- Email: [email protected]
A comparison of functional and regression-based hip joint centers in persons with achondroplasia
Abstracts / Gait & Posture 30S (2009) S1–S153
Digital Locomotory Signature (DLS; see figure), a global index of BCOM dynamics. Harmonic coefficients were used to calculate the Symmetry Index (SI, 0: no symmetry, 1: complete symmetry), namely representing the spatial differences, in BCOM trajectory, between two steps. Differences between age groups (over speed) and between speeds (over age) were assessed by using t-tests. Results No significant differences were found in SI between males and females. In each movement direction, SI was lower in young children (6–13 years; 0.79 ± 0.03, in walking; and 0.75 ± 0.03, in running; p < 0.01) and in elderly adults (56–65 years; 0.82 ± 0.04, in walking; and 0.80 ± 0.03, in running; p < 0.05) than in all the other age groups (pooled 14–55 years; 0.84 ± 0.01, in walking; and 0.82 ± 0.01, in running). Walking forward and vertical SI, in each age group, increased in the speed range 0.83–1.67 m s−1 (p < 0.001); medial/lateral direction SI slightly decreased (p < 0.05). Running forward SI increased with speed (p < 0.001). Discussion Although no gender differences were found, human ‘healthy’ gait is rather asymmetrical. It is interesting to note that, in each testing condition, right and left steps are mostly symmetrical in the medial/lateral direction. Also, global asymmetry is more pronounced at extreme ages: while at early stages of lifespan this result could be ascribed to the process of gait development, old age asymmetries are probably due to structural wearing of musculo-skeletal system. References [1] Minetti AE. IMEC, Banff; 2006. [2] Minetti AE, et al. J Physiol 1993;471:725–35.
S81
Patients/materials and methods Ten healthy subjects (6 females, 4 males; age 22.2 ± 1.9 years, body mass 62.0 ± 8.3 kg) participated in the study. Threedimensional kinematics, ground reaction force and EMG data were collected during quiet standing. A musculoskeletal model (19 degrees of freedom, 92 muscle–tendon actuators) was scaled to match the subject’s anthropometry. Using OpenSim [1], a perturbation analysis computed the contribution of a specific muscle or gravity to the anterior–posterior acceleration of the body mass center. We identified the components (muscles or gravity) that generated ≥80% of both anterior and posterior acceleration. Results In all subjects the plantar flexors (gastrocnemius (14.8%), soleus (33.5%)) produce the largest fraction of the posterior acceleration. Knee extensors (rectus femoris (17.3%), vasti (20.1%)) also contribute to the backwards acceleration. Gravity (35.3%) and tibialis anterior (26.9%) account for most of the anterior acceleration. A substantial contribution of the hip muscles (iliopsoas (24.4%), gluteus medius (13.8%)) is found in a subgroup (n = 5). Discussion Our results show that not only ankle muscles are involved in the acceleration of the body’s center of mass, which indicates that a single-link inverted pendulum might be an oversimplification. Using a double-link inverted pendulum accounts for the movement in the hip. However, we only found a substantial contribution of hip muscles in part of the group. On the other hand, knee-muscles were found to contribute to the anterior–posterior sway in all the subjects. Therefore we suggest to use a multi-joint model that includes the knee joint when studying postural control during stance. Reference [1] Delp, et al. IEEE Transactions on Biomedical Engineering 2007;54(11):1940–50.
doi:10.1016/j.gaitpost.2009.08.119 O116
doi:10.1016/j.gaitpost.2009.08.120
Modelling postural control: Validity of the inverted pendulum assumption
POSTER PRESENTATIONS
Karen Jansen ∗ , Oron Levin, Friedl De Groote, Jacques Duysens, Ilse Jonkers Katholieke Universiteit Leuven, Leuven, Belgium Summary A perturbation analysis was used to compute the contribution of individual muscles and gravity to the anterior–posterior acceleration of the body mass center. Our results indicate that not only ankle muscles, but also knee and hip muscles contribute substantially to the control of postural sway. Conclusions The assumption that the human body acts purely as an inverted pendulum during stance seems to be invalid. Using a multi-joint model including control at the knee as well as ankle and hip joint is necessary when investigating quiet standing. Introduction Many studies describe human quiet stance as a single-link inverted pendulum, only considering ankle motion to control balance. Recent work however, indicates that the movement around the knee and hip cannot be ignored. A double-link inverted pendulum model was therefore proposed to account for the movement in the hip. This study extends previous work using a complex musculoskeletal model to quantify the contribution of individual lower limb muscles to controlling the sway of the body’s center of mass.
P1 A comparison of functional and regression-based hip joint centers in persons with achondroplasia Eva Broström 1,∗ , Elena M. Gutierrez-Farewik 2 , Maria Örtqvist 1 , Lars Hagenäs 1 , Luitgard Neumeyer 3 , Adam Rozumalski 4 , Michael H. Schwartz 5 1
Dept. of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden 2 Royal Institute of Technology, Stockholm, Sweden 3 Astrid Lindgrens Children’s Hospital, Stockholm, Sweden 4 Gillette Children’s Specialty Healthcare, James R. Gage Center for Gait & Motion Analysis, St. Paul, MN, United States 5 University of Minnesota, Minneapolis, MN, United States Summary The validity of using the conventional, regression-based hip model in gait analysis in subjects with achondroplasia as opposed to a functional method was evaluated. The locations of the hip joint centers were largely different between the models. Conclusion Large differences in the calculated hip joint centers could be seen between the two different models. The gait analysis model based on the functional method is favored in this patient group, whose anthropometry cannot be expected to reflect the
S82
Abstracts / Gait & Posture 30S (2009) S1–S153
Table 1 Comparison of the hip centers for the functional method and regression-based method (conventional gait model) in four children with achondroplasia. Subject
Left (+)/right (−) (mm) Functional
Anterior (+)/posterior (−) (mm) Regression
Functional
Superior (+)/inferior (−) (mm)
Regression
Functional
Regression
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
1 2 3 4
65.9 95.0 83.6 89.9
−57.1 −94.5 −74.6 −93.1
69.7 107.2 81.1 100.1
−69.7 −107.4 −81.0 −100.1
−40.2 −22.2 −45.9 −36.7
−26.8 −17.7 −32.0 −22.8
−9.1 −15.1 −17.7 −17.7
−9.1 −16.0 −16.8 −17.7
−63.4 −92.4 −91.2 −88.6
−63.3 −89.9 −85.4 −94.7
−34.0 −39.3 −41.6 −41.6
−34.0 −40.1 −40.8 −40.8
Mean
83.6
−79.8
89.6
−89.6
−36.2
−24.8
−14.9
−14.9
−83.9
−83.3
−39.1
−39.1
regression equation on which the conventional hip model was based. Introduction Achondroplasia is the most common severe skeletal dysplasia. Children with achondroplasia develop anthropometry and joint alignment that differ from able-bodied children, namely a normal pelvis, ankle and foot but much shorter long bones. A varus deformity of the lower limbs is commonly developed in this group of patients during early or mid-childhood. Because of the complex skeletal difference, the validity of assumptions of normal anthropometry on which the conventional gait model is based Davis et al. [1] (i.e. anthropometric regression equations) should be evaluated. Several recent models base the joint centers and axes on functional evaluation [2,3], and should be equally valid for normal as for deviating anthropometry. The aim of this project was to compare one such functional method [3] to the regression-based method used in the conventional gait model (CGM) for this patient group. Patients and methods Four subjects with achondroplasia, age 7–28 (mean 16, SD 9) years were studied. Motion data was collected with an 8-camera Vicon MX40 (Vicon, Oxford, UK). The standard clinical marker set was used (based on Davis et al. [1]), and additional markers were placed on the medial femoral condyles, the medial malleoli, and on the thigh and shank according to Schwartz et al. [2]. Computed hip joint centers and gait kinematics based on the CGM (Vicon Plug-In-Gait model) were compared to those obtained using Ehrig’s method. Results The functional method produced hip centers that are more posterior (mean 15.6 mm, range 1.7–31.3), medial (mean 7.8 mm, range −2.5 to 12.9) and inferior (mean 44.5 mm, range 29.3–53.1) than the CGM (Table 1). Discussion The complex skeletal differences and mal-alignment of the lower limbs in subjects with achondroplasia compared to ablebodied children stress the importance of accurate calculation of joint centers and axes of rotation for reliable gait analysis data. We believe that a functional method to determine joint centers and axes would be more accurate and appropriate in this patient group. References [1] Davis, et al. Hum Mov Sci 1991;(10):575–87. [2] Schwartz, et al. J Biomech 2005;38(1):107–16. [3] Ehrig, et al. J Biomech 2006;39(15):2798–809.
doi:10.1016/j.gaitpost.2009.08.121
P2 Kinetic analysis of knee and hip joint loading during sidecutting in handball—Implications for prevention and rehabilitation after ACL-injuries Jesper Bencke 1,∗ , Christina Krogshede 2 , Jeppe N. Christensen 2 , Line K. Jensen 2 , Derek Curtis 1 1 2
Hvidovre University Hospital, Copenhagen, Denmark Copenhagen School of Physiotherapy, Copenhagen, Denmark
Summary This study is the first to examine the kinetics of the sports specific handball sidecut. In the perspective of ACL-injury risk, the study demonstrated that sidecutting in handball loads the medial hamstrings through external forces producing external knee valgus moments and external knee outward rotating moments. Furthermore, the hip outward rotators may be important to counteract the external inward rotating hip joint moments. Focus on increasing activity of these muscle groups may be important when designing rehabilitation programs. Conclusions The present results show a dependency on the medial hamstrings to counteract the external valgus and outward rotating moments occurring around the knee joint during the sidecut manoeuvre, and that hip extensors, hip outward rotators, and hip adductors are the most loaded hip muscle groups during this crucial early part of the sidecut. Attention to these muscle groups may be important in prevention programs and rehabilitation regimes involving female handball players. Introduction Injuries to the anterior cruciate ligament (ACL) have previously been reported to occur early in the eccentric part of a handball sidecut manoeuvre with the knee near full extension, outwardly rotated and with increased external valgus moments, but the kinematics and kinetics of this sports specific movement has not yet been investigated in 3D. The aim of the study was to explore the kinetics of the sidecut manoeuvre in female handball players. Materials and methods Twenty-four young female handball players (age 15–18 years) agreed, with their parent’s consent, to participate. Five repetitions of each player’s individual sidecut manoeuvre were investigated using an 8 camera Vicon 612 system and an AMTI force platform. Net moments in three planes around the knee and hip joints were calculated, and the net moments during the first 30% of the contact phase were selected as outcome measures. Results The results showed great variation among the participating subjects, but on average a peak external knee valgus moment, coinciding with a peak external outward rotating and a peak internal knee extensor moment were seen at 10–20% of the contact phase.
Digital Locomotory Signature (DLS; see figure), a global index of BCOM dynamics. Harmonic coefficients were used to calculate the Symmetry Index (SI, 0: no symmetry, 1: complete symmetry), namely representing the spatial differences, in BCOM trajectory, between two steps. Differences between age groups (over speed) and between speeds (over age) were assessed by using t-tests. Results No significant differences were found in SI between males and females. In each movement direction, SI was lower in young children (6–13 years; 0.79 ± 0.03, in walking; and 0.75 ± 0.03, in running; p < 0.01) and in elderly adults (56–65 years; 0.82 ± 0.04, in walking; and 0.80 ± 0.03, in running; p < 0.05) than in all the other age groups (pooled 14–55 years; 0.84 ± 0.01, in walking; and 0.82 ± 0.01, in running). Walking forward and vertical SI, in each age group, increased in the speed range 0.83–1.67 m s−1 (p < 0.001); medial/lateral direction SI slightly decreased (p < 0.05). Running forward SI increased with speed (p < 0.001). Discussion Although no gender differences were found, human ‘healthy’ gait is rather asymmetrical. It is interesting to note that, in each testing condition, right and left steps are mostly symmetrical in the medial/lateral direction. Also, global asymmetry is more pronounced at extreme ages: while at early stages of lifespan this result could be ascribed to the process of gait development, old age asymmetries are probably due to structural wearing of musculo-skeletal system. References [1] Minetti AE. IMEC, Banff; 2006. [2] Minetti AE, et al. J Physiol 1993;471:725–35.
S81
Patients/materials and methods Ten healthy subjects (6 females, 4 males; age 22.2 ± 1.9 years, body mass 62.0 ± 8.3 kg) participated in the study. Threedimensional kinematics, ground reaction force and EMG data were collected during quiet standing. A musculoskeletal model (19 degrees of freedom, 92 muscle–tendon actuators) was scaled to match the subject’s anthropometry. Using OpenSim [1], a perturbation analysis computed the contribution of a specific muscle or gravity to the anterior–posterior acceleration of the body mass center. We identified the components (muscles or gravity) that generated ≥80% of both anterior and posterior acceleration. Results In all subjects the plantar flexors (gastrocnemius (14.8%), soleus (33.5%)) produce the largest fraction of the posterior acceleration. Knee extensors (rectus femoris (17.3%), vasti (20.1%)) also contribute to the backwards acceleration. Gravity (35.3%) and tibialis anterior (26.9%) account for most of the anterior acceleration. A substantial contribution of the hip muscles (iliopsoas (24.4%), gluteus medius (13.8%)) is found in a subgroup (n = 5). Discussion Our results show that not only ankle muscles are involved in the acceleration of the body’s center of mass, which indicates that a single-link inverted pendulum might be an oversimplification. Using a double-link inverted pendulum accounts for the movement in the hip. However, we only found a substantial contribution of hip muscles in part of the group. On the other hand, knee-muscles were found to contribute to the anterior–posterior sway in all the subjects. Therefore we suggest to use a multi-joint model that includes the knee joint when studying postural control during stance. Reference [1] Delp, et al. IEEE Transactions on Biomedical Engineering 2007;54(11):1940–50.
doi:10.1016/j.gaitpost.2009.08.119 O116
doi:10.1016/j.gaitpost.2009.08.120
Modelling postural control: Validity of the inverted pendulum assumption
POSTER PRESENTATIONS
Karen Jansen ∗ , Oron Levin, Friedl De Groote, Jacques Duysens, Ilse Jonkers Katholieke Universiteit Leuven, Leuven, Belgium Summary A perturbation analysis was used to compute the contribution of individual muscles and gravity to the anterior–posterior acceleration of the body mass center. Our results indicate that not only ankle muscles, but also knee and hip muscles contribute substantially to the control of postural sway. Conclusions The assumption that the human body acts purely as an inverted pendulum during stance seems to be invalid. Using a multi-joint model including control at the knee as well as ankle and hip joint is necessary when investigating quiet standing. Introduction Many studies describe human quiet stance as a single-link inverted pendulum, only considering ankle motion to control balance. Recent work however, indicates that the movement around the knee and hip cannot be ignored. A double-link inverted pendulum model was therefore proposed to account for the movement in the hip. This study extends previous work using a complex musculoskeletal model to quantify the contribution of individual lower limb muscles to controlling the sway of the body’s center of mass.
P1 A comparison of functional and regression-based hip joint centers in persons with achondroplasia Eva Broström 1,∗ , Elena M. Gutierrez-Farewik 2 , Maria Örtqvist 1 , Lars Hagenäs 1 , Luitgard Neumeyer 3 , Adam Rozumalski 4 , Michael H. Schwartz 5 1
Dept. of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden 2 Royal Institute of Technology, Stockholm, Sweden 3 Astrid Lindgrens Children’s Hospital, Stockholm, Sweden 4 Gillette Children’s Specialty Healthcare, James R. Gage Center for Gait & Motion Analysis, St. Paul, MN, United States 5 University of Minnesota, Minneapolis, MN, United States Summary The validity of using the conventional, regression-based hip model in gait analysis in subjects with achondroplasia as opposed to a functional method was evaluated. The locations of the hip joint centers were largely different between the models. Conclusion Large differences in the calculated hip joint centers could be seen between the two different models. The gait analysis model based on the functional method is favored in this patient group, whose anthropometry cannot be expected to reflect the
S82
Abstracts / Gait & Posture 30S (2009) S1–S153
Table 1 Comparison of the hip centers for the functional method and regression-based method (conventional gait model) in four children with achondroplasia. Subject
Left (+)/right (−) (mm) Functional
Anterior (+)/posterior (−) (mm) Regression
Functional
Superior (+)/inferior (−) (mm)
Regression
Functional
Regression
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
1 2 3 4
65.9 95.0 83.6 89.9
−57.1 −94.5 −74.6 −93.1
69.7 107.2 81.1 100.1
−69.7 −107.4 −81.0 −100.1
−40.2 −22.2 −45.9 −36.7
−26.8 −17.7 −32.0 −22.8
−9.1 −15.1 −17.7 −17.7
−9.1 −16.0 −16.8 −17.7
−63.4 −92.4 −91.2 −88.6
−63.3 −89.9 −85.4 −94.7
−34.0 −39.3 −41.6 −41.6
−34.0 −40.1 −40.8 −40.8
Mean
83.6
−79.8
89.6
−89.6
−36.2
−24.8
−14.9
−14.9
−83.9
−83.3
−39.1
−39.1
regression equation on which the conventional hip model was based. Introduction Achondroplasia is the most common severe skeletal dysplasia. Children with achondroplasia develop anthropometry and joint alignment that differ from able-bodied children, namely a normal pelvis, ankle and foot but much shorter long bones. A varus deformity of the lower limbs is commonly developed in this group of patients during early or mid-childhood. Because of the complex skeletal difference, the validity of assumptions of normal anthropometry on which the conventional gait model is based Davis et al. [1] (i.e. anthropometric regression equations) should be evaluated. Several recent models base the joint centers and axes on functional evaluation [2,3], and should be equally valid for normal as for deviating anthropometry. The aim of this project was to compare one such functional method [3] to the regression-based method used in the conventional gait model (CGM) for this patient group. Patients and methods Four subjects with achondroplasia, age 7–28 (mean 16, SD 9) years were studied. Motion data was collected with an 8-camera Vicon MX40 (Vicon, Oxford, UK). The standard clinical marker set was used (based on Davis et al. [1]), and additional markers were placed on the medial femoral condyles, the medial malleoli, and on the thigh and shank according to Schwartz et al. [2]. Computed hip joint centers and gait kinematics based on the CGM (Vicon Plug-In-Gait model) were compared to those obtained using Ehrig’s method. Results The functional method produced hip centers that are more posterior (mean 15.6 mm, range 1.7–31.3), medial (mean 7.8 mm, range −2.5 to 12.9) and inferior (mean 44.5 mm, range 29.3–53.1) than the CGM (Table 1). Discussion The complex skeletal differences and mal-alignment of the lower limbs in subjects with achondroplasia compared to ablebodied children stress the importance of accurate calculation of joint centers and axes of rotation for reliable gait analysis data. We believe that a functional method to determine joint centers and axes would be more accurate and appropriate in this patient group. References [1] Davis, et al. Hum Mov Sci 1991;(10):575–87. [2] Schwartz, et al. J Biomech 2005;38(1):107–16. [3] Ehrig, et al. J Biomech 2006;39(15):2798–809.
doi:10.1016/j.gaitpost.2009.08.121
P2 Kinetic analysis of knee and hip joint loading during sidecutting in handball—Implications for prevention and rehabilitation after ACL-injuries Jesper Bencke 1,∗ , Christina Krogshede 2 , Jeppe N. Christensen 2 , Line K. Jensen 2 , Derek Curtis 1 1 2
Hvidovre University Hospital, Copenhagen, Denmark Copenhagen School of Physiotherapy, Copenhagen, Denmark
Summary This study is the first to examine the kinetics of the sports specific handball sidecut. In the perspective of ACL-injury risk, the study demonstrated that sidecutting in handball loads the medial hamstrings through external forces producing external knee valgus moments and external knee outward rotating moments. Furthermore, the hip outward rotators may be important to counteract the external inward rotating hip joint moments. Focus on increasing activity of these muscle groups may be important when designing rehabilitation programs. Conclusions The present results show a dependency on the medial hamstrings to counteract the external valgus and outward rotating moments occurring around the knee joint during the sidecut manoeuvre, and that hip extensors, hip outward rotators, and hip adductors are the most loaded hip muscle groups during this crucial early part of the sidecut. Attention to these muscle groups may be important in prevention programs and rehabilitation regimes involving female handball players. Introduction Injuries to the anterior cruciate ligament (ACL) have previously been reported to occur early in the eccentric part of a handball sidecut manoeuvre with the knee near full extension, outwardly rotated and with increased external valgus moments, but the kinematics and kinetics of this sports specific movement has not yet been investigated in 3D. The aim of the study was to explore the kinetics of the sidecut manoeuvre in female handball players. Materials and methods Twenty-four young female handball players (age 15–18 years) agreed, with their parent’s consent, to participate. Five repetitions of each player’s individual sidecut manoeuvre were investigated using an 8 camera Vicon 612 system and an AMTI force platform. Net moments in three planes around the knee and hip joints were calculated, and the net moments during the first 30% of the contact phase were selected as outcome measures. Results The results showed great variation among the participating subjects, but on average a peak external knee valgus moment, coinciding with a peak external outward rotating and a peak internal knee extensor moment were seen at 10–20% of the contact phase.