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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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Impact of muscle element removal emulating a posterior surgical approach on HiL-simulated THR load situation with focus on the sitting down phase of the deep maneuver.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Comparison between the intact (blue lines) and the resected (red lines) case for hip joint rotations q3, q1, q2, measured displacement /c/ between femoral head and acetabular cup, components of the predicted reaction force fr given in the pelvic reference frame [49], and measured resisting torque /τf/. Impingement occurs at ○ and dislocation at ◇. b Direction of the hip joint reaction force with respect to the frontal plane of the pelvic reference frame [49] with illustration of the head position at and after impingement for the intact (above) and the resected (below) case.
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pone.0145798.g008: Impact of muscle element removal emulating a posterior surgical approach on HiL-simulated THR load situation with focus on the sitting down phase of the deep maneuver.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Comparison between the intact (blue lines) and the resected (red lines) case for hip joint rotations q3, q1, q2, measured displacement /c/ between femoral head and acetabular cup, components of the predicted reaction force fr given in the pelvic reference frame [49], and measured resisting torque /τf/. Impingement occurs at ○ and dislocation at ◇. b Direction of the hip joint reaction force with respect to the frontal plane of the pelvic reference frame [49] with illustration of the head position at and after impingement for the intact (above) and the resected (below) case.

Mentions: The outcomes of the emulated posterior surgical approach were contrasted with the results of the HiL simulation with the same implant position, but intact muscles (parameter set ③ vs. ④). The rotational motion remained identical between the two variations throughout the considered maneuver (Fig 8a). Both indicated impingement after 78° hip flexion (27% of the motion cycle). For the posterior approach, the femoral head dislocated after 85° hip flexion (38% of the motion cycle), in contrast to the intact case where the head remained in the cup. The dislocation process observed was accompanied by a lower load level of the reaction force and the resisting torque. The reduced load level was mainly due to the mediolateral force component dropping at peak values from −1172 N for the intact to −638 N for the resected case. The alterations within the force components was reflected by changes in force directions (Fig 8b).


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 muscle element removal emulating a posterior surgical approach on HiL-simulated THR load situation with focus on the sitting down phase of the deep maneuver.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Comparison between the intact (blue lines) and the resected (red lines) case for hip joint rotations q3, q1, q2, measured displacement /c/ between femoral head and acetabular cup, components of the predicted reaction force fr given in the pelvic reference frame [49], and measured resisting torque /τf/. Impingement occurs at ○ and dislocation at ◇. b Direction of the hip joint reaction force with respect to the frontal plane of the pelvic reference frame [49] with illustration of the head position at and after impingement for the intact (above) and the resected (below) case.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0145798.g008: Impact of muscle element removal emulating a posterior surgical approach on HiL-simulated THR load situation with focus on the sitting down phase of the deep maneuver.The HiL simulations are based on parameter sets ②, ③ from Table 1. a Comparison between the intact (blue lines) and the resected (red lines) case for hip joint rotations q3, q1, q2, measured displacement /c/ between femoral head and acetabular cup, components of the predicted reaction force fr given in the pelvic reference frame [49], and measured resisting torque /τf/. Impingement occurs at ○ and dislocation at ◇. b Direction of the hip joint reaction force with respect to the frontal plane of the pelvic reference frame [49] with illustration of the head position at and after impingement for the intact (above) and the resected (below) case.
Mentions: The outcomes of the emulated posterior surgical approach were contrasted with the results of the HiL simulation with the same implant position, but intact muscles (parameter set ③ vs. ④). The rotational motion remained identical between the two variations throughout the considered maneuver (Fig 8a). Both indicated impingement after 78° hip flexion (27% of the motion cycle). For the posterior approach, the femoral head dislocated after 85° hip flexion (38% of the motion cycle), in contrast to the intact case where the head remained in the cup. The dislocation process observed was accompanied by a lower load level of the reaction force and the resisting torque. The reduced load level was mainly due to the mediolateral force component dropping at peak values from −1172 N for the intact to −638 N for the resected case. The alterations within the force components was reflected by changes in force directions (Fig 8b).

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