Do different methods for measuring joint moment asymmetry give the same results?

Comparison of different symmetry indices for the quantification of dynamic joint angles

BACKGROUND

Symmetry is a sign of physiological and healthy movements, as pathologies are often described by increased asymmetries. Nevertheless, based on precisely measured data, even healthy individuals will show small asymmetries in their movements. However, so far there do not exist commonly accepted methods and reference values for gait symmetry in a healthy collective. Therefore, a comparison and presentation of reference values calculated by 3 different methods of symmetry indices for lower limb joint angles during walking, ascending, and descending stairs were shown.

METHODS

Thirty-five healthy participants were analyzed during walking, ascending, and descending stairs with the help of the inertial measurement system MyoMotion. Using the normalized symmetry index (SI_norm), the symmetry index (SI) as the integral of the symmetry function, and another normalized symmetry index (NSI), the symmetry of joint angles was evaluated. For statistical evaluation of differences, repeated measurement models and Bland-Altman-Plots were used.

RESULTS

Apart from a bias between the symmetry indices, they were comparable in the predefined limits of 5%. For all parameters, significantly higher asymmetry was found for ankle dorsi/-plantarflexion, compared with the hip and knee flexion. Moreover, the interaction effect of the joint and movement factors was significant, with an increased asymmetry of the hip and knee during descending stairs greater than while ascending stairs or walking, but a reduced symmetry of the ankle during walking when compared to descending. The movement only showed significant effects when analyzing the SI_norm.

CONCLUSION

Even for healthy individuals, small asymmetries of movements were found and presented as reference values using 3 different symmetry indices for dynamic lower limb joint angles during 3 different movements. For the quantification of symmetrical movements differences between the joints, movements, and especially their interaction, are necessary to be taken into account. Moreover, a bias between the methods should be noted. The potential for each presented symmetry index to identify pathological movements or track a rehabilitation process was shown but has to be proven in further research.

TRIAL REGISTRATION

DRKS00025878.

A novel method for measuring asymmetry in kinematic and kinetic variables: The normalized symmetry index

Gait and movement asymmetries are important variables for assessing locomotor mechanics in humans and other animals and as a predictor of injury risk and success of clinical interventions. The four indices used most often to assess symmetry are not well designed for different variable types, perform poorly when presented with cases of high asymmetry or when variables are of low magnitude, and are easily influenced by small variation in the signal. The purpose of the present study was to test the performance of these indices on previously unpublished data on ACL-R patients and to propose a new index to resolve some of these limitations. The performance of four currently used indices and a new index-the Normalized Symmetry Index (NSI), which is scaled to the range of variables being tested across multiple trials-were compared using force and angular data on participants who had undergone anterior cruciate ligament reconstruction and healthy controls. The NSI performed well compared to all other indices with all variables and had the additional benefit of returning values that range from 0% (full symmetry) to ±100% (full asymmetry). Therefore, the NSI can serve as a universal index for assessing asymmetry in humans, nonhuman animal models, and in a clinical context for assessing risk for injury and clinical outcomes.

Effects of a corrective heel lift with an orthopaedic walking boot on joint mechanics and symmetry during gait

BACKGROUND

Orthopaedic walking boots are commonly prescribed following injury and surgery. The boot creates a leg length discrepancy which is thought to affect limb symmetry and gait mechanics. This study aimed to examine the effects of a corrective heel lift for the contralateral limb on the mechanics and symmetry of walking with an orthopaedic walking boot.

RESEARCH QUESTION

Does a corrective heel lift reduce biomechanical alterations and asymmetries caused by an orthopaedic boot during gait?

METHODS

Healthy males (n=17) walked with normal shoes (Shod), an orthopaedic boot (Boot), and a corrective heel lift on the contralateral limb to the boot (Lift). A 10-camera motion capture system (Vicon, 100Hz) and four force platforms (AMTI, 1000 Hz) recorded lower extremity biomechanics. Pairwise statistics tested for differences in hip and knee kinematics and kinetics, and a symmetry index quantified limb symmetry.

FINDINGS

The Boot affected the sagittal and frontal plane hip mechanics and transverse plane knee mechanics (p<0.05), and increased the asymmetry compared to the Shod condition. The Lift improved the symmetry of some measures but increased the frontal plane hip asymmetry compared to the Boot. However, introducing the Lift did not change all kinematic variables affected by the boot.

SIGNIFICANCE

The Lift reduced some of the asymmetries introduced by the Boot, but also introduced new asymmetry in the hip frontal plane motion. The leg length discrepancy caused by the boot is probably not the only cause of altered gait mechanics. Prescribing a heel lift to a patient with an orthopaedic walking boot should be based on the individual patient's needs.

The effects of low arched feet on lower limb joints moment asymmetry during gait in children: A cross sectional study

BACKGROUND

The prevalence of flexible flat feet in children was reported to be up to 20% in previous studies. However, the role of foot type in the development of musculoskeletal injuries is less clear, particularly in children. The purpose of this study was to investigate the differences in the joint moment asymmetry in children with flexible flat feet and healthy matched control subjects.

METHODS

Fourteen male children with flexible flat feet and 15 healthy control subjects served as the sample of the study. Three dimensional kinematics and kinetic data were collected using a Vicon camera system and two Kistler force platforms during walking. Then between-limb asymmetry was examined for each joint moment.

RESULTS

Normal individuals experienced higher asymmetry in the ankle eversion and the external rotation moments than the flat feet group. Asymmetry indices in the knee abduction, adduction, and the internal rotation moments in the flat feet group were higher than that in the normal group by 15%, 24% and 13%, respectively. Furthermore, in comparison of the two groups, individuals with flat feet had higher asymmetry in the hip flexion moment as well as the hip abduction moment.

CONCLUSIONS

In order to provide appropriate protocols or footwear design for male children with flat feet, clinicians need to understand that flat feet children do not have higher levels of joint moment asymmetry as compared to normal children in all joints and all planes; consequently, they must differentiate their treatments for each specific joint. However, further larger study is warranted.