Mutsuaki Edama1,2, Tomoya Takabayashi3, Takuma Inai3, Takanori Kikumoto3, Wataru Ito3, Emi Nakamura3, Ryo Hirabayashi3, Masahiro Ikezu3, Fumiya Kaneko3, Ikuo Kageyama4. 1. Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Shimami-cho 1398, Kita-ku, Niigata City, 950-3198, Japan. edama@nuhw.ac.jp. 2. Department of Anatomy, School of Life Dentistry at Niigata, Nippon Dental University, Niigata, Japan. edama@nuhw.ac.jp. 3. Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Shimami-cho 1398, Kita-ku, Niigata City, 950-3198, Japan. 4. Department of Anatomy, School of Life Dentistry at Niigata, Nippon Dental University, Niigata, Japan.
Abstract
PURPOSE: The purpose of this study was to investigate the strain applied to each of the tendon fiber bundles of the medial head of the gastrocnemius (MG), the lateral head of the gastrocnemius (LG), and the soleus muscle (Sol) that compose the Achilles tendon (AT) when the subtalar joint is pronated and supinated. METHODS: Three AT twist types (least, moderate, extreme) were investigated. Using the MicroScribe system, the AT and the talocrural and subtalar joints were digitized to reconstruct three-dimensional models. Using this system, subtalar joint rotations in the pronation (20°) and supination (20°) directions were simulated, and the degrees of strain (%) on each tendon were calculated. RESULTS: For all twist types, when the subtalar joint was pronated, MG, LG, and Sol stretched, and when supinated, MG, LG, and Sol shortened. In particular, the least and severe twist types had large degrees of strain of Sol when the subtalar joint was pronated, and furthermore, each tendon fiber composing Sol had different degrees of strain. CONCLUSIONS: The study results suggest that the degree of strain applied within the AT with subtalar joint pronation is not constant, and that, especially in least and extreme twist types, the risk of developing AT disorders may increase.
PURPOSE: The purpose of this study was to investigate the strain applied to each of the tendon fiber bundles of the medial head of the gastrocnemius (MG), the lateral head of the gastrocnemius (LG), and the soleus muscle (Sol) that compose the Achilles tendon (AT) when the subtalar joint is pronated and supinated. METHODS: Three AT twist types (least, moderate, extreme) were investigated. Using the MicroScribe system, the AT and the talocrural and subtalar joints were digitized to reconstruct three-dimensional models. Using this system, subtalar joint rotations in the pronation (20°) and supination (20°) directions were simulated, and the degrees of strain (%) on each tendon were calculated. RESULTS: For all twist types, when the subtalar joint was pronated, MG, LG, and Sol stretched, and when supinated, MG, LG, and Sol shortened. In particular, the least and severe twist types had large degrees of strain of Sol when the subtalar joint was pronated, and furthermore, each tendon fiber composing Sol had different degrees of strain. CONCLUSIONS: The study results suggest that the degree of strain applied within the AT with subtalar joint pronation is not constant, and that, especially in least and extreme twist types, the risk of developing AT disorders may increase.