THR patients.

Show MeSH
Related in: MedlinePlus