Gait in adolescent idiopathic scoliosis: kinematics and electromyographic analysis

Adolescent idiopathic scoliosis (AIS) is a progressive growth disease that affects spinal anatomy, mobility, and left-right trunk symmetry. Consequently, AIS can modify human locomotion. Very few studies have investigated a simple activity like walking in a cohort of well-defined untreated patients with scoliosis. The first goal of this study is to evaluate the effects of scoliosis and scoliosis severity on kinematic and electromyographic (EMG) gait variables compared to an able-bodied population. The second goal is to look for any asymmetry in these parameters during walking. Thirteen healthy girls and 41 females with untreated AIS, with left thoracolumbar or lumbar primary structural curves were assessed. AIS patients were divided into three clinical subgroups (group 1 < 20°, group 2 between 20 and 40°, and group 3 > 40°). Gait analysis included synchronous bilateral kinematic and EMG measurements. The subjects walked on a treadmill at 4 km/h (comfortable speed). The tridimensional (3D) shoulder, pelvis, and lower limb motions were measured using 22 reflective markers tracked by four infrared cameras. The EMG timing activity was measured using bipolar surface electrodes on quadratus lumborum, erector spinae, gluteus medius, rectus femoris, semitendinosus, tibialis anterior, and gastrocnemius muscles. Statistical comparisons (ANOVA) were performed across groups and sides for kinematic and EMG parameters. The step length was reduced in AIS compared to normal subjects (7% less). Frontal shoulder, pelvis, and hip motion and transversal hip motion were reduced in scoliosis patients (respectively, 21, 27, 28, and 22% less). The EMG recording during walking showed that the quadratus lumborum, erector spinae, gluteus medius, and semitendinosus muscles contracted during a longer part of the stride in scoliotic patients (46% of the stride) compared with normal subjects (35% of the stride). There was no significant difference between scoliosis groups 1, 2, and 3 for any of the kinematic and EMG parameters, meaning that severe scoliosis was not associated with increased differences in gait parameters compared to mild scoliosis. Scoliosis was not associated with any kinematic or EMG left–right asymmetry. In conclusion, scoliosis patients showed significant but slight modifications in gait, even in cases of mild scoliosis. With the naked eye, one could not see any difference from controls, but with powerful gait analysis technology, the pelvic frontal motion (right–left tilting) was reduced, as was the motion in the hips and shoulder. Surprisingly, no asymmetry was noted but the spine seemed dynamically stiffened by the longer contraction time of major spinal and pelvic muscles. Further studies are needed to evaluate the origin and consequences of these observations

Interpreting joint moments and powers in gait

Gait analysis is becoming an increasingly important tool to provide a quantitative description of a patient's gait deviations. It is not only used to diagnose walking disorders but also for treatment selection and evaluation. While spatiotemporal, kinematic, and EMG parameters are commonly used to describe movement and muscle activity, kinetic measures are less often evaluated, even though they give insight into the moments and powers that drive human walking. As such, kinetic parameters are able to connect abnormal movement to underlying muscle malfunction and bony malalignment. This chapter focuses on the role of joint moments and powers of the lower extremities in clinical gait analysis. After a brief introduction of normal kinetic patterns, the clinical interpretation of abnormal joint moments and powers is described. Next, typical deviations in lower limb kinetics are illustrated for several patient populations, including stroke, cerebral palsy, Duchenne muscular dystrophy, anterior cruciate ligament (ACL) injury, and osteoarthritis (OA), and for patients walking with prostheses or orthotics. This section also illustrates the clinical usefulness of specific kinetic parameters in these patient populations, including their sensitivity to treatment and ability to predict treatment outcome. The chapter illustrates that the role of kinetics within clinical gait analysis deserves more attention, and potential applications should be further pursued