Compensatory muscle activation during walking in adolescents with excessive external and internal tibial torsion

Abstract

Introduction and aim: In previous studies it has been postulated that excessive tibial torsion (TT) leads to a reduced ability of muscles to extend the knee due to lever arm dysfunction. This may contribute to crouch gait [1,2]. Although the soleus crosses the ankle joint it has also the potential to extend both the knee and the hipwhileworking against gravity [1,3]. To date the effects of excessive external and internal TT on muscles which extend the stance limb during walking has not been investigated by SEMG. Patients/materials and methods: Gait analysis data of 8 patients (mean 13.2 yrs) and 11 legs resp. 16 patients (mean 12.3 yrs) and 23 legs with CT-diagnosed external (mean 49◦) and internal (mean 17◦) TT were studied retrospectively. Exclusion criteria were age 18 years, leg length discrepancy >1 cm, foot deformities, neurological diseases, scoliosis >10◦ and obesity (>PCTL 90). Bilateral SEMG signals (12-channel-wireless, 1000Hz, Noraxon) were examined from vastus medialis (VM), medial hamstrings (MH), and gastrocnemius medialis (GM). For each patient three gait cycles were analysed by means of on/off analysis. Principal Component Analysis (PCA) was used to compare transversal hip kinematic (8 cameras, VICON) between each patient group and 17 healthy, age-matched subjects in order to analyse possible influence on the electromyographic activity. Linear mixed models applied to PC-scores were used to determine the main effects within retained principal components (PCs). Results: An additional activity has been measured during the last 20% of the stance phase in 5 (VM) resp. 2 (MH) of 8 patients with increased TT and in 6 (VM) resp. 7 (MH) of 16 patients with decreased TT. The GM also showed an abnormal SEMG in terms of premature activity at the beginning and at the end of the gait cycle in a total of 13 patients. Hip transversal kinematic was not different between patients with decreased TT and healthy controls (hip PC1: 74.4%, p= .272) in this small sample. However, patients with increased TT rotated the hip significantly more internally during the overall gait cycle compared to the healthy control group (PC1: 72.5%, p< .001) (Fig. 1). Discussion and conclusion: In patientswith excessive external or internal TTwe could show that VMandMHwork actively against the lever armdysfunctionofplantarflexors to support theextension of the knee and hip. In order to compensate for the external foot progression angle, patients with increased TTmay also activate the MH to rotate the hip internally. Activity of gastrocnemius medialis has also been seen as a compensation of lever arm dysfunction. We conclude that patients with abnormal external or internal TT need to strengthen their quadriceps and hamstrings beside the plantar flexors in case of weakness of these muscles.