Eur J Anat, 24 (6): 491-499 (2020)

The architecture of the 6-month-old gastrocnemius: a 3D volumetric study

Luke R. Bradshaw¹, Ethan M. Breinhorst¹, Ngaire S. Stott², Anne M.R. Agur³, Seyed A. Mirjalili¹

¹Department of Anatomy and Medical Imaging, University of Auckland, Auckland, New Zealand²Department of Surgery, School of Medicine, University of Auckland, Auckland, New Zealand³Division of Anatomy, Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Canada

ABSTRACT Gastrocnemius is essential in normal gait, con-tributing to the control of ankle plantarflexion and knee flexion. However, there is a paucity of litera-ture on the architecture of the infant gastrocnemius muscle prior to the onset of weight-bearing and gait. This study investigates the three-dimensional (3D) musculoaponeurotic architecture of the gas-trocnemius in a six-month-old infant. One six-month-old cadaver was used in this study (The University of Toronto Health Sciences Research Ethics Board, #32679, and The University of Auck-land Human Participants Ethics Committee, #016164). Medial (MG) and lateral (LG) heads of the gastrocnemius were serially dissected and a Microscribe G2X� digitizer used to digitize fiber bundles, aponeuroses and tendons. Data were then exported to Autodesk® Maya® to create 3D models. Custom software quantified architectural parameters, including fiber bundle length, penna-tion angle, physiological cross-sectional area, and muscle volume. The intramuscular architecture was assessed to determine whether musculoapo-neurotic partitions were present. Muscle volume was <1cm3 for both MG and LG. Three architec-tural partitions, proximal, middle, and distal, were identified for both MG and LG. Notably, the proxi-mal partitions of both MG and LG had mean fiber bundle length at 2.21 ± 0.41 cm and 2.22 ± 0.27 cm, significantly greater (p<0.05) than the middle and the distal partitions. The results of this study suggest that both MG and LG have architectural partitions before the commencement of gait. Fur-ther longitudinal studies with larger sample sizes are needed to confirm the presence of these archi-tectural partitions, as well as to investigate their growth across the developmental spectrum.

Keywords: Gastrocnemius â?? Infant â?? Muscle architecture â?? Skeletal muscle â?? Digitization â?? Growth â?? Development